Sewage mixing flocculation sedimentation tank with dosing system and sewage treatment process

Abstract

The invention relates to the technical field of water treatment, and discloses a sewage mixing flocculation sedimentation tank with a dosing system and a sewage treatment process, the sewage treatment process comprises the following steps: (1) sewage enters a pretreatment unit, and large-particle suspended solids are removed; (2) enabling the sewage to flow into a pH regulating tank, adding a pH regulator through a dosing system, and regulating the pH value to 9-11; (3) passing through a coagulation reaction tank, adding ferrous sulfate to reduce hexavalent chromium into trivalent chromium, and promoting a flocculation reaction; and (4) further adding polyaluminum chloride through the flocculation reaction tank to form floc. Through a multi-unit combined treatment process, suspended solids and various heavy metals in the sewage are gradually removed, and the effluent quality is ensured to reach the standard. Compact and reasonable process layout is adopted, the occupied area is reduced, and the device is suitable for small and medium-sized sewage treatment plants. An automatic dosing control system is introduced, dosing is accurate, and the operation cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a sewage mixing flocculation sedimentation tank with a dosing system and a sewage treatment process. Background Art

[0002] Municipal sludge, also known as urban sludge or sewage treatment plant sludge, is a byproduct produced during the urban sewage treatment process. It is the semi-solid or solid material remaining after the pollutants such as suspended solids, organic matter and nutrients in the sewage are removed by physical, chemical or biological methods when the sewage treatment plant treats the urban domestic sewage. Municipal sludge contains a large amount of water, organic matter, microorganisms, heavy metals and nutrients. If it is not handled properly, it will cause pollution to the environment.

[0003] Sludge landfill treatment is a method of landfilling sludge in a specific site. Its main purpose is to reduce the volume of sludge, stabilize the treatment and reduce the impact on the environment. However, the sludge cannot be truly managed under the landfill disposal method. Instead, the long-term storage of sludge concentrates environmental risk factors, which can easily cause secondary pollution of the soil, water and air around the landfill. Moreover, under the background of increasingly tight urban construction land, sludge landfills occupy a large area and have a significant restrictive effect on the development of surrounding plots. Therefore, it is necessary to harmlessly treat the sludge in existing sludge landfills. The water content of municipal sludge is relatively high. After the sludge is taken out of the landfill, it will first be separated from the mud and water, and the solid sludge and liquid sewage will be treated separately. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a sewage mixing flocculation sedimentation tank and a sewage treatment process with a dosing system, which solves the problem in the prior art that the effluent quality is unstable and does not meet the standards due to the single treatment process, large floor space, imprecise dosing control and limited removal effect of low-concentration heavy metals.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a sewage mixing flocculation sedimentation tank with a dosing system and a sewage treatment process, the sewage treatment process comprising the following steps: (1) Sewage enters the pretreatment unit to remove large suspended solids; (2) The sewage flows into the pH adjustment tank, and the pH adjuster is added through the dosing system to adjust the pH value to 9-11; (3) Through the coagulation reaction tank, ferrous sulfate is added to reduce hexavalent chromium to trivalent chromium and promote flocculation reaction; (4) further adding polyaluminium chloride through the flocculation reaction tank to form flocs; (5) The sewage enters the Lamela sedimentation tank, where solid-liquid separation removes most of the heavy metal flocs; (6) Further adsorption of residual heavy metals through activated carbon filters; (7) The residual heavy metals such as nickel and cadmium in the wastewater are deeply removed through the cation exchange resin unit, and finally meet the discharge standards.

[0006] The process is combined with a dosing system to achieve automated dosing and precise control, and is adaptable to complex water quality and heavy metal removal requirements.

[0007] Preferably, the pH adjustment is achieved by the following steps: The sewage enters the pH adjustment tank, and the pH value is adjusted to 9-11 by quantitatively adding lime milk or sodium hydroxide solution, so that the heavy metal ions are converted into hydroxide precipitation.

[0008] Preferably, the coagulation reaction in the coagulation reaction tank is completed by adding ferrous sulfate, and the ferrous sulfate reacts with the hexavalent chromium in the sewage to generate trivalent chromium, and the chemical reaction formula is as follows: Preferably, the flocculation reaction tank promotes floc formation and growth by adding polyaluminium chloride and slowly stirring, thereby enhancing its sedimentation performance. The chemical reaction formula is as follows: Al 2 (OH) n Cl 6 -n+M m+ +(OH) - →Al(OH) 3 +M(OH) m ↓ Among them, M m+ is the metal ion, and m is the valence number of the metal ion.

[0009] Preferably, the Lamela sedimentation tank includes an inclined plate sedimentation unit with an inclination angle of 60°, removes flocculated sediments by solid-liquid separation, and is equipped with a scraper and a sludge pump to achieve sludge discharge.

[0010] Preferably, the activated carbon filter is filled with granular activated carbon to a filling height of 1.5-2 meters for adsorbing residual mercury in sewage.

[0011] Preferably, the cation exchange resin system uses a strong acid cation exchange resin with a backwash strength of 50 m 3 / h, backwash time is 10-15 minutes, 31% hydrochloric acid is used in the regeneration process, and the dosage is 0.9m 3 / Second-rate.

[0012] Preferably, the dosing system comprises: Pharmaceutical storage tank, made of PE, volume 1-2m 3 ; The dosing pump uses a quantitative pump with adjustable flow rate, and the flow rate accuracy is ±0.1L / h; The dosing control unit is based on the PLC control system and automatically adjusts the dosage of the agent in combination with the online monitored pH, conductivity, and heavy metal concentration parameters.

