Analysis and application of residential sewage treatment technology?

The following is the analysis and application of domestic sewage treatment technology brought by Zhong Da Consulting for your reference.

Fresh air, tree-lined, quiet and comfortable ecological environment has become the development concept of modern residential quarters. However, with the acceleration of urbanization, the most direct manifestation is that water consumption is increasing, urban pollution is becoming more and more serious, and water resources are becoming more and more tense. How to solve the contradiction between urban construction and water shortage, sewage treatment and reuse is the most direct and important way to reuse urban water resources. Reuse of domestic sewage after treatment can not only beautify the living environment, but also reduce the waste of water resources, thus protecting the environment and reducing pollution.

First, the characteristics of sewage in residential areas

1. The main source of sewage

Residential sewage is mainly domestic sewage, including toilet sewage, kitchen sewage and washing sewage.

2. The main components of sewage

Domestic sewage contains a lot of organic substances such as fiber, grease, starch, protein, inorganic substances such as vegetable leftovers, silt, domestic impurities, and pathogenic bacteria such as viruses and parasite eggs. The concentration of pollutants in domestic sewage is generally low, and BOD5/CODcr is usually around 0.5, which has good biodegradability.

3. Characteristics of sewage generation

Due to the single composition of people in the residential area, most of them are staff and students, and a few are idle people. The water consumption time is very concentrated, mainly at three meals and before going to bed, and the water consumption changes greatly, which also causes the sewage volume to change greatly.

Second, the treatment process of sewage reuse in residential areas

Because of the good biodegradability of sewage in residential areas, biochemical treatment can be adopted. After the effluent reaches the standard, it can be used for greening, landscape water use, road irrigation, car washing, etc.

1. Sewage treatment process

Septic tank → primary treatment (primary sedimentation tank) → biochemical secondary treatment → advanced treatment (coagulation and filtration) → disinfection → reuse.

Due to the small amount of sewage treatment in the residential area, the property management personnel are not necessarily professional. According to the characteristics of sewage in the residential area, the treatment process with less investment, land saving, simple operation, reliable technology and unmanned management must be adopted. In the process design, try to choose a treatment process with less sludge to prevent environmental pollution caused by inadequate sludge treatment.

2. Process suitable for sewage treatment in residential areas

(1) sequencing batch batch batch activated sludge process (SBR process) or CASS process.

SBR process is short for sequencing batch activated sludge process. It has the characteristics of small floor space, low investment, high degree of automation, less sludge, easy precipitation, phosphorus and nitrogen removal, and its effect is better than other aerobic treatment methods. The process consists of reactors that run intermittently in a certain time sequence.

CASS reaction tank is a new technology developed on the basis of SBR process, that is, a biological selector is added at the inlet end of SBR tank to realize continuous water inflow (continuous water inflow in sedimentation period and drainage period) and intermittent drainage. It has the characteristics of small volume, low cost, high degree of automation, high treatment efficiency and phosphorus and nitrogen removal, and is an ideal process for domestic sewage treatment in residential areas. The recycling process is as follows: sewage → grille → regulating tank → lifting pump →SBR or CASS→ filtration → disinfection → effluent reuse.

(2) biological contact oxidation method

Biological contact oxidation is a kind of sewage biological treatment technology between activated sludge process and biofilm process, which has both advantages and is one of the earliest technologies applied to domestic sewage treatment in residential quarters. It has the characteristics of small floor space, strong impact load resistance, many kinds of organisms, less sludge and easy precipitation, no sludge reflux, phosphorus and nitrogen removal and so on. The process is as follows: the biological reaction tank is filled with fillers, and the oxygen-containing sewage submerges all the fillers and flows through the fillers 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.

The recycling process is as follows: sewage → grille → regulating tank → lift pump → contact oxidation tank → sedimentation tank → filtration → disinfection → effluent reuse.

(3) Two-stage activated sludge process (AB process)

Two-stage activated sludge process, abbreviated as AB process. It has the characteristics of strong impact load resistance, stable treatment effect, low operating cost, phosphorus and nitrogen removal and so on. The process is as follows: no primary sedimentation tank is set, the load of grade A is high, the load of grade B is low, and the sludge of grade A and grade B flows back respectively, so as to make full use of the metabolism of microorganisms in the sludge and remove the organic pollutants in the sewage.

The recycling process is as follows: sewage → grille → top air conditioning tank →A-level aeration tank →A-level sedimentation tank →B-level aeration tank →B-level sedimentation tank → filtration → disinfection → effluent reuse.

(4) Anaerobic/aerobic process

A/O process, namely anoxic-aerobic sewage treatment process. It has the characteristics of strong adaptability, impact load resistance, high volume load, less sludge and good denitrification effect, and is especially suitable for small and medium-sized sewage treatment stations. Firstly, the sewage is introduced into an anoxic tank, and the denitrifying bacteria in the returned sludge use the organic matter in the original sewage as a carbon source to reduce a large amount of nitrate nitrogen in the returned mixed liquid into nitrogen, thus achieving the purpose of denitrification; Then the sewage enters the aerobic tank, where most of the organic matter is digested and degraded. A secondary sedimentation tank is arranged behind the aerobic tank, and part of the precipitated sludge flows back to the anoxic tank to provide sufficient microorganisms. At the same time, the mixed liquid in the aerobic tank is returned to the anoxic tank to ensure that there is enough nitrate in the anoxic tank. The recycling process is as follows: sewage → primary sedimentation tank → anoxic tank → aerobic tank → secondary sedimentation tank → filtration → disinfection → effluent reuse.

