The treatment process of domestic waste leachate includes the following steps:
- Large particle filtration: the landfill leachate first enters the regulating tank to intercept the large particle pollution of the influent.
The regulating tank body in the large particle filtration step is rectangular, and the outlet tank is arranged along the diagonal direction. After the wastewater enters the tank on the left and right sides, it flows to the outlet tank after different times, so as to achieve the purpose of automatic regulation and balance. The front end of the regulating tank is provided with a grid.
- Oil filtration: the garbage leachate that removes large particles enters the oil separation sedimentation tank to remove most of the oil.
The oily wastewater in the oil filtration enters the rectangular oil separation and sedimentation tank through the distribution tank and flows slowly along the horizontal direction. The flowing oil products float on the water surface and are pushed to the oil collection pipe by the oil collection pipe or the oil scraper set on the tank surface into the dehydration tank. The heavy oil and other impurities precipitated in the oil separation tank accumulate in the sludge bucket at the bottom of the tank and enter the sludge pipe through the sludge discharge pipe.
- Coagulation sedimentation treatment: the garbage leachate with grease removed enters the coagulation sedimentation device to reduce the content of suspended solids.
In the coagulation sedimentation treatment, the coagulation sedimentation device is a folded plate flocculation tank, and the flocculation time is 12 ~ 20min. The speed in the flocculation process shall be reduced section by section, and the number of sections shall not be less than three. The flow rate of each section can be as follows: the first section: 0.25 ~ 0.35m/s; The second section: 0.15 ~ 0.25m/s; The third section: 0.10 ~ 0.15m/s, the included angle of folded plate is 90 ° ~ 120 °, and the third section adopts straight plate.
- Anaerobic reaction treatment: the landfill leachate with suspended solids removed is introduced into the anaerobic reaction device to degrade the organic matter in the leachate through anaerobic reaction.
In anaerobic reaction treatment, the nutritional and environmental conditions required by anaerobic microorganisms are formed under anaerobic conditions. Through the metabolism of anaerobic bacteria and facultative bacteria, the process of biochemical degradation of organic matter is divided into four stages: hydrolysis stage, fermentation (or acidification) stage, acetic acid production stage and methane production stage.
- Secondary coagulation sedimentation treatment: pass the waste permeate through anaerobic reaction into the reaction tank added with coagulant and coagulant aid to reduce the color of waste permeate.
In the secondary coagulation sedimentation treatment, the coagulant is one of polyaluminium chloride and polyacrylamide.
- DTRO process treatment: the permeate after secondary coagulation is pumped into the disc tube reverse osmosis complete system.
In DTRO process treatment, the complete set of disc tube reverse osmosis system is a membrane column composed of disc diaphragm, guide plate, O-type rubber gasket, central pull rod and pressure sleeve. The diameter of the membrane column is 214 mm and the length is 1400mm. It is composed of 210 guide plates and 209 diaphragms. The diaphragm and guide plate are stacked at intervals, and the O-type rubber gasket is placed in the grooves on both sides of the guide plate, Thread the central pull rod together and put it into the pressure sleeve, and both ends are sealed with metal end plates.
In DTRO process treatment, the raw liquid channel of DTRO process treatment adopts an open channel. The feed liquid enters the pressure vessel through the inlet and flows from the channel between the deflector and the shell to the other end of the component. At the flange of the other end, the feed liquid enters the deflector through eight channels. The treated liquid flows through the filter membrane at the shortest distance and then reverses to the other membrane surface 180 °, Then it flows into the next deflector from the notch in the center of the deflector, so as to form a double “s” shaped route from the circumference of the deflector to the center of the circle, then to the circumference, and then to the center of the circle on the membrane surface. The concentrated liquid finally flows out from the flange at the feed end.
The leachate from domestic waste transfer station has complex water quality and high pollutant concentration. Most of the leachate from the transfer station is directly discharged into the municipal sewage pipe network, which has a great impact on the downstream urban domestic sewage treatment plant. Due to the high content of suspended solids and oil in the leachate, it is easy to block the pipe network, overflow sewage, pollute the surrounding atmosphere, water body and soil, and threaten the health of the surrounding residents, With the improvement of environmental protection requirements, the effective treatment of leachate from domestic waste transfer station has attracted more and more attention. (wedge wire filter basket is the best choise)
In the existing technology, it is difficult to achieve the treatment effect simply by relying on one method. Among them, the biochemical method has low operation cost, but it often requires large equipment volume, which can not be normally applied in the waste transfer station with limited available land; Physicochemical method is widely used in the treatment of leachate in transfer station in recent years because of its small land occupation and fast equipment startup, but it has the characteristics of high operation cost. Therefore, for the treatment of leachate in the transfer station, after comprehensively considering many factors such as equipment floor area and operation cost, we adopt the combination of several methods.