[0013] Preferably, the process automation system comprises: Online monitoring system, used to monitor the pH value and heavy metal ion concentration of sewage in real time; PLC control system, automatically adjusts stirring speed, reagent dosage and sludge discharge cycle; The alarm unit triggers an alarm signal and starts emergency response when the pH or heavy metal concentration exceeds the set value. Preferably, the cation exchange resin treatment unit of the process is arranged in series with the activated carbon filter, and can be switched to the spare treatment unit according to the change of heavy metal concentration to adapt to fluctuating water quality.

[0014] The present invention provides a sewage mixing flocculation sedimentation tank with a dosing system and a sewage treatment process. Beneficial effects: 1. The present invention uses a combined treatment technology solution, through pretreatment, pH adjustment, coagulation, flocculation, precipitation, activated carbon filtration and cation exchange resin and other multi-unit integration, to gradually remove suspended matter and heavy metal ions in sewage, ensuring that the effluent quality fully meets the discharge standards. Compared with the technical solution in the prior art that a single process has poor treatment effect on complex pollutants, the present invention solves the problem that the effluent cannot meet the standards due to a single process, and achieves efficient removal of multiple heavy metal ions.

[0015] 2. The present invention significantly reduces the floor space of the sewage treatment system through a compact and reasonable process layout design, by combining an inclined plate sedimentation tank and a vertical activated carbon filter. Compared with the technical solutions of traditional horizontal flow sedimentation tanks and large-scale filtration devices in the prior art, the present invention overcomes the problems of lengthy equipment and excessive floor space, and is particularly suitable for small and medium-sized sewage treatment plants with limited floor space.

[0016] 3. The present invention achieves the effect of high utilization rate of reagents and low operating costs by dynamically and automatically controlling the dosing system, monitoring water quality in real time and accurately adjusting the dosage of reagents. Compared with the problem of overdosage or underdosage in manual dosing in the prior art, the present invention effectively solves the problems of reagent waste and high operating costs, while improving the stability and continuity of the treatment.

[0017] 4. The present invention further removes residual heavy metal ions by introducing a combined deep treatment unit of activated carbon adsorption and cation exchange resin into the process chain, especially significantly enhancing the deep treatment capacity of nickel and cadmium. Compared with the technical solutions in the prior art that are difficult to remove low-concentration heavy metal ions by physical filtration or chemical precipitation alone, the present invention effectively solves the problem of difficult-to-treat heavy metal residues, making the effluent water quality more stable and safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the sedimentation tank of the present invention; Figure 2 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Please see attached Figure 1 - Figure 2 The embodiment of the present invention provides a sewage mixing flocculation sedimentation tank with a dosing system and a sewage treatment process, comprising the following steps: (1) Sewage enters the pretreatment unit to remove large suspended solids; In this embodiment, the sewage is firstly processed by a screen device.

[0021] Specifically, the grid device is used to intercept larger particles and floating objects in sewage. For example, branches, plastic bags, fibers, etc. that are common in sewage can be effectively removed. As an option, a stainless steel grid with a gap of 5 mm can be used. This grid gap can take into account both the interception efficiency and the smooth flow of water.

[0022] In some embodiments, an automatic cleaning machine may be configured. The cleaning machine can regularly remove debris from the grille to prevent the grille from being blocked, thereby ensuring a stable flow of sewage. Generally, the cleaning frequency of the automatic cleaning machine can be automatically adjusted according to the sewage flow and pollutant concentration.

[0023] Specifically, after passing through the grille device, the sewage will enter the homogenization tank. The function of the homogenization tank is to further stabilize the water quality and water quantity. For industrial sewage, the setting of the homogenization tank is particularly important due to the large fluctuations in water quality and water quantity. In a possible implementation, the volume of the homogenization tank can be determined based on the design flow rate and peak load. Taking this embodiment as an example, the design flow rate is 130m 3 / h, the effective volume of the homogenization tank is set to 260m 3 , to ensure a 2-hour stay.

[0024] As a possible option, an air stirring device can be configured inside the homogenization tank to maintain the uniformity of the water body and prevent the deposition of solid particles in the water. The stirring device can be implemented by aeration, or a mechanical stirrer can be selected. For example, in some embodiments, a frame paddle stirrer can be used, and its speed can be set to 20-30r / min to ensure that the suspended matter in the sewage is evenly distributed while reducing energy consumption.

[0025] In some embodiments, in order to further remove finer suspended particles, a preliminary coagulant may be added to the homogenization tank. For example, the addition of polyaluminium chloride (PAC) or other flocculants can promote the aggregation of small particles in the sewage and improve the subsequent sedimentation efficiency. The dosage can generally be controlled at 10-50 mg / L, depending on the concentration of suspended matter in the sewage.

[0026] In some cases, in order to improve the operating stability of the homogenization tank, liquid level sensors and flow meters can also be installed. These devices are used to monitor the inflow of sewage and the water level in the tank. Through linkage with the PLC control system, it can automatically adjust the situation of large fluctuations in water volume to ensure uniform water inflow to the subsequent pH adjustment unit.

