Urban sewage (municipal sewage) is the general name of sewage discharged into urban sewage system. In the combined drainage system, it also includes production wastewater and intercepting rainwater.
Urban sewage mainly includes domestic sewage and industrial sewage, which is collected by urban drainage pipe network and transported to sewage treatment plant for treatment.
I. Emission standards
According to the information provided by the construction unit, the average displacement is 40m? /h
Attached Table: Water Quality Standards for Sewage Inlet and Discharge
CODcr
(mg/L)
Biochemical oxygen demand (mg/L)
sage
(mg/L)
Animal and vegetable oil
(mg/L)
ammonia nitrogen
(mg/L)
pH value
Sewage inflow quality
350
180
200
take no account of
35
6-9
GB8978-88
100
30
100
15
6-9
Note: The attached data are obtained according to the data provided by the owner and the Implementation Manual of Water Supply and Drainage Standards and Specifications, in which Party A requires SS effluent standard to be100 mg/L. ..
Second, the treatment plan
Domestic sewage is generally treated by biochemical method at home and abroad, because the BOD5/CODcr of domestic sewage is ≈ 0.5, which is highly biodegradable. The contact oxidation method has the advantages of high volume load, short residence time, good organic matter removal effect, simple operation and small occupied area. Therefore, we choose the contact oxidation method with mature technology and reliable operation. (bod injection is biological oxygen demand and cod is chemical oxygen demand. )
Third, the design basis
1, GB 189 18-2002 discharge standard of pollutant concentration for urban sewage treatment plants
2. Water Quality of Urban Miscellaneous Water for Urban Sewage Reuse GB/T 18920-2002
Fourth, deal with the problem.
The treatment process of urban sewage is generally based on the utilization or discharge direction of urban sewage, and considering the natural purification ability of water body, to determine the degree of sewage treatment and the corresponding treatment process. Whether the treated sewage is used for industry, agriculture or groundwater recharge, it must meet the relevant water quality standards promulgated by the state.
Modern sewage treatment technology can be divided into primary, secondary and tertiary treatment processes according to the degree of treatment. Physical methods, such as screening and precipitation, are used to remove insoluble suspended solids and floating objects in the primary treatment of sewage. The secondary treatment of sewage is mainly the application of biological treatment method, that is, the process of substance transformation through microbial metabolism, which oxidizes and degrades all kinds of complex organic substances in sewage into simple materials. Biological treatment has certain requirements for sewage quality, water temperature, dissolved oxygen in water and pH value. The tertiary treatment of sewage is based on the primary and secondary treatment, using physical and chemical methods such as coagulation, filtration, ion exchange and reverse osmosis to remove insoluble organic matter, phosphorus, nitrogen and other nutrients in sewage. The composition of pollutants in sewage is very complex, and the combination of the above methods is often needed to meet the treatment requirements.
The primary treatment of sewage is mainly pretreatment, and the secondary treatment is the main body. The treated sewage can generally meet the discharge standard. Tertiary treatment is advanced treatment, and the effluent quality is good, even reaching the drinking water quality standard, but the treatment cost is high, and it is rarely used except in some countries and regions that are extremely short of water. Many cities in China are planning to build and expand secondary sewage treatment plants to solve the increasingly serious water pollution problem.
Verb (short for verb) treatment method
Physical treatment method:
Wastewater treatment methods for separating and recovering insoluble pollutants (including oil film and oil beads) in wastewater by physical action can be divided into gravity separation method, centrifugal separation method and screen filtration interception method. The treatment method based on heat exchange principle also belongs to physical treatment method.
Chemical treatment method:
A wastewater treatment method is characterized in that dissolved and colloidal pollutants in wastewater are separated and removed or converted into harmless substances through chemical reaction and mass transfer. In the chemical treatment method, the treatment units based on the chemical reaction caused by adding chemicals include coagulation, neutralization, redox and so on. The treatment units based on mass transfer include extraction, stripping, stripping, adsorption, ion exchange, electrodialysis and reverse osmosis. The latter two treatment units are also called membrane separation technology. Among them, the treatment unit using mass transfer has both chemical action and physical action related to it, so it can also be separated from the chemical treatment method and become another treatment method, which is called physical chemistry method. Domestic sewage treatment
Biological treatment method:
Through the metabolism of microorganisms, organic pollutants in solution, colloids and fine suspended solids in wastewater are transformed into stable and harmless substances. According to different microorganisms, biological treatment can be divided into aerobic biological treatment and anaerobic biological treatment. Aerobic biological treatment is widely used in wastewater biological treatment. Traditionally, aerobic biological treatment is divided into activated sludge process and biofilm process. Activated sludge process itself is a kind of treatment unit, which has many operation modes. The treatment equipment of biofilm process includes biological filter, biological turntable, biological contact oxidation tank and biological fluidized bed. Biological oxidation pond method is also called natural biological treatment method. Anaerobic biological treatment, also known as biological reduction treatment, is mainly used to treat high-concentration organic wastewater and sludge. The processing equipment used is mainly digester.
