Research On The Fish-vegetable Co-exiting And Bio-floc Water Purification Technology Application In Saline-alkaline Ponds In The Northwest China

To study the effects of Ipomoea aquatica floating-bed and adding carbonresource (molasses) on water quality and plankton of the saline-alkaline ponds in thenorthwest China in fish-vegetable and bio-floc technology. We have conducteddifferent coverage rate of Ipomoea aquatica floating-bed (5%and10%) on twotreatment fish ponds, and added the molasses100%,75%and50%of the theoreticaladded amount to three treatment fish ponds from May to September, aimed atproviding some technical reference and basic information of this two technologiesapplicated in saline-alkaline ponds in the northwest of China. The main results aresummarized as follows:(1) With the Ipomoea aquatica floating-bed building in ponds, the transparencyof the water was inproved obviously, made dissolved oxygen stayed at above3mg/L,but have less impact on temperature, pH value and electrical conductivity in ponds.The highest removal rate of NH4+-N, NO3--N, NO2--N, TN, TP and COD in treatmentponds was58.2%,34.8%,53.8%,9.46%,39.3%and31.3%, respectively. The averageconcentration of NH4+-N, NO3--N, NO2--N, TN, TP and COD in treatment ponds wereboth significantly (P<0.05) lower than the control pond.The density and biomass of phytoplankton, the density of zooplankton intreatment ponds were both significantly (P<0.05) lower than the control pond, but thebiomass of of zooplankton was significantly (P<0.05) higher than the control pond.The Shannon-Weaver diversity and Pielou evenness index of phytoplankton were bothsignificantly (P<0.05) higher than the control pond. The Shannon-Weaver diversityand Pielou evenness index of zooplankton in treatment10%pond was significantly(P<0.05) higher than the control pond.Different coverage rate of Ipomoea aquatica floating-bed can effectivelyimproved the water quality, but the treatment10%was better than the treatment5%.(2) Adding different amount of molasses to ponds could improve thetransparency of the water, reduce the value of COD, but had no significantly impact on the concentration of TP of the water. The concentration of NH4+-N, NO3--N,NO2--N of three treatment ponds decreased respectively by58.20%、77.48%、39.81%and25.71%、31.42%、21.92%and52.94%、76.19%、47.82%, which was significantlydifferent.The density of cyanobacteria in treatment ponds ranged from812.5×104to1263.0×104ind./L and the biomass ranged from25.34to54.31mg/L, correspondingly,the density of cyanobacteria in control pond ranged from1079.2×104to1216.5×104ind./L and the biomass ranged from34.01to58.54mg/L, which was significantly(P<0.05) different. The Shannon-Weaver diversity of zooplankton of treatment100%and75%decreased by15.18%and16.83%, and it was significantly (P<0.05) lowerthan the control pond which decreased by32.56%.Adding with100%and75%of the theoretical amount of the molasses to pond,the concentration of some harmful substances decreased，cyanobacteria reproductioncontrolled, the biodiversity of plankton increased, the water quality could beimproved effectively, the treatment adding molasses with75%of the theoreticaladded amount is more economical and practical.