BOD stands for biochemical oxygen demand: a comprehensive index of the content of aerobic pollutants such as organic matter in water.
SS stands for suspended solids: refers to solid substances suspended in water, including inorganic substances, organic substances, mud and sand, clay and microorganisms.
Sewage treatment (wastewater treatment) is a process to make sewage meet the water quality requirements for discharge or reuse, and to purify it. Sewage treatment is widely used in construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical treatment, catering and other fields, and it has also entered the daily life of ordinary people more and more. The upstream suppliers of sewage treatment industry are mainly sewage treatment equipment manufacturers and sewage treatment chemicals suppliers. All belong to industries with fast development and good demand.
Treatment methods Village sewage is mainly composed of domestic sewage and agricultural wastewater. The composition of domestic sewage is relatively fixed, mainly containing carbohydrates, protein, amino acids, fats and other organic substances, which is more suitable for the growth of bacteria and becomes a place for the survival and reproduction of bacteria and viruses; Domestic sewage is generally non-toxic and has certain fertilizer efficiency, so it can be used to irrigate farmland. The composition of agricultural wastewater is varied. Different seasons, different places and villages with different development goals need different treatment methods. When treating sewage, in order to reduce the sewage discharge and its complexity, the toilet flushing water (black water) should be separated from other domestic water (gray water) in combination with the construction of biogas digesters that the country is vigorously promoting. Grey water is treated by natural purification system, while black water and human and animal manure are treated by anaerobic biogas digesters, which can not only reduce the discharge, complexity and treatment cost of sewage, but also have great significance for developing clean new energy in rural areas, protecting human settlements and promoting sustainable development of rural economy and society.
The function of sewage treatment station is to treat production and domestic sewage to meet the prescribed discharge standards, and it is an important facility to protect the environment. Sewage treatment stations are very common in developed countries, but there are few township sewage treatment stations in China, but they will gradually increase in the future. To make these sewage treatment stations play a real role, we must rely on strict discharge system and organizational management system to ensure it.
Conditional villages should be combined with villages or single villages to build sewage treatment stations. And shall meet the following requirements:
(1) When rain and sewage are separated, the sewage will be transported to the sewage treatment station for treatment;
(2) When rainwater and sewage meet, the combined sewage will be transported to the sewage treatment station for treatment; Interception wells should be set in front of the sewage treatment station to eliminate the combined sewage in rainy season;
③ The sewage treatment station can adopt biochemical treatment technologies such as constructed wetland, biofilter or stabilization pond according to local conditions, or other treatment technologies with engineering examples or mature experience.
Constructed wetland is suitable for treating pure domestic sewage or rain-sewage combined sewage, which covers a large area and should be connected in series in two stages. The plane shape of biofilter should be circular or rectangular. The filler should be firm, corrosion resistant, high in strength, large in specific surface area and high in porosity, and inorganic filter materials such as gravel, pebble, slag and coke should be used. When the geographical environment is suitable and the technical conditions permit, the village sewage can be treated by stable pond systems such as wasteland, wasteland, pit pond and depression. As a secondary treatment stabilization pond system, the treatment scale should not be greater than 5000m3/d.
The location of the station should be arranged below the dominant wind direction in summer, downstream of villages and towns, and in a low-lying place, so as to facilitate the sewage to flow into the sewage treatment station without polluting the water used in villages and towns, and to facilitate the downstream discharge after treatment. There is a protective distance from the residential areas of villages and towns to reduce the pollution to the residential areas. If sewage is used for farmland irrigation and sludge fertilizer field, its location should be close to farmland irrigation area to facilitate transportation. The sewage from medical institutions must be strictly disinfected before it can be discharged into the sewage pipe network, and it should conform to the current national standard "Design Code for Hospital Sewage Treatment" (CECS07:2004). When using reclaimed water, the water quality should comply with the current national standards "Code for Design of Reclaimed Water in Buildings" (GB50336-2002) and "Code for Design of Wastewater Recycling Engineering" (GB503352002), and switch devices should be set up to stop using it in case of public health emergencies.
The effluent from the sewage treatment station shall conform to the current national standard "Discharge Standard of Pollutants for Urban Sewage Treatment Plants" (GB18918-2002); When the effluent from sewage treatment station is used for farmland irrigation, it should comply with the relevant provisions of the current national standard "Water Quality Standard for Farmland Irrigation" (GB5084-2005). There are many methods for sewage treatment and utilization, and the following factors should be considered when selecting the scheme:
(1) Environmental protection requirements for sewage treatment;
② Quantity and quality of sewage;
3 investment ability. Sewage treatment technology is to separate pollutants contained in sewage by various methods, or convert pollutants into harmless substances, thus purifying sewage.
Foreign sewage treatment has the following characteristics:
First, the standardization, finalization, serialization and complete sets of urban sewage and industrial wastewater treatment equipment have formed a water treatment equipment industry with complete categories and high commercialization.
The second is water treatment unit equipment, such as precipitation, filtration, extraction, adsorption, microfiltration, electrodialysis and so on. , has formed a professional scale production, varieties, specifications, quality is relatively stable, reliable performance parameters, convenient for users to choose.
Third, the complete sets of urban sewage treatment equipment are developing to large scale, and the industrial wastewater treatment equipment tends to be specialized and complete with the maturity of the process.
Fourth, the general equipment such as fans, pumps and valves for water treatment will gradually realize professional design and organize production to meet special needs.
Fifth, the shortage of water resources, eutrophication and drinking water safety have led to the rapid development of advanced wastewater treatment equipment and disinfection equipment.
Sixth, the anaerobic treatment technology has been paid attention to again, which has promoted the application of anaerobic treatment equipment in the treatment of high-concentration organic wastewater.