A method for deep dehydration and conditioning of sludge in urban sewage treatment plants

Abstract

The invention discloses a method for deep dehydration and conditioning of sludge in a municipal sewage treatment plant, and relates to the technical field of environmental engineering. The invention first conditions concentrated sludge with polyhexamethylene biguanide to form polyhexamethylene biguanide conditioned sludge, then adds pupa powder slurry formed by sulfuric acid treatment of black soldier fly pupa shells to the polyhexamethylene biguanide conditioned sludge, forms pupa powder slurry-polyhexamethylene biguanide combined treatment sludge, finally adds polydimethyldiallylammonium chloride to obtain conditioned sludge, and mechanically dehydrates the conditioned sludge to obtain deep dehydrated sludge. The sludge deep dehydration method of the present invention can significantly reduce the moisture content of the sludge, and can reduce the addition of inorganic dehydrating agents at the same time, so that the sludge can well meet the requirements of subsequent treatments such as composting and incineration.

Description

Technical Field

[0001] The invention relates to the technical field of environmental engineering, and in particular to a method for deep dehydration and conditioning of sludge in a municipal sewage treatment plant. Background Art

[0002] Sludge is a secondary product of the sewage treatment process in sewage treatment plants. It has a high organic matter content and can easily cause secondary pollution if not properly handled. The current sludge disposal methods mainly include land use, incineration, landfill and building material utilization. Among them, landfill and land use require the sludge moisture content to be less than 60%, direct incineration requires the sludge moisture content to be less than 50%, and the sludge building material utilization moisture content must be less than 40%.

[0003] Dehydration is an important means to reduce the volume and weight of sludge. However, due to the small size, high viscosity and strong hydrophilicity of sludge particles, the dehydration performance of sludge is very poor. With conventional conditioning-mechanical dehydration, the moisture content of the mud cake is still as high as about 80%. Generally speaking, sludge composting requires the moisture content to be reduced to 50%-60%, and the moisture content of sludge mixed into landfills for landfill disposal is required to be reduced to below 60%. When it is incinerated, the moisture content control requirements are higher. Therefore, it is very important to deeply treat the sludge.

[0004] The key to achieving deep dehydration of sludge lies in improving its dehydration performance. At present, the technology on the market that can reduce the moisture content of sludge to below 60% after dehydration is mainly achieved by adding a large amount of inorganic agents such as lime and iron salts to the sludge and then performing high-pressure filtration. However, the dehydration product has a high inorganic content and low calorific value, which is not suitable for land use and incineration. In the context of sludge landfill disposal becoming increasingly unpopular, it is very important to develop a technology that can significantly improve the dehydration performance of sludge using inorganic agents. Summary of the invention

[0005] The purpose of the present invention is to provide a method for deep dehydration and conditioning of sludge in urban sewage treatment plants to solve the problems existing in the above-mentioned prior art, reduce the moisture content of the sludge, and at the same time reduce the addition of inorganic dehydrating agents, so that the sludge can meet the requirements of subsequent treatment such as composting and incineration.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for deep dehydration of sludge from a municipal sewage treatment plant, comprising the following steps:

[0008] (1) adding polyhexamethylene biguanide to concentrated sludge with a water content of 96% to 98% in a municipal sewage treatment plant to form polyhexamethylene biguanide treated sludge;

[0009] (2) adding pupa shell powder slurry and polydimethyldiallyl ammonium chloride to the polyhexamethylene biguanide treated sludge so that the pH value of the sludge is 6.1-6.8 to obtain conditioned sludge;

[0010] The method for preparing the pupa shell powder slurry comprises the following steps: grinding the black soldier fly pupa shell, adding sulfuric acid and soaking it to obtain the pupa shell powder slurry;

[0011] (3) Dehydrating the conditioned sludge obtained in step (2) using a high-pressure plate and frame dehydrator to obtain deeply dehydrated sludge.

[0012] Furthermore, in step (2), the mass concentration of the sulfuric acid is 30%; the mass volume ratio of the sulfuric acid to the black soldier fly pupa shell is 30%-60% (W / V); and the soaking time is more than 60 min, preferably 70-90 min, and more preferably 30-90 min.

