1 Project Background
"Twelfth Five-Year Plan" period is China's economic and social development and transportation industry to transform the development mode of the critical period, the development and construction of ecological and environmental load-bearing pressures, pressure on the demand for resources, and other contradictions will be further highlighted. National environmental pollution control will be shifted from the current total amount of pollutants to the total amount of control and improvement of environmental quality, and the control of pollution emissions will be more stringent. The pollution management of the transportation industry is facing higher requirements from the state.
2 Project Overview
Three Xi Expressway Xiping to Siwan (Yu-Eqi Provincial Boundary) section is located in the territory of Nanyang City, Henan Province, is the rise of the central region of the highway network, "seven vertical, nineteen horizontal" layout of the seventh longitudinal Houma ~ Shiyan Expressway is an important part. Temple Bay service area as an important part of it, with large passenger and freight traffic flow, long stay characteristics, the construction of the sewage treatment station for the service area of the ecological construction and the natural environment plays a decisive role in the protection of water resources is to realize the rational allocation of water resources, scientific protection, recycling is an important means of wastewater through a set of reasonable, economic, high efficiency of the operation of the process of treatment in order to achieve the standard of water reuse, to reduce sewage discharge, reduce the impact on the service area, and to reduce the impact on the water supply. Reduce the discharge of sewage, reduce the environmental pollution around the service area. This is not only for the protection of the local environment, reduce environmental pollution has a decisive significance, and at the same time to realize the recycling of resources, and other highway service area has a demonstration significance.
3 Sewage treatment and reuse engineering design
Highway service areas are generally far from the city, the sewage produced can not be discharged into the municipal sewage treatment system, if not directly discharged after treatment, it will have a negative impact on the surrounding environment. At the same time, the service area also consumes a large amount of water for living, car wash water, watering green water, fire water, etc., in addition to the strict requirements of the water quality indicators of living water, can only be used in the municipal water supply or self-supplied water, other water can be processed to meet the appropriate standards can be recycled, so that not only can completely eliminate pollutants discharged on the surrounding areas of pollution, while saving a large amount of fresh water. A wastewater treatment and reuse system with aeration biofluidized bed + artificial wetland + disinfection as the core process is constructed in the service area to treat the domestic sewage and car washing wastewater generated in the service area.
Based on the experience of similar projects, the quality of designed influent water is determined as follows:
CODCr≤250 mg/L, BOD5≤150 mg/L, ammonia nitrogen≤30 mg/L, SS≤120 mg/L
The quality of designed effluent water, as required by the construction unit, should reach the standard of urban greening water in the "Urban Sewage Recycling Water Quality for Miscellaneous Water Use in Cities" (GB18920-2002). 2002) in the urban green water standards, the main indicators are as follows:
BOD5 ≤ 20mg / L, ammonia nitrogen ≤ 20mg / L, total coliform / (a / L) ≤ 3, dissolved oxygen / (mg / L) ≥ 1.0
According to the data provided by the construction unit: the project's daily treatment of wastewater water volume of 240m3 / d, i.e., 10m3 / h.
Process description: The process is based on a combination of the following: chemical water treatment, chemical water treatment and water treatment.
Brief description of the process: septic tank effluent through the grille treatment to remove most of the suspended solids, after removing the gravel by the sand sedimentation tank, into the regulating tank, sewage in the regulating tank to adjust the amount of water, water quality, and then lifting pumps to the biofluidized bed, in the state of aeration, the microorganisms in the pool through aerobic action of the majority of pollutants in the water to decompose and digest the degradation of organic matter into water and carbon dioxide, so that the water quality has been purified. The water quality is purified. The effluent from the fluidized bed enters into the second sedimentation tank, and the mud and water separation is carried out in the sedimentation tank, and a part of the settled sludge is refluxed to the biofluidized bed by the sludge pump, and a part of the remaining sludge is discharged into the sludge tank, and the supernatant is refluxed into the regulating tank, and the thickened sludge is transported to the outside for treatment after storage. The effluent from the secondary sedimentation tank enters the artificial wetland to further remove pollutants including N, P, SS, organic matter, pathogens and other pollutants. The effluent can reach the standard of reuse water, and the effluent from the artificial wetland enters the reuse pool for storage and disinfection, and can be discharged or reused. The process flow is sewage→grid→sedimentation tank→regulation tank→biological fluidized bed→second sedimentation tank→artificial wetland→disinfection→reuse.
4 main structures
Grid sedimentation tank: the grid is mainly to intercept the larger debris in the sewage, the grid is a simple artificial grid.
Sedimentation tank is the use of natural sedimentation to remove sand or other inorganic particles in the water with a large specific gravity of the structure.
