The development of integrated sewage treatment equipment is mainly to realize the transformation of sewage treatment from centralized to decentralized, from large centralized to small decentralized. It has the characteristics of less capital investment, small floor space, and can reduce the construction of pipe network, so it is widely used. Integrated sewage treatment equipment mainly has four processes:
1, A/O process
A/O process takes activated sludge as biological carrier, and the sewage is oxygenated by the action of oxygen and aeration of fan. A pool is equipped with mechanical stirring, and the reflux liquid from O pool flows back to A pool, where denitrification reaction is carried out to reduce most nitrate nitrogen to nitrogen, and nitrogen overflows from wastewater through stirring, so as to achieve the purpose of removing ammonia nitrogen; Effluent from pool A enters into pool O, which is equipped with blast aeration to remove most organic pollutants and convert most ammonia nitrogen into nitrate nitrogen. According to the needs of wastewater, the concentration of activated sludge in the O-class tank can be adjusted, and the organic matter in wastewater can be adsorbed, oxidized and decomposed through the bacterial micelles in the activated sludge; The removal rate of organic matter and ammonia nitrogen is high. However, because there is no independent sludge reflux system, sludge with unique functions cannot be cultivated, and the degradation rate of refractory substances is low; At the same time, in order to improve the nitrogen removal efficiency, it is necessary to increase the internal circulation ratio, thus increasing the operating cost. In addition, the internal circulating liquid comes from the aeration tank and contains a certain amount of DO, which makes it difficult to maintain the ideal anoxic state in section A and affects the denitrification effect, and the denitrification rate is difficult to reach 90%.
2.SBR process
SBR process is an advanced activated sludge treatment method developed in recent years. The treatment process integrates aeration tank and sedimentation tank, with continuous water inflow and intermittent aeration. When the gas stops, the sewage precipitates and the supernatant is skimmed, it becomes a cycle. There is no sedimentation tank and sludge reflux equipment in SBR process, but SBR process is intermittent and needs multiple treatment units. Water intake and aeration are switched, and the control is complicated. In order to ensure the overflow rate, SBR process has high requirements for the production of decanter equipment, which must be refined, otherwise the final effluent quality will easily fail to meet the standard. At present, there is no good quality decanting equipment in China, so it is troublesome and expensive to buy imported equipment, and the later maintenance cost is also high. The concentration of sludge in SBR process pool is measured by concentration meter to control the discharge of excess sludge. At present, the domestic concentration meter technology is not mature, which is easy to cause problems such as difficult control of SBR sludge discharge.
3. Contact oxidation process
Biological contact oxidation is a traditional biochemical treatment method, and biological packing is a semi-soft packing in a fixed bed. As the attachment carrier of microorganisms, semi-soft fillers are evenly distributed on biological fillers, which avoids the phenomenon of uneven distribution of microorganisms. At the same time, organisms adhere to the surface of the filler and do not flow with the water flow. Because the biofilm is directly stirred by the rising air flow, it is constantly updated, thus improving the purification effect. The contact oxidation method has the advantages of short treatment time, small volume, good purification effect, good and stable effluent quality, no need for sludge backflow or expansion and low energy consumption.
4.MBR process
MBR is a new type of high-efficiency sewage treatment process which combines high-efficiency membrane separation technology with traditional activated sludge process. It adopts a submerged membrane module with a unique structure and is placed in an aeration tank. After aerobic aeration and biological treatment, the water is filtered by the pump and pumped out. It is very different from the traditional sewage treatment method and replaces the secondary sedimentation tank and tertiary treatment process in the traditional biochemical process. Because of the existence of membrane, the solid-liquid separation ability of the system is greatly improved, thus greatly improving the effluent quality and volume load of the system. Combined with different processes, the effluent can meet the standard of landscape water or miscellaneous water. Because of membrane filtration, microorganisms are completely trapped in the bioreactor, which realizes the complete separation of hydraulic retention time and activated sludge age, and eliminates the sludge bulking problem in the traditional activated sludge process. Membrane bioreactor has the advantages of high pollutant removal efficiency, strong nitrification ability, good nitrification and denitrification effects, stable effluent quality, low excess sludge output, compact equipment and simple operation. At present, it is widely used in the treatment and reuse of domestic sewage and various biodegradable industrial wastewater.
Second, the comprehensive sewage treatment equipment process
The process flow of sewage treatment by integrated sewage treatment equipment is roughly as follows: firstly, the sewage to be treated is removed through the grid, then it flows into the regulating tank for homogenization treatment, and then it is lifted by the lifting pump into the integrated sewage treatment equipment, and then it passes through the biochemical treatment of pre-denitrification zone, anaerobic zone, anoxic zone and aerobic zone in turn, and finally the mud-water separation is realized in the sedimentation zone. Finally, the precipitated water is disinfected by an ultraviolet sterilizer and then discharged. The specific process is as follows:
1, grille
Sewage is collected and transported to the sewage treatment station through the pipe network. Firstly, the large solid particles or floating objects contained in the sewage are removed through the grid to ensure the stable operation of the subsequent treatment device, and the grid slag is regularly transported to foreign countries for disposal.
2. Regulating pool
The whole regulating system consists of auxiliary systems such as regulating tank, lifting pump and liquid level gauge. Here, the flow and concentration of sewage are buffered and adjusted, and the adjustment of water quantity and quality has good stability for the indicators of sewage entering the subsequent biochemical treatment system, which promotes the treatment efficiency of the system. The sewage is lifted to the integrated sewage treatment equipment by the regulating pool lift pump.
3. Integrated sewage treatment equipment
Comprises an anaerobic tank, an anoxic tank, an MBBR aerobic tank, a secondary sedimentation tank, a flocculation reaction tank, an efficient sedimentation tank, an equipment room and supporting auxiliary units. Combined packing is arranged in the anaerobic tank and the anoxic tank; The MBBR tank is filled with MBBR suspended filler, forming two macro and micro A/A/O environments; Nitrate at the end of MBBR aerobic tank is pumped back to anoxic tank, and sludge in secondary sedimentation tank is pumped back to anaerobic tank. In MBBR aerobic tank, organic nitrogen in sewage is transformed into nitrate by ammoniation and biological nitrification. In the anoxic tank, denitrifying bacteria convert nitrate brought by internal reflux into nitrogen and escape to the atmosphere through biological denitrification, thus achieving the goal of complete denitrification. In the anaerobic tank, phosphorus accumulating bacteria in the returned sludge release phosphorus and absorb easily degradable organic substances such as lower fatty acids; However, in the MBBR aerobic tank, the phosphorus accumulating bacteria in the activated sludge absorb excess phosphorus, and the excess sludge is discharged through the precipitation in the secondary sedimentation tank to achieve the purpose of phosphorus removal.
4, disinfection
The precipitated water is discharged after being disinfected by an ultraviolet sterilizer.
5. Sludge pond
A small amount of surplus sludge generated by integrated sewage treatment equipment is first discharged into the sludge concentration tank for concentration, and the concentrated supernatant is refluxed to the regulating tank, and the concentrated sludge is regularly disposed and transported abroad.