Selection and application of reclaimed water reuse technology combination in building community?

What are the specific contents of the selection and application of water reuse technology combination in building communities? Zhong Da Consulting will answer your questions below.

1 reclaimed water in building community

Reclaimed water is a kind of non-potable water between sewage and tap water, which can be used in a certain field. Reclaimed water in cities is often used for greening, road cleaning and building toilet flushing, and is also regarded as the second water source of cities by more and more large and medium-sized cities. The main sources of reclaimed water include: urban sewage, cooling drainage, washing drainage, kitchen drainage, toilet drainage and so on.

Reclaimed water treatment and reuse [1] is a decentralized sewage treatment method. When centralized sewage treatment facilities and pipelines can not be implemented or the cost is high, decentralized treatment is an option to protect the water environment and save water resources, such as scenic spots, villages and towns. Building community is the smallest unit with sewage treatment device, with a stable sewage source and a large number of non-drinking water needs, such as greening, road washing, waterscape and so on. With the national and local protection of water resources and water environment, compared with urban sewage centralized pipe network and centralized treatment, the local treatment and reuse of residential sewage has greater economic and social benefits, and has also been supported by many cities' policies. For example, Dalian stipulates that a new residential area must be built in the afternoon of 20 14. Construction of reclaimed water facilities [2].

Compared with the centralized treatment of urban sewage, the technology of reclaimed water reuse in building communities needs three conditions: first, the stability of technical effect, the changing inlet water quality and the established recycling path require that the recycling technology needs stable outlet water quality; Second, the operability and simplicity of equipment and technology. Usually, the property management department maintains and operates facilities and equipment. The complex combination of systems and technologies is not conducive to the normal operation of facilities. It is a direction to realize automatic and unmanned treatment and recycling. Third, the economy of equipment and operation. The economy of reclaimed water reuse in residential quarters should be better than that of direct use of tap water to ensure the economic interests of owners and property management companies.

2 the choice of technology combination

2. 1 core technology

The core technology of water treatment directly determines the quality, stability and economy of effluent. Membrane bioreactor, biofilter and contact oxidation are commonly used core technologies in decentralized water treatment technology [3].

Membrane bioreactor is a wastewater treatment system combining membrane separation technology and biological treatment technology. The membrane module is used to replace the terminal secondary sedimentation tank of the traditional biological treatment technology, so as to maintain a high concentration of activated sludge in the bioreactor and increase the organic load of biological treatment, thereby reducing the occupied area of sewage treatment facilities, and reducing the amount of excess sludge by maintaining a low sludge load. Membrane bioreactor has the advantages of small floor space, good effluent quality, no need to set up a secondary sedimentation tank and simple operation and maintenance. Among them, the flat membrane MBR process [3] is more popular than the hollow membrane MBR process because of its sludge concentration as high as 15000 ~ 20000 mg/L, smaller floor space, online cleaning and less sludge production. However, the membrane is easy to be polluted [6], which limits the use of membrane bioreactor, and a large number of aeration and frequent cleaning make its operating cost higher. Most of them are used in urban sewage treatment, with a treatment capacity of less than 387.5 m3/d, and aeration accounts for 20% ~ 50% and 80% ~100% of the total energy consumption of split MBR and integrated MBR respectively [7].

Biological filter is a biological treatment structure composed of gravel or plastic product filler. Based on the principle of soil self-purification, artificial biological treatment technology for purifying sewage by contacting sewage with microbial membrane growing on the surface of filler [8]. The biofilter has good treatment effect, does not produce secondary pollution, and microorganisms can grow on the organic matter in the filler without adding additional nutrients. The biofilter has a large buffer capacity, can automatically adjust the peak concentration to make microorganisms always work normally, and has strong impact load resistance. Can be fully automatic control, very stable, can achieve unmanned operation. The tank body of the biological filter is assembled, which is convenient for transportation and installation; At the same time, the energy consumption is very low, and when the processing capacity is increased, only components need to be added, which is easy to realize and convenient for separate processing under the condition of dispersed gas sources. However, the slow sewage flow rate, small water treatment capacity and large equipment occupation area of the biological filter are its obvious defects. In addition, the biological filter has poor phosphorus removal effect because it is difficult to create an aerobic and anaerobic alternate environment [9].

