Including design, construction, operation and maintenance, the underground urban sewage treatment
plant recently mentioned the "construction drawing".
On December 19, the China Environmental Protection Industry Association issued the "Engineering Technical Guide for Underground Urban Sewage Treatment Plants" for the first time. While further standardizing the overall design of the project, the Guidelines set clear requirements for underground plant areas, ground floors, major auxiliary projects, labor safety and occupational health, construction and process commissioning, and operation and maintenance techniques.
With the goal of sewage treatment, regeneration and reuse, and improvement of the ecological environment, the Guide proposes that underground sewage treatment is suitable for land use in construction projects such as tight land use, densely populated or environmentally sensitive areas, and should be combined with investment costs, land occupation indicators, and ecological environment. Requirements, comprehensive utilization of water resources, etc. At the same time, underground sewage treatment plants can be constructed independently or combined with urban water environment comprehensive treatment projects and ecological complexes.
In terms of technology and equipment, the Guide clearly defines the principles of safety, reliability, advanced technology, and reasonable cost, and adheres to the technical guidelines of provincial occupation, less maintenance, and automation. Adopting a layered layout, the vertical layout can be divided into water treatment structure layer, equipment operation layer and ground layer. Of particular concern is that buildings such as sludge digesters, biogas tanks, and diesel generator
rooms should be located on the ground floor.
For an underground sewage treatment plant with gravity flowing water, the water inlet should be equipped with dual safety protection measures of water inlet speed closing gate and electric gate. In the pre-processing stage, an ultra-fine grid should be set in front of the membrane biological treatment system or membrane filtration system
, and it should be installed after the settling tank or primary sedimentation tank, and it should be selected according to the type of membrane element or membrane group. The design of the sand settling tank should be a high-efficiency sand removal device to enhance the sand removal effect. Combined with the characteristics of the sand in the water, it should be strengthened to remove sand particles in the range of 0.1mm-0.2mm particle size.
In response to the demand for nitrogen and phosphorus removal from wastewater, the anaerobic-aerobic process and its improved processes include multi-stage A / O, high-efficiency biofilm, and membrane bioreactors. The water depth of the biological reaction tank is generally 7.0m-8.0m, and it can be appropriately deepened. The specific depth should be determined in consideration of the geological conditions and the performance of the aeration equipment. The top plate of the biological reaction tank should be provided with holes for observation, sampling and maintenance. The cover plate of the hole should be made of anti-corrosive materials such as hot-dip zinc steel and glass fiber reinforced plastic.
When using a secondary sedimentation tank, a single-layer or double-layer rectangular sedimentation tank should be used. The former water inlet layout should be the surrounding water inlet and the surrounding water outlet. The surface hydraulic load is 1.2m³ (㎡ · h) —1.6m³ (㎡ · h). The solid load of sludge should not be greater than 200kg / (㎡ · d). The effective water depth It should be 4.0-4.5m. The double-layer rectangular advection type secondary sedimentation tank should fully consider the uniformity of the upper and lower water inlet distribution. If the upper sedimentation tank adopts the mud scraping method to discharge mud, consideration should be given to avoid the disturbance of the upper pond body's mud to the lower pool body water distribution area, and a mud blocking valve plate should be set in front of the lower pool body water distribution area.
When using a membrane bioreactor, the width of the membrane pool should be determined in consideration of both the column network and the size of the membrane group. The aerator of the blast aeration system should use products with high oxygenation performance, uniform air distribution, small resistance, not easy to block, corrosion resistance, convenient operation management and maintenance. The advanced treatment process should be selected according to different water quality objectives, and different process units and their combined forms should be compared with multiple schemes to meet the requirements of compact land occupation, stable operation, and economical and reasonable requirements. When the coagulation and sedimentation process is adopted as the advanced treatment process, the efficient precipitation process should be adopted, and the mixing time is 1.0-3.0min.
Sewage should be disinfected with ultraviolet light, if necessary, sodium hypochlorite can be used for auxiliary disinfection. The concentrated dehydration of sludge is carried out in the underground plant area, and integrated equipment should be used for treatment. When it is necessary to dewater the sludge to 80% moisture content in the underground plant area, a direct belt concentration dehydration integrated machine or a centrifugal concentration concentration dewatering integrated machine will become preferred. When it is necessary to further dewater the sludge in the underground plant area to a moisture content of 30% -60%, a low-temperature sludge drying process should be selected. In addition, the "Guide" makes clear requirements for deodorizing equipment, noise control, and underground boxes in underground urban sewage treatment plants.
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