Installation and commissioning of pure water equipment, reverse osmosis equipment and water treatment equipment in Shenzhen Hongjie water production Co., Ltd

What is the relationship between water quality grade and sewage treatment standard? When negotiating sewage treatment projects, customers often ask: what kinds of effluent quality can your equipment and projects achieve. In fact, the effluent standard and water quality classification of sewage treatment equipment are different concepts. Today, let's talk about water quality grade and sewage treatment standard.

Water quality grade

According to the environmental functions and protection objectives of surface water areas, China divides the water quality into five categories, and the water of each level is clearly distinguished from the function and use.

Class I. It is mainly applicable to source water and national nature reserves. This kind of water can be used as drinking water after simple treatment and disinfection. Typical class I water quality lakes are Erhai Lake, Fuxian Lake, Lugu Lake and Bangong Lake, while the famous Qiandao Lake is an important reservoir with class I water quality.

Class I water is mostly clear to the bottom

Class II. It is mainly applicable to the first-class protection area of the surface water source of centralized domestic and drinking water, the habitat of rare aquatic organisms, the spawning ground of fish and shrimp, the feeding ground of larvae and juveniles, etc. Class II water can also be used as drinking water after purification treatment (such as flocculation, sedimentation, filtration, disinfection, etc.).

Class II water

Class III. It is mainly applicable to centralized domestic and drinking water surface water source secondary protection area, fish and shrimp wintering ground, migration channel, aquaculture area and other fishery waters and swimming areas. This kind of water needs to be deeply treated before it can be used for domestic drinking.

Class III water

Class IV. It is mainly applicable to general industrial water areas and entertainment water areas in which human body is not in direct contact.

Class IV water

Class v. It is mainly applicable to agricultural water areas and water areas with general landscape requirements.

Class V or inferior class V

Standard limit of basic items of surface water environmental quality standard unit: mg / L

The water quality grade is calculated according to up to 80 indicators such as dissolved oxygen, metal elements, microorganisms and chemicals in the water. Of course, there are obvious differences in the appearance characteristics of all kinds of water. Water quality grade and sewage treatment standard are different concepts.

Sewage treatment standard

According to the environmental functions and protection objectives of urban sewage treatment plants discharged into surface waters and the treatment process of sewage treatment plants, the standard values of conventional pollutants of basic control projects are divided into class I standards, class II standards and class III standards. The first level standard is divided into a standard and B standard. Some class I pollutants and selected control items are not classified.

Class A and class B refer to the provisions in the discharge standard of pollutants for urban sewage treatment plants (GB18918-2002):

Standard a of the first level standard is the basic requirement for the effluent of urban sewage treatment plant as reuse water. When the effluent from the sewage treatment plant is introduced into rivers and lakes with small dilution capacity as urban landscape water and general reuse water, the a standard of the first level standard shall be implemented.

When the effluent from urban sewage treatment plant is discharged into gb3838 surface water class III functional waters (except the designated drinking water source protection area and swimming area), gb3097 seawater class II functional waters and closed or semi closed waters such as lakes and reservoirs, standard B of class I standard shall be implemented.

The effluent from urban sewage treatment plant shall be discharged into gb3838 surface water class IV and V functional waters or gb3097 sea water class III and IV functional waters, and the secondary standard shall be implemented.

For sewage treatment plants in non key control basins and established towns in non water source protection areas, when the first-class enhanced treatment process is adopted according to the local economic conditions and water pollution control requirements, the third-class standard shall be implemented. However, the locations of secondary treatment facilities must be reserved to meet the secondary standard by stages.

Therefore, it seems that there is little gap between level a and level B standards of rural sewage projects, but there is still a certain gap in terms of technology and investment. Class I B effluent is roughly equivalent to class V standard, and class I a effluent can reach class IV standard only after artificial wetland or further purification.