Method and arrangement for predicting chemical oxygen demand load in a waste water treatment process

Abstract

A method for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process is disclosed. The pulping process comprises a pulp bleaching process, wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process, wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage. The method may comprise obtaining a value of at least one parameter of the pulp bleaching process, wherein said parameter is indicative of COD concentration in the waste water stream, determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process, and providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage.

Description

[0001] METHOD AND ARRANGEMENT FOR PREDICTING CHEMICAL OXYGEN

[0002] DEMAND LOAD IN A WASTE WATER TREATMENT PROCESS

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a method and arrangement for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process and to a computer program .

[0005] BACKGROUND

[0006] In industrial processes , environmental regulations for emis sions to be released from the industrial processes may be in place . Typically, such regulations involve environmental licenses or permits that define how much emissions of certain compounds or components may be released to the environment without penalties . An optimal treatment level for waste water obtained from such industrial processes is typically sought in order to keep emissions within the environmental license and, on the other hand, not to use unnecessary amounts of treatment chemicals . Such treatment chemicals may be costly, and their excessive use may not be sustainable . Further, the chemical treatment for reducing the emissions may pose environmental challenges of their own . For example , such a chemical treatment may produce sludges containing aluminium or iron, which may be challenging to dewater and which may not be allowed to be landfilled .

[0007] Further, in certain processes , emission loads may be quite variable , which may make it more challenging to select optimal treatment levels .

[0008] SUMMARY

[0009] This Summary is provided to introduce a selection of concepts in a s implif ied form that are further described below in the Detailed Description . This Summary is not intended to identify key features or essential features of the claimed subj ect matter, nor is it intended to be used to limit the scope of the claimed subj ect matter .

[0010] A method for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process is disclosed , the pulping process may comprise a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage . The method may comprise obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0011] An arrangement for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process is disclosed . The pulping process may comprise a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage . The arrangement may comprise means for obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, means for determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0012] A computer program for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping proces s is al so di sclosed . The pulping process may comprise a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage . The computer program may comprise instructions which, when executed by an apparatus , cause the apparatus to perform at least the following : obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and provide control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings , which are included to provide a further understanding of the described embodiments and constitute a part of this specification, illustrate various advantageous features and examples of their combinations . In the drawings :

[0015] Figure 1 illustrates a flow chart representation of a method for predicting COD load in a waste water treatment process in connection with a pulping process according to an embodiment ;

[0016] Figure 2 illustrates a block diagram of an arrangement according to an embodiment ;

[0017] Figure 3 illustrates an arrangement according to an embodiment as a block diagram and schematically an exemplary waste water treatment process and an exemplary pulping process ; and

[0018] Figure 4 shows an example of the predicted COD (mg / 1 , dashed line ) and measured COD (mg / 1 , solid line ) in a waste water treatment process for a period of two weeks .

[0019] DETAILED DESCRIPTION

[0020] A method for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process is disclosed . The pulping process may comprise a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage .

[0021] The method may comprise obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0022] An arrangement for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process is also disclosed . The pulping process may comprise a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage .

[0023] The arrangement may comprise means for obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, means for determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0024] The method and arrangement may be used to select and adj ust suitable control actions in the waste water treatment process based on the control information in waste water treatment processes obtaining waste water from pulping processes , in which the COD loads may be quite variable and may vary e . g . in a cyclic manner .

[0025] The method and arrangement may be used to select and adj ust suitable control actions in the pulping process . The method and arrangement may be used to select and adj ust suitable control actions in the pulp bleaching process .

[0026] Further, the method and arrangement may allow for the waste water treatment process to be prepared for changes in COD load and to implement suitable control actions in real time as necessary . For example , in waste water treatment processes that do not contain a tertiary treatment stage , it may be challenging to react to a high incoming COD load, which may lead to exceeding limits of environmental permits , licenses or regulations .

[0027] The method and arrangement may be a method and arrangement for controlling COD load in a waste water treatment process in connection with a pulping process .

[0028] COD may be understood as referring to a measure of the amount of oxygen that can be consumed by chemical reactions in the waste water . COD (COD concentration) is commonly expressed in mass of oxygen consumed over volume of waste water as milligrams per litre (mg / 1 ) . It may be used as a quantitative indication of oxidi z able organic matter in the waste water . COD load may be expressed as kg / d ( i . e . kg / day) . Many governments impose strict regulations regarding the maximum COD allowed in waste water before it may be discharged to the environment . Waste water obtained from a pulping process may typically contain so-cal led hard COD, i . e . COD that is refractory to biological treatment . Thus such waste water may contain significant concentrations and / or loads of COD after primary and secondary treatment stages . The hard COD may include organic aromatic compounds originating from wood, such as lignin and / or compounds derived from lignin .

[0029] With the method and arrangement , it may be possible to avoid direct measurements of the COD concentration and / or load in waste water streams . For example , online measurements of COD concentration in waste water streams from a pulping process may be challenging, as fibers remaining in the waste water streams may eas ily clog the measuring equipment .

[0030] In a relatively s imple form of the method and arrangement , the value of at least one parameter of the pulp bleaching process may be well correlated with the COD concentration in the waste water stream after the primary treatment stage and / or after the secondary treatment stage . Then the method may comprise obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream after the primary treatment stage and / or after the secondary treatment stage , determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and providing control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0031] The arrangement may comprise means for obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream after the primary treatment stage and / or after the secondary treatment stage , means for determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0032] In other embodiments , the method may comprise obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, estimating COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentration and / or load in the waste water stream, and providing control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0033] The arrangement may comprise means for obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, means for estimating COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , means for determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentration and / or load in the waste water stream, and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0034] The value of the at least one parameter of the pulp bleaching process may be obtained e . g . by an online measurement of the value of the at least one parameter of the pulp bleaching process . The pulping process may measure such parameters onl ine routinely e . g . for the purposes of monitoring the pulp bleaching process .

[0035] The method may thus comprise measuring the value of the at least one parameter of the pulp bleaching process , for example on-line . The arrangement may comprise means for measuring the value of the at least one parameter of the pulp bleaching process , for example online means . However, the pulping process may already have the value of the at least one parameter of the pulp bleaching process available , and may provide or input the value of the at least one parameter of the pulp bleaching process to the arrangement . Thus the arrangement may obtain and / or receive the value from the pulp bleaching process .

[0036] The means for measuring the value of at least one parameter of the pulp bleaching process may comprise or be e . g . an analysis apparatus for measuring Kappa number, for example an online Kappa analyzer or other laboratory equipment . Kappa number may be determined e . g . according to the standard I SO 302 : 2004 . The means for measuring the value of at least one parameter of the pulp bleaching process may comprise e . g . a pH meter , a thermometer, and / or a conductivity measurement apparatus .

[0037] Change in Kappa number may be determined from measurements of Kappa number, for example the Kappa number determined before and after a bleaching stage . Thus a change in Kappa number may be determined e . g . by obtaining values of Kappa number and by determining the change in Kappa number based on the values of Kappa number . The arrangement may thus comprise means for determining a change in Kappa number, e . g . by obtaining values of Kappa number and by determining the change in Kappa number based on the values of Kappa number .

[0038] The at least one parameter of the pulp bleaching process may comprise or be at least one of

[0039] - incoming Kappa number,

[0040] - change in Kappa number,

[0041] - dosing of chlorine dioxide in the pulp bleaching process ,

[0042] - brightness of the pulp,

[0043] - change in brightness of the pulp,

[0044] - pH of the waste water stream or the first waste water stream,

[0045] - temperature of the waste water stream or the first waste water stream, or

[0046] - conductivity of the waste water stream or the first waste water stream .

[0047] In this context , the first waste water stream refers to a first waste water stream according to one or more embodiments described below in this specification .

[0048] The at least one parameter of the pulp bleaching process may comprise or be at least one of incoming Kappa number ; change in Kappa number ; dosing of chlorine dioxide in the pulp bleaching process ; brightness of the pulp ; or change in brightness of the pulp . These parameters may be highly indicative of the COD concentration in the waste water stream ( s ) .

[0049] The at least one parameter of the pulp bleaching process may comprise or be incoming Kappa number . The incoming Kappa number may be understood as referring to the Kappa number of the pulp incoming to the (entire ) pulp bleaching process , i . e . incoming to the first bleaching stage of the pulp bleaching proces s . In particular, the incoming Kappa number may refer to the Kappa number of the pulp incoming to a Do stage , when the Do stage is the first bleaching stage of the pulp bleaching process . The Kappa number estimates the amount of chemicals required during the bleaching of pulp to obtain a pulp with a given degree of brightness .

[0050] The at least one parameter of the pulp bleaching process may compri se or be change in Kappa number, i . e . delta Kappa . In some embodiments , the change in Kappa number may be understood as referring to a change in Kappa number acros s the f irst and last stage of the pulp bleaching process . In other words , the change in Kappa number may be understood as referring to the difference between Kappa number before the first bleaching stage and after the last bleaching stage . In some embodiments , the change in Kappa number may be understood as referring to the change in Kappa number across a ( single ) stage , for example across the first bleaching stage of the pulp bleaching process , or across one or more stages of the pulp bleaching process . The change in Kappa number is correlated with the amount of lignin removed in the pulp bleaching stage and thereby highly indicative of COD concentration in a waste water obtained from the pulp bleaching stage .

