COD represents chemical oxygen demand: it means that reducing substances in water include various organic matter, nitrite, sulfide, ferrous salt, etc.
BOD stands for biochemical oxygen demand: a comprehensive indicator of the content of oxygen-demanding pollutants such as organic matter in water.
SS stands for suspended matter: refers to solid matter suspended in water, including inorganic matter, organic matter, mud, sand, clay, microorganisms, etc. that are insoluble in water.
Sewage treatment (wastewater treatment) is the process of purifying sewage to meet the water quality requirements for drainage into a certain water body or reuse. Sewage treatment is widely used in various fields such as construction, agriculture, transportation, energy, petrochemicals, environmental protection, urban landscape, medical care, catering, etc., and is increasingly entering the daily lives of ordinary people. The upstream suppliers in the sewage treatment industry are mainly manufacturers of sewage treatment equipment and suppliers of sewage treatment chemicals. They are all industries with rapid development and good demand. Treatment methods
Village and town sewage mainly consists of domestic sewage and agricultural wastewater. The composition of domestic sewage is relatively fixed, mainly containing organic matter such as carbohydrates, proteins, amino acids, and fats. It is more suitable for the growth of bacteria and becomes a place for bacteria and viruses to survive and reproduce. However, domestic sewage generally does not contain toxicity and has a certain fertilizer effect, so it can be used to irrigate farmland. The composition of agricultural wastewater is diverse. Different seasons, different places, and villages and towns with different development goals require different treatment methods for their wastewater. When treating sewage, in order to reduce the amount and complexity of sewage discharge, the construction of biogas digesters that is being vigorously promoted by the country should be combined with the domestic water to separate toilet flushing water (black water) and other domestic water (grey water). Gray water is treated with a natural purification system, and black water and human and animal excrement are treated in anaerobic biogas pools. This can not only reduce the discharge volume, complexity and treatment costs of sewage, but also contribute to the development of clean new energy in rural areas, protect the living environment, and promote the rural economy. The sustainable development of society is of great significance.
The role of the sewage treatment station is to treat production and domestic sewage to meet the prescribed discharge standards. It is an important facility for protecting the environment. Sewage treatment stations are already common in industrially developed countries, while there are very few sewage treatment stations in villages and towns in my country, but they will gradually increase in the future. For these sewage treatment stations to truly function, strict discharge systems, organization and management systems are required to ensure them.
Villages that have the conditions should build sewage treatment stations in joint villages or single villages. And should comply with the following regulations:
① When rainwater and sewage are diverted, the sewage is transported to the sewage treatment station for treatment;
② When rainwater and sewage are combined, the combined sewage is transported to the sewage treatment station For treatment; in front of the sewage treatment station, interception wells should be set up to exclude the combined sewage in the rainy season;
③ The sewage treatment station can use biochemical treatment technologies such as artificial wetlands, biological filters or stabilizing ponds, or it can be based on Depending on local conditions, other treatment technologies with engineering examples or mature experience should be adopted.
Constructed wetlands are suitable for treating pure domestic sewage or combined rainwater and sewage. They occupy a large area and should be connected in two stages; the planar shape of the biological filter should be circular or rectangular. The filler should be hard, corrosion-resistant, high-strength, with a large specific surface area and high porosity. Inorganic filter materials such as gravel, pebbles, slag, and coke should be used. When the geographical environment is suitable and technical conditions permit, village sewage can be considered to use wasteland, Wasteland, ponds, depressions and other stable pond treatment systems. For stable pond systems used as secondary treatment, the treatment scale should not be greater than 5000m3/d.
The location of the station should be arranged below the prevailing wind direction in summer, downstream of the water body of villages and towns, at a low level, so that sewage can flow into the sewage treatment station without polluting the water in villages and towns, and it can be easily discharged downstream after treatment. It has a protective distance from the residential areas of villages and towns to reduce pollution to residential areas. If sewage is considered to be used for farmland irrigation and sludge fertilization, the location should be close to the farmland irrigation area to facilitate transportation. The sewage from medical institutions must undergo strict disinfection treatment and meet the prescribed discharge standards before it can be discharged into the sewage pipe network, and should comply with the relevant provisions of the current national standard "Design Code for Hospital Wastewater Treatment" (CECS07:2004).
When using reclaimed water, the water quality should comply with the relevant provisions of the current national standards "Code for Design of Reclaimed Water in Buildings" (GB50336-2002) and "Code for Design of Wastewater Recycling Projects" (GB503352002), and opening and closing devices should be installed to protect the water in case of emergencies. Stop use during public health emergencies.
The effluent from the sewage treatment station should comply with the relevant provisions of the current national standard "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB18918-2002); when the effluent from the sewage treatment station is used for farmland irrigation, it should comply with the current national standards. Relevant provisions of "Farmland Irrigation Water Quality Standards" (GB5084-2005). There are many methods of sewage treatment and utilization, and the following factors should be considered when choosing a plan:
① Environmental protection requirements for the degree of sewage treatment;
② The quantity and quality of sewage;
③Investment ability. Sewage treatment technology uses various methods to separate pollutants contained in sewage or convert pollutants into harmless substances, thereby purifying sewage.
Foreign sewage treatment has the following characteristics:
First, urban sewage and industrial wastewater treatment equipment have been standardized, finalized, serialized and complete sets, and have formed a complete range of commercialization High degree of water treatment equipment industry.
Second, water treatment unit equipment, such as precipitation, filtration, extraction, adsorption, microfiltration, electrodialysis, etc., has formed specialized large-scale production, with relatively stable varieties, specifications, and quality, reliable performance parameters, and user choice Very convenient.
Third, urban sewage complete sets of equipment are developing towards large-scale development, and industrial wastewater treatment equipment tends to be specialized and complete as the technology matures.
Fourth, general equipment such as fans, water pumps, valves and other equipment supporting water treatment have gradually realized specialized design and organized production to meet special needs.
Fifth, water shortages, water eutrophication, and drinking water safety have led to considerable development of advanced wastewater treatment equipment and disinfection equipment.
Sixth, anaerobic treatment technology has attracted renewed attention, promoting the application of anaerobic treatment equipment in the treatment of high-concentration organic wastewater.