[0027] Furthermore, in this embodiment, the grid and the homogenizing tank are connected by a transition pipe. The pipe is made of PVC material, with a smooth inner wall and strong corrosion resistance, which can reduce the corrosion of the pipe during the transmission of sewage. At the same time, the diameter of the transition pipe must meet the sewage flow requirements. Taking the design flow of 130m 3 / h as an example, it is recommended to use a pipe with a diameter of DN150 to ensure sufficient flow capacity.

[0028] In some embodiments, in order to prevent the grid from being incompletely cleaned or the particles in the sewage from being suspended again, a fine grid or screen device can be set at the front end of the homogenization tank. For example, the gap of the fine grid can be set to 1 mm to further remove the fine particle pollutants remaining in the sewage.

[0029] In addition, in special cases, such as when the raw sewage contains a lot of oil and fat pollutants, an oil removal device can be added to the homogenization tank. For example, the floating oil on the sewage surface can be collected into the oil collection tank through an oil scraper and cleaned regularly. The oil removal device can be designed in combination with the homogenization tank, or it can be used as an independent module in series with the subsequent treatment unit.

[0030] A flow control valve is provided at the outlet of the homogenization tank to adjust the flow rate of the sewage entering the subsequent pH adjustment tank. In a specific implementation, the flow control valve can be an electric valve and connected to a PLC control system to achieve automatic flow control.

[0031] Through the comprehensive design and application of the above technical features, the pretreatment unit provided in this embodiment can effectively remove large suspended solids and floating objects, stabilize the water quality and water volume of sewage, and provide good process conditions for subsequent pH adjustment and coagulation reaction. The disclosure of the formula part enables those skilled in the art to fully understand its working principle and reproduce and optimize it according to the description content.

[0032] (2) The sewage flows into the pH adjustment tank, and the pH adjuster is added through the dosing system to adjust the pH value to 9-11. In this embodiment, the sewage flows from the homogenization tank into the pH adjustment tank, and the pH value of the sewage is monitored in real time through the online monitoring system, and the pH adjuster is accurately added in combination with the PLC control system.

[0033] Specifically, the volume of the pH adjustment tank is determined according to the treatment flow rate and reaction time. 3 / h, the effective volume of the regulating tank is 8m 3 , to provide a retention time of about 3 minutes. A frame paddle agitator is set in the regulating tank with a rotation speed of 20-30r / min to ensure that the pH regulator and sewage are fully mixed and evenly distributed.

[0034] In a possible implementation, the pH regulator added may be lime milk (Ca(OH) 2 The concentration of lime milk is generally 5% to 10%, and it is quantitatively added through a metering pump. Lime milk dissociates in water to generate OH - Ions react with heavy metal ions in water to form insoluble hydroxide precipitates. The main chemical reaction formula is as follows: M m+ +mOH - →M(OH) m ↓ in, M m+ For heavy metal ions in water, such as Ni 2+ 、Cd 2+ Cr 3+ wait; m is the valence of the metal ion; M(OH) m The resulting precipitate.

[0035] As another option, sodium hydroxide (NaOH) solution can also be used as a pH regulator. The use of sodium hydroxide is more suitable for treating sewage containing high concentrations of acidic pollutants. In some embodiments, the dosage of sodium hydroxide can be estimated by the following formula: Q=C w ×V×(pH target -pH initial ) in, Q is the dosage (mol), C w is the buffer capacity of sewage, V is the volume of sewage (L), pH target is the target pH value, pH initial is the initial pH value.

[0036] Specifically, if the initial pH value of the sewage is 7.0, the target pH value is 10.0, and the buffer capacity is 0.002 mol / L, then when treating 100 m 3 The required sodium hydroxide dosage for sewage is: Q=0.002×100000×(10.0-7.0)=600mol When adding, the dosage of the agent is controlled within this range through the flow control system of the metering pump.

[0037] In some special cases, the acid concentration in the sewage is high. In order to reduce the amount of pH regulator, a partial front-end neutralization unit can be set in the homogenization tank, such as adding sodium carbonate (Na 2 CO 3 ) or sodium bicarbonate (NaHCO 3 ) as a buffer to buffer the pH fluctuation range. This method can reduce the subsequent addition of alkaline agents, thereby reducing operating costs.

[0038] In some embodiments, in order to improve the uniformity of pH adjustment, multiple dosing ports may be provided in the adjustment tank. Generally, multiple dosing ports can avoid the situation where the agent is locally excessive or insufficient in the tank, thereby improving the adjustment efficiency.

[0039] In another possible implementation, a pH sensor is installed at the outlet of the regulating tank to monitor in real time whether the pH value of the outlet sewage meets the standard. If the outlet pH value is lower than the target range (such as lower than 9.0), the PLC control system will automatically increase the dosage of the reagent; if it is higher than the target range (such as higher than 11.0), it will appropriately reduce the dosage to ensure that the subsequent coagulation reaction unit can operate in an ideal pH environment.

[0040] Through the above implementation, the pH adjustment unit in this embodiment can accurately adjust the pH value of the sewage to stabilize it within the range of 9-11, meeting the chemical requirements of the subsequent heavy metal coagulation and precipitation reaction. The disclosure of the formula and specific parameters enables those skilled in the art to select appropriate reagents and equipment parameters according to the actual situation of the sewage, and optimize the design of the treatment effect.

