Double-mode nitrogen-phosphorus treating system for sewage and method

Abstract

The invention discloses a double-mode nitrogen-phosphorus treating system for sewage and a method and belongs to the field of sewage treatment. The method is characterized in that sewage passes through a reaction tank and a secondary settling tank in sequence to realize enhanced denitrification and dephosphorization; when the overflowing sludge operation mode is adopted, the total-phosphorus removing ratio is more than 90% or the effluent TP is less than 1mg/L, deltaBOD/deltaTN is less than 4, the maximum flow flux of all areas in the system is not more than 2.2Q, and the phosphorus containingratio of returned sludge is more than 4%. The double-mode nitrogen-phosphorus treating system disclosed by the invention has the advantages that high-efficiency denitrification and dephosphorizationis achieved, the operation is energy-saving and low-carbon, the load is high, the occupied area is small, the denitrifying dephosphorization is realized, the TN removing ratio is not limited by the return ratio, the control is simple and the operation and the management are convenient and the like. The double-mode nitrogen-phosphorus treating system consists of the reaction tank, the secondary settling tank and a connecting pipeline; the reaction tank comprises a pre-hypoxic area, an anaerobic area, a middle settling area, an aerobic nitrating area, a denitrifying area, an aerobic decarbonizing area and a water discharging area in sequence from the water feeding end to the water discharging end; connecting pipelines include a main water feeding pipe, a branch water feeding pipe, a water discharging pipe, a sludge overflowing pipe, a sludge returning pipe, a remaining-sludge discharging pipe and the like; the technological process is simple.

Description

technical field [0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a dual-mode sewage nitrogen and phosphorus treatment system and method. Background technique [0002] Biochemical treatment of sewage is mostly based on the traditional mechanism of nitrogen and phosphorus removal. Nitrification process, including nitrification and denitrification; nitrification, that is, autotrophic nitrifying bacteria (AOB, NOB) under aerobic conditions, NH 4 + -N→NO 2 - -N→NO 2 - -N; denitrification, that is, denitrifying bacteria under anoxic conditions, with NO X - as electron acceptor, organic matter as electron donor, NO 3 - -N→NO 2 - -N→N 2 . The biological phosphorus removal process includes anaerobic phosphorus release, aerobic transitional phosphorus absorption, and discharge of excess sludge to achieve biological phosphorus removal; in the anaerobic process, phosphorus-accumulating bacteria absorb organic matter and s...

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Problems solved by technology

[0006] 3) There is competition for carbon sources in nitrogen and phosphorus removal, phosphorus accumulating bacteria can only use volatile fatty acids in organic matter, and other forms of organic matter need to be hydrolyzed into volatile fatty acids before they can be used by phosphorus accumulating bacteria; The requirements for carbon sources are slightly lower than those of phosphorus accumulating bacteria, but they can only use low-carbon organic matter. There is a competition for the quality and quantity of carbon sources between denitrifying bacteria and phosphorus accumulating bacteria; in general, biological denitrification requires influent C / N>4, biological nitrogen and phosphorus removal requires influent C / N>7, while domestic general domestic sewage influent C / N is generally <4, which belongs to insufficient carbon source and needs external carbon source; No organic carbon source is needed, and when the organic carbon source exceeds a certain amount, it will inhibit the metabolism of the nitrifying bacteria

The dual-sludge system, that is, two sets of biological systems, bears long-sludge-age and short-sludge-age bacteria respectively. The system structure is complicated, the control is difficult, and the requirements for operation and management are high, so it is difficult to apply in a large area in the project

in the traditional A 2 Increase biofilm in / O, such as installing fixed packing in the aerobic area, but the hydraulic shear provided by normal aeration is not enough to promote the normal renewal of microorganisms on the fixed packing, and long-term operation will produce dead sludge areas, which will seriously reduce nitrification efficiency; If in traditional A 2 / O is loaded with a suspended carrier, although a mud film composite process has been formed, it cannot create conditions for denitrification and phosphorus removal, and the suspended carrier system, when the concentration of suspended sludge in the system is too large, the suspended sludge will be mixed with the suspended carrier The biofilm on the surface will compete and reduce the nitrification efficiency

[0009] At the same time, it should be noted that although denitrification and phosphorus removal can improve the utilization rate of carbon sources, once the C / N of influent water increases, its carbon source consumption has limitations, which may lead to excessive organic flow into the nitrification area, affecting the nitrification of the system function; however, if the design considers the nitrification design when the C / N is high, it will inevitably increase the pool capacity of the nitrification area and increase the cost, which is uneconomical; Flexible adjustment of pure membrane process and mud-membrane composite process can ensure the treatment effect, reduce investment and improve operating efficiency

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