[0013] Furthermore, in step (2), the amount of the pupa shell powder slurry added to the polyhexamethylene biguanide treated sludge is 0.5%-2% by volume; and the amount of the polydimethyldiallylammonium chloride added is 0.1%-0.3% by volume of the polyhexamethylene biguanide treated sludge.

[0014] Furthermore, in step (1), polyhexamethylene biguanide is added in the form of an aqueous solution; wherein the mass concentration of the polyhexamethylene biguanide solution is 10%.

[0015] Furthermore, the volume addition amount of the polyhexamethylene biguanide solution in the concentrated sludge is 0.5%-1.0%.

[0016] Furthermore, the water content of the concentrated sludge from the urban sewage treatment plant is 96%-98%.

[0017] The invention firstly processes concentrated sludge through polyhexamethylene biguanide to form polyhexamethylene biguanide conditioned sludge, then adds pupa shell powder slurry formed by treating black soldier fly pupa shells with sulfuric acid to the polyhexamethylene biguanide conditioned sludge to form pupa shell powder slurry-polyhexamethylene biguanide combined treatment sludge, finally adds polydimethyldiallylammonium chloride to obtain conditioned sludge, and finally mechanically dehydrates the conditioned sludge to obtain deep dehydrated sludge with a moisture content of about 60%.

[0018] The technical principles of the present invention are as follows:

[0019] Polyhexamethylene biguanide is a kind of green and environmentally friendly fungicide. Adding polyhexamethylene biguanide to sludge can destroy the permeability of bacterial cell membranes and release the cytoplasm of bacteria in the sludge into the environment. In addition, the hydrophilic group formed after ionization in water has strong positive charge, which can change the Zeta potential of sludge and promote sludge flocculation, thereby greatly improving the sludge dewatering performance.

[0020] The shell of black soldier flies has a substance similar to chitosan, and its acid leaching product has a large number of hydrophilic groups such as hydroxyl (-OH) and amino (-NH2). The addition of polyhexamethylene biguanide further improves the sludge dewatering performance. After the sludge is conditioned by these two substances, the dewatering performance is greatly improved. After flocculation by polydimethyldiallyl ammonium chloride flocculant and dehydration by high-pressure plate and frame machine, the moisture content can be reduced to about 60%.

[0021] More specifically, the technical solution of the present invention comprises the following steps:

[0022] (1) The shells discarded after the extraction of black soldier fly pupae are ground with a crusher to a particle size of 1.0-10 microns, which is pupa shell powder. Pupa shell powder and sulfuric acid (concentration of 30%) are mixed in a mass volume ratio of 30%-60% and treated for 70-90 minutes to form a pupa shell powder slurry.

[0023] (2) Dissolve polyhexamethylene biguanide in tap water to prepare a 10% solution, input concentrated sludge with a water content of 96%-98% from a sewage treatment plant into a storage tank, add 0.5%-1.0% polyhexamethylene biguanide aqueous solution by volume (V / V), stir and mix at a stirring rate of 60-120 rpm for 2-5 minutes to form polyhexamethylene biguanide treated sludge.

[0024] (3) In the polyhexamethylene biguanide treated sludge, pupa shell powder slurry is added to the sludge at a volume ratio of 0.5%-2.0% (V / V). After mixing evenly, polydimethyldiallylammonium chloride is added at a mass volume ratio of 0.1%-0.3% (W / V). At this time, the sludge pH is 6.1-6.8, which is the conditioned sludge.

[0025] (4) The conditioned sludge is pumped into a high-pressure plate and frame dehydrator for dehydration to form a sludge cake with a moisture content of 60%, which is a deep dehydration product.

[0026] The present invention discloses the following technical effects:

[0027] The sludge deep dehydration method of the present invention can significantly reduce the water content of the sludge and can reduce the addition of inorganic dehydrating agents, so that the sludge can well meet the requirements of subsequent treatments such as composting and incineration.

