Study On Comprehensive Treatments On Litchi Lake

When studied in Shenzhen Institute of Environmental Science, I participated in movementdebugging of the fourth comprehensive treatments of lichi lake and part experiments of theNational High Techlogy Research and Development Program(863 Program)'Constructed WetlandWater Quality Purification System Parament Optimization techlogy', above is the main contents ofthis paper.Litchi lake was made in 1983, which stands at FuTian borough ShenZhen city. The lake is109100m², the effective depth is 1.5 meters, the common water-holding capacity is 10⁵ cubicmeters. For many reasons, the water-pollution had been gradually grave. The litchi lake had beento an eutrophication lake, which has much affections on resident's life and park sight.The ShenZhen water bureau carried out the fourth comprehensive treatments on litchi lake. Themain measures includedâ‘ reducing polluted water to lichi lake,â‘¡suppling clean water to litchilake,â‘¢clearing away stink and rubbish in litchi lake,â‘£clearing suilage, filled the hole, disposedpoint source pollution in litchi lake and so on,⑤treatments on litchi lake water. This paperstudied vertical flow constructed wetland and zoology gravel bed crafts on litchi lake water, andthe water changing trend in litchi lake.The minotoring datas in many months indicates that: the lake water had became better andbetter. The comprehensive nutrition index (Kaersen index) were 52.08～58.45 from August, 2006to January, 2007. The contamination concentration in every lake area descended, and five lakearea Kaersen index were 53.46～56.82. That indicates litchi lake is a low-grade eutrophication lakenow.COD, NH₃-N, TP, and chlorophyl-a (Chl-a) of the influent water to the vertical flowconstructed wetland were 14.4～24.4mg/L, 0.2～0.9mg/L, 0.06～0.11mg/L, and 14.9～35.2mg/m³respectively. The corresponding removal efficiency were 60.68%, 37.08%, 28.83%, and 38.15%,COD, NH₃-N, TP, and Chl-a of the effluent water were 6.1～10.9mg/L, 0.05～0.35mg/L,0.009～0.04mg/L, and 14.9～35.2mg/m³ respectively.COD, TN, NH₃-N, TP, and Chl-a of the influent water to the ecology gravel bed were16.7～30.7mg/L, 0.78～1.55mg/L, 0.1～0.7mg/L, 0.057～0.12mg/L and 15.7～47.7mg/m³respectively. The corresponding removal efficiency were 36.93%, 6.6%,＞82%, 53.1% and 37.1%, COD, TN, NH₃-N, TP, and Chl-a of the effluent water were 10.2～21.1mg/L,1.05～1.55mg/L,＜0.04mg/L, and 10.5～32.8mg/m³ respectively.The vertical flow constructed wetland experiments system studied:â‘ the carrier materialinfluence to vertical flow constructed wetland,â‘¡the kind of plants influence to vertical flowconstructed wetland. The datas indicated:1 different pound load has less impact to vertical flow constructed wetland and wetland hassteady contamination removal efficiency,2 the vertical flow constructed wetland with special components is better than wetland withonly sand and stone in decreasing contamination. The decreasing order was scrap iron＞shuck＞sand and stone,3 different kind of plants in decreasing contamination order was grassiness＞windmill grass＞thalia dealbate,4 comprehensive treatments on litchi lake has great effect. The water had becameâ…¢from theproject carried out,5 in wasterwater disposal, vertical flow constructed wetland has nicer efficiency to dispoal ofCOD, TN, NH3-N, TP, and Chl-a and so on,6 in wasterwater disposal, ecology gravel bed has well efficiency to dispoal of COD, TN,NH₃-N, TP, and Cha-a and so on.