In recent years, with the continuous improvement of science and technology, the sewage treatment process has a larger development, urban comprehensive sewage usually first after preliminary treatment or secondary biochemical treatment, sewage treatment after the main pollutants are nitrogen, phosphorus and other nutrients, rich and recycling wastewater land treatment system for deep processing for it. Primary treatment is to remove suspended solid pollutants in sewage, the method has grille, precipitation, grit, oil separation and air flotation, etc. Secondary treatment goal is significantly remove sewage in the state of colloidal and dissolved organic pollutants, the common method to deal with for activated sludge process and their modified form, can mix process for first and second level processing, some part has reached level 3 mixed processing, in order to remove nitrogen and phosphorus in sewage, and further biological nitrogen removal technology was developed. Strains of its characteristic is to use the advantage in hypoxia - anaerobic - aerobic treatment process (especially in the process of aerobic) need a lot of oxygen for the growth of the principle of reducing phosphorus and nitrogen content in the sewage, the sewage in the process to tertiary treatment.

   Industrial sewage disposal adjust measures to local conditions

Industrial sewage water due to contain large amounts of metal ions, such as mercury, chromium, cadmium, and alkali, and salt inorganic sulfide and show the unique color, polluting is very strong. If the industrial sewage directly into aquatic ecosystems, microorganisms not only does not reduce the concentration of heavy metal, instead can also enrichment, amplify its effect. According to research shows that heavy metals into the organism, can accumulate in some organs caused by cumulative poisoning, ultimately endanger life.

   Sewage pollution inorganic some deterioration in water quality, harmful aquatic organisms and harm agriculture; Some chronic poisoning, damage the body's normal physiological processes, including heavy metals most harmful to human body, and even cancer. Industrial wastewater inorganic composition differ in thousands ways, however, as a result, effective governance of industrial sewage, to adjust measures to local conditions, particular case is particular analysis, with appropriate water treatment technology and reducing the pollution treatment equipment combining the work of the specific industry, can effectively reduce the toxic elements in the industrial wastewater. The most effective method of endogenous sewage purification for the factory, namely direct near the industrial plant or its targeted with sewage treatment methods. Now, the industrial sewage directly purification technology is the national strategy of energy conservation and emissions reduction in frontier technology of great vitality.

   Sludge treatment of land use

   Our country is an agricultural big country, whether from the economic factors, or from use of fertilizer effect factors, the sludge disposal methods of land use is in accordance with our national conditions. Agricultural sludge from the concrete situation in our country is the most feasible and realistic disposal scheme. Agricultural sludge can be a large amount of sludge disposal, in principle only sludge can be used to reach the relevant state standard farmland; Natural material cycle of sludge in farmland, nitrogen, phosphorus, potassium and organic matter in sludge and trace elements are good agricultural fertilizer, has effect on increasing yield of crops; Sludge of organic matter, humus can improve soil structure, is a good soil conditioner; Sludge agricultural use to lower production cost, is suitable for the economic development of China's current situation.

An important aspect of sludge compost farm, it is a process of using the sludge microbial fermentation. This technology as early as the beginning of the 20th century, in Europe, development research is successful, began to only be used for urban garbage treatment, then this method is applied in farmland is referenced to the sludge treatment.

   In sewage sludge processing work, comprehensive control, reasonable layout; To strengthen environmental protection consciousness propaganda and education; To strengthen the management, and strive to get rid of the high economic development high pollution emissions now "play dates" dilemma. (source: China's environmental protection online)