[0041] (3) Through the coagulation reaction tank, ferrous sulfate is added to reduce hexavalent chromium to trivalent chromium and promote flocculation reaction; After pH adjustment in step (2), the pH of the sewage has been adjusted to an appropriate range (pH 9-11). At this time, the heavy metal ions in the water are converted into a stable form, providing the necessary chemical conditions for the subsequent coagulation reaction. The coagulation reaction is one of the core links in the entire sewage treatment process. It mainly treats the heavy metal ions further by adding coagulants (such as ferrous sulfate) to form flocculants and precipitate them, and adsorbs and aggregates other tiny particles and suspended matter in the water. The process effect of this link directly affects the efficiency of subsequent flocculation precipitation and deep treatment.

[0042] In general, heavy metal ions such as hexavalent chromium (Cr 6+ ) has high toxicity and solubility and needs to be converted into trivalent chromium (Cr 3+ ). At the same time, other heavy metals (such as lead and nickel) will also generate insoluble hydroxides or form complex precipitates with coagulants during the coagulation reaction, thereby being effectively removed. As an option, ferrous sulfate is used as the main coagulant in this step, which combines with multivalent metal ions through a reduction reaction to generate a precipitate.

[0043] In this embodiment, sewage flows from the pH adjustment tank into the coagulation reaction tank. The design volume of the coagulation reaction tank is 12m 3 , provide sufficient reaction time and space to ensure that the coagulant reacts fully with the pollutants in the sewage.

[0044] Specifically, a frame-paddle stirring device is installed in the coagulation reaction tank, and the stirring speed is 25r / min. The function of the stirrer is to enhance the uniformity of the distribution of the coagulant and avoid the occurrence of water short circuit. The stirring device is made of stainless steel, which has strong corrosion resistance and can operate for a long time.

[0045] In one possible implementation, ferrous sulfate (FeSO 4 ) is added to the reaction tank as the main coagulant. Ferrous sulfate dissociates in water to form Fe 2+ , Fe 2+ It reacts with the hexavalent chromium remaining in the water to reduce Cr 6+ Converted to Cr 3+ The reaction formula is: Among them, Fe 2+ The divalent iron ions provided by ferrous sulfate, is the hexavalent chromium ion in the sewage, H + The above reaction can significantly reduce the toxicity of hexavalent chromium and generate trivalent chromium precipitate, which is convenient for subsequent separation.

[0046] At the same time, the trivalent iron (Fe 3+ ) has strong adsorption and will react with other metal ions (such as Pb 2+ 、Ni 2+ ) or suspended particles combine to form a precipitate. The main reaction formula is as follows: Fe 3+ +3OH - →Fe(OH) 3 ↓ M m+ +mFe(OH) 3 →M(OH) m ↓+Fe(OH) 3 Where M m+ It is the heavy metal ion in sewage, Fe(OH) 3 is the generated iron hydroxide, M(OH) m It is a heavy metal hydroxide precipitate.

[0047] As an option, in order to improve the efficiency of the coagulation reaction, the ferrous sulfate can be added in stages. For example, in some embodiments, 70% of the total dosage is added at the inlet of the reaction tank, and the remaining 30% is added in the middle. This method can improve the thoroughness of the coagulation reaction without increasing the dosage of the reagent.

[0048] In some special cases, when the concentration of suspended solids in sewage is high, auxiliary coagulants such as polyaluminium chloride (PAC) can be added on the basis of ferrous sulfate. PAC releases multi-nuclear complexes to form larger flocs with suspended particles, thereby improving sedimentation performance.

[0049] To ensure accurate control of the dosage, the addition of ferrous sulfate is completed by a metering pump. The flow range of the metering pump is 0.1-5L / min, and the accuracy is ±0.1L / min. The concentration of the agent is calculated based on the concentration of heavy metal ions in the sewage and the flow rate. Under normal circumstances, the dosage of ferrous sulfate is 10-50mg / L. For example, Cr in sewage 6+ When the concentration is 0.5 mg / L, the required ferrous sulfate dosage can be calculated according to the following formula: Where, Q is the dosage of ferrous sulfate (mg), C Cr is the hexavalent chromium concentration (mg / L), V is the wastewater volume (L), and M Cr are the molar masses of ferrous sulfate and hexavalent chromium respectively, and n is the molar ratio of iron to chromium in the reaction.

[0050] In some embodiments, in order to optimize the reaction effect, an online turbidity meter can be configured at the outlet of the coagulation reaction tank to monitor the concentration of suspended particles in the effluent water. The PLC system feedbacks data to dynamically adjust the dosage of ferrous sulfate to ensure the operation stability of the reaction tank.

[0051] As a further extension, a transition pipeline is provided between the coagulation reaction tank and the subsequent flocculation reaction tank. A static mixer can be added in the transition pipeline to prevent the coagulant from settling and enhance the effect of the flocculant.

[0052] Through the above specific implementation, this step realizes the reduction of hexavalent chromium in sewage and the flocculation and precipitation of other heavy metals. The detailed description of the above formula and equipment parameters ensures the full disclosure of the technology, so that those skilled in the art can effectively reproduce it according to the disclosed content and optimize and adjust the actual process.

[0053] (4) further adding polyaluminium chloride through the flocculation reaction tank to form flocs; After the coagulation reaction is completed, most of the heavy metal ions in the sewage have been generated into precipitates through chemical reactions, but the generated precipitate particles are small and have poor sedimentation performance. Flocculation reaction is required to further aggregate and grow the particles, thereby enhancing the sedimentation effect. Flocculation reaction is an important link in the entire sewage treatment process that connects coagulation reaction and sedimentation treatment. The main purpose of this step is to promote the aggregation of fine particles produced by coagulation to form stable flocs by adding flocculants (such as polyaluminium chloride, PAC) or other coagulants. These flocs can settle quickly in the subsequent sedimentation tank to further remove heavy metals and suspended particles in the water.

