| Sewage reuse plays an important role in relieving water resources shortage. Urban sewage reuse, which is a key factor for sustaining stable freshwater resources, could improve wastewater reuse rate and decrease need for natural water resources, and at the same time, it could diminish pollution load for water environment and disturbance for natural water cycle. Especially in water-shortage areas and drought season, it is a feasible measure for solving water scarcity.Small-size power plants occupy a quite big proportion in China. In the northern part of China, most power plants are used for heat supply, which have small installed capacity and only need little water quantity. But because most power plants are built early, which wastewater treatment technique is quite lag, and often discharge much wastewater. So sewage advanced treatment and reuse technique is useful measure to economically use water and realize zero pollution. Based on the analysis on quality characteristics of different water systems in small-size power plants, this paper studies on the operation and effect of sewage discharge technique, and provides sewage advanced treatment and reuse technique, which tries to realize wastewater zero discharge.一,Analysis on Quality Characteristics of Different Water Systems Insmall-Sizepower PlantsWastewater in small-size power plants includes many types, such as wastewater from eliminating ash, discharge water from cooling system, discharge water from chemical water treatment system, wastewater from transferring coal system, residential wastewater from factory community, wastewater with oil and discharge water from other systems, etc. Among which, wastewater from eliminating ash and cooling system occupy 80% of the total discharge water, and others are decided by the actual condition of the power plant. Generally, discharge water from cooling system has better water quality, which only has higher temperature and COD value, but wastewater from eliminating ash has worse water quality, and has higher COD, SS and other heavy metal elements. Wastewater from cooling systems could be used for recharge water for low-level water system like rinsing ash system. Wastewater from coal factory and rinsing ash system has worse water quality and many heavy metals, so it is better to set up closed cycle within washing coal and rinsing ash water. Wastewater with oil and discharge water from chemical treatment system could be used for recharge water for system.二,Case Studr on Sewage Advanced Treatment And Reuse Technique in Small-Size Power PlantAccording to characteristics of different water systems and discharge wastewater, the paper takes a northern power plant as the example, and improve original technical route of sewage treatment, which includes physical-chemical treatment pretreatment, secondary biological treatment of wastewater and tertiary advanced wastewater treatment. The improved technique route is the followings:1. Improve concentrated rate of cooling system and diminish discharge quantity. Wastewater could be used for transmitting coal, watering and washing coal and fuel pump.2. Set up the integrated systems of desulfurizing and diminishing ash, and construct calcareousness-slurry systems, which could supply calcareousness slurry to integrated system, and calcareousness left after desulfurizing are dumped into ash ditch.3. Wastewater treatment is divided two parts. Wastewater with oil and wastewater from chemical water treatment are used for recharge water to calcareousness-slurry systems.4. Balance water quantity and build adjusting pond for washing calcareousness water to diminish wastewater because of water quantity fluctuation and realize zero discharge. 三,Feasible Research on Sewage Advanced Treatment And Reuse Technique in Beipiao Power PlantAnnual water quantity in Beipiao Power Plant is 3860000t, among which factory and residential occupy 3300000t and 560000t respectively. Discharge wastewater is 106t/h, among which cooling water is 43t/h, product and living water...
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