at present, the sewage treatment work has become an important work of our government, especially for the sewage treatment work in cities and towns. the shortage of sewage treatment work has become an important factor restricting the local development. therefore, for the sewage treatment plants in cities and towns, it is necessary to improve the sewage treatment standards of sewage treatment plants and ensure that the treated water quality meets the discharge requirements of the state. requirements are imminent, therefore, the upgrading of sewage treatment plants must be put on the agenda. in this paper, the necessity of upgrading the municipal wastewater treatment plants in china is discussed, and the technology of upgrading is analyzed in detail. the process of upgrading the municipal wastewater treatment plants is analyzed in depth in order to improve the effect of municipal wastewater treatment and make the drainage meet the national standards.
1. necessity of bidding improvement of urban sewage treatment plants in china
1.1 equipments are aging and out of repair
at present, most of the sewage treatment plants in cities and towns in china have been established for a long period of time. in the long-term operation of the equipment, various equipment and systems have not been paid attention to. the lack of effective management and daily maintenance makes the equipment of the sewage treatment plants out of repair for a long time, and the sewage treatment work is difficult to carry out normally. in addition, there are many shortcomings in sewage treatment equipment due to financial problems.
1.2 processing capacity does not match processing requirements
compared with the rapid development of cities and towns, the composition of urban sewage is more complex and the sewage treatment work is more difficult. in addition, due to the prevailing concept of sustainable development and environmental protection, the state has put forward stricter sewage discharge standards. however, due to its early design, municipal sewage treatment plants can only meet the discharge standards formulated by the earlier state, and can not meet the current national discharge standards. therefore, the treatment capacity of many municipal wastewater treatment plants is limited, which can not meet the current treatment capacity and treatment standards.
1.3 the commissioning was not in place when the plant was built.
after the completion of the sewage treatment plant, the debugging of the process is very important, which is the basis to ensure the normal operation of sewage treatment equipment and to meet the treatment standards. however, in the early stage of many sewage treatment plants, insufficient attention has been paid to the process debugging, and the debugging is not in place. as a result, in the later stage of operation, the equipment operation is unstable, the treatment technology is not up to the standard, and the operation cost will increase.
2. improvement technology of sewage treatment plant
2.1 biological aerated filter
biological aerated filter (baf) is mainly used for advanced treatment to remove total nitrogen, especially for tertiary treatment. suitable for the bidding transformation of sewage plant under the condition of land shortage, the project built in the city requires beautiful and less land occupation. biological aerated filter (baf) integrates the characteristics of aeration, high filtration rate, suspended solids interception and regular backwashing. the principle of the process is to fill a certain amount of granular filter material with smaller particle size in the filter. the surface of the filter material is attached with biofilm. when the filter is aerated inside and the sewage flows through, the strong oxidation degradation ability of the high concentration biofilm on the filter material is used to quickly purify the sewage and complete the bio-oxidation degradation process.
it has the following main advantages: 1) saving land area and capital investment; 2) high efficiency of oxygen transmission, low aeration and low consumption of oxygen supply power. (3) easy film hanging and quick start-up; (4) biological aerated filter adopts modular structure, which facilitates the construction of the second phase of the phased project and the reconstruction and expansion of the project.
2.2mbbr biofilm and activated sludge compound
the combined process of biofilm and activated sludge is an organic combination of activated sludge process and fluidized bed biofilm (mbbr) process in the same process tank. therefore, this process not only has the characteristics of impact load resistance, long sludge age, less excess sludge and no sludge bulking, but also has the high efficiency and flexibility of activated sludge process. on the other hand, the influence of temperature change on mbbr process is far less than that on activated sludge process. mbbr has a strong tolerance when temperature change, sewage composition change, or sewage toxicity increase.
it has some other advantages: 1. it occupies a small area, accounting for 20-30% of the capacity of conventional biological treatment ponds. (2) when the actual running water quality or water quantity changes, only by increasing the filling rate of filler, the original design of biological pond capacity can be guaranteed to meet the original design of effluent standards. mbbr process has the characteristics of flexibility and simplicity in design and operation. it can adopt various pool types (deep and shallow square circles/different building structures) without affecting the treatment effect of the process. suitable for upgrading and renovation of existing urban and industrial sewage treatment plants
3. advanced treatment technology of bid-winning transformation in sewage treatment plant
3.1 selection of advanced treatment process
the pollutants in secondary biological treatment effluent are a mixture of organic matter and inorganic matter, including bacteria, pathogens, algae and primitive organisms. whether organic or inorganic substances, according to the size of their particles in sewage, they can be divided into suspended matter (>1 micron), colloid (1 micron-1 nanometer) and solute (<1 nanometer). generally speaking, suspended matter and colloid particles can be removed by coagulation and precipitation and other conventional processes. the emphasis of enhanced treatment is to form turbidity and bod5, codcr particles, colloidal impurities, phosphorus removal and disinfection.
3.2 activated sand filter
activated sand filter is a continuous filtration equipment which integrates flocculation, clarification and filtration. it is widely used in drinking water, industrial water, advanced treatment of sewage and reclaimed water treatment. the system adopts the principle of upflow flow flow bed filtration and single homogeneous filter material. the filtration and sand washing are carried out simultaneously. it can run continuously and automatically for 24 hours, and the structure of sand lifting and washing is skillfully replaced by that of sand lifting and washing.
3.3 high efficiency fiber filter
high-efficiency fiber filter is a new type of gravity filter. it uses a new type of fiber bundle soft packing as filter element. the diameter of the filter material can reach tens of microns or even several microns. it has the advantages of large specific surface area and low filtration resistance. the small diameter of the filter material greatly increases the specific surface area and surface free energy of the filter material, increases the contact opportunity between impurity particles and the filter material and the adsorption capacity of the filter material, thus improving the filtration efficiency and the capacity of intercepting pollutants. in order to give full play to the specialty of fiber filter material, there are backwash drainage tank, fiber density regulating device, fiber bundle filter material, filter plate, air distribution device and water distribution device from top to bottom.
3.4 fiber rotary disc filter
fiber filter is one of the most advanced filters in the world. it is mainly used for advanced treatment of wastewater and reuse of intermediate water. at present, this technology has been widely used in the world. its main characteristics are good treatment effect, high quality of effluent, stable effluent, continuous operation, strong ability to withstand high hydraulic and suspended solids load, automatic operation, easy operation and maintenance, low operation cost, low civil construction cost and minimal land occupation.
3.5 magnetic coagulation filter
magnetic coagulation process is to add magnetic powder to conventional coagulation and sedimentation process, and make magnetic powder and coagulation floc effectively combined. because of the large proportion of magnetic powder, the proportion of coagulation flocs is greatly increased, and the settling speed of flocs is accelerated. the sludge reflux system is set up in the magnetic coagulation process, so that magnetic powder and coagulant can be recycled in the sludge, which is conducive to saving the amount of coagulant.
4, conclusion
generally speaking, the existing urban sewage treatment plants and their equipment can not meet the current sewage treatment needs and meet the current high standards of sewage treatment. therefore, it is very necessary to practice the upgrading of urban sewage treatment plants. biofilter and biofilm technology are important technologies in upgrading municipal wastewater, which should be more widely used. in addition, various advanced treatment processes are also indispensable.
source: polaris water treatment network
legal statement: if there is any infringement, please contact qingquan to delete it at the first time.