[0051] The at least one parameter of the pulp bleaching process may comprise or be dosing of chlorine dioxide in the pulp bleaching process . The dosing of chlorine dioxide in the pulp bleaching process may be understood as referring to the dosing of chlorine dioxide (CIO2 ) in one or more bleaching stages of the pulp bleaching process . For example , it may include the dosing of chlorine dioxide in a Do stage , in a Dx stage, or in both the DO stage and the Dx stage .

[0052] The at least one parameter of the pulp bleaching process may comprise or be brightness of the pulp . The brightness of the pulp may be understood as referring to the brightness of the pulp incoming to the (entire ) pulp bleaching process , or to the brightness of the pulp incoming to a ( single ) stage of the pulp bleaching process . The brightness of the pulp may be used e . g . as an alternative to the incoming Kappa number or the change of Kappa number . The at least one parameter of the pulp bleaching process may comprise or be change in brightness of the pulp, for example across one or more stages of the pulp bleaching process , or across the first and last bleaching stage . Brightness may be measured e . g . using the standard I SO 2470 - 1 .

[0053] The method may further comprise obtaining a value of the flow rate of the waste water stream ( s ) . The arrangement may further comprise means for obtaining a value of the flow rate of the waste water stream .

[0054] The arrangement may further comprise means for obtaining a value of the flow rate of the waste water stream, wherein the COD concentration in the waste water stream is determined and / or estimated based on the value of the at least one parameter of the pulp bleaching process and the COD load in the first waste water stream is determined and / or estimated based on the estimated COD concentration and on the value of the flow rate of the water stream .

[0055] The (predicted) COD load in the waste water stream may be determined and / or estimated based on the estimated COD concentration and on the value of the flow rate of the waste water stream . When the value of the flow rate of the waste water stream is known, the (predicted) COD load in the waste water stream may be calculated from the estimated and / or predicted COD concentration and on the value of the flow rate of the waste water stream . Alternatively, it may be possible to determine and / or estimate the COD load in the waste water stream based on the estimated and / or predicted COD concentration and an average flow rate of the waste water stream .

[0056] The method may further comprise measuring a value of the flow rate of the waste water stream . The arrangement may further comprise means for measuring a value of the flow rate of the waste water stream .

[0057] The method may further comprise measuring a value of the flow rate of the waste water stream, wherein the (predicted) COD concentration in the waste water stream is determined and / or estimated based on the value of the at least one parameter of the pulp bleaching process and on the value of the flow rate of the water stream . The arrangement may further comprise means for measuring a value of the flow rate of the waste water stream, wherein the (predicted) COD concentration in the waste water stream is determined and / or estimated based on the value of the at least one parameter of the pulp bleaching process , and the (predicted) COD load in the first waste water stream is determined and / or estimated based on the predicted or estimated COD concentration and on the value of the flow rate of the water stream. In this context , the waste water stream may refer to any waste water stream described in this specification, such as the first , second, or further waste water stream, and / or the combined waste water stream .

[0058] The method may further comprise using a meas urement apparatus to measure the flow of the waste water stream . The arrangement may thus further comprise a measurement apparatus for measuring or configured to measure the flow of the waste water stream. In this context, the waste water stream may refer to any waste water stream described in this specification, such as the first, second, or further waste water stream, and / or the combined waste water stream.

[0059] The pulp bleaching process may comprise a sequence of bleaching stages. The pulp bleaching process may comprise, for example, at least one D stage (chlorine dioxide stage) and at least E stage (alkaline extraction stage) , such as an Eo(alkaline extraction stage reinforced with oxygen) or an Eopstage (alkaline extraction stage reinforced with oxygen and peroxide) . The pulp bleaching process may comprise a Dostage, wherein the Dostage may be the first stage of the pulp bleaching process, i.e. the first stage of the pulp bleaching process may be a (first) chlorine dioxide stage. The pulp bleaching process may further comprise a Dx stage, i.e. a further chlorine dioxide stage. However, as a skilled person is well aware, various possible sequences may be contemplated.

[0060] The first bleaching stage may be e.g. an acidic A stage followed by a D stage without a washing stage between them. This is the so-called A / Do bleaching stage .

[0061] The waste water stream (or the first waste water stream) may be obtainable from a D stage in the pulp bleaching process. The waste water stream may be obtainable from a Do stage, from a Dx stage, or from both. D stages may be acidic. The method may further comprise obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the D stage. The arrangement may further comprise means for obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the D stage.

[0062] Waste water streams obtained from bleaching stages may be acidic or alkaline, depending on the specific stage and the chemicals used therein. In this context , the term "bleaching stage" may refer to any stage after brown stock stages , and should be understood as also including oxygen delignification stage ( s ) , which selectively removes lignin, hexenuronic acid and / or metals . In this context , the term "bleaching stage" may also refer to any stages immediately following the oxygen stage .

[0063] Any pulp bleaching stage , or each pulp bleaching stage , may comprise a washing stage , for example using countercurrent flow . Waste water streams may be obtained e . g . as filtrates from such washing stage ( s ) .

[0064] The waste water stream ( or the first waste water stream) may be obtained ( at least partially) from the first stage of the pulp bleaching process . The method may further comprise obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the first stage of the pulp bleaching process . The arrangement may further comprise means for obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the first stage of the pulp bleaching process .

[0065] It is also possible to obtain more than one waste water stream from the pulp bleaching process . Thus the term "waste water stream" may herein refer to one or more waste water streams . For example , a plurality of waste water streams from the pulp bleaching process may be obtained, combined into a combined waste water stream or to a first waste water stream, and conducted to the waste water treatment proces s . The plurality of waste water streams from the pulp bleaching process may be obtained from different stages , for example from one or more of a D stage ( a Doand / or Dx stage ) , an E0Pstage , or an A / DQ stage . The method may further comprise obtaining and / or measuring values of the flow rates of the plurality of waste water streams . The arrangement may further comprise means for obtaining and / or measuring values of the flow rates of the plurality of the waste water streams .

[0066] COD concentration may be estimated for each of the plurality of the waste water streams separately, such that the at least one parameter of the pulp bleaching process may be selected independently for each of the plurality of the waste water streams e . g . from any one of the parameters of the pulp bleaching process described in this specification .

[0067] The plurality of waste water streams may comprise waste water streams obtainable from two or more of the following : a Do stage , an Eopstage , or a Dx stage .

[0068] The at least one parameter of the pulp bleaching process , the value of which is obtained, may depend on from which stage the waste water stream or the plurality of waste water streams is / are obtained .

[0069] In an embodiment , the waste water stream ( or the first waste water stream) is obtained ( at least partially) from the first pulp bleaching stage . The first pulp bleaching stage may be e . g . a Do stage or an / DQ stage . In such an embodiment , the value of the at least one parameter may comprise or be , for example , a value of incoming Kappa number of the pulp incoming to the f irst pulp bleaching stage ; a value of a change in Kappa number across the first pulp bleaching stage ; brightness of the pulp incoming to the first pulp bleaching stage ; and / or change of brightness of the pulp across the first pulp bleaching stage ; and optionally pH, temperature , and / or conductivity of the ( first ) waste water stream obtained from the Do stage . I f the first pulp bleaching stage is a Do stage , the value of the at least one parameter may comprise or be , for example , the dosing of chlorine dioxide in the Do stage . The method may further comprise obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the first pulp bleaching stage . The arrangement may further comprise means for obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the first pulp bleaching stage .

[0070] In an embodiment , the waste water stream ( or the first waste water stream) is obtained ( at least partially) from a Do stage . In such an embodiment , the value of the at least one parameter may comprise or be , for example , a value of incoming Kappa number of the pulp incoming to the Do stage ; a value of a change in Kappa number across the Do stage ; the dosing of chlorine dioxide in the Do stage ; brightness of the pulp incoming to the Do stage ; and / or change of brightness of the pulp across the Do stage ; and optionally pH, temperature , and / or conductivity of the ( first ) waste water stream . The method may further comprise obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the Do stage . The arrangement may further comprise means for obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the Do stage .

[0071] In an embodiment the waste water stream ( or the first waste water stream) is obtained ( at least partially) from an Eopstage . In such an embodiment , the value of the at least one parameter may comprise or be , for example , a value of incoming Kappa number of the pulp incoming to the Eopstage ; a value of a change in Kappa number across the Eopstage ; brightness of the pulp incoming to the Eopstage ; and / or change of brightness of the pulp across the Eopstage ; and optionally, pH, temperature , and / or conductivity of the ( first ) waste water stream obtained from the Eopstage . The method may further comprise obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the Eopstage . The arrangement may further comprise means for obtaining and / or measuring a value of the flow rate of the waste water stream obtained from the Eopstage . In an embodiment the waste water stream ( or the first waste water stream) is obtained ( at least partially) from a Dx stage . In such an embodiment , the value of the at least one parameter may comprise or be , for example , a value of incoming Kappa number of the pulp incoming to the Dx stage ; a value of a change in Kappa number across the Dx stage ; brightness of the pulp incoming to the Dx stage ; change of brightness of the pulp across the Dx stage ; and / or the dosing of chlorine dioxide in the Dx stage , or the dosing of chlorine dioxide both in the Do and Dx stages ; and optionally pH, temperature , and / or conductivity of the waste water stream obtained from the Dx stage . However, waste water streams obtained from Do and Dx stages may have quite different COD concentrations ; less waste water may often be derived from Dx stages and it may contain less impurities , so that it may be easier to recycle . Therefore it may be beneficial to estimate COD concentration and COD load for waste water streams obtained from Do and Dx stages separately .