[0028] The invention provides a new technical means for solving the current sludge landfill, composting and incineration treatment, and has the advantages of low cost, simple operation and obvious effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] Example 1

[0037] Deep dehydration and conditioning of sludge in urban sewage treatment plants:

[0038] (1) A concentrated sludge with a water content of 96% was taken from a sewage treatment plant, and a 0.5% (V / V) polyhexamethylene biguanide aqueous solution (10 wt%) was added, and the mixture was stirred at a stirring rate of 90 rpm for 3 minutes to form polyhexamethylene biguanide treated sludge.

[0039] (2) Preparation of pupa shell powder slurry: The shells discarded after the extraction of black soldier fly pupae are ground with a crusher to a particle size of 1 micron, which is the pupa shell powder. Subsequently, sulfuric acid (mass concentration of 30%) is added to the pupa shell powder. The mass volume ratio (W / V) of pupa shell powder and sulfuric acid is 30%. The process is continued for 30 minutes to form a pupa shell powder slurry.

[0040] (3) In the polyhexamethylene biguanide treated sludge obtained in step (1), pupa shell powder slurry is added to the sludge at a ratio of 0.5% (V / V), mixed evenly, and then 0.2% (W / V) polydimethyldiallylammonium chloride is added. At this time, the pH of the sludge is 6.4, which is the conditioned sludge.

[0041] (4) The conditioned sludge is pumped into a high-pressure plate and frame dehydrator for dehydration to form a sludge cake with a moisture content of 58%. The calorific value of the dehydrated sludge cake is as high as 2130Kcal / Kg. The organic matter content and dry calorific value are almost the same as the dry calorific value of the sludge before treatment (concentrated sludge with a moisture content of 96%).

[0042] Example 2

[0043] Deep dehydration and conditioning of sludge in urban sewage treatment plants:

[0044] (1) A concentrated sludge with a water content of 97% was taken from a sewage treatment plant, and a 1.0% (V / V) polyhexamethylene biguanide aqueous solution (10 wt%) was added thereto. The mixture was stirred and mixed at a stirring rate of 90 rpm for 3 minutes to form polyhexamethylene biguanide treated sludge.

[0045] (2) Preparation of pupa shell powder slurry: The shells discarded after the extraction of black soldier fly pupae are ground with a crusher to a particle size of 8 μm, which is pupa shell powder; sulfuric acid (mass concentration of 30%) is then added to the pupa shell powder, and the mass volume ratio (W / V) of pupa shell powder and sulfuric acid is 30%, and the process is carried out for 45 minutes to form a pupa shell powder slurry.

[0046] (3) In the polyhexamethylene biguanide treated sludge obtained in step (1), the pupa shell powder slurry is added to the sludge at a ratio of 2% (V / V), mixed evenly, and then 0.2% (W / V) of polydimethyldiallylammonium chloride is added. At this time, the pH of the sludge is 6.4, which is the conditioned sludge.

[0047] (4) The conditioned sludge is pumped into a high-pressure plate and frame dehydrator for dehydration to form a sludge cake with a moisture content of 55%. The calorific value of the dehydrated sludge cake is as high as 2090Kcal / Kg. The organic matter content and dry calorific value are almost the same as the dry calorific value of the sludge before treatment (concentrated sludge with a moisture content of 96%).

[0048] Example 3

[0049] Deep dehydration and conditioning of sludge in urban sewage treatment plants:

[0050] (1) A concentrated sludge with a water content of 98% was taken from a sewage treatment plant, and a 1% (V / V) polyhexamethylene biguanide aqueous solution (10 wt%) was added thereto. The mixture was stirred and mixed at a stirring rate of 90 rpm for 3 minutes to form polyhexamethylene biguanide treated sludge.

[0051] (2) Preparation of pupa shell powder slurry: The shells discarded after the extraction of black soldier fly pupae are ground with a crusher to a particle size of 10 μm, which is pupa shell powder; sulfuric acid (mass concentration of 30%) is then added to the pupa shell powder, and the mass volume ratio (W / V) of pupa shell powder and sulfuric acid is 30%, and the process is carried out for 90 minutes to form a pupa shell powder slurry.