[0054] In general, flocculation reaction is sensitive to stirring conditions, and strong stirring should be avoided to prevent floc rupture. At the same time, flocculation reaction has high requirements on the type and dosage of flocculants, and optimization design should be carried out according to experimental results under different water quality conditions. As an option, polyaluminium chloride (PAC) or polyacrylamide (PAM) can be used as flocculants, and the specific selection is determined by the type and concentration of heavy metals in the water.

[0055] In this embodiment, the sewage flows from the coagulation reaction tank into the flocculation reaction tank. The designed volume of the flocculation reaction tank is 30m 3 , to provide a residence time of 20 minutes to meet the needs of flocculation reaction.

[0056] Specifically, the flocculation reaction tank is equipped with a plug-flow stirring device, and the stirring speed is set to 10r / min. Plug-flow stirring can avoid floc rupture and ensure uniform distribution of flocculants. The blades of the stirring device are made of corrosion-resistant materials (such as stainless steel or PVC) to adapt to the chemical composition of the sewage.

[0057] In one possible implementation, polyaluminium chloride (PAC) is used as the main flocculant and is quantitatively added to the flocculation reaction tank through a metering pump. PAC is hydrolyzed in water to form a multi-nuclear complex, which combines with colloidal particles or heavy metal hydroxides in sewage to form flocs. Its main chemical reactions are as follows: [Al 2 (OH) n Cl 6 -n]+M(OH) x →Al(OH) 3 ↓+M(OH) x ↓ In the formula, [Al 2 (OH) n Cl 6 -n] is the main active ingredient in PAC, M(OH) x It is the heavy metal hydroxide precipitate formed in the coagulation reaction, Al(OH) 3 It is the main precipitation product after PAC hydrolysis.

[0058] As an option, when the sewage contains a large amount of suspended particles, a small amount of polyacrylamide (PAM) can be added as a coagulant. The active groups in the molecular structure of PAM can enhance the stability of the flocs and improve their sedimentation performance. In some embodiments, the dosage of PAM is generally controlled at 1-2 mg / L to avoid excessive increase in water viscosity.

[0059] In a possible implementation, in order to further improve the flocculation reaction efficiency, multiple agent injection ports are set in the flocculation reaction tank. Multi-point injection can ensure uniform distribution of flocculants in sewage and avoid insufficient or excessive local reactions.

[0060] In some special cases, such as when the types of heavy metals in sewage are complex and the concentration is high, the flocculant can be added in stages. In the first stage, 50% of the total dosage is added at the inlet of the tank for initial flocculation, and in the second stage, the remaining 50% of the dosage is added in the middle of the tank to enhance the strength and sedimentation performance of the flocs.

[0061] In order to dynamically control the dosage of flocculant, an online turbidity monitor is set at the outlet of the flocculation reaction tank in this embodiment. The turbidity monitor monitors the concentration of suspended particles in the effluent in real time and transmits the data to the PLC control system. The control system automatically adjusts the dosage of flocculant according to the monitoring data to achieve accurate and optimized dosing.

[0062] In addition, the overflow design of the flocculation reaction tank needs to take into account the characteristics of floc formation. In some embodiments, a slow flow plate is provided at the outlet of the tank body to prevent the flocs from being broken due to excessive flow velocity and to reduce the phenomenon of the flocs flowing out of the tank body with water.

[0063] In the extended design, in order to enhance the adaptability of this step, a temperature regulating device can be added to the flocculation reaction tank. When the sewage temperature is low (such as below 10°C), the chemical reaction rate will be significantly reduced. At this time, the water temperature can be raised to 15-25°C by the heating device in the tank, which can significantly improve the efficiency of the flocculation reaction.

[0064] Through the above specific implementation, the flocculation reaction unit of this embodiment can efficiently realize the generation and stabilization of flocs, providing good conditions for the subsequent solid-liquid separation in the sedimentation tank. The above formula and detailed description of the equipment parameters provide complete technical details and optimization directions for those skilled in the art, so that they can design and reproduce this technical solution according to actual sewage treatment needs.

[0065] (5) The sewage enters the Lamela sedimentation tank, where solid-liquid separation removes most of the heavy metal flocs; After the flocculation reaction is completed, flocs in the sewage have been formed, and have a larger particle size and better sedimentation performance. At this time, the sewage enters the sedimentation unit, and solid-liquid separation is carried out by physical sedimentation to remove flocs and suspended particles in the sewage, thereby further reducing the concentration of heavy metals in the water. The flocculation sedimentation unit is closely connected with the flocculation reaction unit, which is a key step to ensure that the effluent water quality meets the standards. This step utilizes the design of the inclined plate sedimentation tank to improve the sedimentation efficiency, shorten the residence time, and reduce the floor space by expanding the sedimentation area and optimizing the solid-liquid separation process.

[0066] In general, the effect of flocculation sedimentation depends on the particle size of the flocs, the sedimentation velocity, the water flow distribution in the sedimentation tank, and the discharge frequency of the sludge. As an option, this step adopts a modular design of inclined plates to effectively increase the sedimentation area and improve the hydraulic conditions, thereby improving the sedimentation efficiency.