[0072] In an embodiment , the waste water stream ( or the first waste water stream) is obtained ( at least partially) from a Do stage and from an Eopstage . The Do stage may be followed by the Eopstage . In such an embodiment , the value of the at least one parameter may comprise or be , for example , a value of a change in Kappa number across the Do stage and the Eopstage . The method may further comprise obtaining and / or measuring values of the flow rates of the waste water streams obtained from the Do stage and the Eopstage . The arrangement may further comprise means for obtaining and / or measuring values of the flow rates of the waste water streams obtained from the Do stage and the Eopstage .

[0073] In the context of this specification, the waste water treatment process may be a process to which waste water stream ( s ) incoming from one or more sources are directed and in which they are treated so that the waste water may be emitted, e . g . discharged, from the waste water treatment process .

[0074] The waste water treatment process may comprise a primary treatment stage , a secondary treatment stage , and optionally a tertiary treatment stage .

[0075] In the context of this specification, the term "primary treatment stage" may be understood as referring to a treatment stage intended to remove coarse , suspended and floating solids from raw waste water . It may comprise screening for trapping solid obj ects and sedimentation for removing suspended solids . The primary treatment stage may comprise e . g . a primary sedimentation tank .

[0076] In the context of this specification, the term "secondary treatment stage" may be understood as referring to a treatment stage including a biological treatment stage and intended to remove dissolved organic matter, phosphorus and nitrogen remaining after the primary treatment . The secondary treatment stage may comprise a biological treatment stage ( including e . g . an aeration tank) and a secondary clarification ( sedimentation) stage .

[0077] In the context of this specification, the term "tertiary treatment stage" may be understood as referring to a treatment stage that may follow the primary and secondary treatment stage and that is intended to at least partially remove dissolved organic matter, phosphorus and nitrogen that may remain after primary and secondary treatment stages . The tertiary treatment stage may increase the qual ity of the waste water before it is emitted ( discharged) from the waste water treatment process . The tertiary treatment stage may involve physical-chemical separation techniques such as coagu- lation / f locculation / precipitation, carbon adsorption, membranes for advanced filtration, ion exchange , dechlorination, and / or reverse osmosis , depending e . g . on the required quality of the resulting waste water to be emitted from the wastewater treatment process . The tertiary treatment stage may thus comprise e . g . a flocculation stage and / or a precipitation stage . The tertiary treatment stage may comprise a control treatment , in which at least one control chemical is added to the waste water in order to f locculate / precipitate at least a part of the COD . The tertiary treatment stage may comprise a coagulation, flocculation and / or precipitation stage . The tertiary treatment stage may further comprise a separation stage , such as a flotation, sedimentation and / or clarification stage . Thus , after the flocculation and / or precipitation, the resulting floc or precipitate may be separated . The tertiary treatment stage may, additionally or alternatively, comprise a Fenton process stage . The Fenton process ( Fenton oxidation) is an advanced oxidation process which uses hydrogen peroxide and Fe2+to oxidi ze and decompose organic materials .

[0078] In the context of this specification, the term "control treatment" may be understood as referring to a treatment that is intended to control the COD load, e . g . to remove or reduce the COD at least partially . The control treatment may comprise or be a chemical treatment , a physical treatment, or a combination of a chemical and physical treatment . For example , the control treatment may comprise dosing of at least one control chemical and subsequent removal of suspended solids in the waste water treatment proces s . In other words , the control treatment may comprise or be dosing of at least one control chemical . The control treatment may comprise a physical control treatment , such as sedimentation, clarification, flocculation, membrane purification, Fenton process and / or ultraviolet light treatment .

[0079] The pulping process may comprise the pulp bleaching process and at least one other process . In such embodiments , further waste water streams , such as a second waste water stream, may be obtained from the at least other process . In such an embodiment , a first waste water stream (e . g . any waste water stream described above ) may be obtained from the pulp bleaching process and a second waste water stream from the at least one other process , wherein the first and second waste water stream are combined into a combined waste water stream and conducted to the waste water treatment process , wherein the method comprises obtaining the value of the at least one parameter of the pulp bleaching process and a value of at least one parameter of the at least one other process , wherein said parameters are indicative of COD concentrations in the first and second waste water streams , estimating COD concentration and COD load in the f irst waste water stream based on the value of the at least one parameter of the pulp bleaching process , estimating COD concentration and COD load in the second waste water stream based on the value of the at least one parameter of the at least one other process , determining a predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentrations and loads in the first and second waste water stream, and providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0080] In an embodiment of the arrangement, the pulping process comprises a pulp bleaching process and at least one other process , wherein a first waste water stream i s obtained from the pulp bleaching process and a second waste water stream is obtained from the at least one other process , and wherein the first and second waste water stream are combined into a combined waste water stream and conducted to the waste water treatment process , wherein the waste water treatment proces s comprises a primary treatment stage and a secondary treatment stage ; wherein the arrangement comprises means for obtaining a value of at least one parameter of the pulp bleaching process and a value of at least one parameter of the at least one other process , wherein said parameters are indicative of COD concentrations in the first and second waste water streams , means for estimating COD concentration and COD load in the first waste water stream based on the value of the at least one parameter of the pulp bleaching process , means for estimating COD concentration and COD load in the second waste water stream based on the value of the at least one parameter of the at least one other process , means for determining a predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentrations and loads in the first and second waste water stream, and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0081] The first and second waste water stream may be combined into the combined waste water stream prior to conducting them into the waste water treatment process , or they may be combined e . g . in the primary treatment stage , for example in a primary sedimentation tank . In embodiments in which a plurality of waste water streams are obtained from the pulp bleaching process , they may be combined into the first waste water stream . Alternatively, the first waste water stream may be understood as compri sing the plurality of the waste water streams obtained from the pulp bleaching process . In other words , the first waste water stream may include one or more waste water streams from one or more ( dif ferent ) pulp bleaching stages . The plurality of the waste water streams may include any waste water stream described in this specification, e . g . above .

[0082] The method may further comprise obtaining a value of the f low rate of the first waste water stream and a value of the f low rate of the second waste water stream, wherein the COD concentration in the first waste water stream is estimated based on the value of the at least one parameter of the pulp bleaching process , and the COD load in the first waste water stream is determined and / or estimated based on the estimated COD concentration and on the value of the flow rate of the first water stream, and wherein the COD concentration in the second waste water stream i s estimated based on the value of the at least one parameter of the at least one other process , and the COD load in the second waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the second waste water stream .

[0083] The arrangement may further comprise means for obtaining a value of the flow rate of the first waste water stream and a value of the flow rate of the second waste water stream, wherein the COD concentration in the first waste water stream is estimated based on the value of the at least one parameter of the pulp bleaching process , and the COD load in the first waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the first water stream, and wherein the COD concentration in the second waste water stream is estimated based on the value of the at least one parameter of the at least one other process, and the COD load in the second waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the second waste water stream.

[0084] The at least one other process may comprise or be e.g. at least one of a papermaking process, a cardboard manufacturing process, or an evaporation process, for example the evaporation process of black liquor. Such other processes may produce condensation water that may form the second waste water stream or a part thereof. Papermaking processes, such as paper mills, may include water circuits (e.g. primary, secondary, and tertiary circuits) . Overflow from the water circuit (s) of a papermaking or cardboard manufacturing process may form the second waste water stream or a part thereof. Such second waste water streams may contain e.g. coating pigments, fillers, fines, methanol and / or other organic compounds. Many such waste water streams may be recycled, but often the water containing the largest emission (e.g. COD) loads are directed to waste water treatment processes. The at least one other process may often be a more minor source of COD than e.g. the first pulp bleaching stages.

[0085] In other words, the second waste water stream may comprise one or more of a waste water stream from a papermaking process, such as an overflow from a water circuit of a papermaking process, a waste water stream from a cardboard manufacturing process, such as an overflow from a water circuit of a cardboard manufacturing process, or a waste water stream from an evaporation process , for example the evaporation process of black liquor .

[0086] In embodiments in which a plurality of waste water streams are obtained from the at least one other process , they may be combined into the second waste water stream . Alternatively, the second waste water stream may be understood as comprising the plurality of the waste water streams obtained from the at least one other process . In other words , the second waste water stream may include one or more waste water streams from one or more (different ) processes of the at least one other process .

[0087] The at least one parameter of the at least one other process may comprise or be at least one of

[0088] - pH of the second waste water stream,

[0089] - temperature of the second waste water stream, conductivity of the second waste water stream,

[0090] - suspended solids in the second waste water stream,

[0091] - turbidity of the second waste water stream, or

[0092] - redox potential ( oxidation reduction potential ) of the second waste water stream .

[0093] The at least one parameter of the at least one other process may be at least one parameter of the second waste water stream .

[0094] The at least one parameter of the at least one other process may comprise or be pH of the second waste water stream .

[0095] The at least one parameter of the at least one other process may comprise or be temperature of the second waste water stream .

[0096] The at least one parameter of the at least one other process may comprise or be conductivity of the second waste water stream . The at least one parameter of the at least one other process may comprise or be suspended solids in the second waste water stream .

[0097] The at least one parameter of the at least one other process may comprise or be turbidity of the second waste water stream .

[0098] The at least one parameter of the at least one other process may comprise or be redox potential ( oxidation reduction potential ) of the second waste water stream .

[0099] The method may further comprise obtaining and / or measuring a value of the flow rate of the second waste water stream . The arrangement may further comprise means for obtaining and / or measuring a value of the flow rate of the second waste water stream .

