Sterilizing and cleaning method of industrial wastewater recycling membrane system

Abstract

The invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a sterilization and cleaning method of an industrial wastewater recycling membrane system, which comprises the following steps: (1) performing graded chlorine disinfection on an aeration tank: continuously adding sodium hypochlorite at the water inlet end of the aeration tank; (2) stripping and cleaning the filter slime, namely periodically cleaning the filter by adopting a slime stripping agent, injecting the dissolved slime stripping agent into the filter, and combining static soaking with dynamic gas scrubbing; (3) performing impact addition of the non-oxidizing bactericide before reverse osmosis: performing impact addition of the non-oxidizing bactericide for 2-4 times every week in a reverse osmosis water inlet section, wherein the single-time addition time is 30-60 minutes; and (4) optimizing a reverse osmosis chemical cleaning process: adopting a'double alkali cleaning 'combined process. According to the method, a systematic and multi-node cooperative sterilization and cleaning mode is adopted, all pollution nodes of the whole process are covered, microorganism prevention and control in the whole process from water inlet to water production are achieved, and the operation stability of a membrane system under high-temperature and high-pollution water quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, and in particular relates to a sterilization and cleaning method for an industrial wastewater reuse membrane system. Background Technology

[0002] Membrane systems play a crucial role in industrial wastewater reuse and demineralized water preparation; however, their long-term stable operation is susceptible to microbial contamination, especially under high-temperature conditions in summer. Industrial wastewater typically contains suspended solids and has high COD and oil content, with significant fluctuations in water quality and quantity, providing favorable conditions for microbial growth. Microorganisms proliferate on the membrane surface and within the system channels, forming biofilms that lead to membrane channel blockage, increased pressure differential, decreased permeate production, and frequent cleaning, severely impacting the system's continuous operation and economic viability.

[0003] Traditional sterilization methods often involve the local application of oxidizing bactericides (such as sodium hypochlorite), but these methods are prone to producing drug-resistant strains and cannot cover all contamination points throughout the entire process, leading to repeated microbial growth in pretreatment, filtration, and reverse osmosis stages. Furthermore, conventional chemical cleaning processes have limited effectiveness in removing biofilms and organic fouling, resulting in rapid rebound of contamination after cleaning. Summary of the Invention

[0004] The purpose of this invention is to provide a sterilization and cleaning method for industrial wastewater reuse membrane systems, which solves the problems of traditional sterilization methods that easily generate drug-resistant strains, cannot cover all pollution nodes in the entire process, leading to repeated proliferation of microorganisms in the pretreatment, filtration and reverse osmosis stages, and the limited effectiveness of conventional chemical cleaning processes in removing biofilm and organic fouling.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A sterilization and cleaning method for an industrial wastewater reuse membrane system, the membrane system comprising an aeration tank, which is sequentially connected to a radial flow sedimentation tank, a multi-media filter, a filtered water tank, a self-cleaning filter, an ultrafiltration unit, an ultrafiltration permeate tank, a primary reverse osmosis unit, one branch of the primary reverse osmosis unit being connected to a demineralized water tank of a combined pumping station, the demineralized water tank of the combined pumping station being connected to an external water supply line, and the other branch of the primary reverse osmosis unit being sequentially connected to a secondary reverse osmosis unit, a secondary demineralized water tank, a mixed bed, a high-quality demineralized water tank, and an external water supply line, including the following: (1) Staged chlorine disinfection in aeration tank Sodium hypochlorite at a concentration of 50-80 ppm is continuously added at the inlet of the aeration tank to maintain the residual chlorine in the ultrafiltration effluent at 1-1.5 mg / L. (2) Filter slime removal and cleaning The filter is periodically cleaned using a slime remover with penetrating and dispersing functions. After the agent is dissolved, it is injected into the filter. Static soaking and dynamic air scrubbing are combined. The filter is aerated and stirred for 10-20 minutes every 2-3 hours, with a total reaction time of 12-15 hours. After the reaction is completed, the filter is thoroughly backwashed 5-6 times to ensure that the turbidity of the effluent is consistently below 0.5 NTU. (3) Shock dosing of non-oxidizing bactericides before reverse osmosis In the reverse osmosis feed section, non-oxidizing bactericides are added 2-4 times per week at a concentration of 200-300 ppm, with each addition lasting 30-60 minutes, to inhibit microorganisms from entering the reverse osmosis system and prevent membrane oxidative damage. (4) Optimization of reverse osmosis chemical cleaning process The "dual-alkali washing" combined process involves the following steps: non-oxidizing bactericide circulation cleaning for 2-3 hours; alkaline cleaning agent circulation soaking for 4-6 hours; alkaline cleaning agent enhanced circulation for 2-3 hours; and acidic cleaning agent circulation for 2-4 hours to neutralize the pH. The hydrogen ions in the acidic cleaning agent react with the inorganic scale to dissolve it, generating soluble salts and releasing gas, thus breaking down the scale and removing the inorganic scale.

