Influence Of Different Control Conditions On Water Quality Of Reclaimed Water For Landscape Water

Nowadays,with the increasing demands of living environment,the urban water landscape becomes more and more important.It is well known that China is awater-stressed country,especially in most area of the north where water resources are extremely scarce.It is obviously unreasonable to vigorously develop the water landscape in this situation.In China,volume and quality of reclaimed water is adequate and stable,respectively.Sothe use of reclaimed water to substitute tap water in landscape design can not only save water resources effectively and improve utilization rateof water resources,but also reduce the running cost of water landscape.It easily results in the eutrophication of water body by the use of reclaimed water for landscape water,because of high concentrations of nutrient such as nitrogen and phosphorus in reclaimed water.Therefore,the landscape water body will lose its ornamental performance.In order to better apply reclaimed water to landscape water,it is necessary to control the quality ofreclaimed landscape water effectively to prevent its eutrophication,besides adopting measures to reduce nutrient concentrations in reclaimed water.Through the construction of a small artificial landscape water body,the paper simulates the water quality changes of reclaimed landscape water under different conditions including pH values,HRT and sediment and aquatic plants.The results are as follows:(1)The pH value of reclaimed water is of great importance to the growth ofalgae.When the pH of reclaimed water is 6 or 10,the concentration of chlorophyll-a in water body will remainin a low situation for a long time,and thewater quality is with good characteristics including limpidity,no variation of color,high transparency,low turbidity,and no odor.When the pH is 7,8 or 9,the algae will multiply greatly at some time which results in the drastically increase of chlorophyll-a concentration,then because of the eutrophication phenomena occurring in the water body,water quality conditions are extremely deteriorating.Due to the growth of algae,water body become low transparency,and the color become dark green or dark brown.At the same time there is strong fishy smell in the water body.(2)In general,the fluidity of landscape water is poor.If the HRT is too long,it is very easy occur eutrophication phenomenon by external interference factors,so it is important to restrain the eutrophication of the landscape water by controlling HRT.In summer,the light and temperature conditions are suitable for algae growth which can easily lead to water bloom phenomenon.When HRT is 2d,the concentration of chlorophyll-a in the water body maintain a lower range for quite a long time,meanwhile,the water quality condition also maintains well.The water body is with good characteristics including limpidity,high transparency and no variation of color.When HRT is 4d or 6d,algae begin to grow on the tenth day,and then the concentration of chlorophyll-a rises sharplywith the growth ofalgae.Thusthe water quality deteriorates and the eutrophication phenomenon occurs.When HRT is 8d,algae begin to grow on the sixth day,and then the eutrophication occurs.In winter,the water temperature basically maintains below 10 ℃.Light time is short and light intensity is not high.In this environmental condition,algae reproduction is greatly nfluenced and HRT has little influence on its growth.Therefore,as long as the HRT is less than 20 d,it can ensure that the concentration of chlorophyll-a in the water keeps a lower level for a long time,meanwhile,the water body is with good characteristics including limpidity,high transparency,low turbidity,and no odor.(3)Different sediments and aquatic plants have different effects on algal growth.When aquatic plants exist in water,it can effectively restrain the growth and reproduction of algae,and ensure that the water quality maintainsin relatively good condition.In this experiment,it is found that loess can effectively absorb the nutrients like nitrogen,phosphorus and so on in reclaimed water body.Therefore,when reclaimed water is used to replenish urban landscape water,it can be considered that plant a certain number of aquatic plants,which can not only improves water quality,but also prevent the occurrence of eutrophication effectively.In addition,a certain proportion of loess can be injected to reduce the concentration of nitrogen and phosphorus nutrients in the water body.