General description: due to the rapid development in the design of China continuously, the growth of the population and the rise of industrial sewage, waste water discharge has become a problem, which not only threaten our nature, the more serious damage to our life safety, so the sewage treatment has become a primary problem of social development。 The design flow of this project is 20000m /d fund in the design of water quality, BOD5:200mg, L-1, COD:400mg, L-1, SS:200mg, L-1, 30mg, L-1, TP:7mg, NH3-N, L-1, TN:45mg, L-1。 The design of the water quality to meet the national effluent standard of urban 20mg: BOD5 = L-1, SS = 20mg, L-1, COD = 60mg - L-1, ammonia nitrogen is less than or equal to 5mg - L-1, TP - L-1 = 1mg, TN = 20mg, L-1, PH, 6-9。 The main task of this project is to complete the design process of the transformation of plant purifying water quality Long bridge。

Long bridge water purification factory was built in the last century in 80s, when using the traditional activated sludge treatment process, to reduce the sewage pollution load BOD5 and suspended solids as the main treatment targets。 However, with the improvement of environmental protection requirements and the strict control of nitrogen and phosphorus removal, the existing process is difficult to meet the requirements。 Therefore, need to transform the old technology。 This paper is combined with the process of the original plant, transformation。

There are about five types of nitrogen and phosphorus removal process in our waste water treatment plant: A/O process, SBR and its improved process, A/A/O process, inverted A/A/O process, SBR and improved process。

This design using the A/A/O inversion。 The process is to reverse the anaerobic zone and anoxic zone of A/A/O process, and reverse sludge and mixed liquid are denitrifying in anoxic tank。 Accordingly, the problem of insufficient carbon dioxide in the process of operation is solved accordingly。 The organic matter in sewage is used as carbon source, and a large amount of nitrate in the mixed liquid of A2/O reaction tank is recycled into an anoxic tank through an inner loop, and the denitrification principle is carried out in it。

The design of the main process below:

The design process of A2/O is: the sewage into the coarse grid by wells, pumping station into the aerated grit chamber, and then flows into the primary settling tank, inverted A2/O reactor, through the reactor recirculation, and then flows into the radial flow sedimentation tank two, after ultraviolet disinfection, will eventually waste water into Zhang tong。 The sludge from the primary sedimentation tank enters the sludge thickening tank, and the sludge in the two clarifier enters the sludge concentration tank, and then enters the sludge storage tank and sludge dewatering tank in turn。 Among them, the supernatant of sludge concentration tank and the water in the sludge dewatering are returned to the primary sedimentation tank, and the sludge in the aeration grit tank is transported outwards。 Finally, the sludge is processed by the related process。

The role of Grid: used to intercept sewage such as broken skin, hair and other coarse floating and suspended solids, the purpose is to prevent the blocked water pump, aerator etc。 structures, reducing scum, in order to ensure the normal operation of sewage treatment facilities。 Aeration grit tank has the following characteristics: (1) the ordinary grit pool contains about 15% organic matter, while the aeration grit tank contains only 5%。 (2) aeration equipment is used in the tank to play the role of pre aeration。 (3) the vertical flow of water in the tank and the main stream can be carried out。 (4) in the process of sand removal, it is almost free from the interference of water flow。 The pipe type aerator from the material on the rubber model EPDM and silicone rubber membrane and polyurethane film three EPDM, the most commonly used, the price is low, but the anti aging tensile strength and transverse tension and other physical properties in high and low temperature resistance than the other two materials, in addition to a silicone rubber membrane resistance is large, the price is good。 The design uses roots blower, L83WD blower 2 (one for one)。 The degradation process of activated sludge has two stages: stabilization stage and adsorption stage。 The stabilization stage is the organic matter of microorganisms using activated sludge, which can be completed at around 15~45min, with a short time and a long stable stage。 Activated sludge has a large surface area and has a polysaccharide of sticky substance, so organic matter in sewage can be transferred to activated sludge。