[0067] In this embodiment, the sewage flows from the flocculation reaction tank into the Lamela sedimentation tank. The designed treatment capacity of the sedimentation tank is 130m 3 / h, mainly used for solid-liquid separation and centralized discharge of sludge.

[0068] Specifically, the Lamela sedimentation tank is equipped with an inclined plate assembly, and the inclination angle of the inclined plate is designed to be 60°. The setting of the inclined plate can significantly increase the sedimentation area, shorten the particle sedimentation path, and improve the sedimentation efficiency. According to the design calculation, the specific surface area of ​​the inclined plate can reach 5m 2 / m 3 The inclined plate is made of PVC or fiberglass reinforced plastic (FRP), which has strong corrosion resistance and long service life.

[0069] In one possible implementation, sewage enters the sedimentation tank evenly through the water inlet distribution device. The water inlet distribution device adopts a sawtooth overflow weir, which can effectively disperse the water flow and prevent the flocs from breaking or short-circuiting due to excessive flow rate. Generally, the water inlet flow rate is controlled within the range of 0.05-0.1m / s to ensure that the flocs can enter the sedimentation area smoothly.

[0070] When the flocs in the sewage settle between the inclined plates, they sink under the action of gravity, and at the same time, the water flows upward along the inclined plates, forming good conditions for solid-liquid separation. After the flocs sink, they gather at the bottom of the sedimentation tank, and the sludge is pushed to the sludge outlet for discharge by the sludge scraper.

[0071] As an option, in order to further improve the sedimentation efficiency, a sludge concentration zone can be set in the sedimentation tank. The sludge concentration zone further concentrates the sludge by reducing the bottom water flow velocity, thereby reducing the sludge discharge. In some embodiments, the design retention time of the sludge concentration zone is 30 minutes to 1 hour, and the specific parameters are determined according to the sludge concentration and the sedimentation tank load.

[0072] In another possible implementation, a clean water collection device is provided at the outlet of the sedimentation tank. The clean water collection device adopts a multi-point overflow design, and the overflow ports are distributed at the top of the sedimentation tank, which can ensure the uniformity of the effluent water quality and prevent suspended matter from being carried out.

[0073] In order to monitor the sedimentation effect in real time, an online turbidity meter is installed at the outlet of the sedimentation tank in this embodiment. The turbidity meter can detect the concentration of suspended solids in the outlet water in real time and transmit the data to the PLC control system. The control system adjusts the water inlet flow rate or mud discharge frequency according to the turbidity data to ensure that the sedimentation tank is always in the best operating state.

[0074] In addition, the sludge at the bottom of the sedimentation tank is regularly discharged to the sludge treatment system through a sludge pump. The flow rate and sludge discharge frequency of the sludge pump are set according to the sludge concentration and volume. For example, in some embodiments, the flow rate of the sludge pump is 10-20m 3 / h, and the sludge discharge frequency is 1-2 times / hour to ensure the normal operation of the sedimentation tank.

[0075] In order to reduce the accumulation of sludge on the surface of the inclined plate, the surface of the inclined plate in this embodiment is smoothed, and the water flow self-cleaning function is considered in the design. By optimizing the inclined plate spacing and water flow speed, it is ensured that the sludge can slide smoothly to the bottom of the pool.

[0076] In some special cases, such as when the concentration of suspended solids in sewage is high, a pre-sedimentation unit can be added to share the load of the sedimentation tank. The pre-sedimentation unit is generally designed between the flocculation reaction tank and the sedimentation tank to remove part of the suspended solids in the sewage and reduce the operating pressure of the sedimentation tank.

[0077] (6) Further adsorption of residual heavy metals through activated carbon filters; After the flocculation and sedimentation in step (5), most of the suspended particles and heavy metal precipitates in the sewage have been separated, but a small amount of soluble heavy metal ions or trace pollutants (such as mercury and lead) may still remain in the water. The removal of these trace heavy metals is difficult and requires further deep treatment through adsorption processes. In this step, an activated carbon filter device is used to remove the remaining heavy metal pollutants and other organic impurities in the sewage using the high specific surface area and strong adsorption capacity of activated carbon, thereby providing higher water quality assurance for subsequent discharge or reprocessing. The activated carbon filter device is closely connected to the sedimentation unit to ensure that the water inlet flow rate is uniform and to avoid excessive water flow impact on the activated carbon layer.

[0078] In general, activated carbon filtration is suitable for treating low-concentration pollutants, and its working efficiency is closely related to the type of activated carbon, filling height and filtration speed. As an option, granular activated carbon (GAC) is selected as the main adsorption material in this step, and its large specific surface area and porosity help to adsorb a variety of heavy metal ions and trace organic matter.

[0079] In this embodiment, the sewage flows out of the Lamela sedimentation tank and enters the activated carbon filter unit. The processing capacity of the activated carbon filter is designed to be 130m 3 / h, matching the processing flow of the upstream sedimentation tank to ensure the continuity and stability of the system operation.

[0080] Specifically, the activated carbon filter adopts a vertical cylindrical structure, with a height of 3.5 meters and an inner diameter of 4.5 meters. The filter is filled with a 2-meter-thick granular activated carbon layer (GAC), with a particle size of 0.5-2 mm and a specific surface area of ​​more than 900 m 2 / g, and the pore size distribution range is 1.5-2.5 nanometers.