[0100] In embodiments in which a plurality of waste water streams are obtained from the at least one other process , the method may further comprise obtaining and / or measuring values of the flow rates of the plurality of waste water streams . The arrangement may further comprise means for obtaining and / or measuring values of the flow rates of the plurality of the waste water streams .

[0101] The predicted COD concentration and / or load in the waste water stream or the combined waste water stream after the primary treatment stage may be determined at least 2 hours , or about 2 - 15 hours , or about 4 - 8 hours in advance .

[0102] Thus the value of the at least one parameter of the pulp bleaching proces s may be obtained at least 2 hours , or about 2 - 12 hours , or about 4 - 8 hours before the waste water stream or the combined waste water stream leaves the primary treatment stage . In other words , the predicted COD concentration and / or load may be predicted e . g . at least 2 hours , or about 2 - 12 hours , or about 4 - 8 hours before the waste water stream or the combined waste water stream from which the value of the at least one parameter of the pulp bleaching process has been obtained or to which the value of the at least one parameter of the pulp bleaching process relates leaves the primary treatment stage .

[0103] The predicted COD concentration and the COD load in the waste water stream or the combined waste water stream after the secondary treatment stage may be determined e . g . at least 6 hours , or about 6 - 72 hours , or about 24 - 48 hours in advance . Thus the value of the at least one parameter of the pulp bleaching process may be obtained at least 6 hours , or about 6 - 72 hours , or about 24 - 48 hours before the waste water stream or the combined waste water stream leaves the secondary treatment stage . In other words , the predicted COD concentration and the COD load in the waste water stream or the combined waste water stream after the secondary treatment stage may be determined e . g . at least 6 hours , or about 6 - 72 hours , or about 24 - 48 hours before the waste water stream or the combined waste water stream from which the at least one parameter of the pulp bleaching proces s has been obtained or to which the value of the at least one parameter of the pulp bleaching process relates leaves the secondary treatment stage .

[0104] The estimating of the COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , or on the at least one parameter of the at least one other process , may be done when it is known how the values of the at least one parameter of the pulp bleaching process or the values of at least one parameter of the at least one other process relate to the COD concentration and / or to the COD load .

[0105] For example , when the correlation between the at least one parameter of the pulp bleaching process and the COD concentration is known, the estimation may be done by calculating an estimate of the COD concentration based on the value of the at least one parameter of the pulp bleaching process and the correlation of the COD concentration .

[0106] The correlation of the at least one parameter of the pulp bleaching process and the COD concentration may be determined ( or may have been determined) earlier . Likewise , the correlation of the at least one parameter of the at least one other process and the COD concentration may be determined ( or may have been determined) earlier .

[0107] The COD concentration and the COD load in the waste water stream or in the first and second waste water stream may be estimated using data obtained earlier . The data obtained earlier may compri se values of the at least one parameter of the pulp bleaching process , COD concentration and optional ly COD load in the waste water stream or the first waste water stream, and optional ly values of the at least one parameter of the at least one other process ; and / or the data obtained earlier may comprise values of the at least one parameter of the pulp bleaching process , the COD concentration and optionally the COD load in the waste water stream or the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage , and optional ly values of the at least one parameter of the at least one other process .

[0108] The data obtained earlier may be e . g . historical data or long-term data, which includes data on values of the at least one parameter of the pulp bleaching process , the COD concentration and optionally the COD load in the waste water stream or the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage , and optionally values of the at least one parameter of the at least one other process , wherein the data is obtained or has been obtained before the method and / or arrangement described herein is used or applied . For example , the data may include measurements of COD concentration in the waste water stream or in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage . The data obtained earlier may have been obtained during a time period of e . g . at least a month, or at least six months , or at least a year . The data obtained earlier may be gathered e . g . in the form of values of the at least one parameter of the pulp bleaching process values and of corresponding values of the COD concentration and optionally COD load in the waste water stream or the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage , and optionally corresponding values of the at least one parameter of the at least one other process .

[0109] The data obtained earlier may exhibit cyclical variation . For example , waste water streams incoming to the waste water treatment process that is obtained from a pulping process , such as from a pulp bleaching process , may often exhibit cyclical variation . In such embodiments , the data obtained earl ier may be obtained from a time period exhibiting the cyclical variation for a plurality of cycles .

[0110] The arrangement may further comprise means for gathering and / or storing the data obtained earlier .

[0111] The correlation between the at least one parameter of the pulp bleaching process and the COD concentration may be determined e . g . by correlation analysis of the data obtained earlier . For example , incoming Kappa number tends to typically correlate well with the COD concentration .

[0112] The method may comprise preprocessing the value ( s ) of the at least one parameter of the pulp bleaching process and optionally of the at least one parameter of the at least one other process . The arrangement may comprise means for preprocessing the value ( s ) of the at least one parameter of the pulp bleaching process and optionally of the at least one parameter of the at least one other process . In other words , the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage may be predicted based on the preprocessed value of the at least one parameter of the pulp bleaching process and optionally on the preprocessed value of the at least one parameter of the at least one other process .

[0113] The preprocessing may comprise e . g . at least one of filtering, averaging, outlier removal , lagging or delaying of the value ( s ) of the at least one parameter of the pulp bleaching process . The preprocessing may utili ze e . g . a cross-correlation, time lagged crosscorrelation ( TLCC) or windowed time lagged cross-correlation (WTLCC) method .

[0114] In an embodiment , the method may comprise obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, preprocessing the value ( s ) of at least said one parameter of the pulp bleaching process , determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the (preprocessed) value of the at least one parameter of the pulp bleaching process , and providing control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0115] The control information provided may include e . g . an indication that one or more control actions in the waste water treatment process should be implemented . Subsequently, the one or more control actions in the waste water treatment process may be implemented . Providing the control information may be understood e.g. as outputting the control information. The control information may be provided or output e.g. to a display for an operator of the waste water treatment process. The control information may be provided or output e.g. in the form of an alert and / or suggestions to the operator of the waste water treatment process. The control information may be provided or output e.g. in the form of a control signal to the waste water treatment process. The control information may be provided or output e.g. to an apparatus for implementing the one or more control actions in the waste water treatment process based on at least the control information. The control information may be provided or output e.g. to an apparatus for monitoring and controlling a treatment of a waste water stream as described in WO 2020 / 099723, which is herein incorporated in its entirety. The control information may be provided or output e.g. to an apparatus for controlling a coagulant dosage in a water treatment system as described in WO 2023 / 052681, which is herein incorporated in its entirety.

[0116] The method may further comprise using the control information for controlling the COD load in the waste water treatment process. The arrangement may further comprise means for using the control information for controlling the COD load in the waste water treatment process.

[0117] The method may further comprise implementing one or more control actions in the waste water treatment process based on at least the control information.

[0118] The arrangement may further comprise means for implementing one or more control actions in the waste water treatment process based on at least the control information .

[0119] The one or more control actions may comprrse at least one of controlling dosing of at least one control chemical in a control treatment of the COD load in the waste water treatment process , adj usting a parameter of a tertiary treatment stage in the waste water treatment process , collecting the waste water stream or the combined waste water stream in an equali zation basin for a time period and conducting the collected waste water stream or combined waste water stream to the waste water treatment process after the time period, or adj usting a parameter of the secondary treatment stage , such as a rate of aeration of an aerobic treatment in the secondary treatment stage .

[0120] The one or more control actions may comprise controlling dosing of at least one control chemical in a control treatment of the COD load in the waste water treatment process .

[0121] Such control chemicals may flocculate and / or precipitate COD, such that it may be removed at least partially by clarification, sedimentation, flotation and / or filtration .

[0122] Controlling the dosing of at least one control chemical in a control treatment of the COD load in the waste water treatment process may comprise or be e . g . increasing the dosing of the at least one control chemical .

[0123] The at least one control chemical may be dosed e . g . in the primary treatment stage , such as in the waste water stream ( or the combined waste water stream) incoming to the primary sedimentation tank .

[0124] The at least one control chemical may be dosed e . g . in the secondary treatment stage . In embodiments in which the waste water treatment process comprises a secondary treatment stage , which comprises a biological treatment stage ( and e . g . an aeration tank) and a secondary clarification ( sedimentation) stage , at least a part of sludge from the secondary clarification stage may be returned to the biological treatment (e.g. in the aeration tank) in the secondary treatment stage as return sludge (i.e. return activated sludge) , and the at least one control chemical, such as a coagulant, may be dosed in the return sludge. Additionally or alternatively, the at least one control chemical, such as a polymer or an inorganic coagulant, may be added to the secondary clarification stage, e.g. to the waste water stream (or the combined waste water stream) incoming to the secondary clarification.

[0125] The at least one control chemical may, additionally or alternatively, be dosed e.g. in the tertiary treatment stage.

[0126] The at least one control chemical may comprise or be at least one of a coagulant, such as aluminium- based coagulant or an iron-based coagulant, or of a flocculant, such as a polymer. The at least one control chemical may comprise a coagulant, such as an inorganic coagulant, and a flocculant. The capability of coagulants to remove the COD at least partially may be improved by the flocculant.

