Study On The Correlation Between The Substrate Enzyme And Its Activities And Purification Of Pond Aquaculture Wastewater In The Constructed Wetland

Pond culture acts as the dominant practice of aquaculture industry in China,its output shared more than 75%of total freshwater aquaculture production.But now,in the course of aquaculture,the deterioration of water quality,the occurrence of disease,the decline of aquaculture product quality and the discharge of aquaculture wastewater without any treatment have made s serious impact on the sustainable development of aquaculture industry.So aquaculture wastewater treatment is urgently needed.Wetland systems are more and more used to treat domestic sewage,industrial wastewater and agricultural runoff in recent decades.This wetland treatment process has been international interested and applied due to its low operational and maintenance costs and high removal capacity for normal water pollution control.The present research was carried on applying constructed wetland to treatment aquaculture wastewater and study on the correlation between the substrate enzymatic activities and purification of aquaculture wastewater.The main research contents and main results are summarized as follows:1:The efficiencies of constructed wetland for purifying the fish cultivating pond effluent were evaluated.The results showed that under the 600mm/d hydraulic loading in 4-10 month,the average removal rate of TSS,COD is 85.8%and 62.1%;the average COD,TSS concentration in effluent is 4.7 mg/L and 9.0mg/L;the average removal rate of NH₄⁺—N,NO₂^-—N,NO₃^-—N,TN is 39.6%,69.0%,22.0%and 40.1%,respectively;the average NH₄⁺—N,NO₂^-—N,NO₃^-—N,TN concentration in effluent is 0.38mg/L,0.013 mg/L,0.061 mg/Land 1.52 mg/L,respectively;the average removal rate of TP is 43.5%, the average TP concentration in effluent is 0.23 mg/L;TSS,COD,NH₄⁺-N and TP concentration of outlet from constructed wetland could meet the standard of national fishery water quality.The removal rate of TSS has no significant change after plant harvested.Effects of aeration on aquaculture wastewater removal of constructed wetlands were studied.The removal rate of NH₄⁺—N,NO₂^-—N,COD increased significantly after aeration,and the aeration could improve outlet water quality,which is a good measure for improve purifying the fish cultivating pond effluent.2:The substrate enzyme activities of constructed wetlands were studied.The results showed that the substrate enzyme of phosphatase,urease,proteinase,dehydrogenas and acellulase ranged 9.2-14.3 mg/100g,0.98-2.06mg/100g,29.9-56.1mg/100g, 142.1-280.4uL/100g and 8.5-15.4mg/100g,respectively;the plant harvesting has a certain effect on phosphatase,urease,dehydrogenas,proteinase activities of substrate,but the substrate acellulase activities have no significant change after plant harvesting;the phosphatase,urease,dehydrogenas and acellulase activities of substrate increased after aeration,the proteinase has no significant change after aeration;enzymatic activities in the upper,medium level of substrate was higher than the lower level of substrate,upper and medium level of substrate is the most effective purification space;the enzyme activity in root zone were significantly higher than those in non-root zone.Difference in enzyme activity existed between plant species.3 The Correlation Between the Substrate Enzymatic Activities and Purification of Aquaculture Wastewater in the Constructed Wetland were studied.There was significant positive correlation between activities of phosphatase in the substrate and removal rate of TP;There was certain positive correlation between activities of urease in the substrate and removal rate of TN,NO₂^--N,particularly,removal rate of TN showed significant positive correlation;There was certain positive correlation between activities of dehydrogenas in the substrate and removal rate of COD,TP,particularly,removal rate of COD showed significant positive correlation.In general,all these conclusion will give reference to future researches on utilizing substrate enzymatic activities as evaluating purification efficiency and choosing ideal wetland plant species.