[0081] In one possible implementation, wastewater enters the filter evenly from the bottom and flows upward through the activated carbon layer. Heavy metal ions (such as Hg 2+ and Pb2+ ) undergoes physical adsorption with activated carbon. The adsorption process of activated carbon includes electrostatic action, van der Waals force and micropore filling, and its main adsorption reaction can be expressed as: Hg 2+ +C active →(Hg-C) adsorbed Pb 2+ +C active →(Pb-C) adsorbed In the formula, C active is the active site on the activated carbon surface, (Hg-C) adsorbed and (Pb-C) adsorbed For the adsorbed mercury and lead ions.

[0082] To avoid premature saturation of activated carbon, in some embodiments, pretreatment means can be used to reduce the clogging of the activated carbon layer by large particle pollutants in the water. For example, a quartz sand filter layer can be set as a pre-filter before entering the activated carbon filter. The thickness of the quartz sand filter layer can be designed to be 30 cm to capture residual suspended particles and large molecular organic matter.

[0083] In another possible implementation, the operating cycle of the activated carbon filter is dynamically adjusted according to the effluent water quality. Generally, the filtration cycle is set to 24 hours, and a backwash operation is performed after each operation. Backwashing adopts a combined upper and lower water washing method, and the water washing intensity is 7L / (s·m 2 ) for 20 minutes to remove particles attached to the surface of activated carbon. At the same time, air washing can be assisted, with an air washing intensity of 10L / (s·m 2 ), the time is 10 to 15 minutes.

[0084] Specifically, in order to improve the backwashing effect, the backwashing water is discharged through the top overflow port, and the backwashing wastewater after cleaning can be returned to the homogenization tank or treated separately to avoid waste of resources.

[0085] In order to monitor the adsorption effect of activated carbon, in this embodiment, online heavy metal ion concentration monitoring devices are installed at the inlet and outlet of the activated carbon filter. 2+ , Pb 2+ By real-time monitoring of plasma concentration, the system can determine the saturation state of activated carbon and send a replacement or regeneration prompt signal through the PLC control system.

[0086] In some special cases, such as when the concentration of organic pollutants in sewage is high, coconut shell activated carbon or other special adsorption materials can be used to improve the removal effect of organic pollutants. The pore size distribution of coconut shell activated carbon is more suitable for capturing low molecular weight organic matter, and it also has strong anti-wear performance.

[0087] In further extended design, a spare activated carbon filter device can be added. When the main filter enters the backwash state, the spare filter automatically switches to operation to ensure the continuity of the sewage treatment system.

[0088] (7) The residual heavy metals such as nickel and cadmium in the sewage are deeply removed through the cation exchange resin unit, and finally meet the discharge standards.

[0089] After the activated carbon filtration in step (6), the suspended particles and some soluble heavy metals in the sewage have been removed, but there may still be trace amounts of heavy metal ions (such as nickel and cadmium) that are difficult to remove by adsorption. In order to further reduce the concentration of heavy metals in the water and ensure that the effluent meets the standards, cation exchange resin treatment is used to deeply remove the residual heavy metal ions. This step utilizes the selective ion exchange characteristics of the cation exchange resin to replace the metal ions dissolved in the water and adsorb them onto the resin through an ion exchange reaction, thereby achieving effective removal of heavy metals. This treatment unit is closely connected to the activated carbon filtration unit and is an important deep treatment link in the sewage treatment system.

[0090] In general, the efficiency of cation exchange resin treatment is closely related to the type of resin, operating conditions (such as pH value, flow rate) and ion concentration in sewage. As an option, strong acid cation exchange resin can be used preferentially, whose strong acidic groups can effectively exchange heavy metal ions in a wide pH range.

[0091] In this embodiment, the sewage after activated carbon filtration is introduced into the cation exchange resin device for treatment. The treatment flow rate is designed to be 130m 3 / h, consistent with the upstream unit to ensure the overall smooth operation of the system.

[0092] Specifically, the cation exchange device adopts a vertical columnar reactor structure with an inner diameter of 2.6 meters and a total height of 3.5 meters. The column is filled with a 1.5-meter-thick layer of strongly acidic cation exchange resin, the main group of which is sulfonic acid (SO 3 H - ), whose active form is hydrogen (H + The particle size of the resin ranges from 0.3 to 1.2 mm, and the specific surface area is 50 to 60 m 2 / g, with high exchange capacity and anti-pollution ability.

[0093] In one possible implementation, the cation exchange resin undergoes an ion exchange reaction with the heavy metal ions in the sewage, and the generated metal complex is adsorbed on the resin surface. The main chemical reaction is as follows: In the formula, is the active group of the cation exchange resin, M n+ Heavy metal ions in sewage (such as Ni 2+ 、Cd 2+ ), n is the charge number of the heavy metal ion, It is a combination of metal ions and resin.

[0094] As an option, the operating conditions can be optimized according to the specific types and concentrations of heavy metal ions in the influent. For example, when treating wastewater with a nickel concentration of 0.1 mg / L and a cadmium concentration of 0.05 mg / L, the resin operation cycle can be set to 24-27 hours, and the specific regeneration cycle is dynamically adjusted based on the outlet water quality monitoring results.

[0095] In order to extend the service life and exchange capacity of the resin, an online metal ion monitoring device is set at the outlet of the cation exchange column in this embodiment. The device detects the concentration of heavy metal ions in the water in real time and adjusts the operating parameters through the PLC system feedback. When the adsorption capacity of the resin is close to saturation, the system will automatically trigger the regeneration program.