Biological contact oxidation method:
The biological contact oxidation method is used to treat wastewater, that is, the biological contact oxidation process is used to fill the filler in the biological reaction tank, and the oxygenated sewage submerges all the filler and flows through the filler at a certain flow rate. The filler is covered with biofilm, and the sewage is in extensive contact with biofilm. Under the action of microbial metabolism on biofilm, organic pollutants in sewage are removed and sewage is purified. Finally, the treated wastewater is discharged into the biological contact oxidation treatment system for mixed treatment with domestic sewage, and the chlorine gas is disinfected and discharged up to the standard. Biological contact oxidation is a biofilm process between activated sludge process and biofilter, which is characterized in that fillers are arranged in the tank, and the sewage in the tank is oxygenated through bottom aeration, so that the sewage is in a flowing state to ensure full contact with the fillers immersed in the sewage and avoid the defect of uneven contact between the sewage and the fillers in the biological contact oxidation tank. This aeration device is called blast aeration.
Sixth, the treatment process
A, sewage treatment station equipment level 1 enhanced treatment process:
The primary enhanced treatment should be based on the planning requirements and construction scale of urban sewage treatment facilities, and technologies such as physical and chemical enhanced treatment, AB process, hydrolytic aerobic process and high-load activated sludge process should be selected.
Second, the sewage treatment station equipment secondary treatment process:
1 day sewage treatment facilities with a treatment capacity of more than 200,000 cubic meters (excluding 20 cubic meters/day) generally adopt the conventional activated sludge method, and other mature technologies can also be adopted.
2. For sewage treatment facilities with daily treatment capacity of100 ~ 200,000 cubic meters, mature processes such as conventional activated sludge process, oxidation ditch process, SBR process and AB process can be selected.
3. For sewage treatment facilities with daily treatment capacity less than 10 cubic meter, oxidation ditch method, SBR method, hydrolytic aerobic method, AB method, biological filter and other technologies can be selected, and conventional activated sludge method can also be selected.
Three, sewage treatment station equipment secondary enhanced treatment:
1, the two-stage enhanced treatment process refers to the treatment process with strong phosphorus and nitrogen removal functions in addition to effectively removing carbon source pollutants.
2. In areas where nitrogen and phosphorus pollutants are required to be controlled, sewage treatment facilities with daily treatment capacity of100,000 cubic meters generally adopt technologies such as A/O method and A/A/O method, and other technologies with the same effect can also be carefully selected.
3. In addition to A/O method and A/A/O method, oxidation ditch method, ABR method, hydrolytic aerobic method and biological filter method with phosphorus and nitrogen removal effects can also be used for sewage treatment facilities with daily treatment capacity below100000 cubic meters.
4. If necessary, physical and chemical methods can also be used to strengthen the phosphorus removal effect.
Four, sewage treatment station equipment natural purification process:
1. Under the conditions of strict environmental impact assessment, compliance with relevant national standards and self-purification capacity requirements of water bodies, the disposal method of urban sewage discharged into rivers or deep seas can be cautiously adopted.
2. Conditional areas can make use of available conditions such as wasteland and idle land, and adopt various types of natural purification technologies such as land treatment and stabilization ponds.
3. When the secondary treatment effluent of urban sewage cannot meet the requirements of water environment, natural purification technologies such as land treatment system and stabilization pond can be used for further treatment if conditions permit.
4, using land treatment technology, should strictly prevent groundwater pollution.
Five, sewage treatment station equipment sludge treatment:
1. Sludge produced by municipal sewage treatment should be treated stably by anaerobic, aerobic and composting methods. It can also be properly disposed of by sanitary landfill.
2, the daily processing capacity of more than one hundred thousand cubic meters of sewage sludge produced by secondary treatment facilities, anaerobic digestion process should be adopted for treatment, biogas should be comprehensive utilization.
3. Sludge produced by sewage treatment facilities with daily treatment capacity less than100000 cubic meters can be composted and comprehensively utilized.
4. For sewage treatment facilities that adopt oxidation ditch method, SBR method and other processes to extend aeration, sludge should be stabilized. Sewage treatment facilities with physical and chemical first-level intensive treatment should properly treat and dispose of the generated sludge.
5. The treated sludge can be used in farmland if it meets the requirements of stabilization and harmlessness; Sludge that cannot be used for farmland should be disposed of in sanitary landfill according to standards and requirements.
Seven, processing equipment
Electromagnetic flowmeter The measuring principle of electromagnetic flowmeter is programmed according to Faraday's electromagnetic law, digital excitation is realized by embedded technology of single chip microcomputer, and it can also be equipped with 4-20MA current output signal for recording or mediation. The main components of the sensor are: measuring tube, electrode, excitation coil, iron core and shell. HNLD electromagnetic flowmeter is mainly used to measure the volume flow of conductive liquid and liquid in closed pipeline, including acidic liquid, alkaline liquid and salty liquid, and is widely used in chemical industry, petroleum, textile, papermaking, metallurgy, pharmacy and water treatment, environmental protection, municipal management, water conservancy construction and other industrial fields. Orifice flowmeter is the finalized product of Jiangsu Huaneng Automation Instrument Co., Ltd. Orifice flowmeter is a newly developed pressure difference generating device, in which throttling device includes orifice valve core and nozzle. It can measure the flow of various fluids in the pipeline with differential pressure transmitter or pressure transmitter, three-valve resistor and condenser. The measurable media are liquid, gas and steam, which are widely used in petroleum, chemical industry, metallurgy, light industry, coal mine and other industrial sectors.