Study On Water Quality Maintenance Technology In Palm Lake

Along with urbanization speeding up, many natural lakes have allentered the city planning and the development scope. Compared with the large-scale shallow lakes, research with regard to small shallow lakes surroundded by city is relatively weak. Lakes in the city have integrated function, including slowering and storage drain, drainage stormwater, water supply, traveling and so on, they are extremely important to urban ecology. Therefore, the water environment of medium and small shallow lakes locate in city is not allowed to be neglected. Moreover, the duty of maintenance and improvement of water environment is especially stern. First, the lake own is relatively closed, flow rate is slow, waters'replacement cycle of lakes is long, all of these are disadvantageous to dilution and diffusion of polluted waters; Next, the lake is located in humanity's compact district, the destructive power of humanity is far bigger than those away from city, specially those closed, surroundded by city and supplied directly by rivers, the pollution load is usually bigger than self-purification capacity, the ecology vulnerability is only more remarkable.As a lake located in developing village, Palm Lake has not only the generality of lake, but also the particularity. The paper seeks water safeguard measure and water quality maintenance technology suited Palm Lake,accoding to water budget and water quality analysis of Palm Lake and its influent region, economical analysis, technological analysis and environmental benefit analysis of program; and validates whether water quality maintenance technology is feasible, with excavating some new question about water quality and its key, accoding flow field simulation and analysis, water quality and its change mechanism analysis, limited nutrition factor determination and eutrophication appraisal.The water budget showed that the annual surplus water of Palm Lake stand at 1.69×104m3, the number of water replacement n1 reach 0.12 times annually;after Early Palm Spring Ecological Residential Village supplying, the annual surplus water stand at 11.61×104m3, the number of water replacement n2 reach 0.81 times annually; with Secondary Palm Spring Ecological Residential Village completed, the annual surplus water stand at 31.98×104m3, the number of water replacement n3 get to 2.24 times annually. So, water safeguard measure of Palm Lake, to take runoff of village and precipitation as main nourishment source, as well as to take tap water as auxiliary nourishment source in dry season, is to be established. Water quality maintenance engeering technology is also to be established, it is comprised of runoff minimization technology, substrate sludge dredging and shore renovation, waters'ecology control as well as management and pollution from construction site minimization technology. Embedded water budget indicates all of nutritions from runoff of Secondary Palm Spring Ecological Residential Village into Palm Lake are higher than those of Early Village, and the influence power of water quality engendered by Secondary Village is greater than Early Village, fortunately, the nutrition sum into Palm Lake various is not too big, therefore, water quality management of Secondary Village should be keystone. Thereinto, estimation of nutrition input of SS(replaced by turbidity), CODCr, NH3-N and TP of Early Plot of Land is in turn 0.271 t/a, 0.897 t/a, 0.014 t/a and 0.006 t/a, with those of Secondary Plot of Land of 4.392 t/a, 2.830t/a, 0.331 t/a, and 0.038t/a respectively; While the reduction rate of SS, CODCr, NH3-N and TP of Early and Secondary Plot of Land altogether is 85.5%, 13.9%, 42.5% and 30.2% respectively.The flow field simulation confirms that inlet and outlet has not been set inside of shore is uppermost cause which induces that the effect of mixture and replacement and the metabolism ability in Palm Lake worse off. Forasmuch, Outlet of runoff should be endeavoured to set inside of shore, and flow rate is to be allowed to be bigger than those outside comparatively.The pattern of waters, temperature stratification structure in spring and summer and convection and mixture in autumn and winter, controls transportation and circulation of nutrition and seasonal circulation primary productive force of Palm Lake; Wind-driven current promotes exchange and mixture of waters in different water area and mixture of waters between superstratum and substratum in certain depth of Palm Lake, but it possibly affects water because of to exchange and mix excessively between superstratum and substratum in spring and summer, for the sake of reducing nutrition load of epilimnion in autumn and winter, fountain is to be considered to overturn substratum waters in spring and summer, to promote artificially growth of floating plant; Distribution of various water-quality factors by depth basically reflects the pattern, temperature stratification structure in summer and mixture in winter. Water quality of hypolimnion is worse than of epilimnion and metalimnion in summer, and aeration is considered to overturn substratum and to urges waters of hypolimnion to consumpt nutrition load of hypolimnion, so is done eliminating water of hypolimnion; Theory deduction analysis and single nutrient enrichment experimentation prove that phosphorus is the limited nutrition factor of Palm Lake.therefore, phosphorus degradation should be taken as chief goal in runoff processing, and phosphorus control in water quality maintenance.Most of factor average levels in water-quality autumn and winter of Palm Lake are higher than those in water-quality spring, thereinto, the increased range of turbidity, CODCr, TP, NH3-N and TN is in turn 95.3%, -28.0%, 200.0%, 19.4% and 57.7%, meanwhile they are higher in spring than in summer. Palm Lake is still to be polluted after water replacement, the pollution mainly comes from waterwater in construction site and runoff. But factor average levels in whole year have greatly reduced than the phase not be in exploitation, thereinto, the fall range of NH3-N, TP, TN and CODMn is respectively 64.6%, 90.0%, 34.0% and 35.1%, and satisfy V of water-quality standard of surperficial water.Eutrophication appraisal rank is highest in water-quality winter, with lowest in water-quality summer, it is classed as light eutropher and has not appear hyper eutropher in whole year. The change of eutrophication rank is consistent with of water quality in whole year, therefore, water quality maintenance technology and water environment management play a positive role.