[0006] Preferably, (1) further includes 2-4 shock doses of sodium hypochlorite per week at a concentration of 100-150 ppm for 30-60 minutes to kill bactericidal micelles and early-stage organisms.

[0007] Preferably, the stripping agent in (2) is one or more of benzalkonium chloride, hydrogen peroxide, fatty alcohol polyoxyethylene ether, and benzotriazole.

[0008] Preferably, the non-oxidizing bactericides in (3) and (4) are one or two of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), methylisothiazolinone (MIT), 2,2-dibromo-3-nitropropionamide (DBNPA), and glutaraldehyde.

[0009] Preferably, the alkaline cleaning agent in (4) is sodium hydroxide, a chelating agent (Na4EDTA), a surfactant (Na-SDS), and a dispersant (Na5P3O). 10 A mixture of sodium hydroxide (0.1%-1.0%), chelating agent (Na4EDTA) (0.5%-2.0%), surfactant (Na-SDS) (0.5%-2.0%), and dispersant (Na5P3O4). 10 The concentration is 0.01%-0.1%; the percentages here are based on the total cleaning solution, the rest of the components are demineralized water; the solvent is demineralized water, and the indicators are conductivity 20-50μs / cm and hardness 5-10mg / L.

[0010] Preferably, the acidic cleaning agent in (4) is a mixture of hydrochloric acid and citric acid, with a hydrochloric acid concentration of 0.1%-0.3% and a citric acid concentration of 1%-2%; the percentages here are based on the percentage of the total cleaning solution, the remaining components are demineralized water, the solvent is demineralized water, and the indicators are conductivity of 20-50 μs / cm and hardness of 5-10 mg / L.

[0011] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) By combining continuous addition of sodium hypochlorite and shock addition of sodium hypochlorite in the aeration tank, the biological load is reduced from the source, and the biological pollution of the downstream ultrafiltration and reverse osmosis systems is delayed; the filter sludge removal is carried out by "soaking and air scrubbing" to deeply remove the sludge trapped by the filter media, restore the filter's fouling capacity and ensure low turbidity permeate; the shock addition of non-oxidizing bactericide before reverse osmosis inhibits the entry of microorganisms into the reverse osmosis system under the premise of protecting the membrane itself, and prevents membrane biofouling and oxidative damage; the reverse osmosis cleaning process adopts the "double alkali washing" combination process, and through the step-by-step synergistic cleaning strategy, it can more thoroughly remove composite pollutants on the membrane surface, efficiently restore membrane performance and extend service life; (2) This method adopts a systematic, multi-node collaborative sterilization and cleaning approach, covering all pollution nodes in the entire process, realizing microbial control throughout the entire process from water intake to water production, and improving the operational stability of the membrane system under high temperature and high pollution water quality. Detailed Implementation

[0012] The technical solution of the present invention will be described in detail below with reference to the embodiments.

