Reclaimed water/circulating cooling water reuse device
Reclaimed water/circulating cooling water reuse device
- Commodity name: Reclaimed water/circulating cooling water reuse device
The construction and operation of sewage treatment plants, especially industrial sewage treatment plants, are restricted and affected by many factors. Among them, the determination of the water plant process plan is the most critical to ensure the operational performance of the treatment plant and reduce costs. Therefore, it is necessary to follow the determined standards. and general principles, starting from the concept of overall optimality, combined with the design scale, sewage water quality characteristics and local actual conditions and requirements, select a feasible and economical and reasonable treatment process plan, and select the best overall solution after a comprehensive technical and economic analysis Process plan and implementation.
Based on the determined conditions and requirements, the following principles will be followed in the design of the overall process plan:
(1) Based on the water quality characteristics, the selected treatment process has a better purification effect on wastewater.
(2) The selected process technology is advanced and mature, has strong adaptability to changes in water quality, has stable operation, and can ensure that the effluent water quality meets the requirements of the discharge standards.
(3) The selected process minimizes infrastructure investment and operating costs, is fully and efficiently coupled with existing treatment facilities and reserved pipelines, saves floor space and reduces energy consumption.
(4) The selected process is easy to operate, flexible in operation and easy to manage. According to the incoming water quality and quantity, the process operating parameters and operations can be appropriately adjusted.
(5) The selected process is easy to realize automatic control and improves the level of operation and management.
(6) The selected process minimizes adverse effects on the surrounding environment (odor, noise, aerosol, etc.).
The process flow chart is as follows:
Ultrafiltration process description
The activated carbon filter water inlet pump lifts and pressurizes the raw water. After pressure filtration, the water is sent to the pre-ultrafiltration precision filter. Suspended particles larger than 100µm in the water are removed. It also protects the ultrafiltration membrane element port from large particulate matter. Damaged by scratches. The pressurized water filtered by the filter enters the ultrafiltration membrane module. Due to the characteristics of the ultrafiltration membrane itself, most bacteria, algae, colloidal substances and tiny (greater than 0.025 microns) particulate matter are trapped on the surface of the membrane, and the water and Water-soluble substances pass through the membrane pores, and the water quality is purified in the membrane system. Through the filtration function of the ultrafiltration membrane, TSS and colloidal substances are basically removed. After filtration for a certain period of time, a layer of pollution will be deposited on the surface of the membrane, and the membrane element needs to be backwashed: the backwash water pump lifts and pressurizes the ultrafiltration effluent and then enters the system through the ultrafiltration water production pipe. The backwash water under pressure will clean the membrane. Surface contaminants are flushed out of the system and membrane element flux is restored. Since the water contains various bacteria, organic matter, inorganic matter, etc., backwashing with clean water alone cannot completely restore the membrane flux. Therefore, after the membrane element has been filtered for a certain period of time, the membrane needs to be chemically enhanced backwashed, that is, after backwashing Chemicals are added from time to time to completely remove pollutants on the membrane surface through chemicals.
The sewage after normal backwashing is directly discharged into the factory pretreatment system (raw pool), and the ultrafiltration chemical backwash (CEB) wastewater is discharged into the demand-side high salt water system and cannot enter the factory pretreatment system.
Introduction to ultrafiltration technology
The ultrafiltration membrane technology used is a membrane filtration technology developed specifically for large-scale water treatment projects. The average pore size of this high-performance ultrafiltration membrane is 0.030~0.035mm, and the maximum pore size does not exceed 0.025mm. This can fully ensure that particles in the water with a size larger than 0.025mm, such as colloids, solid particles, viruses, bacteria, cryptospores, etc., are filtered out. This series of ultrafiltration membranes has a bacterial removal rate >6log, a virus removal rate >4log, and the SDI value of the effluent water quality is guaranteed to be ≤3. This ensures that the filtered effluent does not contain any suspended solids, maintains high quality for a long time, and can be used directly. The ultrafiltration membrane used in this project has excellent chemical corrosion resistance. Therefore, it can operate in the pH range of 1-13 and is resistant to oxidation. It can be used to treat chlorinated water and clean with strong oxidants.
