Domestic sewage, including drainage used for toilet rush, kitchen, shower and washing, is a kind of sewage produced by people’s daily life. It contains massive organic and inorganic pollutants such as CODcr, BOD5, SS, coli group, animal and vegetable oils and ammonia nitrogen. The sewage will definitely cause the breeding and spreading of pathogenic bacteria and endanger human health if it is discharged without treatment. The organic pollutants in domestic sewage will also consume nutrients in water rapidly after entering the natural environment, causing death of fish and other organisms. Furthermore, it will cause deterioration of water quality and pollution of the environment, doing great harm to the environment.
Application of domestic sewage treatment process
1. Hotels, restaurants, nursing homes, hospitals
2. Residential districts, villages, towns
3. Stations, airports, seaports, ships
4. Factories, mines, troops, tourist spots and scenic spots
5. Industrial organic wastewater similar to municipal sewage
After collected by drainage system, the sewage will enter the screen well of the sewage treatment plant to accept the removal of particulate matter. Then it will enter regulating pond to be homogenized. The regulating pond is equipped with pre-aeration system. Then the sewage will be pumped into A-level biological contact oxidation tank to carry on acid hydrolysis, nitrification and denitrification, signaled by level controller. This course can reduce the concentration of organic compounds and remove some ammonia nitrogen. Then the sewage will enter O-level biological contact oxidation tank to carry on aerobic biochemical reaction. During this course, most organic pollutants degrade through biological oxidation and adsorption. The outcome enters secondary settling tank to carry on solid-liquid separation. The supernatant enters disinfecting pool and disinfected by adding chlorine tablets. It will be discharged after killing the harmful bacteria in water and reaching the standard finally.
The printing and dyeing wastewater is discharged by printing and dyeing mills processing cotton, linen, chemical fiber and other blended products. Water consumption of printing and dyeing is large. 100~200 tons of water is needed to print and dye 1 tons of textile, among which, 80~90% will be wastewater. Printing and dyeing wastewater has the following features: large water consumption, high content of organic pollutants, strong alkalinity and large water quality changes. In the wastewater, there are substances such as dyes, pastes, additives, oils, acids and bases, fiber impurities, sands, mineral salts etc.
Application of printing and dyeing wastewater treatment process
1．Sewage treatment for traditional textile and dyeing enterprises;
2．Sewage treatment for modern textile and dyeing enterprises;
3．Sewage treatment for textile and dyeing enterprises processing chemical fiber;
There are three methods for treating printing and dyeing wastewater: physical, chemical, and biological methods. Physical method includes techniques such as screen well, regulation, precipitation, air flotation, filtration, separation and membrane techniques. Chemical method includes neutralization, coagulation, electrolysis, oxidation, adsorption and disinfection etc. Biological method includes anaerobic, facultative and aerobic methods.
The water consumption of food processing industry is large, so as the discharge of wastewater. The wastewater contains massive dissolved organic compound though it has little toxicity. The organic compound will consume large amounts of dissolved oxygen after entering natural water, causing water hypoxia and death of fish and aquatic organisms consequently. The suspended solids in wastewater sink to the river bottom and resolve under anaerobic conditions. This course will produce odorous gas to pollute the environment. If we use this kind of wastewater to irrigate farmland, the fruit taste will be affected, and the underground water will be polluted.
Application of grocery wastewater treatment process
1. Food and feed processing enterprises mainly focusing on rice husking and milling industry;
2. Feed processing enterprises mainly producing protein feed, aquatic feed and mixed feed;
3. Enterprises producing edible vegetable oil such as soybean oil, peanut oil and rapeseed oil; enterprises producing non edible vegetable oil such as tung oil and castor oil
4. Sugar enterprises producing cane sugar, half machine-processed sugar and beet sugar; enterprises producing highly processed sugars such as crystal sugar and cube sugar
5. Various slaughtering and processing enterprises of livestock and poultry; enterprises processing products and by-products of livestock and poultry
6. Enterprises processing aquatic products such as fish, shellfish and algae
Grocery wastewater will enter regulating pond first, and be pumped into dissolved air flotation to carry on removal of most insoluble impurities and fats. Then, it will undergo anaerobic / aerobic biological treatment. Finally, the wastewater will be discharged after biochemical treatment and reaching the standard.