Regulating pool: used to equalize the water quality, water quantity, reduce the subsequent processing facilities operating load. This system sets up a regulating pool, the pool is equipped with 2 sets of sewage lifting pumps, perforated aeration mixing device 1 set, which can be opened intermittently to mix the sewage and prevent sedimentation.
Biofluidized bed: used to degrade carbon source organic matter, is the core unit of biological treatment of sewage, its carrier in the fluidized bed in a fluidized state, so that the solid (biofilm), liquid (wastewater), gas (air) 3-phase get in full contact with each other, particles of violent collision between the surface of the biofilm is constantly renewed, and microorganisms are always in the stage of vigorous growth. This technology can keep high concentration of biomass in the bed, and the mass transfer efficiency is very high, which leads to fast substrate degradation of wastewater, short hydraulic retention time, 10-20 times higher operating load than general activated sludge method, and strong shock load resistance.
This system is equipped with one biological fluidized bed, with biological carriers and aeration devices arranged in the tank, the upper part of which is the sedimentation area, the lower part is the fluidized bed area, and the bottom part is the sludge hopper; the upper part of the sedimentation sludge flows into the lower part of the fluidized bed, and the excess sludge is discharged into the bottom sludge hopper.
The secondary sedimentation tank: mud-water separation of the mixed liquor from the fluidized bed; the concentrated sludge in the lower part of the secondary sedimentation tank is pumped by the sludge pump back to the fluidized bed, and the remaining sludge is discharged to the sludge tank; the supernatant of the upper part of the tank enters into the artificial wetland for in-depth treatment by the self-flowing flow. The second sedimentation tank adopts vertical flow type sedimentation tank.
Artificial wetland: sewage through artificial construction and control to run and swamp similar to the ground, the sewage controlled allocation to the wetland, so that the sewage in the wetland soil crevices and the surface of the flow along a certain direction of the process of the soil, artificial media, plants, microorganisms, the use of soil, artificial media, plants, physical, chemical, biological triple synergism, the treatment of sewage is a technology. Its ecosystem action mechanism includes adsorption, retention, filtration, sedimentation, microbial decomposition, transformation, redox, plant shading, residue accumulation, transpiration water and nutrient uptake and other actions of various types of animals.
This project adopts horizontal submerged artificial wetland; specification: 45×16×1.3m; structure: semi-underground composite organization; equipment: 1) water distribution system: 1 set; 2) water collection system: 1 set; 3) wetland filler: 720m3; 4) aquatic plants: 10,000 plants.
The function of the reuse pond is to store the water from the artificial wetland temporarily, and then use it as greening water in the station area after disinfection. This system is equipped with 1 reuse pool, which is equipped with a device for adding disinfectant and a reuse water pump.
Sludge tank: mainly used to store the remaining sludge generated by the entire system, to reach a certain amount, by the pumping truck for disposal, the top of the tank is equipped with an overflow port, the supernatant can be overflowed to the regulating pool. Specification: 4×4×4.5m; Structure: underground steel concrete.
Comprehensive room is built on the regulating pool, and the room is placed with a blower, chlorine dioxide generator, power distribution cabinet, automatic control cabinet and so on.
5 Conclusion
Currently, the service area sewage treatment and reuse mainly adopts the technologies of contact oxidation, MBR, biofilter, biofluidized bed, etc. Combined with the site conditions, the project chooses the sewage treatment and reuse technology with the aeration biofluidized bed+artificial wetland+disinfection as the core process by taking the operating cost, treatment effect, management and maintenance, service life and system stability into comprehensive consideration. The technology is applied in this service area. This technology has the advantages of good purification effect, low treatment cost, simple management and maintenance, high technical maturity and landscape effect.
The sewage from the auxiliary facilities is discharged into the sewage network after being treated in septic tank, the sewage discharged from the restaurant is discharged into the sewage network after being treated in grease separator tank, and the rest of the domestic sewage and the waste water from car washing is directly discharged into the sewage network, and the effluent meets the requirements of "Quality Standard for Miscellaneous Water for Daily Use" (GB/T18920-2002) after being treated in the water treatment system with the submerged artificial wetland as the core process, and then is stored in the central pool, and then is stored in the water pool through the frequency conversion system. After being treated by the submerged flow artificial wetland core technology water treatment system, the effluent water meets the requirements of "Water Quality Standard for Miscellaneous Domestic Water" (GB/T18920 2002) and is stored in the pool, and then conveyed to the toilet flushing and greening points by the frequency conversion water supply system.
Energy saving and emission reduction benefits: all sewage in the service area is collected and treated for reuse without pollutant discharge. The treated sewage reaches the standard of water reuse and can be used for toilet flushing and greening, saving a lot of new water resources.
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