Contact oxidation is a biofilm process between activated sludge process and biofilter, which is characterized by setting fillers (dispersed or suspended) in the tank, and aerating the bottom of the tank to oxygenate the sewage, so that the sewage in the tank is in a flowing state to ensure full contact between the sewage and the fillers. Biological contact oxidation can remove pollutants from domestic sewage. Firstly, the filler and biofilm have adsorption and retention effects on organic matter, and then the organic matter is decomposed aerobically under the action of microorganisms. Biological contact oxidation method has the advantages of less excess sludge, strong impact load resistance and simple operation and management [4]. The research shows that [5] biological contact oxidation method is obviously superior to activated sludge method in treatment effect, power consumption, economic benefit and maintenance management, and has achieved satisfactory results in the treatment of organic wastewater and domestic sewage.

The above three core technologies have their own advantages and disadvantages, and they are also applied in water treatment engineering practice of buildings and communities. It can be selected according to the water consumption scale of the community, the size of the available plots, the professionalism of property management and other factors.

2.2 disinfection technology

Disinfection is a necessary step of sewage treatment, and disinfection is also an important post-treatment step in the process of water treatment and utilization in residential quarters. Disinfection methods are usually chemicals (solid, liquid, gas), ultraviolet rays, etc. Sodium hypochlorite, ultraviolet rays and ozone are mainly used in the process of sewage regeneration. Different disinfection technologies are suitable for different processes. The combined disinfection process of ozone and sodium hypochlorite should be selected for disinfection of sand filtration effluent, which can greatly reduce the ecological safety risk of effluent use. Disinfecting MBR effluent with sodium hypochlorite, ultraviolet rays and ozone alone has a good removal effect on microorganisms [10].

Besides the effect, the choice of disinfection technology or disinfectant should also consider the particularity of buildings and communities. Sodium hypochlorite is a strong alkali, which can be liquid or solid powder. Its use and preservation should avoid light and heat sources, and people should also be avoided during use. The disinfectant has a wide range of uses and strong disinfection ability, and is widely used in building communities. The disinfection effect of ultraviolet lamp is good, and the impact on environment and people can be minimized through equipment design and shielding, but a larger disinfection area is needed to meet the requirements of its transmission depth and irradiation time. Ozone disinfection has good operability [1 1], easy to realize automatic control, small floor space and fast reaction speed, and is an excellent water disinfection technology in building communities. 20 16 June Green Science and Technology Issue 12

Peng Li, etc. Selection and application of water reuse technology combination in building community.

Environment and safety

Application of reclaimed water reuse technology in No.3 residential area

Reclaimed water reuse has been widely used in various projects in building communities and achieved good results. See table 1 for the engineering application of reclaimed water reuse technology in residential areas, including core technology and disinfection technology, operating cost, effluent quality standard and water quantity.

From the table 1, it can be seen that contact oxidation and MBR technology are the core technologies mainly used in engineering, and ozone disinfection is the main disinfection technology. Two-stage series contact oxidation enhances the impact load resistance of the system and ensures the effluent quality. It is reported that in 2000, Beijing investigated and evaluated four reclaimed water projects completed in one year, and found that 1 project adopted biological contact oxidation method, accounting for 85%.

Most of the water sources in the community are domestic sewage, and the effluent after septic tank treatment is used as raw water, while the less polluted wastewater such as bathing, washing, laundry and rainwater is also good raw water if the collection system allows it. Reclaimed water is mostly used for domestic miscellaneous purposes such as landscape, greening water or toilet flushing, and the Water Quality Standard for Urban Wastewater Reuse (GB/T 18920-2002) is also adopted, and relevant standards such as agricultural irrigation production water are also adopted as needed.

At present, the operation, management, maintenance and business model of reclaimed water treatment system are not perfect. Many reclaimed water systems are designed and built together with residential buildings, but the main body of the system is property companies, developers or government departments, and the costs, benefits and property rights involved are not clear, which may lead to problems in operation and management. Private capital can be supplied independently or through BOT and TOT.

4 conclusion

The core technologies of water treatment in building communities mainly include membrane bioreactor, contact oxidation and biofilter. Membrane bioreactor has good effluent quality, small floor space and convenient operation, but the membrane is easy to be polluted and the operating cost is high. Contact oxidation method has the advantages of small floor space, simple operation and management, low operating cost and so on, and is suitable as the core process of water treatment in building communities. Ozone disinfection is easy to realize automatic control, occupies a small area and can be used immediately. It is an excellent water disinfection technology for building communities.

Reclaimed water reuse has been widely used in various projects in building communities and achieved good results. Contact oxidation is mostly used in the project. The raw water comes from the domestic sewage in the residential area, and the water quality standard for reuse also adopts the water quality standards for urban sewage reuse and urban miscellaneous water. The operation, management, maintenance and business model of reclaimed water treatment system are not perfect, and private capital and market-oriented mechanism have the possibility and conditions to enter.

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