[0096] Specifically, the regeneration process uses hydrochloric acid solution (concentration of 31%) as a regeneration agent. Hydrochloric acid restores the exchange capacity of the resin by replacing heavy metal ions adsorbed on the surface of the resin. The regeneration chemical reaction is as follows: During the regeneration process, in order to improve the regeneration efficiency, the amount of hydrochloric acid added is generally calculated according to the following formula: In the formula, Q acid is the dosage of hydrochloric acid (mol), C metal is the metal ion concentration in sewage (mol / L), V water is the sewage volume (L), M acid and M metal are the molar masses of hydrochloric acid and heavy metals, respectively.

[0097] During the regeneration process, a backwash step is also included to remove solid particles attached to the resin surface. Generally, the backwash water flow rate is 50m 3 / h, and the duration is 15 minutes. The wastewater after backwashing can be sent back to the front flocculation sedimentation tank for centralized treatment.

[0098] In one possible implementation, in order to ensure continuous operation, the cation exchange device is set to a dual-column parallel operation mode. Under normal operating conditions, the two columns are used alternately, one column treats sewage and the other column is regenerated. Automatic switching is achieved through a PLC control system to ensure the continuity and stability of the treatment process.

[0099] In addition, to avoid excessive use of acid and secondary pollution, the discharged regeneration waste liquid can be neutralized in a neutralization tank. The neutralizing agent can be sodium hydroxide or sodium carbonate, and the specific dosage is dynamically adjusted according to the acidity (pH) of the waste liquid.

[0100] In further extended design, resin pretreatment units can be added according to the specific properties of sewage. For example, when the concentration of suspended particles in sewage is high, a quartz sand protective layer with a thickness of 20-30 cm can be set above the resin layer to intercept large particle pollutants and reduce pollution to the resin.

[0101] The process is combined with a dosing system to achieve automated dosing and precise control, and is adaptable to complex water quality and heavy metal removal requirements.

[0102] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sewage mixing flocculation sedimentation tank with a dosing system and a sewage treatment process, characterized in that: The sewage treatment process comprises the following steps: (1) Sewage enters the pretreatment unit to remove large suspended solids; (2) The sewage flows into the pH adjustment tank, and the pH adjuster is added through the dosing system to adjust the pH value to 9-11; (3) Through the coagulation reaction tank, ferrous sulfate is added to reduce hexavalent chromium to trivalent chromium and promote flocculation reaction; (4) further adding polyaluminium chloride through the flocculation reaction tank to form flocs; (5) The sewage enters the Lamela sedimentation tank, where solid-liquid separation removes most of the heavy metal flocs; (6) Further adsorption of residual heavy metals through activated carbon filters; (7) The residual heavy metals such as nickel and cadmium in the wastewater are deeply removed through the cation exchange resin unit, and finally meet the discharge standards.

2. The process is combined with a dosing system to achieve automated dosing and precise control, and is suitable for complex water quality and heavy metal removal requirements.

3. A sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The pH adjustment is achieved by the following steps: The sewage enters the pH adjustment tank, and the pH value is adjusted to 9-11 by quantitatively adding lime milk or sodium hydroxide solution, so that the heavy metal ions are converted into hydroxide precipitation.

4. A sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The coagulation reaction in the coagulation reaction tank is completed by adding ferrous sulfate, and the ferrous sulfate reacts with the hexavalent chromium in the sewage to generate trivalent chromium, and the chemical reaction formula is as follows:

5. The sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The flocculation reaction tank promotes the formation and growth of flocs by adding polyaluminium chloride and slowly stirring, thereby enhancing its sedimentation performance. The chemical reaction formula is as follows: Al2(OH) n Cl6-n+M m+ +(OH) - →Al(OH)3+M(OH) m ↓ Among them, M m+ is the metal ion, and m is the valence number of the metal ion.

6. The sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The Lamela sedimentation tank includes an inclined plate sedimentation unit with an inclination angle of 60°, which removes flocculated sediments through solid-liquid separation and is equipped with a scraper and a sludge pump to achieve sludge discharge.

7. The sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The activated carbon filter is filled with granular activated carbon to a height of 1.5-2 meters for adsorbing residual mercury in sewage.

8. The sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The cation exchange resin system uses a strong acid cation exchange resin, and its backwash strength is 50m 3 / h, backwash time is 10-15 minutes, 31% hydrochloric acid is used in the regeneration process, and the dosage is 0.9m 3 / Second-rate.

9. The sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The dosing system comprises: Pharmaceutical storage tank, made of PE, volume 1-2m 3 ; The dosing pump uses an adjustable flow metering pump with a flow accuracy of ±0.1L / h; The dosing control unit is based on the PLC control system and automatically adjusts the dosage of the agent in combination with the online monitored pH, conductivity, and heavy metal concentration parameters.

10. The sewage mixing flocculation sedimentation tank and sewage treatment process with a dosing system according to claim 1, characterized in that: The process automation system comprises: Online monitoring system, used to monitor the pH value and heavy metal ion concentration of sewage in real time; PLC control system, automatically adjusts stirring speed, reagent dosage and sludge discharge cycle; Alarm unit, when pH or heavy metal concentration exceeds the set value, triggers the alarm signal and starts the emergency treatment procedure; The cation exchange resin treatment unit of the process is arranged in series with the activated carbon filter, and can be switched to the standby treatment unit according to the change of heavy metal concentration to adapt to the fluctuating water quality.

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