[0013] The Taiyuan Iron & Steel Group (TISCO) Energy Department's industrial wastewater deep treatment system is responsible for treating comprehensive wastewater from steel rolling, smelting, and other steel-related processes. The incoming water contains relatively high levels of microorganisms and organic matter, and microbial contamination of the membrane system is severe during the hot summer months. This invention provides a sterilization and cleaning method for an industrial wastewater reuse membrane system. The membrane system includes an aeration tank, which is sequentially connected to a radial flow sedimentation tank, a multi-media filter, a filtered water tank, a self-cleaning filter, an ultrafiltration unit, an ultrafiltration permeate tank, a primary reverse osmosis unit, and one path of the primary reverse osmosis unit is connected to a combined pumping station demineralized water tank. The combined pumping station demineralized water tank is connected to an external water supply line. The other path of the primary reverse osmosis unit is sequentially connected to a secondary reverse osmosis unit, a secondary demineralized water tank, a mixed bed, a high-quality demineralized water tank, and an external water supply line. The system includes the following components: (1) Sodium hypochlorite with a concentration of 60 ppm was continuously added to the inlet of the aeration tank, and sodium hypochlorite with a concentration of 120 ppm was added twice a week for 30 minutes. (2) Use a slime remover to periodically clean the filter. The slime remover is a mixture of benzalkonium chloride, hydrogen peroxide and fatty alcohol polyoxyethylene ether. After the agent is dissolved, it is injected into the filter. Static soaking is combined with dynamic gas scrubbing. The filter is aerated and stirred for 10 minutes every 2 hours. The total reaction time is 12 hours. After the reaction is completed, the filter is thoroughly backwashed 5 times. (3) In the reverse osmosis feed section, a non-oxidizing bactericide (a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and methylisothiazolinone) is added twice a week. The concentration of the non-oxidizing bactericide is 200 ppm and the single addition time is 30 minutes. (4) The "double alkali washing" combined process is adopted. First, a non-oxidizing bactericide (a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and methylisothiazolinone) is circulated for 2 hours; then an alkaline cleaning agent is circulated for 4 hours; then an alkaline cleaning agent is circulated for 2 hours; and finally an acidic cleaning agent is circulated for 2 hours. The alkaline cleaning agent consists of sodium hydroxide, a chelating agent (Na4EDTA), a surfactant (Na-SDS), and a dispersant (Na5P3O). 10 A mixture of sodium hydroxide (0.1%-1.0%), chelating agent (Na4EDTA) (0.5%-2.0%), surfactant (Na-SDS) (0.5%-2.0%), and dispersant (Na5P3O4). 10 The concentration of the cleaning agent is 0.01%-0.1%; the acidic cleaning agent is a mixture of hydrochloric acid and citric acid, with a hydrochloric acid concentration of 0.1%-0.3% and a citric acid concentration of 1%-2%; the percentages here are based on the percentage of the total cleaning solution, and the remaining components are demineralized water; the solvent is demineralized water, with the indicators being a conductivity of 20-50 μs / cm and a hardness of 5-10 mg / L.

[0014] After implementing this method, the reverse osmosis membrane pressure differential decreased from 0.35 MPa to 0.21 MPa, and the permeate flow rate per unit increased from 150 m³ / h. 3 / h increased to 182m 3 The system's operating cycle has been restored to 30 days, saving approximately 1.98 million yuan in annual operating costs and significantly improving system stability.