[0127] The coagulant may comprise or be an inorganic (anionic or cationic) coagulant, an organic (polyelec- trolytic) coagulant or any mixture or combination thereof. The inorganic coagulant may comprise or be e.g. a salt of aluminium, iron, magnesium, calcium, zirconium, zinc, or any mixture or combination thereof. The inorganic coagulant may comprise or be e.g. a chloride, sulphate, chlorosulphate, chlorohydrate, silicate, nitrate, or any mixture or combination thereof. The inorganic coagulant may comprise or be e.g. aluminium sulphate, polyaluminium sulphate, iron sulphate, aluminium chloride, polyaluminium chloride, polyaluminium chlorosulfate, polyaluminium hydroxychlorosulfate, aluminium chlorohydrate, sodium aluminate, ferric sulfate, polyferric sulfate, ferric chloride, ferric chlorosulphate, polyferric chloride, ferrous sulfate, ferrous chlorosulphate, ferrous chloride, aluminium triformate, polyaluminium formate, polyaluminium nitrate, polyaluminum silicate, magnesium chloride calcium chloride, calcium sulphate, zinc chloride, or any mixture or combination thereof. The organic (polyelec- trolytic) coagulant may comprise or be e.g. polyacrylamide, polyamine, polyDADMAC, polyethyleneimine, dicyandiamide, polyvinyl amine, or any mixture or combination thereof .

[0128] The flocculant may comprise or be e.g. an inorganic polymer, such as activated silica; a natural polymer, such as starch or alginate; a synthetic polymer, or any mixture or combination thereof. Polymers may be cationic, anionic, nonionic, or amphoteric. The synthetic polymer may comprise or be e.g. polyacrylamide, polyamine, polydiallyldimethylammoniumchloride (polyDADMAC) , or any mixture or combination thereof.

[0129] The one or more control actions may be implemented e.g. in the tertiary treatment stage. A parameter of the tertiary treatment stage may be adjusted in embodiments in which the waste water treatment process comprises a tertiary treatment stage. In embodiments in which the tertiary treatment stage comprises a flotation stage, the parameter of a tertiary treatment stage may include e.g. a rate of aeration of the flotation stage and / or a parameter of a scraper of the flotation stage. The parameter of the tertiary treatment stage may, alternatively or additionally, comprise the dosing of the at least one control chemical dosed in the tertiary treatment stage.

[0130] The one or more control actions may comprise collecting the waste water stream or the combined waste water stream in an equalization basin for a time period and conducting the collected waste water stream or the combined waste water stream to the waste water treatment process after the time period. The collected waste water stream or the combined waste water stream may then be conducted to the waste water treatment process after the time period gradually or in relatively small portions , so as not to overload the waste water treatment process .

[0131] The one or more control actions may comprise adj usting a parameter of the secondary treatment stage , such as a rate of aeration of an aerobic treatment in the secondary treatment stage and / or a dose of nutrients dosed in the secondary treatment stage ( for example , urea and / or phosphoric acid) .

[0132] The method may further comprise providing control information for controlling the pulping process , such as the pulp bleaching process . The method may further comprise using the control information for controlling the pulping process , such as the pulp bleaching process . The method may further comprise implementing one or more control actions in the pulping process , such as in the pulp bleaching process , based on at least the control information .

[0133] The arrangement may further comprise means for providing control information for controlling the pulping process , such as the pulp bleaching process .

[0134] The arrangement may further comprise means for using the control information for controlling the pulping process , such as the pulp bleaching process .

[0135] The method may further comprise implementing one or more control actions in the pulping process , such as in the pulp bleaching process , based on at least the control information .

[0136] The arrangement may further comprise means for implementing one or more control actions in the pulping process , such as in the pulp bleaching process , based on at least the control information .

[0137] In other words , the COD concentration and / or load may also be controlled within the pulping process , before the waste water stream ( s ) is / are conducted to the waste water treatment process . The one or more control actions in the pulping process may comprise at least one of dosing at least one control chemical in a waste water stream obtained from the pulp bleaching process and / or from the at least one other process , controlling the dosing of at least one control chemical in a control treatment of the COD load in the pulping process , adj usting at least one parameter in the pulping process , such as at least one parameter of the pulp bleaching process , adj usting at least one parameter in a pulp washing stage preceding the pulp bleaching process .

[0138] The at least one parameter in the pulp washing stage preceding the pulp bleaching process may comprise e . g . at least one of improving the washing of the pulp before it enters the pulp bleaching process ( i . e . the extent of the washing of the pulp before it enters the pulp bleaching process ) ; a dosing of at least one washing chemical (e . g . defoamer, dispersing agent) or washing water in a pulp washer preceding the pulp bleaching process . Such parameters may adj ust the pulping process before the pulp, i . e . brownstock, i s fed into the pulp bleaching process .

[0139] A computer program for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping proces s is al so di sclosed, the pulping process comprising a pulp bleaching process , wherein a waste water stream i s obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment proces s compri ses a primary treatment stage and a secondary treatment stage ; the computer program comprising instructions which, when executed by an apparatus , cause the apparatus to perform at least the following : obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and provide control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0140] The various means described in this specification may comprise or be the same or different means , for example the same apparatus , computing unit or processor, or different apparatuses , computing units or processors , which may arranged at one or more locations .

[0141] The means may comprise at least one processor and at least one memory including computer program code . The at least one memory and the computer program code may be conf igured to , with the at least one processor, cause the arrangement to perform the method according to one or more embodiments described in this specification .

[0142] The arrangement may comprise at least one processor and at least one memory including computer program code , the at least one memory and the computer program code conf igured to , with the at least one processor, cause the arrangement to perform the method according to one or more embodiments described in this specification, e . g . : obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and provide control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0143] The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain and / or receive a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, estimate COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentration and / or load in the waste water stream, and provide control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0144] The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream after the primary treatment stage and / or after the secondary treatment stage , determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and provide control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0145] The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, estimate COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentration and / or load in the waste water stream, and provide control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0146] The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain or measure a value of the flow rate of the waste water stream .

[0147] The at least one memory and the computer program code may be further conf igured to , with the at least one processor, cause the arrangement to : obtain or measure a value of the flow rate of the waste water stream, wherein the COD concentration in the waste water stream i s estimated based on the value of the at least one parameter of the pulp bleaching process and the COD load in the first waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the water stream .

[0148] The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain and / or receive the value of the at least one parameter of the pulp bleaching process and a value of at least one parameter of the at least one other process , wherein said parameters are indicative of COD concentrations in the first and second waste water streams , estimate COD concentration and COD load in the first waste water stream based on the value of the at least one parameter of the pulp bleaching process , estimate COD concentration and COD load in the second waste water stream based on the value of the at least one parameter of the at least one other process , determine a predicted COD concentration and / or load in the combined waste water stream after the pri mary treatment stage and / or after the secondary treatment stage based on the estimated COD concentrations and loads in the first and second waste water stream, and provide control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage .

[0149] The at least one memory and the computer program code may be further configured to , with the at least one processor, cause the arrangement to : obtain a value of the f low rate of the first waste water stream and a value of the f low rate of the second waste water stream, wherein the COD concentration in the first waste water stream is estimated based on the value of the at least one parameter of the pulp bleaching process , and the COD load in the first waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the first water stream, and wherein the COD concentration in the second waste water stream i s estimated based on the value of the at least one parameter of the at least one other process , and the COD load in the second waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the second waste water stream .

[0150] There is provided a computer program comprising instructions which, when executed by an apparatus , cause the apparatus to perform the method according to one or more embodiments described in this specification .

[0151] A computer program comprising instructions is also disclosed . The instructions , when executed by an apparatus , cause the apparatus to perform at least the following : obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and provide control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage . There is further provided a computer-readable medium comprising instructions which, when executed by an apparatus , cause the apparatus to perform the method according to one or more embodiments described in this specification .

[0152] EXAMPLES

[0153] Reference will now be made in detail to various embodiments , an example of which is il lustrated in the accompanying drawings .

[0154] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utili ze the embodiments based on the disclosure . Not all steps or features of the embodiments are discussed in detail , as many of the steps or features will be obvious for the person skilled in the art based on this specification .

[0155] Figure 1 illustrates a flow chart representation of a method for predicting COD load in a waste water treatment process 101 (WWTP) in connection with a pulping process 102 according to an embodiment .

[0156] The pulping process 102 comprises at least a pulp bleaching process 103 ; further details of the pulping process 102 and of the pulp bleaching process

[0157] 103 have been omitted for clarity . A waste water stream

[0158] 104 is obtained from the pulp bleaching process 103 and conducted to the WWTP 101 . The waste water treatment process 101 may comprise a primary treatment stage and a secondary treatment stage , as well as optionally a tertiary treatment stage , which are not shown in this Fig . for clarity .

[0159] At 105 , a value of at least one parameter of the pulp bleaching process is obtained . The at least one parameter may be selected such that it is indicative of the COD concentration in the waste water stream 104 . For example , it may be correlated with the COD concentration in the waste water stream 104 .

[0160] The value of the at least one parameter of the pulp bleaching process may be obtained or received in various ways . For example , the pulping process 102 and / or the pulp bleaching process 103 may provide the value of the at least one parameter of the pulp bleaching process , which may have been obtained e . g . by an online measurement . In some embodiments , the method may comprise at 105 measuring the value of the at least one parameter of the pulp bleaching process . As a further example , in arrangements comprising at least one processor and at least one memory including computer program code , the value of the at least one parameter of the pulp bleaching process may be obtained from the at least one memory of the arrangement , where it may have been stored ( for example , in a database ) .

[0161] At 105 , the value of at least one parameter of the pulp bleaching process may be preprocessed, if desired .

