With the acceleration of urbanization and the continuous growth of urban population, urban sewage, mainly domestic sewage, has become the main pollution source of water environment, which has increasingly aggravated the eutrophication of lakes and the deterioration of water environment in China, directly threatening people's drinking water safety and the sustainable development of urban economy. In recent years, limited by technical and technological conditions, China's urban sewage treatment has a large investment, high cost, low treatment rate and unsatisfactory effect. According to the data, at present, the treatment rate of urban sewage in China is only 20%, a large number of urban domestic sewage can not meet the discharge standard, and the water environment situation is grim.

According to experts, at present, the activated sludge method is mainly used in urban sewage treatment technology in China. Its technical principle is to use the active components (mainly various microbial components) in sludge to degrade the nutrients such as phosphorus, nitrogen and algae that cause water pollution through engineering treatment, so as to achieve the purpose of natural water purification. Activated sludge process commonly used in China mainly includes several modes, such as A/O process, A2/O process, oxidation ditch process and SBR process. However, due to the problems of high cost, incomplete treatment and easy to cause "secondary pollution" to the environment, it is neither economical nor satisfactory. Biofilm technology is a new technology developed in recent years. Its principle is to use modern bioengineering technology to cultivate and ferment active bacteria with different functions in high density according to the composition of water pollutants, and then mix them in proportion to form a biofilm (also known as "biological zone"), which is directly thrown into polluted water to decompose and transform nutrient-rich elements, so as to achieve the purpose of purifying water. Compared with Europe, America, Japan and other countries, at present, China's biofilm technology is mainly used in aquaculture, which has created huge economic benefits and initially showed its application prospect in the field of water treatment. According to experts, compared with the traditional activated sludge process, biofilm technology has five obvious technical advantages in urban sewage treatment:

1. Investment province. At present, the infrastructure investment of domestic urban sewage treatment plants is large, which requires a large number of engineering facilities such as mechanical equipment and pipe networks. The investment cost per ton of sewage treatment is about 1000 yuan; However, the application of biofilm technology has the advantages of less equipment investment, small floor space, and less than 500 yuan per ton of sewage treatment, saving more than 50% than the cost. 2. Low operating cost. According to estimates, the direct operating cost of domestic urban sewage treatment plants is generally between 0.5 ~ 0.8 yuan per ton of sewage per day; The application of biofilm technology to sewage treatment only needs about 0.2 yuan per ton per day. 3. Less silt and no "secondary pollution". The traditional activated sludge process is often used to treat urban sewage, which often causes "secondary pollution" to the environment due to the accumulation of a large amount of sludge; On the other hand, once the sewage is purified, the microorganisms and bacteria that make biofilm will die out automatically due to lack of "nutrition" and will not cause "secondary pollution". 4. High efficiency. Due to the large specific surface area of biofilm and high microbial density, the microbial population per gram of preparation reaches 5-20 billion, which is much higher than the natural microbial active components in sludge. At the same time, it can be put in many times, which is convenient and fast, and the treatment effect is obviously better than the traditional activated sludge method. Using biofilm technology can not only effectively control the eutrophication of lakes, but also help to repair and strengthen the ecological function of lakes and improve the self-purification ability of water bodies. 5. Suitable for small sewage treatment with low organic load, such as urban living quarters. Due to low investment, low operation cost and saving the cost of pipe network construction, the application of biofilm technology to treat urban sewage such as urban living quarters has incomparable advantages over activated sludge method. At present, the State Key Laboratory of Microbiology of Huazhong Agricultural University has successfully developed this new technology. Hubei Keliang Bioengineering Co., Ltd. took the lead in realizing the application of this technology in urban sewage treatment project in China through this process, and achieved outstanding results, attracting many domestic units to visit and signing an intentional contract of more than 200 million yuan.