Reclaimed water reuse technology and its application analysis?

Sewage reuse includes the reuse of urban sewage, industrial sewage and domestic sewage in building communities. Among them, the reuse of water in buildings refers to the domestic miscellaneous drainage of concentrated residential quarters and dense buildings, which is collected and treated on the spot and used for washing, greening and other domestic miscellaneous purposes in nearby buildings and residential quarters. Reclaimed water reuse not only saves water resources, but also reduces the load of urban water supply and drainage networks and treatment facilities, which is an effective way to solve the problem of water shortage.

Introduction of reclaimed water reuse technology

It is characterized by using various physical, chemical, biological and other means to treat industrial wastewater with different depths to achieve the water quality required by the process, and then reuse it in the process, thus achieving the purpose of saving water resources and reducing environmental pollution. There are two main recycling technologies:

1. 1 cooling water technology

Saving cooling water is the main way to save water in industry;

1, change direct cooling water into indirect cooling water.

In the cooling process, especially in the chemical industry, if the direct cooling method is adopted, more pollutants will often be entrained in the cooling water, making it lose its reuse value. This disadvantage can be overcome if indirect cooling can be used instead.

2. Reduce cooling demand and cooling water consumption.

3. Non-water cooling is adopted.

For example, in the production of a certain process, air cooling or oil cooling is used to achieve the purpose of cooling.

4. Use artificial cold source or seawater as cooling water to reduce the amount of groundwater or fresh water.

5. Rational use of cooling water.

The used cooling water can be reused after certain cooling measures, and can also be used in other occasions with low requirements on water quality and water temperature after being used as cooling water for the first time.

When adopting this method, we should pay attention to the close cooperation of water supply systems in various workshops, strengthen the management of cooling water, and avoid affecting the water supply in other workshops because of problems in one link.

6. Recycling of cooling water

This cooling water utilization technology mainly refers to that the hot water changed by the cooler lowers the water temperature to the water temperature of recycled water through the cooling structure, so as to be recycled.

When the cooling water is recycled, attention should be paid to the problems such as the reproduction of bacteria, the formation of scale, the corrosion of equipment, the change of water pressure and water quantity.

1.2 One-water multi-purpose or sewage purification and reuse

Due to the different water quality standards of each link in the production process, some links of water can be reused or used in other links with low water quality requirements after proper treatment. So as to achieve the purpose of saving water. For example, clean water can be used as cooling water first, and then sent to a water treatment station for softening, and used for boiler water supply. Urban sewage is used for production and life after centralized treatment.

Examples of reclaimed water reuse technology

Let's briefly introduce the water in life.

Domestic water mainly refers to the miscellaneous use of domestic sewage after being treated to meet the use standard, such as flushing toilets, greening, landscape, spraying roads, supplementing cooling water, etc. The quality of reclaimed water should meet the water quality standard of domestic miscellaneous water.

1, reclaimed water source

When selecting reclaimed water, you should first choose high-quality miscellaneous drainage water, which can generally be selected in the following order:

A, cooling water B, shower drainage C, washing drainage D, laundry drainage E, kitchen drainage F, toilet drainage

2. Processing technology

When high-quality miscellaneous drainage and miscellaneous drainage are used as the source of reclaimed water, the technological process mainly based on physical and chemical treatment can be adopted, or the technological process combining biological treatment and physical and chemical treatment can be adopted.

When domestic sewage is used as renewable water source, two-stage biological treatment or a combination of biological treatment and physical and chemical treatment can be adopted.

3, water design and construction regulations

All construction projects should be designed in accordance with regulations, and water facilities must be designed and built in the following situations:

A the construction area of hotels (brigades), restaurants, shops, apartments, comprehensive service buildings and high-rise residential buildings is over 20,000 square meters. B. Institutions, scientific research institutions, institutions of higher learning and large-scale comprehensive cultural and sports facilities with a building area of over 30,000 square meters.

C. The planned population of the residential area is more than 30,000 people (or the reclaimed water reuse amount is more than 750 cubic meters/day).

The management of reclaimed water facilities shall be implemented in accordance with the Interim Measures for the Management of Urban Reclaimed Water Facilities issued by the Ministry of Construction, and the design of reclaimed water facilities shall be implemented in accordance with the Code for Design of Reclaimed Water in Buildings compiled by China Engineering Construction Standardization Association.

