Bioremediation Of The Pond Water By The Multilevel Biosystem

The pond culture occupies an important position in fisheries development and economics of China.It also plays a great role in adjustment of agricultural industrial structure and overall development of rural economy.However,in order to obtain high economic returns,fishermen often use the culture model with high density stocking and high forage-fed,which leading to the water quality deterioration and serious pollution increasingly.Under the guidance of building up scientific development concept,developing the type of resources saving and friendly environment aquaculture,this study established a model of multilevel bioremediation system in pond aquaculture,which consisted of three parts: immobilized biofilm structure of the artificial substrates,floating island planting unit and submerged plants unit.Through the synergistic effect of these three aspects,the water condition was purified and the nutriment was utilized multilevel.The more and more economical and social benefits were obtained at the cost of less resources consumption and environment pollution,and it finally realized sustainable development of pond cultrue.Efficacy of the multilevel biosystem in aquaculture pond is evaluated through analyzing the dynamic changes of microbe and plankton in water,and measuring water quality index in TN,NH₄⁺-N,NO₃^--N,NO₂^--N,TP,PO₄^3--P,COD_Mn,Chlorophyll-a,etc.The results indicated:using elastic biological stuffing as artificial substrates to study bioremediation of the immobilized biofilm structure in pond and in-situ remediation of aquaculture water body structured upon the indigenous and exogenous microorganisms as bacterial source.The result demonstrates:when water temperature is between 30±2℃,the immobilized biofilm structure generally form around 30d in the water body using the indigenous microorganisms as bacteria resource.However,the immobilized biofilm structure generally form around 20 to 30 d[a little bit earlier]in the water body using the exogenous microorganism as bacteria resource with mainly Bacillus sp.and Lactobacillus sp..Elastic biological stuffing can upgrade the bacteria at 10³ times order of magnitude in pond water body to 10⁶ times order of magnitude in the biofilm structure or upgrade by above 1000 times.Additional exogenous microorganism can increase nearly times bacteria adhesion content than the indigenous microorganism in pond.Analysis on the length of elastic biological stuffing indicates that there mainly the enrichment of bacteria flora of mainly aerobic microorganisms such as nitrobacteria and amonifying bacteria at the 10⁵ times order of magnitude at 50 cm under the water surface;as well as of mainly anaerobic and facultative microorganisms such as denitrifying bacteria at the 10⁵ times order of magnitude at 100 cm under the water surface.Seen from distribution area of elastic biological stuffing,the result of water quality remediation is better in 15%experimental groups than in 10%experiment groups,while the significance is not clear(P＞0.05).Judged by the result of in-situ remediation of aquaculture water body in pond,treatment technology of bioremediation of microorganism can upgrade by 100%the content of microorganism in water body,remove 11.27%to 90.00%of TN,TP,ammonia nitrogen,nitrite and COD_Mn, with marked results(P＜0.05).In particular,the content of chlorophyll-a in pond can be decreased by 36.90%to 57.25%and it shows very good result of control of water quality eutrophication.Researches indicate that the utilization of the immobilized biofilm structure system in pond structured using the artificial substrate is an effective method of in-situ remediation of pond aquaculture water body.It had been studied that the effects on distribution of the microorganisms and nitrogen cycle in the pond water body under planted float system which made of Ipomoea aquatica. The results showed that the planted float system could obviously regulate the numbers of the bacteria(such as nitrogen cycle bacteria) and fungi at different depth of water in the pond,so that the different physiological kinds of the microorganisms could survive together at the same depth of the water.By the action of the planted float system,the nitrogen cycle in the water could be accelerate and the capability of self-purification could be raised, respectively,suggesting that the waste water produced during the aquaculture process could be treated.The purifying efficiency of the planted float had relationship with its occupied area in the water.Within 90 days of the treating period,there was a sufficient and high removal rate of nitrogen under the planted float system,which occupy 20%area of the pond. The removal rate of TN,NH₄⁺-N,NO₂^--N,NO₃^--N was 38.8%,51.2%,49.7%,69.6%.The results indicated that it was a good method to bioremediation the pond aquaculture environment on site by the planted float system.Submerged plants in pond play a very important role in amelioration of water quality and growth control of algae.The study points that both Elodea Canadensis and Potamogeton pectinatus L.have allelopathy on Scenedesmus obliquus,and perform the phenomenon that "low concentration promoted,high inhibited".Compared the effects of restraining growth of algae,extract of Potamogeton pectinatus L.performs better than Elodea Canadensis in restraint to Scenedesmus obliquus.Constructing of restoration system with submerged plant of Potamogeton pectinatus L.could reduce nutrition of nitrogen and phosphorus,simultaneity increase the diaphaneity and debase the quantity of phytoplankton.On the 90th day of treatments,the removal rates of submerged plants which occupied 15%area of the pond are 63.09%,27.90%,51.61%,55.00%and 41.45% correspond to Chlorophyll-a,TN,NH₄⁺-N,TP and COD_Mn.On the other hand,the amount of phytoplankton reduced 34.97%of group 15%,the amount of blue algae and green algae which are considered the main algae of water eutrophication reduce by 31.18%and 35.33%.Construction of the multilevel biosystem in pond would perform the best remendation effect when in the proportion of 10%artifical substrate,10%planted float system and 10% submerged plants.Within 90 days,the removal rate of different treatments to Chlorophyll-a, TN,NH₄⁺-N,TP and COD_Mn are 68.07%,32.52%,70.00%,54.55%and 45.93%.The amount of phytoplanlton reduced by 48.04%,and the amounts of blue algae and green algae are 28.47%and 29.32%compared to the control group.The kinds of zooplankton changed from Protozoa to big algae-eaten zooplankton such as Rotifers and Cladocera.The economic benefits of multilevel bioremediation system technology are also analyzed.It is shown that using multilevel bioremediation system has a positive role in the transformation and improving freshwater aquaculture technology.It also purifies pond water,and develop new fishery of energy saving and pollution reduction.The multilevel bioremediation system will be beneficial to protect environmental as well as to increase economic benefit,and the bioremediation technology has the environmental benefits,both economic and social benefits.It also has generalizable value and developable prospects.