[0162] At 105 , the flow of the waste water stream 104 may also be determined (e . g . measured) , or it may otherwise be known or estimated e . g . as an average flow .

[0163] At 106 , COD concentration and COD load in the waste water stream 104 is estimated based on the value of the at least one parameter of the pulp bleaching process . I f the value of the at least one parameter of the pulp bleaching process has been preprocessed, the preprocessed value may be used in the estimation . The estimation may be done when it is known how the value of the at least one parameter of the pulp bleaching process relates to the COD concentration and / or to the COD load . For example , when the correlation between the values of the at least one parameter of the pulp bleaching process and the COD concentrations is known, the estimation may be done by calculating an estimate of the COD concentration based on the value of the at least one parameter of the pulp bleaching process and the correlation of the COD concentration . The correlation of the at least one parameter of the pulp bleaching process and the COD concentration may have been determined earlier e . g . by correlation analyses of historical data .

[0164] At 107 , a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage is determined based on the estimated COD concentration and / or load in the waste water stream . For example , when the COD concentration in the waste water stream 104 has been estimated, and the flow of the waste water stream 104 has been determined (e . g . measured) or otherwi se known or estimated e . g . at 105 , the COD load incoming to the WWTP 101 and thereby leaving or entering the primary treatment stage and / or the secondary treatment stage may be estimated .

[0165] At 108 , control information for controlling the waste water treatment process 101 based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage is provided or output . The control information may be provided or output e . g . to the WWTP 101 , for example to an operator or control system of the WWTP 101 . The control information may be provided or output e . g . in the form of an alert and / or suggestions to the operator or as a control signal to the control system of the WWTP 101 .

[0166] The method may further comprise controlling the WWTP 101 , e . g . by implementing one or more control actions in the waste water treatment process based on at least the control information at 109 .

[0167] Figure 2 illustrates a block diagram of an arrangement 210 according to an exemplary embodiment . The arrangement 210 comprises one or more processors 211 , and one or more memories 212 that comprise computer program code 213 . The arrangement 210 may also include an input / output module (not shown in Fig . 2 ) , and / or a communication interface 214 for wired and / or wireless communication . Although the arrangement 210 is depicted as including only one processor 211 , the arrangement 210 may include more than one processor . In an exemplary embodiment , the memory 212 is capable of storing instructions , such as an operating system and / or various applications . The memory 212 may additionally be capable of storing the value of the at least one parameter of the pulp bleaching process and other data, such as data on COD concentration and the COD load in the waste water stream or in the first and second waste water stream obtained earlier . For example , the arrangement 210 may comprise a database for storing or conf igured to store the data obtained earl ier, which data may include e . g . values of the at least one parameter of the pulp bleaching process , COD concentration and optionally COD load in the waste water stream or the first waste water stream, and optionally values of the at least one parameter of the at least one other process ; and / or values of the at least one parameter of the pulp bleaching process , the COD concentration and optionally the COD load in the waste water stream or the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage , and optionally values of the at least one parameter of the at least one other process .

[0168] Furthermore , the processor 211 is capable of executing the stored instructions . In an exemplary embodiment , the processor 211 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core processors and one or more single core processors . For example , the processor 211 may be embodied as one or more of various processing devices , such as a coprocessor, a microprocessor, a controller, a digital signal processor ( DSP) , a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as , for example , an application specific integrated circuit (AS IC) , a field programmable gate array ( FPGA) , a microcontroller unit (MCU) , a hardware accelerator, a special-purpose computer chip, or the like . In an exemplary embodiment , the processor 211 may be configured to execute hard- coded functionality . In an exemplary embodiment , the processor 211 may be embodied as an executor of software instructions , wherein the instructions may specifically configure the processor 211 to perform the algorithms and / or operations described herein when the instructions are executed, for example , the steps discussed with respect to Fig . 1 .

[0169] The memory 212 may be embodied as one or more volatile memory devices , one or more non-volatile memory devices , and / or a combination of one or more volatile memory devices and non-volatile memory devices . For example , the memory 212 may be embodied as semiconductor memories ( such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM ( random access memory) , etc . ) .

[0170] In an embodiment , the at least one memory 212 may store program instructions (program code ) 213 that , when executed by the at least one proces sor 211 , cause the arrangement 210 to perform the functionality of the various embodiments discussed herein . Further, in an embodiment , at least one of the processor 211 and the memory 212 may constitute means for implementing the discussed functionality . Further, the arrangement 210 may be configured to perform at least some of the examples and embodiments discussed above .

[0171] Exemplary embodiments may be implemented in software , hardware , application logic or a combination of software , hardware and application logic . The exemplary embodiments can store information relating to various methods described herein . This information can be stored in one or more memories , such as a hard disk, a sol id state drive ( SSD) , an optical di sk, a magnetooptical disk, an RAM, and the like . One or more databases can store the information used to implement the exemplary embodiments ( for example , the data of the COD concentrations and values of the at least one parameter of the pulp bleaching process obtained earlier, or their correlations ) . The databases can be organi zed using data structures (e . g . , records , tables , arrays , fields , graphs , trees , li sts , and the li ke ) included in one or more memories or storage devices listed herein . The methods described with respect to the exemplary embodiments can include appropriate data structures for storing data collected and / or generated by the methods of the devices and subsystems of the exemplary embodiments in one or more databases .

[0172] The components of the exemplary embodiments may include computer readable medium or memories for holding instructions programmed according to the teachings and for holding data structures , tables , records , and / or other data described herein . In an exemplary embodiment , the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media . In the context of this document, a "computer-readable medium" may be any media or means that can contain, store , communicate , propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus , or device , such as a computer . A computer- readable medium may include a computer-readable storage medium that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus , or device , such as a computer . A computer readable medium can include any suitable medium that participates in providing instructions to a processor for execution . Such a medium can take many forms , including but not limited to , non-volatile media, volatile media, transmission media, and the like .

[0173] The functionality of the arrangement 210 may be implemented us ing a cloud computing system or other type of distributed computing system .

[0174] Figure 3 illustrates an arrangement 310 according to an exemplary embodiment . The arrangement 310 i s i llustrated as a block diagram . The arrangement 310 may be similar to the arrangement 210 described in Fig . 2 . Figure 3 also illustrates schematically a waste water treatment process 301 that may or may not be considered to be a part of the arrangement 310 . Further, Figure 3 illustrates schematically a pulping process 302 that may or may not be considered to be a part of the arrangement 310 .

[0175] The pulping process 302 comprises a digestion stage 315 for cooking pulp 317 from lignocellulosic material . From the digestion stage 315 , the pulp 317 (often called "brownstock" at this stage of the process ) is conveyed to a washing stage 316 for washing the pulp . The washing stage 316 may contain e . g . one or more brownstock washers , typically using countercurrent flow . The washed pulp is conveyed to a pulp bleaching process 303 . The pulp bleaching process 303 is illustrated schematically as comprising three pulp bleaching stages 303 ' , 303 ' ' and 303 ' ' ' . The washed pulp typically contains a significant amount of lignin, which is removed at least partially from the pulp in the pulp bleaching process 303 . The lignin contributes significantly to the COD concentration in waste water streams obtained from the pulp bleaching process 303 ; further, other organic material may further contribute to the COD concentration in waste water streams obtained from the pulp bleaching process 303 . Further details of the pulping process 302 and of the pulp bleaching process 303 have been omitted for clarity . The pulp bleaching stage 303' may be, for example, a Do stage, in which chlorine dioxide is dosed to the pulp. The pulp bleaching stage 303' ' may be e.g. an EOp stage, which is an alkaline extraction stage reinforced with oxygen and peroxide. The pulp bleaching stage 303' ' ' may be e.g. a Dp stage, in which chlorine dioxide is dosed to the pulp. Further or other pulp bleaching stages could be contemplated. Each pulp bleaching stage 303' , 303' ' and / or 303' ' ' may comprise a washing stage, for example using countercurrent flow. Waste water streams may be obtained e.g. from such washing stages. Separate washing stages are not shown in the Fig. for clarity.

[0176] The pulping process 302 may further comprise at least one other stage 318, for example a papermaking process, a cardboard manufacturing process, or an evaporation process. A condensate may be obtained from the at least one other stage 318. Such processes may be present e.g. in pulping processes in which black liquor originating from the washing stage 316 is concentrated through evaporation, and / or in integrated pulp and paper and / or cardboard mills. Naturally the pulping process 302 may further comprise various other stages and processes, which are not included in this Fig. for clarity.

[0177] A waste water stream 319, which may be considered a first waste water stream, may be obtained from the first pulp bleaching stage 303' , for example from the washing stage of the pulp bleaching stage 303' . A value of at least one parameter of the pulp bleaching process is obtained, for example measured, in the pulp bleaching process 303, for example specifically in the first pulp bleaching stage 303' , and provided or input to the arrangement 310. A value of the flow rate of the first waste water stream 319 may also be obtained and provided or input to the arrangement 310. For the first waste water stream 319, the value of the at least one parameter may comprise or be, for example, a value of incoming Kappa number of the pulp incoming to the first pulp bleaching stage 303 ' ; a value of a change in Kappa number across the first pulp bleaching stage 303 ' ; brightness of the pulp incoming to the first pulp bleaching stage 303 ' ; pH, temperature , and / or conductivity of the first waste water stream 319 . Additionally or alternatively, if the pulp bleaching stage 303 ' is a Do stage , the value of the at least one parameter may comprise or be , for example , the dosing of chlorine dioxide in the Do stage .