The flow pattern of aqueous solution in the membrane can be divided into two types: full-flow filtration and cross-flow filtration. Full-flow filtration is generally suitable for groundwater with relatively clean water sources, while cross-flow filtration is generally suitable for surface water with poor water sources or reused water from sewage treatment plants. The ultrafiltration operation mode adopted in this project is cross-flow filtration. Each membrane module is 2.2 meters long, hollow fiber type, with an inner diameter of 0.7 mm. The membrane area of each membrane group is 75 m2.
The use of cross-flow filtration greatly reduces the membrane clogging frequency. The typical filtration pressure difference is 0.1~0.8bar. The solid particles deposited on the membrane surface are removed through regular air washing and water backwashing. This backwashing does not require the addition of any chemical cleaning agents. Solid contaminants are removed during regular backwashing, thus avoiding their deposition near the membrane.
The contaminants that are adsorbed on the membrane surface and cannot be removed by backwashing are removed through online chemically enhanced backwashing (CEB). At this time, the membrane module does not need to be removed and can be cleaned online. During the chemically enhanced backwash process, a small amount of chemical cleaning agent is added. After a short period of soaking (usually 5-10 minutes), the chemical cleaning agent is discharged, and the ultrafiltration membrane returns to a clean state like a new membrane. The ultrafiltration membrane used in the design of this project does not need to be disassembled and cleaned, thus avoiding possible cross-contamination caused by repeated use of cleaning agents. In addition, there is no need for manual monitoring during the operation of the equipment.
Requirements for designing ultrafiltration membranes
Compared with other membrane elements, the ultrafiltration membrane used in the plan has the following characteristics:
1) The highly integrated layout greatly reduces the equipment footprint;
2) High membrane flux and low operating pressure. The ultrafiltration membrane designed and used in this project requires a flux of 45l/m2h. Due to the high performance of the membrane, the operating pressure of the ultrafiltration system is very low, so the system only requires very low operating energy consumption.
3) The membrane material has strong oxidation resistance and can be operated and cleaned in a wide range of chemical environments. The pH value during cleaning can tolerate any range from 1 to 13. And with high oxidation resistance, the membrane can be used to treat chlorinated water and clean with strong oxidants such as sodium hypochlorite and hydrogen peroxide.
4) Through unique online enhanced chemical backwashing, the consumption of cleaning agents can be reduced, thereby reducing cleaning costs.
5) The ultrafiltration membrane system operates completely automatically: filtration, backwashing, and chemically enhanced backwashing are all monitored by the control system.
6) The normal service life of the ultrafiltration membrane reaches more than 3 years.
How ultrafiltration systems work
1) Water production
Open the automatic valves 2, 4, and 10 of the ultrafiltration system, and close the automatic valves 6, 8, 12, and 14; the membrane filtration working time is 20 to 60 minutes. In this state, according to the requirements of raw water quality or product water quality, the oxidizing bactericide is directly added to the membrane filtration raw solution system through the metering pump. Oxidants include chlorine, ozone, chlorine dioxide, sodium hypochlorite, etc., with a concentration of 0.5 to 10 ppm.
Gas and water backwashing: close automatic valves 2, 4, 6, and 10, open automatic valves 8, 12, and 14, start the backwash pump and adjust the backwash liquid flow to 0.3t/h·branch, and the cleaning gas flow to 2.5 to 5.0 m3/h·support, cleaning time is 20 to 60 seconds. When compressed air is introduced, the hollow fibers swing due to the effect of the upward airflow, causing the hollow fibers to rub and collide with each other, thereby peeling off the pollutants attached to the walls of the hollow fibers. The purpose of backwashing at this time is to loosen the deposits on the membrane surface and keep the membrane module filled with liquid, so as to maximize the effect of air oscillation. During backwashing in this state, oxidative cleaning chemicals can be added to the backwash liquid through the one-way valve 3 according to water quality requirements. Oxidants can be chlorine, ozone, chlorine dioxide, sodium hypochlorite, etc., with a concentration of 2 to 1000 ppm; acidic scale inhibitors, such as hydrochloric acid, etc.; alkaline degreasing agents, such as sodium hydroxide, etc. Depending on water quality needs, one or two chemicals can be added at the same time.
Water backwashing: close valves 2, 4, 10, and 14, open valves 6, 8, and 12, adjust the backwash flow to 2.3t/h·branch, and the cleaning time is 10 to 60 seconds. The purpose of this cleaning process is to wash away the pollutants on the membrane pores and hollow fiber membrane surface through large-flow backwashing, and to discharge the concentrated sewage through the lowest valve 6.
