Development And Experimental Research Of Step-feed Activated Sludge Process

Due to economic development，rapid industrial growth, multiple pressuresgenerated by population and development and a substantial increase in fertilizer andpesticide usage, the quality of our surface water and groundwater are facing withserious threat. Nitrogen and phosphorus contained in the sewage are the twoimportant nutritional elements which caused pollution. Nitrogen and phosphorus arethe necessary materials in plant growth and development. With economicdevelopment and continued population growth, the use of nitrogen and phosphatefertilizer in agricultural production is increasing. The increasing usage of residents’detergent dosage and discharging standards of urban sewage cause a rising number ofphosphorus, nitrogen and other nutrient elements in natural surface. The proportionand the presence of the form of nitrogen and phosphorus are very suitable for thesurvival and reproduction of algae and other aquatic plants. they result in a lot ofproliferation of algae. The rise of algae in the water causes series of waterenvironmental issues such as the decline of dissolved oxygen, which is said as thewater eutrophicationIn the history of the development of biological nutrient removal technology,nitrogen and phosphorus removal technology has been continued developed andimproved, such as improved A~2/O technology, improved UCT technology, UCTtechnology, MSBR technology, VIP technology, new oxidation ditch process andBCFS technology, etc. However, the combined processes of nitrogen and phosphorusremoval mentioned above are basically based on the principle of the traditionalbiological nutrient removal. They all have obvious deficiencies though restructuredand recombinated. It mainly manifested that multiple backflow of sludge and themixture are contained in the majority of process. Thereby it increases the complexityof the system and the cost of capital construction and operating. Meanwhile, it costsmore oxygen and CODcr in the nitrogen and phosphorus removal process. Theremaining sludge which is a huge amount to process contains major phosphorus.These shortcomings can not meet the requirements of sustainable development of environment in the new situation of the12th Five-Year plan.Therefore, the main contents of this subject are how to use the activated sludgeeffectively to reduce the process and time of microbial activation and hibernation,while to improve the efficiency of denitrification. Through theoretical analysis andpreliminary test, the research group proposed the idea of "segmented activated sludgesewage treatment process". The significance of this test is that the activated sludgeprocess system has opened up a brand new direction of development, and it hasfar-reaching significance in the progress of the activated sludge process and thetransformation of the old process.There are several conclusions after tested:1) In the removal of ammonia nitrogen and total nitrogen, segmented A2/Osystem has an obvious advantage than ordinary A2/O system. The difference in thesludge concentration has better reflection of the characteristics of segmented A2/Osystem.2) Segmented A2/O system indeed has a low efficiency of phosphorus removal,however denitrification is more important in sewage treatment. Because nitrogenremoval can only rely on the biological role, phosphorus removal can rely on thephysico-chemical treatment, which has high treatment efficiency.3) Due to adding the splitter, it can not only separate the effective bacterium ineach processing unit, but also improve the activity for faster proliferation and increasethe removal efficiency of the system. Meanwhile, the enrichment of effectivebacterium can reduce the residence time of the system. Concluded through tests:Based on the wastewater in this test, water inflow can increase to40L/h in removingCODcr, water inflow can increase to30L/h in removing NH4-N, water inflow canincrease to30L/h in removing TN. The removal efficiency of the system will notchange much.4) The mud and water separator is the core content of the process, the volumeand separation efficiency of the separator are the key indicators in the efficiency ofthe system. Because the volume of the separator is the one occupying the stage ofprocessing units, the test uses a percentage in the separator of total unit volume to measure the size of the separator. The results showed that, appropriate increase in theproportion of the aerobic zone separator helps the removal of ammonia nitrogen andtotal nitrogen, but it is adverse for CODcr and TP removal. An increasing proportionof the anaerobic zone and anoxic zone separator helps the removal of TN, and it isadverse for TP removal, it has little effect to ammonia nitrogen and CODcr.