[0178] A second waste water stream 322 , for example a condensate , may be obtained from the at least one other process 318 . The at least one other process may comprise or be e . g . at least one of a papermaking process , a cardboard manufacturing process , or an evaporation process , for example the evaporation process of black liquor . The second waste water stream 322 may comprise e . g . a waste water stream from a papermaking process , such as an overflow from a water circuit of a papermaking process , a waste water stream from a cardboard manufacturing process , such as an overf low from a water circuit of a cardboard manufacturing process , and / or a waste water stream from an evaporation process , for example the evaporation process of black liquor . A value of at least one parameter of the at least one other process 318 is obtained, for example pH, temperature , conductivity, suspended solids , turbidity, and / or redox potential of the second waste water stream 322 , and provided or input to the arrangement 310 . A value of the flow rate of the second waste water stream 322 may also be obtained and provided or input to the arrangement 310 .

[0179] A plurality of waste water streams may be obtained from the pulp bleaching process 303 . For example , in this exemplary embodiment , a further or third waste water stream 320 is obtained from a second pulp bleaching stage 303 ' ' , for example from a washing stage of the second pulp bleaching stage 303' ' . A value of at least one parameter of the pulp bleaching process is obtained, for example measured, in the second pulp bleaching stage 303' ' and provided or input to the arrangement 310. A value of the flow rate of the third waste water stream 320 may also be obtained and provided or input to the arrangement 310. For the third waste water stream 320, the value of the at least one parameter may comprise or be, for example, a value of incoming Kappa number of the pulp incoming to the second pulp bleaching stage 303' ' ; a value of a change in Kappa number across the second pulp bleaching stage 303' ' ; brightness of the pulp incoming to the second pulp bleaching stage 303' ' ; pH, temperature, and / or conductivity of the third waste water stream 320. For example, if the second pulp bleaching stage 303' ' is a Eopstage, the value of the at least one parameter may comprise or be, for example, the change in Kappa number across the second pulp bleaching stage 303' ' .

[0180] One or more further waste water streams 321 could be obtained e.g. from the third pulp bleaching stage 303' ' ', for example from the washing stage of the third pulp bleaching stage 303' ' ' . A value of at least one parameter of the pulp bleaching process could then be obtained, for example measured, in the pulp bleaching process 303, for example specifically in the third pulp bleaching stage 303' ' ' , and provided or input to the arrangement 310. For such a further (or fourth) waste water stream 321, the value of the at least one parameter may comprise or be, for example, a value of incoming Kappa number of the pulp incoming to the third pulp bleaching stage 303' ' ' ; a value of a change in Kappa number across the third pulp bleaching stage 303' ' ' ; brightness of the pulp incoming to the third pulp bleaching stage 303' '' ; pH, temperature, and / or conductivity of the further (fourth) waste water stream 321. Additionally or alternatively, if the third pulp bleaching stage 303 ' ' ' is a Dx stage , the value of the at least one parameter could compri se or be , for example , the dosing of chlorine dioxide in the Dx stage, or the dosing of chlorine dioxide both in the Do and Dx stages . In such an embodiment , the dosing of chlorine dioxide both in the Do and Dx stages could be indicative of COD concentration in the first waste water stream 319 and further ( fourth) waste water stream 321 as combined .

[0181] As a skilled person will understand, the sequence of the pulp bleaching stages included in the pulp bleaching process 303 may vary and does not necessarily include the sequence or the stages described in this exemplary embodiment .

[0182] The waste water streams 319 , 320 and 322 are combined into a combined waste water stream 323 and conducted to the waste water treatment process 301 . However, it should be understood that at least one of the waste water streams 319 , 320 and 321 , or any combination thereof , may be obtained and conducted to the waste water treatment process 301 . Alternatively, they could be conducted to the waste water treatment process 301 and combined in the first stage of the waste water treatment process 301 .

[0183] The first stage of the waste water treatment process 301 may be the primary treatment stage 324 . The primary treatment stage 324 may comprise e . g . a primary sedimentation tank or basin 325 , to which the combined waste water stream 323 or the waste water streams 319 , 320 and 322 are conducted . The delay of the combined waste water stream 323 or the waste water streams 319 , 320 and 322 in the primary treatment stage 324 may be e . g . 2 - 12 h, typically about 8 h .

[0184] From the primary treatment stage 324 , the combined waste water stream 323 is conducted to the secondary treatment stage 326 . The secondary treatment stage 326 may comprise a biological treatment stage 327 ( including e . g . an aeration tank) and a secondary clarification ( sedimentation) stage 328 . The combined delay of the combined waste water stream 323 in the primary treatment stage 324 and in the secondary treatment stage 326 may be e . g . about 6-72 hours , typically about 48 h .

[0185] The waste water treatment process 301 may further comprise a tertiary treatment stage 329 . However, many waste water treatment processes do not comprise a tertiary treatment stage . The tertiary treatment stage 329 may comprise e . g . a flocculation stage and / or a precipitation stage 330 . The combined waste water stream may be emitted as emitted waste water 331 after the tertiary treatment stage 329 , or in embodiments in which there is no tertiary treatment stage , after the secondary treatment stage 326 .

[0186] The arrangement 310 may be configured to estimate COD concentration and COD load in the waste water streams 319 , 320 and 321 or in the combined waste water stream 323 based on the value of the at least one parameter of the pulp bleaching process 303 and to determine a predicted COD concentration and / or load in the combined waste water stream 323 after the primary treatment stage 324 and / or after the secondary treatment stage 326 based on the estimated COD concentration and / or load in the waste water streams 319 , 320 and 321 , as illustrated in Fig . 3 with dashed arrows .

[0187] The arrangement 310 may further comprise an apparatus 332 for monitoring and controlling a treatment of the waste water stream, for example after the secondary treatment stage 326 , as shown in the Fig . , or e . g . before the secondary treatment stage 326 . The apparatus 332 may be configured to monitor and control COD concentration and optionally COD load in the combined waste water stream 323 and / or to monitor flow of the combined waste water stream 323 . The apparatus 332 may receive control information, such as a control signal , from the arrangement 310 . The processor 311 may be embodied as an executor of software instructions , wherein the instructions may specifically configure the processor 311 to perform the algorithms and / or operations described herein when the instructions are executed, for example, the steps discussed with respect to Fig . 1 . The arrangement 310 may further provide or output control information to the waste water treatment process 301 .

[0188] As illustrated with the arrow 309 , the arrangement may be configured to provide or output control information for controlling the waste water treatment process 301 based on the predicted COD concentration and / or load in the combined waste water stream 323 after the primary treatment stage 324 and / or after the secondary treatment stage 326 . One or more control actions in the waste water treatment proces s 301 may be implemented based on at least the control information 309 .

[0189] For example , the apparatus 332 may further be configured to use the control information and / or to implement one or more control actions in the waste water treatment process 301 . Thus the control information may be may be provided or output by the arrangement 310 e . g . to the apparatus 332 for implementing one or more control actions in the waste water treatment process based on at least the control information .

[0190] The apparatus 332 may thus be configured to implement the one or more control actions in the waste water treatment process 301 based on at least the control information 309 , for example by starting a control treatment of the COD load in the waste water treatment process 301 , controlling dosing of at least one control chemical in a control treatment of the COD load in the waste water treatment process 301 , adj usting a parameter of the secondary treatment stage 326 in the waste water treatment process 301 ( for example , adj usting a rate of aeration of the biological treatment stage 327 in the secondary treatment stage 326 ) , or adj usting a parameter of the tertiary treatment 329 in the waste water treatment process 301 (for example, in embodiments in which the tertiary treatment stage 329 comprises a flotation stage, the parameter of a tertiary treatment may include e.g. a rate of aeration of the flotation stage and / or a parameter of a scraper of the flotation stage) . For example, the apparatus 332 may be configured to control the dosing of at least one control chemical 333 at one or more stages of the waste water treatment process 301.

[0191] The at least one control chemical 333 may be dosed e.g. in the primary treatment stage 324, such as in the waste water stream incoming to the primary sedimentation tank or basin 325.

[0192] The at least one control chemical 333 may, additionally or alternatively, be dosed e.g. in the secondary treatment stage 326, for example to the secondary clarification 328. In some embodiments, at least a part of sludge from the a secondary clarification stage 328 may be returned to the biological treatment stage 327 (e.g. in the aeration tank) in the secondary treatment as return sludge, and the at least one control chemical, such as a coagulant, may then be dosed in the return sludge. Additionally or alternatively, the at least one control chemical, such as a polymer or an inorganic coagulant, may be added to the secondary clarification (sedimentation) stage 328.

[0193] The at least one control chemical 333 may, additionally or alternatively, be dosed e.g. in the tertiary treatment 329. The tertiary treatment stage 329 may comprise a control treatment, in which the at least one control chemical 333 is added to the waste water in order to f locculate / precipitate at least a part of the COD load.

[0194] The one or more control actions may also comprise e.g. collecting the waste water stream or the combined waste water stream 323 in an equalization basin 334 for a time period and conducting the collected waste water stream or the combined waste water stream 323 to the waste water treatment process 301 after the time period .

[0195] EXAMPLE 1

[0196] The method was tested with data obtained from a pulping process , in which the pulp bleaching process included a Do bleaching stage and an E0Pbleaching stage . Waste water streams were obtained as the Do filtrate and as the E0Pfiltrate . All of the wastewater streams , i . e . filtrates , were combined and conducted to a waste water treatment process containing a primary treatment stage (primary sedimentation) and a secondary treatment stage ( aerobic treatment and secondary sedimentation) .

