Study On Technology And Mechanism Of Improvement Of Aquatic Habitat In Urban Landscape Water

Habitat improvement is the key factor to restore the healthy aqua-ecosystem of urban landscape water body,and its transparency enhancing is the emphasis and difficulty,which is one of the important indicators of urban landscapes water body. That transparency of urban-landscapes water was not high enough was due to phytoplankton over-growth.The effects of nutrient concentrations and water flow state in water on the diversity and consistency of phytoplankton in urban landscape water was remarkable.The technologies,their mechanisms and engineering application to reduce nutrient concentrations and improving water flow state in urban landscape water body were investigated in order to enhance its water transparency under supporting by national"863"project(2006AA06Z343).The water quality and habitat characteristics of typical landscape water body in Beijing were analyzed by monitoring and field study.Attapulgite was used as adsorbent to reduce phosphor(P)concentration in water by simulating water and field water at small-scale experiment condition.That the plug flow reaeration-biofilm technology was used to reduce the ammonia-nitrogen concentration and improve the flow state in water was conducted to compare their effects under medium-scale condition using 0.5 t filed water,and the application of those technologies were studied as following.According to the research,main conclusions are found as:The aquatic vegetation is few and total nitrogen concentration of water is under V level in Shishahai Lake and Luoma Lake.Transparency in eastern area of Shishahai was 70 cm,but that in Luoma Lake was only 27 cm.The difference of P concentration may be the reason that the phosphor concentration was 0.042mg/L in Shishahai and 0.36mg/L in Luoma Lake.Therefore,P concentration is the limiting factor of algae growth,which is negative correlation with transparency of water.The depth of Liuyin Lake is only 0.5 m,less than light compensation depth,the photosynthesis of aquatic vegetation is met.Hence,submerged and emerging vegetation both are flourish.However,the depth of Luoma Lake is 1 m,more than light compensation depth,the aquatic vegetation cannot be developed.Therefore,the algae growth can be controlled by aquatic vegetation,and the light intensity under water is the guarantee for aquatic vegetation photosynthesis,and water transparency is the main important factor that affects the light intensity under water.The effect of P removed by natural vermiculite and attapulgite was weak,and their capacity after modification by acid pickling also was low.However,the sorption P capacity of the natural vermiculite and attapulgite after modification increased significantly,and the best condition for calcining modification was burning for 2 hours at 700℃and 500℃.If the P in overlying water was sorbed by vermiculite calcining modification,its pH of the solution increased rapidly.However,the pH increases little for attapulgite. Therefore,using of attapulgite calcining modification is batter than vermiculite as P adsorbent.For instance,the 7g/L of attapulgite calcining modificationthe was added in overlying water with 0.226 mg/L P and pH 8.04 from Qing River.Result showed that about 83.53%P was removed and its P concentration decreased to 0.037mg/L.The concentration of ammonia nitrogen and COD in overlying water decreased little putting biofilm filler under the condition of without plugging flow and aerating, which were decreased largely under the condition of pluging flow and adding biofilm together,and their transparency of overlying water increased from 24 cm to 90 cm.So under the condition of low organic compounds concentration,the effect of transparency enhancing was not obvious by aerating on the base of pluging flow and adding biofilm together.The situation and speed of the overlying water were changed by plugging flow and adding biofilm,and the ammonia nitrogen concentration was reduced,which is maybe the reason that water transparency can be improved.Reducing of ammonia nitrogen concentration in water maybe result in algae bloom limited growth.However, this point needs to be proved in future.The application of plugging flow and adding biofilm technologies indicated that the transparency can be improved obviously under the condition of low nitrogen and phosphorus concentrations in overlying water.For the water body that its depth is 1 m and area is 10000 m~2,500,000 RMB is needed,and the run fee was about 1000 RMB per month.Management was very convenient.As the whole,the attapulgite calcining modification can be utilized to remove P from landscape water,its transparency can be enhanced and P concentration can be reduced.The ammonia nitrogen concentration and situation,flow speed of overlying water all can be improved the by using plugging flow and adding biofilm,the algae growth was limited and its transparency also was increased.