(5) Anaerobic biofilter

Anaerobic biofilter is an anaerobic biofilm treatment device with filler as microbial carrier. It has the characteristics of no energy consumption, low cost, simple management, no noise, no odor, fast film formation, less excess sludge, good effluent quality and stable operation effect. The process is as follows: anaerobic microorganisms grow on the surface of the carrier, and when the sewage passes through the fixed bed formed by the carrier from bottom to top, under the action of anaerobic microorganisms, the organic matter in the sewage is anaerobically decomposed to produce biogas. The essence of this process is similar to that of A/O process, except that facultative anaerobic biofilter strengthens the anaerobic stage. The recycling process is as follows: sewage → sedimentation tank → anaerobic digester → anaerobic biofilter → exhaust pipe → oxidation ditch → inlet and outlet wells → filtration → disinfection → effluent reuse.

3. Sewage reuse technology

(1) membrane technology

The effluent of residential domestic sewage is treated by reverse osmosis (RO) and other membrane technologies for secondary treatment and advanced treatment, and the effluent can be used as industrial water or domestic water. Membrane technology mainly refers to membrane separation technologies such as nanofiltration, ultrafiltration, osmosis and reverse osmosis. Membrane technology has high investment cost and troublesome operation and management, and is rarely used in domestic advanced sewage treatment.

(2) Membrane bioreactor

Membrane bioreactor (MBR) is an efficient sewage treatment technology that combines membrane separation technology with traditional sludge process. Because of membrane filtration, organisms are completely trapped in the bioreactor, which realizes the complete separation of hydraulic retention time and sludge age, and keeps the bioreactor with high MLSS, strong nitrification capacity and high pollutant removal rate. As a new sewage treatment and reuse technology, MBR has a good application prospect in residential sewage reuse, but the membrane itself is expensive, the operating system is complex and the running cost is high, so it is rarely used in residential sewage reuse treatment.

(3) Multi-media filter

Multi-media filter (filter bed) is a media filter that uses more than two media as the filter layer, also known as mechanical filter. Commonly used filter materials are quartz sand, anthracite, activated carbon, magnetite, garnet, porous ceramics, plastic balls and so on. It is used to remove suspended or colloidal impurities in sewage, absorb oil stains, especially to effectively remove tiny particles and bacteria that can not be removed by precipitation technology, so that the effluent quality can meet the reuse requirements. It is a common treatment method for advanced sewage treatment.

Third, the engineering example

Take the living area where the author lives as an example. The residential area is a newly-built high-grade residential area with complete living facilities and 24-hour hot water. The population is about 1.200, and the per capita water consumption standard is 300 L/d. ..

1. Maximum design sewage volume

1200× 300/100× 0.80 = 288 m3/day (12 m3/hour).

2. Design sewage quality

( 1)pH = 7.5；

(2)COD = 360mg/L；

(3)bo D5 = 200mg/L；

(4)SS = 180mg/L；

(5) N-NH4 = 25mg/L. 。

3. Design effluent quality

The treated effluent quality meets the standard requirements of Landscape Environmental Water Quality for Urban Wastewater Reuse (GB/T 1892 1-2002), that is, pH=6.0-9.0, COD≤50mg/L, BOD5≤6mg/L and SS ≤1.

4. Adopt processing technology

The residential area adopts underground sewage treatment integrated equipment with a treatment capacity of 15m3/h, and the ground is used for greening or landscape. The secondary treatment adopts A/O method, and the tertiary treatment adopts multi-media filter. After being disinfected by hypochlorous acid, it can be reused as landscape water and residential landscape water. The generated odor is deodorized by soil and surrounding flowers and plants. The whole set of equipment adopts automatic control and alarm system, which is unattended and only needs regular maintenance, and the operation and maintenance are relatively simple.

Fourth, benefit analysis.

The total investment of the project is 450,000 yuan, and the operating cost is 0.50 yuan, which is lower than the sewage charge standard. Taking COD as an example, the design COD of sewage is 360 mg/L, the remaining 50mg/L in the circulating water after treatment, and the treated COD is 310 mg/L. According to the sewage treatment capacity of 288m3/d, the maximum amount of COD can be reduced by 0.09kgCOD per day, and the discharge of COD in a community can be reduced by 32.85 kg per year.

Construction of residential sewage treatment and reuse station, the effluent can be used for planting aquatic plants in constructed wetlands, breeding fish and ducks in landscape ponds, spraying lawns, watering trees and so on. It not only achieves the effect of saving water resources by sewage treatment and reuse, but also reduces the load of urban sewage treatment and improves the living environment of residential areas, which has considerable environmental benefits. Reuse of sewage after treatment is the best way to save water and control pollution, which is imperative.

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