[0052] (3) In the polyhexamethylene biguanide treated sludge obtained in step (1), pupa shell powder slurry is added to the sludge at a ratio of 0.5% (V / V), mixed evenly, and then 0.2% (W / V) polydimethyldiallylammonium chloride is added. At this time, the pH of the sludge is 6.4, which is the conditioned sludge.

[0053] (4) The conditioned sludge is pumped into a high-pressure plate and frame dehydrator for dehydration to form a sludge cake with a moisture content of 53%. The calorific value of the dehydrated sludge cake is as high as 2150Kcal / Kg. The organic matter content and dry calorific value are almost the same as the dry calorific value of the sludge before treatment (concentrated sludge with a moisture content of 96%).

[0054] Example 4

[0055] Deep dehydration and conditioning of sludge in urban sewage treatment plants:

[0056] (1) A concentrated sludge with a water content of 98% was taken from a sewage treatment plant, and a 1% (V / V) polyhexamethylene biguanide aqueous solution (10 wt%) was added thereto. The mixture was stirred and mixed at a stirring rate of 90 rpm for 3 minutes to form polyhexamethylene biguanide treated sludge.

[0057] (2) Preparation of pupa shell powder slurry: The shells discarded after the extraction of black soldier fly pupae are ground with a crusher to a particle size of 8 μm, which is pupa shell powder; sulfuric acid (mass concentration of 30%) is then added to the pupa shell powder, and the mass volume ratio (W / V) of pupa shell powder and sulfuric acid is 30%, and the process is carried out for 75 minutes to form a pupa shell powder slurry.

[0058] (3) In the polyhexamethylene biguanide treated sludge obtained in step (1), the pupa shell powder slurry is added to the sludge at a ratio of 2% (V / V), mixed evenly, and then 0.2% (W / V) of polydimethyldiallylammonium chloride is added. At this time, the pH of the sludge is 6.4, which is the conditioned sludge.

[0059] (4) The conditioned sludge is pumped into a high-pressure plate and frame dehydrator for dehydration to form a sludge cake with a moisture content of 50%. The calorific value of the dehydrated sludge cake is as high as 2110Kcal / Kg. The organic matter content and dry calorific value are almost the same as the dry calorific value of the sludge before treatment (concentrated sludge with a moisture content of 96%).

[0060] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for deep dehydration of sludge from a municipal sewage treatment plant, characterized in that: The following steps are involved: (1) adding a polyhexamethylene biguanide solution to concentrated sludge from a municipal sewage treatment plant to form polyhexamethylene biguanide treated sludge; (2) adding pupa shell powder slurry and polydimethyldiallyl ammonium chloride to the polyhexamethylene biguanide treated sludge so that the pH value of the sludge is 6.1-6.8 to obtain conditioned sludge; (3) dehydrating the conditioned sludge obtained in step (2) using a high-pressure plate and frame dehydrator to obtain deeply dehydrated sludge; The method for preparing the pupa shell powder slurry comprises the following steps: grinding the black soldier fly pupa shell, adding sulfuric acid and soaking it to obtain the pupa shell powder slurry; In the method for preparing the pupa shell powder slurry, the mass concentration of sulfuric acid is 30%, the mass volume ratio of the black soldier fly pupa shell to the sulfuric acid is 30%-60%, and the soaking time is more than 60 minutes; In step (2), the amount of the pupa shell powder slurry added to the polyhexamethylene biguanide treated sludge is 0.5%-2% by volume; the amount of the polydimethyldiallylammonium chloride added is 0.1%-0.3% by volume of the polyhexamethylene biguanide treated sludge by mass volume; The mass concentration of the polyhexamethylene biguanide solution is 10%; The volume addition amount of the polyhexamethylene biguanide solution in the concentrated sludge is 0.5%-1.0%; The concentrated sludge of the urban sewage treatment plant has a water content of 96%-98%.

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