Studies On Aaquaculture Water Treatment And Recycling System Of Land "Crab Pond And Fish Pond"

Accompanying the widely distributed pond in our country farming,the priority model is still following the traditional mode as high density,high throw of the bait and high rate to change wate. Under this model, onthe one hand, the discharge of breed aquatics wastewater often causeseutrophication, destroys the ecological environment. On the other hand, itcaused the problems of low survival rate, food safety problems and so on.The improvement on the traditional breeding mode and breeding therationalization of wastewater treatment, become the key problems to besolved. This paper specifics to the pollution problem caused by thetraditional mode of aquaculture, arounding the change of economical landfarming pond model, Combining the study on the Effect of differentdensity Elodea nuttallii planting on ecological culture of Eriocheir sinensis,raising the stable situ ecological restoration pond （crab pond）. The study area was ground-launched culture zones near Zhihu bay in Binhu District inWuxi, where the main pollution sources, way, characteristics andconveying flux was investigated. The wastewater of peripheral breedingpond was processed in situ and ectopic. The "crab pond-fish ponds" watercirculating system was established. Studied the efficiency of purifying andrecycle of breeding water body. The results were as follows:1. Effect of different density Elodea nuttallii planting on ecological cultureof Eriocheir sinensisEffect of different density Elodea nuttallii planting on ecological cultureof Eriocheir sinensis was studied. The results showed that:Elodea nuttalliican significantly reduce nutrient concentration, improve water transparency,effective inhibition of algae from eutrophic water. With the increasing ofthe Elodea nuttallii density, the reduction degree of the nutrient in crabpond is gradually increased. And when the Elodea nuttallii density is15kg/m², The concentrationNO₃-N、NH₄-N、TN、TP、CODMnand Chl a wassignificantly lower than that of after experiment before the concentration （P <0.01）, decreased by59.8%,70%,79.5%,92.2%,70.9%and63.3%.butwhen the Elodea nuttallii plant density is higher than15kg/m², thepurification is efficiency significantly. The protein, fat, calcium, zinc andthe yield of the Crab was significantly higher than that of the control group（P <0.01）, in Elodea nuttallii density is15kg/m², the highest yield ofcrab was1575kg/hm².2. characteristics of traditional aquaculture pollution and transport fluxesof experimental areaUnder the traditional cultivation pattern, the main pollutants are TN andCODMn, both the total output flux of88.1%; In turtle pond, fish pond andfish pond,TN concentration changes with time,.In crab pond, TNconcentration has always been maintained at a high level, which increasedsignificantly in the summer, Organic pollution is serious, there is a similartendency in the breeding pond, the remaining indexes all the year round ina smooth; Emissions of TN from fry pond and fish ponds to waterenvironment were135.9kg/hm²and97.5kg/hm².TP, CODMn, and other contaminants are all highest object in the farming pond; In the traditionalcultivation pattern, there is a higher mortality rates raise crab, pollution ofunit production of aquatic products are more serious; utilization per unitarea of land farmed fish and fry ’s total output of pollutants flux is high,were377.85kg/hm²and485.7kg/hm², turtle pond is5⁶times, whichmade a greater pressure on the environment; Output flux of TN and NO₂-Nwith greater correlation of0.97and0.94, and lower correlation withCODMnof0.79.3. Influence on the microbial community in the ecological restorationaquacultureCompared the microbe in the breeding pond between2009and2010inthe harvest season. The results show that: After the processing of situecological restoration and ectopic wetland ecological restoration, thenumber of heterotrophic bacteria decreased obviously. The microorganismquantity in crab pond No.1and No.2used comprehensive treatmenttechnology were from6.5x10³and1.1x104ind/mL in2009fell to1.5x 10³and2.0x10³ind/mL in2010, respectively. In the system, the diversityof microbial also rised obviously. The Shannon-Wiener index in8pointsare more than2.0.4. Effcet of sequencing batch type circular treatment of the breedingwastewaterIn the circulating water system "Crab-Fish ponds", the water quality ofcrab pond is stable. The main physical and and biochemical indicators isbetter than the fish ponds. The water quality reached to the nationalstandard of surface water by grade II-â…¢. The ectopic restoration result ofcrab pond to fish ponds was obviously. In fish pond, the extinction ratio ofCODMn, NH₄-N, TP, TN and Chl a were58%,55%,75%,65%and60%,respectively; In pond for fry, the extinction ratio of CODMn, NH₄-N, TP,TN and Chl a were more than45%. And the water quality reached to gradeâ…¢. And the NH₄-N in fish ponds was grade â…¡At the same time, thehydraulic loading of ectopic wetland ecological restoration system waslarger. As the HRT for30to40d, breeding for6336m3per wastewater, the hydraulic loading was0.02-0.03m3/（m²d.）. this can made bad â…¤gradebreeding waste water purification to grade â…¢, and maintaining relativestability.