Study On Design Scheme Of Surface Water Plant With A Water Plant In Jining City As An Example

Water supply plants in North China have mostly used groundwater as water sources.With the acceleration of urbanization,the scale of water supply has increased rapidly.Long-term overexploitation of groundwater has brought about a series of problems that are difficult to recover and solve,such as ground subsidence and secondary groundwater pollution with a drop in groundwater level.Therefore,it is of great practical significance to analyze the water quality characteristics of surface water sources in North China,to study the corresponding water treatment plant treatment processes,and to gradually realize the goal of using surface water as the main water supply source.Taking Jining City of Shandong Province as an example,the main problems of using groundwater as a water supply source for urban water were analyzed.At present,the proven amount of groundwater in Jining City is 410,000 cubic meters per day.Since 2011,the actual amount of mining has reached 500,000 cubic meters per day,which has been seriously over-exploited for a long time.Moreover,at present,five water supply wells have been scrapped due to groundwater pollution,and the water quality of the other three water supply wells is gradually deteriorating.The water quality characteristics of the surface water source in Nansi Lake of Jining City were investigated and reported:the algae content was high,and the average annual monitoring concentration reached 39.28 million/L;it belongs to organic micro-polluted source water and the average annual monitoring value of COD_Mn is 9.5mg/L;the inorganic salt ions exceeded the standard in winter,and the average values of sulfate and chloride were 395mg/L and 610mg/L,respectively;the characteristics of low temperature and low turbidity in winter were significant.The average value of water temperature in winter is-5°C,and the average value of turbidity is25 NTU.Through the technical and economic comparison of various pretreatment,conventional treatment and advanced treatment processes,the water purification process of the A water supply plant was determined.In addition to conventional coagulation（mechanical flap flocculation tank）,sedimentation（advection sedimentation tank）,filtration（V-type filter tank）,disinfection（sodium hypochlorite disinfection）,in view of the water quality characteristics of the high water algae content,the algae removal unit with permanganate+sodium hypochlorite pre-oxidation was set up;after the sedimentation process,a flat flow air floatation tank was added to remove the fine floating flocs to eliminate the adverse effects of low temperature and low turbidity in winter;the organic micro-pollutants in the raw water were degraded by O₃/UV/H₂O₂;in order to remove the inorganic salt ions in the raw water to the utmost extent,a nanofiltration membrane advanced treatment technique was adopted.For the muddy water produced in the production process of A water plant（including sedimentation tank discharged mud water,air floatation tank scum,V-type filter tank and activated carbon filter backwashing wastewater）and concentrated brine produced by nanofiltration membrane advanced treatment process,special treatment and disposal measures were studied.After the filter backwashing wastewater is collected and precipitated,the supernatant liquid is returned to the raw water pipe,and the sediment is concentrated and dehydrated together with the sludge in the sedimentation tank and the scum of the air floatation tank;the nanofiltration brine is mixed and diluted with the tail water of the Jiezhuang Sewage Treatment Plant of Jining City,and then discharged after meeting the Class III water standard stipulated in the Surface Water Environmental Quality Standard（GB3838-2002）.The daily water supply scale of the surface water source A water plant built according to the research plan is 200,000 m³/d.The long-term stable operation of the factory water quality meets the requirements of the“Sanitary Standard for Drinking Water”（GB5749-2006）.It has important strategic significance for fundamentally solving the problem of over-exploitation of groundwater,improving the water supply security level of Jining and even the sustainable development of Jining City.It also provides a successful engineering example for the improvement and optimization of water supply structure in North China.