Claims

1. A method for sterilization and cleaning of an industrial wastewater reuse membrane system, the membrane system comprising an aeration tank, wherein the aeration tank is sequentially connected to a radial flow sedimentation tank, a multi-media filter, a filtered water tank, a self-cleaning filter, an ultrafiltration unit, an ultrafiltration permeate tank, a primary reverse osmosis unit, one path of the primary reverse osmosis unit being connected to a demineralized water tank of a combined pumping station, the demineralized water tank of the combined pumping station being connected to an external water supply line, and the other path of the primary reverse osmosis unit being sequentially connected to a secondary reverse osmosis unit, a secondary demineralized water tank, a mixed bed, a high-quality demineralized water tank, and an external water supply line, characterized in that, Includes the following: (1) Staged chlorine disinfection in aeration tank Sodium hypochlorite at a concentration of 50-80 ppm is continuously added at the inlet of the aeration tank to maintain the residual chlorine in the ultrafiltration effluent at 1-1.5 mg / L. (2) Filter slime removal and cleaning The filter is periodically cleaned using a slime remover with penetrating and dispersing functions. After the agent is dissolved, it is injected into the filter. Static soaking and dynamic air scrubbing are combined. The filter is aerated and stirred for 10-20 minutes every 2-3 hours, with a total reaction time of 12-15 hours. After the reaction is completed, the filter is thoroughly backwashed 5-6 times to ensure that the turbidity of the effluent is consistently below 0.5 NTU. (3) Shock dosing of non-oxidizing bactericides before reverse osmosis In the reverse osmosis feed section, non-oxidizing bactericides are added 2-4 times per week at a concentration of 200-300 ppm, with each addition lasting 30-60 minutes, to inhibit microorganisms from entering the reverse osmosis system and prevent membrane oxidative damage. (4) Optimization of reverse osmosis chemical cleaning process The "dual-alkali washing" combined process involves the following steps: non-oxidizing bactericide circulation cleaning for 2-3 hours; alkaline cleaning agent circulation soaking for 4-6 hours; alkaline cleaning agent enhanced circulation for 2-3 hours; and acidic cleaning agent circulation for 2-4 hours to neutralize the pH. The hydrogen ions in the acidic cleaning agent react with the inorganic scale to dissolve it, generating soluble salts and releasing gas, thus breaking down the scale and removing the inorganic scale.

2. The sterilization and cleaning method for an industrial wastewater reuse membrane system according to claim 1, characterized in that, The (1) also includes 2-4 shock doses of sodium hypochlorite per week at a concentration of 100-150 ppm for 30-60 minutes to kill bacterial micelles and early-stage organisms.

3. The sterilization and cleaning method for an industrial wastewater reuse membrane system according to claim 1, characterized in that, The stripping agent in (2) is one or more of benzalkonium chloride, hydrogen peroxide, fatty alcohol polyoxyethylene ether, and benzotriazole.

4. The sterilization and cleaning method for an industrial wastewater reuse membrane system according to claim 1, characterized in that, The non-oxidizing bactericides in (3) and (4) are one or two of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), methylisothiazolinone (MIT), 2,2-dibromo-3-hypopropoxylamide (DBNPA), and glutaraldehyde.

5. The sterilization and cleaning method for an industrial wastewater reuse membrane system according to claim 1, characterized in that, The alkaline cleaning agent in (4) is sodium hydroxide, chelating agent (Na4EDTA), surfactant (Na-SDS), and dispersant (Na5P3O). 10 A mixture of sodium hydroxide (0.1%-1.0%), chelating agent (Na4EDTA) (0.5%-2.0%), surfactant (Na-SDS) (0.5%-2.0%), and dispersant (Na5P3O4). 10 The concentration is 0.01%-0.1%; the percentages here are based on the total cleaning solution, the rest of the components are demineralized water; the solvent is demineralized water, and the indicators are conductivity 20-50μs / cm and hardness 5-10mg / L.

6. The sterilization and cleaning method for an industrial wastewater reuse membrane system according to claim 1, characterized in that, The acidic cleaning agent in (4) is a mixture of hydrochloric acid and citric acid, with a hydrochloric acid concentration of 0.1%-0.3% and a citric acid concentration of 1%-2%. The percentages here are based on the percentage of the total cleaning solution. The remaining components are demineralized water, the solvent is demineralized water, and the indicators are conductivity of 20-50 μs / cm and hardness of 5-10 mg / L.