[0197] COD concentration as mg / L in waste water stream after the secondary treatment stage was predicted based on the kappa change across Do and E0Pstages .

[0198] It was found that the delta Kappa number across the Do and E0Pstage was a good estimator for the COD concentration in the waste water stream leaving the aerobic treatment .

[0199] Fig . 4 shows an example of the estimated COD concentration (mg / 1 , dashed line ) and the actual measured COD concentration (mg / 1 , solid line ) in the waste water stream entering the tertiary treatment stage , x- axis presents time , time period is 2 weeks . The estimated and measured COD concentrations exhibited good correlation, suggesting that the model can be used for predicting COD in the waste water stream after the secondary treatment stage .

[0200] While there have been shown and described and pointed out fundamental novel features as applied to preferred embodiments thereof , it will be understood that various omissions and substitutions and changes in the form and details of the devices and methods described may be made by those skilled in the art without departing from the spirit of the disclosure . For example, it is expressly intended that all combinations of those elements and / or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the disclosure . Moreover, it should be recogni zed that structures and / or elements and / or method steps shown and / or described in connection with any disclosed form or embodiments may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice . Furthermore , in the claims means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents , but also equivalent structures .

[0201] The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features , to the extent that such features or combinations are capable of being carried out based on the present specification as a whole , in the light of the common general knowledge of a person skilled in the art , irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims . The applicant indicates that the disclosed aspects / embodiments may consist of any such individual feature or combination of features . In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the disclosure .

[0202] It is obvious to a person skil led in the art that with the advancement of technology, the basic idea may be implemented in various ways . The embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims . The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A method, a product , an arrangement , or a use, disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages . It will further be understood that reference to ' an ' item refers to one or more of those items . The term "comprising" or "including" is used in this specification to mean including the feature ( s ) or act ( s ) followed thereafter, without excluding the presence of one or more additional features or acts .

Claims

CLAIMS1 . A method for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process , wherein the pulping process comprises a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process compri ses a primary treatment stage and a secondary treatment stage ; wherein the method comprises obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and providing control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .2 . The method according to claim 1 , wherein the method comprises obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, estimating COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , determining a predicted COD concentration and / or load in the waste water stream after the primarytreatment stage and / or after the secondary treatment stage based on the estimated COD concentration and / or load in the waste water stream, and providing control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .3 . The method according to claim 1 or 2 , wherein the method further comprises obtaining a value of the flow rate of the waste water stream, wherein the COD concentration in the waste water stream is estimated based on the value of the at least one parameter of the pulp bleaching process , and the COD load in the waste water stream is estimated based on the estimated COD concentration and on the value of the f low rate of the waste water stream .4 . The method according to any one of claims 1- 3 , wherein method further comprises preprocessing the value ( s ) of the at least one parameter of the pulp bleaching process .5 . The method according to any one of claims 1- 4 , wherein the pulping process comprises the pulp bleaching process and at least one other process , the first waste water stream is obtained from the pulp bleaching process and a second waste water stream from the at least one other process , and wherein the first and second waste water stream are combined into a combined waste water stream and conducted to the waste water treatment process , wherein the method comprises obtaining the value of the at least one parameter of the pulp bleaching process and a value of at least one parameter of the at least one other process , wherein said parameters are indicative of COD concentrations in the first and second waste water streams ,estimating COD concentration and COD load in the first waste water stream based on the value of the at least one parameter of the pulp bleaching process , estimating COD concentration and COD load in the second waste water stream based on the value of the at least one parameter of the at least one other process , determining a predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentrations and loads in the first and second waste water stream, and providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage .6 . The method according to claim 5 , wherein the method further comprises obtaining a value of the f low rate of the first waste water stream and a value of the flow rate of the second waste water stream, wherein the COD concentration in the first waste water stream is estimated based on the value of the at least one parameter of the pulp bleaching process , and the COD load in the first waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the first water stream, and wherein the COD concentration in the second waste water stream i s estimated based on the value of the at least one parameter of the at least one other process , and the COD load in the second waste water stream is estimated based on the estimated COD concentration and on the value of the flow rate of the second waste water stream .7 . The method according to any one of claims 1 - 6 , wherein the at least one parameter of the pulp bleaching process comprises or is at least one of- incoming Kappa number,- change in Kappa number,- dosing of chlorine dioxide in the pulp bleaching process ,- brightness of the pulp,- change in brightness of the pulp,- pH of the waste water stream or the first waste water stream,- temperature of the waste water stream or the first waste water stream, or- conductivity of the waste water stream or the first waste water stream .8 . The method according to any one of claims 5- 7 , wherein the at least one parameter of the at least one other process comprises or is at least one of- pH of the second waste water stream,- temperature of the second waste water stream, conductivity of the second waste water stream,- suspended solids in the second waste water stream,- turbidity of the second waste water stream, or- redox potential of the second waste water stream .9 . The method according to any one of claims 1- 8 , wherein the method further comprises implementing one or more control actions in the waste water treatment process and / or in the pulping process , such as in the pulp bleaching process , based on at least the control information .10 . The method according to claim 9 , wherein the one or more control actions comprise at least one of controlling dosing of at least one control chemical in a control treatment of the COD load in the waste water treatment process ,adj usting a parameter of a tertiary treatment stage in the waste water treatment process , collecting the waste water stream or the combined waste water stream in an equali zation basin for a time period and conducting the collected waste water stream or the combined waste water stream to the waste water treatment process after the time period, or adj usting a parameter of the secondary treatment stage , such as a rate of aeration of an aerobic treatment in the secondary treatment stage and / or a dose of nutrients dosed in the secondary treatment stage ; and / or dosing at least one control chemical in a waste water stream obtained from the pulp bleaching process and / or from the at least one other process , controlling the dosing of at least one control chemical in a control treatment of the COD load in the pulping process , adj usting at least one parameter in the pulping process , such as at least one parameter of the pulp bleaching process , adj usting at least one parameter in a pulp washing stage preceding the pulp bleaching process .11 . The method according to any one of claims 1 - 10 , wherein the predicted COD concentration and / or load in the waste water stream or the combined waste water stream after the primary treatment stage are determined at least 2 hours , or about 2 - 15 hours , or about 4 - 8 hours in advance .12 . The method according to any one of claims 1 - 11 , wherein the predicted COD concentration and the COD load in the waste water stream or the combined waste water stream after the secondary treatment stage are determined at least 6 hours , or about 6 - 72 hours , or about 24 - 48 hours in advance .13 . The method according to any one of claims1 12 , wherein the COD concentration and the COD loadin the waste water stream or in the first and second waste water stream is / are estimated using data obtained earlier, wherein the data obtained earlier comprises values of the at least one parameter of the pulp bleaching process , COD concentration and COD load in the waste water stream or the first waste water stream, and optionally values of the at least one parameter of the at least one other process ; and / or wherein the data obtained earlier comprises values of the at least one parameter of the pulp bleaching process , the COD concentration and / or load in the waste water stream or the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage , and optionally values of the at least one parameter of the at least one other process .14 . The method according to any one of claims 1 - 13 , wherein the at least other process comprises or is at least one of a papermaking process , a cardboard manufacturing process , or an evaporation process .15 . An arrangement for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping proces s , wherein the pulping process comprises a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage ; wherein the arrangement comprises means for obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, means for determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondarytreatment stage based on the value of the at least one parameter of the pulp bleaching process , and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .16 . The arrangement according to claim 15 , wherein the arrangement comprises means for obtaining a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, means for estimating COD concentration and COD load in the waste water stream based on the value of the at least one parameter of the pulp bleaching process , means for determining a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentration and / or load in the waste water stream, and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage17 . The arrangement according to claim 15 or 16 , wherein the pulping process comprises a pulp bleaching process and at least one other process , wherein a first waste water stream is obtained from the pulp bleaching process and a second waste water stream is obtained from the at least one other process , and wherein the first and second waste water stream are combined into a combined waste water stream and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage ;wherein the arrangement comprises means for obtaining a value of at least one parameter of the pulp bleaching process and a value of at least one parameter of the at least one other process , wherein said parameters are indicative of COD concentrations in the first and second waste water streams , means for estimating COD concentration and COD load in the first waste water stream based on the value of the at least one parameter of the pulp bleaching process , means for estimating COD concentration and COD load in the second waste water stream based on the value of the at least one parameter of the at least one other process , means for determining a predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the estimated COD concentrations and loads in the first and second waste water stream, and means for providing control information for controlling the waste water treatment process based on the predicted COD concentration and / or load in the combined waste water stream after the primary treatment stage and / or after the secondary treatment stage .18 . A computer program for predicting chemical oxygen demand (COD) load in a waste water treatment process in connection with a pulping process , the pulping process comprises a pulp bleaching process , wherein a waste water stream is obtained from the pulp bleaching process and conducted to the waste water treatment process , wherein the waste water treatment process comprises a primary treatment stage and a secondary treatment stage ; the computer program comprising instructions which, when executed by an apparatus , cause the apparatus to perform at least the following :obtain a value of at least one parameter of the pulp bleaching process , wherein said parameter is indicative of COD concentration in the waste water stream, determine a predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage based on the value of the at least one parameter of the pulp bleaching process , and provide control information for control ling the waste water treatment process based on the predicted COD concentration and / or load in the waste water stream after the primary treatment stage and / or after the secondary treatment stage .

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