The coal-bearing waste water of the power plant is of high color and relatively turbid water quality. Although the traditional physical sedimentation method can remove some suspended coal cinders, it is not strong in the ability to complete the tasks such as sludge cinder treatment and BOD reduction. The waste water treatment process is mostly in the sump, sedimentation tank and other plants, with low systematization and low effluent quality. Here, this paper conceives a systematic solution for coal-bearing wastewater from power plants. The relevant process structure is as follows.
3.1 Main equipment for new technology of coal-bearing wastewater treatment
The new process coal-bearing wastewater treatment system is mainly composed of three parts, including wastewater purification part, sludge treatment part and make-up water part. Among them, the electrical components required for wastewater purification include purifier, chemical treatment device, power plant lift pump, backwash pump, mixed pipe, electromagnetic meter, pipe network valve, water pipe system, electrical control device, etc; The sludge treatment part requires the following equipment: sludge lift pump, water pipe system, coal sludge compression equipment, sludge suction pump, pipe network valve, etc; The make-up water part includes ion exchanger, filter, water electrolysis device and other equipment.
3.2 Operation mode of new technology for coal-bearing wastewater treatment
In this new treatment system, coal-bearing wastewater is mainly treated in a workshop, which includes all functions such as water collection, sedimentation, regulation and supply. Before operation, it is necessary to make regulations on the quality of incoming and outgoing water: the level of suspended particles before treatment is less than 4500mg/L, the level of suspended solids after treatment is less than 10mg/L, and the level of BOD after treatment is between 10-20mg/L.
After being put into use, the system operates twice a day, and each operation time is controlled between 5 and 7 hours. The control center adopts semi-automatic PLC system control, which is responsible for the whole system motor startup, variable frequency speed regulation, return water supply and other processes.
3.3 New process flow of coal-bearing wastewater treatment
After the motor is started, the new system will receive the coal-bearing wastewater from the water pipe of the power plant. The waste water first flows into the waste water purification section and receives physical precipitation, chemical decomposition, BOD treatment and other processes. After coarse sedimentation, the coal-bearing waste water flows into the pre-sedimentation tank through water pipes for static sedimentation. The time is controlled between 45 and 60 minutes, and the surface load of honeycomb inclined pipe is controlled at 3 m3/m2 • h. After the completion of the sedimentation process, the wastewater flows into the chemical treatment area, where it is subject to coagulation, reaction and filtration treatment in the regulating tank to remove coal slag and coal particles. The stagnation time is controlled at 60~90 min.
Since then, the visibility of coal-bearing wastewater has been improved, and most of the suspended pollutants have been treated. It is necessary to remove sludge and reduce the BOD content of wastewater. After being led into the sludge treatment room through the conduit, the sludge is filtered by the sludge scraper, most of the sludge is removed, and then it is led into the sludge bucket. After the action of the lift pump, the cinder sludge fully contacts with the coagulant, and the waste water subsequently enters the compression unit. After centrifugal concentration, air flotation concentration and other treatment, the remaining mud volume is reduced and the water content is increased. After compression treatment, the coal-bearing wastewater of the power plant becomes clear, and the filtered sludge can be converted into coal blocks to realize recycling.