The circulating cooling water system uses water as the cooling medium, and the circulating operation takes away the heat in the process. Generally, part of the water is evaporated through the cooling tower to cool down.
Pure water is lost by evaporation, and dissolved salts are concentrated in the remaining cooling water.
When the dissolved salts in the cooling water reach a certain concentration, part of the cooling water must be discharged to avoid a series of problems such as scaling, corrosion, deposition, and microbial breeding.
70% to 80% of my country’s industrial water is supplementary water for circulating water.
Due to the different levels of salt content in the make-up water, a part of the concentrated water must be discharged when the circulating water is concentrated to a certain number, and the consumption of water resources and the discharge of sewage is very large.
If this part of concentrated water is treated and reused, it can not only reduce sewage discharge and improve water utilization rate but also improve the overall operation of the cooling circulating water system.
The existing circulating cooling water wastewater reuse treatment system generally uses a reverse osmosis membrane (RO membrane) to remove the organic matter and salt in the cooling wastewater, and the produced water is returned to the circulating water tank, and the concentrated water is discharged.
In order to meet the influent conditions of RO membrane and ensure its stable operation, one or more combinations of coagulation air flotation or sedimentation, sand filtration and microfiltration membrane (MF membrane), or ultrafiltration membrane (UF membrane) are generally used for pre-treatment. The treatment process is used to remove the dispersed and stable fine particles and biological sludge in the cooling sewage.
However, the actual operation of the circulating cooling water wastewater reuse treatment system has the following problems:
- The use of coagulation-air flotation or sedimentation treatment process requires the use of a large amount of inorganic coagulants to remove the stable and dispersed tiny particles in the sewage and generate a large amount of sludge.
- Using the coagulated sand filtration treatment process, if the inorganic coagulant is excessively added, not only the frequency of sand filter backwashing will increase, but also the inorganic coagulant that penetrates the sand filter will foul and block the MF or UF membrane, security filter element and RO membrane. Insufficient dosage of inorganic coagulant.
The ultra-small particles close to the membrane pore size in the sewage will block the MF or UF membrane pores, resulting in insufficient water production, frequent cleaning and easy damage of the MF or UF membrane.
- Using the combined treatment process of coagulation air flotation or sedimentation, sand filtration, MF or UF membrane and RO membrane, the operation is stable and reliable.
However, there are disadvantages such as large occupation of land, high cost, complicated and laborious operation and maintenance, etc., and it is difficult to meet the needs of cooling and wastewater reuse in buildings or small and medium-sized industries.
The invention provides a recycling treatment method and device for circulating cooling water sewage, so as to solve the problems of long processing process flow, a large area of treatment facilities, and high investment and operating costs in the existing recycling treatment of circulating cooling water sewage. , complicated and laborious operation and maintenance and the generation of waste sludge.
In order to solve the above-mentioned problems, the technical scheme of the present invention is as follows:
- The bottom of the circulating pool is provided with a side filter water inlet pipe.
- The bypass filter water inlet pipe is connected to the bypass filter via the bypass filter water pump.
- The water outlet of the side filter is respectively connected with the side filter production water pipe and the cooling sewage pipe.
- The heat exchanger is a working device for circulating cooling water, and multiple heat exchangers can be connected in parallel or in series.
- The side filter is provided with a sewage outlet which is connected with the backwashing sewage pipe.
- A blowdown valve is arranged on the cooling blowdown pipe, and the blowdown valve is an automatic blowdown valve, which is connected with an external automatic control system.
- The side filter is a filter device with anthracite or sand as the filter material, preferably a garnet filter material with a particle size of 0.35-0.45mm.
A method for reusing and treating circulating cooling water drainage water of the present invention is characterized in that, using the reusing treatment device of the present invention, comprising the following steps:
- Part of the cooling water of the circulating water pool 2 enters the side filter water inlet pipe L1, and after adding cationic organic filter aids, it is supplied to the side filter 6 through the side filter water pump 5 for filtration; the side filter of the side filter 6 produces water. Return to the circulating water tank 2 through the bypass filter production water pipe L2.
- The product water permeating the MF or UF membrane is sent to the RO membrane device 8 for membrane filtration, the RO product water is sent back to the circulating water tank 2 through the water product pipe L6, and the concentrated brine is discharged through the concentrated brine discharge pipe L7.
- Cationic organic filter aids are polydiallyl dimethyl ammonium chloride, dialkylamine-epichlorohydrin polycondensate, polydimethylaminoethyl methacrylate alkyl quaternary ammonium chloride, polyethylene One or more of amine, dialkylamine-dichloroalkylene polycondensate.
- When the pressure difference of the side filter 6 exceeds the set value, backwashing is performed to discharge the trapped particulate matter, and the backwashing water is discharged through the backwashing sewage pipe L3.
The circulating cooling water treatment system and the sewage reuse treatment system are organically combined to give full play to their respective advantages to achieve the purpose of removing pollutants in the cooling water, saving water, reducing emissions and optimizing the overall cost: In the circulating cooling water treatment system, a small part of the circulating cooling water is added with a specific cationic organic filter aid, and then the fine suspended solids and biological slime are removed through a side filter.
In the sewage reuse treatment system, part of the by-pass filtered water is used as sewage to remove tiny particles, colloids and microorganisms through the MF or UF membrane, and the product water of the MF or UF membrane is then removed by the RO membrane to remove organic matter and salt. The water is returned to the circulating pool, and the concentrated water is discharged.
Making full use of the bypass filter of the circulating cooling water treatment system can not only continuously and effectively improve the cooling water quality of the circulating cooling water treatment system but also save the coagulation and air flotation or sedimentation and sand filtration of the circulating cooling water drainage and sewage reuse treatment system. Pretreatment process unit.
The reuse of the produced water and the filtration by the dosing side improve the water quality of the whole circulating cooling water system. reduced by more than 20%.
For the recycling treatment system of circulating cooling water and sewage, the water produced by side filtration is used as cooling and sewage, which makes the reused water quality better, the treatment process is simple, the area of treatment facilities is reduced by more than 50%, and the investment cost is reduced by more than 30%. , the operating cost is reduced by more than 20%, the operation and maintenance are simpler and no waste sludge is generated; for the overall system, the final sewage discharge is reduced by more than 60%.