3) Sewage discharge or positive flushing
Close valve 12, keep the other valves in the same state as cleaning state 2, and discharge the residual concentrated sewage in the membrane module and membrane device pipeline through the lowest valve 6.
Open automatic valves 2 and 8, and close the remaining automatic valves. In this state, use raw water to discharge residual pollutants in the membrane module from the return port of the membrane module.
4) The water permeability of the membrane module changes with the water temperature. The operating temperature is 5～45℃
Membrane integrity testing
Membrane integrity is determined based on the rate of air flow, that is, the movement of air through the membrane under specific conditions. A complete ultrafiltration membrane is a gas-impermeable fiber filament, so for a complete membrane, the speed of gas flow is equal to the diffusion speed. Once there is a damaged membrane fiber, the gas will immediately penetrate directly into the water outlet. This results in a significant increase in the air flow rate and water discharge rate.
First, the water at the water inlet end is discharged, and then compressed air of a certain pressure is provided at the water inlet end. The air pressure flowing on the membrane surface can push the water to be discharged to the water outlet where the pressure is standard atmospheric pressure. The rate of water discharge at the water outlet can be measured by a flow meter installed at the water outlet.
This method can not only test a UF system or a part of a UF system, but also determine and determine in which pressure vessel the membrane filament has broken. However, to achieve this function, a water outlet isolation valve must be installed at each pressure housing. Since it is not necessary to test each membrane module to determine the location of membrane filament breakage, detection time is greatly saved.
The airflow method integrity test includes the following steps:
1) The ultrafiltration unit stops the filtration process
2) Discharge the water in the ultrafiltration unit from the water inlet end.
3) Pass compressed air into the ultrafiltration system at the water inlet end, and increase the pressure to 1bar. During this process, the remaining water at the water inlet end permeates the membrane under pressure, causing the gas flow rate to increase.
4) After waiting for a period of time, a stable flow will be obtained.
5) The test window displays the representative air flow rate.
6) Pressure relief of ultrafiltration unit
7) Ultrafiltration unit exhaust
8) The ultrafiltration device returns to filtration state or is on standby.
Reverse Osmosis (RO) Process Description
In this set of equipment, reverse osmosis (RO) is the core equipment of the system.
The RO membrane adopts anti-pollution rolled membrane modules suitable for the purchaser. The RO process is a pressure separation process using a semi-permeable membrane, which can effectively remove TDS in water.
During the operation of the RO process, while producing purified water, pollutants/salts are concentrated on the concentrated water side, exceeding the natural solubility in water, causing the concentrated water to easily scale. The process selects different scale inhibitors to destroy the formation of scale on the concentrated water side of the RO membrane and the crystal lattice structure to reduce the scaling tendency.
After the RO equipment has been running for a period of time, the pollutants on the concentrated water side have concentrated the various pollutants in the raw water 2-4 times. Due to concentration polarization, various types of dirt may be generated on the surface of the RO membrane, causing RO Membrane performance declines, water production decreases, and desalination rate decreases. At this time, chemical cleaning must be performed to restore the water permeability of the membrane. The cleaning cycle should be determined when the membrane operating pressure exceeds 10% under the same water production volume or when the water production volume decreases by 10% under the same pressure. The membrane flux recovery is better and the membrane water production volume can be restored to close to the original level.
When the RO system shuts down due to various reasons, the hardness of the water inside the membrane element is 4 times concentrated. When the water flow is stationary, it is easy to cause the deposition and structure of pollutants, and contaminate the membrane module. The designed RO system has an online automatic flushing device. When the system is shut down, the surface of the membrane element can be automatically flushed to replace the contaminated water on the membrane surface with purified water to reduce the contamination of surface sediments and ensure the normal life of the membrane element.
According to the specification requirements and usage habits, the RO water supply pump is designed to operate at power frequency, and the RO high-pressure pump is designed to operate at variable frequency;Key words:
Jinan Headquarters Address: 419.420, Dream Valley Building, Swallow Villa, Jingshi Road, Lixia District, Jinan City, Shandong Province
Zibo Engineering Center: Qilu E-commerce Valley, High-tech Zone, Zibo City, Shandong Province
Production and Processing Center: North Road, 150 m East of Chuangye Avenue and Songhua River Intersection, Xianchuang District, Zibo City, Shandong Province