2. Water quality requirements for reclaimed water reuse

The quality of reclaimed water must meet the following conditions:

2. 1 meets the hygiene requirements. Its indicators mainly include the number of coliforms, the total number of bacteria, residual chlorine, suspension toughness, cod, bod5, phosphide and so on.

2.2 Satisfy people's sensory requirements, that is, all quick feelings. Its measurement indicators mainly include turbidity, chromaticity, odor and so on.

2.3 meet the requirements of equipment structure, that is, the water quality is not easy to cause serious corrosion and scaling of equipment and pipelines. Its determination indexes include ph value, hardness, evaporation residue, soluble matter and so on.

In recent years, the research on reclaimed water in China has become more and more in-depth. In order to ensure the safe, reliable and reasonable utilization of reclaimed water as domestic miscellaneous water, 1989 officially promulgated the Water Quality Standard for Domestic Miscellaneous Water (cj25 1-89).

3. Standards and methods of reclaimed water reuse

3. 1 Domestic Urban Miscellaneous Water Standard

The Water Quality Standard for Domestic Miscellaneous Water (cj25. 1-89) issued by the Ministry of Construction 1989 is the first ministerial standard on the water quality of urban miscellaneous water in China. This standard specifies the water quality requirements for domestic miscellaneous water such as toilet flushing, urban greening, car washing and cleaning. In 2002, Zhongnan Municipal Design and Research Institute revised the standard and raised it to the national standard (gb/t 18920—2002 "Water Quality of Urban Sewage Reuse for Urban Miscellaneous Water"). In the revision, the application scope of miscellaneous water was adjusted, and water for fire fighting and building construction was increased.

3.2 Reclaimed water reuse method

Cities can choose different recycling methods according to sewage treatment capacity and local conditions. Generally speaking, there are the following types: ① selective reuse, that is, laying pipelines in some communities around sewage treatment plants to implement water supply reuse in different quality; (2) Zoning reuse mode, that is, according to the urban conditions, the sewage is recycled by zones; (3) The whole city circulation method, that is, laying reclaimed water pipelines in the whole city, is suitable for new towns and small towns with sewage treatment capacity.

4. Main ways of reclaimed water reuse

4. 1 industrial recycling.

According to different uses, the wastewater discharged from sewage treatment plants can be directly or after further treatment used in industrial production to achieve higher water quality, such as cooling water, quenching water and slag water, hydraulic conveying slag water, watering the factory green space, cleaning the ground, equipment and vehicles and fire fighting water, among which the most common and representative use is industrial cooling water.

4.2 Other uses of the city

The ways of urban reclaimed water reuse mainly include the following aspects: first, the flushing water for urban domestic toilets; Second, urban commercial water (such as car washing industry); Third, road sprinkling and urban green space irrigation; Fourth, non-contact landscape water and fire water. Among them, urban domestic water is a relatively stable water channel, and road spraying water and urban green space irrigation have certain seasonality.

4.3 Agricultural irrigation

The wastewater discharged after treatment by sewage treatment plant can meet the water quality standard of agricultural irrigation water only by simple filtration, and its environmental sanitation and agricultural products sanitation are in good condition. Reclaimed water is used to irrigate farmland. Through the mechanisms of soil filtration, adsorption, ion exchange, chemical reaction, soil microbial metabolism and crop root absorption, water quality is further purified, soil structure is improved, water and fertilizer content is increased, crop yield is increased, a large amount of chemical fertilizer is saved, and good economic benefits are obtained. When reclaimed water is reused for agricultural irrigation, it is generally necessary to build some storage irrigation projects to achieve the purpose of full utilization. Agricultural irrigation water is obviously affected by seasonality.

4.4 Water conservancy project

4.4. 1 urban secondary river landscape water body. The state has formulated water quality standards for landscape water, and the effluent quality of secondary sewage treatment plants is similar to that of river landscape water. After re-processing, all health indicators can meet the standard. As long as the river is flowing, it has a certain self-purification ability, which not only improves the urban landscape, but also provides water channels for reclaimed water reuse units on both sides of the river.

4.4.2 Used for storage and restoration of underground aquifers. Due to over-exploitation of groundwater, the ground sank. In order to control the settlement, in addition to restricting or prohibiting mining, recharge measures should be taken. Reclaimed water can be used as one of the reinjection sources, but it can only be reinjected after further treatment meets the requirements of groundwater reinjection quality.

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