Study The Effect Factors On Purifying Marine Aquaculture Wastewater With Moving Bed Biofilter

Seawater circulating water aquaculture is through purification treatment ofaquaculture wastewater, so as to achieve the purpose of recycling sea water. Movingbed biological filter disposing aquaculture wastewater is the core unit in wastewatertreatment of mariculture, as well as the largest energy-consuming unit. Thisexperiment aims at finding the best gas-water ratio and hydraulic retention timethrough studying two most influential factors, gas-water ratio and hydraulic retentiontime (HRT) on moving bed biological filter. The main conclusions are as follows:1. This experiment uses natural biofilm culturing, and HRT is40minin this stage,the water inlet temperature is15~20℃,influent ammonia is4.5~5mg/L, CODMnis19~24mg/L, pH is7.8~8.0, gas-water ratio adopted is10:1, the process of naturalhanging membrane needs71d, at this time, ammonia removal ration is stabilized atabout15%, the concentration of nitrogen accumulation is stabilized at0.005mg/L~0.006mg/L, and COD removal ration is stabilized at12%~15%, biofilm culturing ismature.2. Under different gas-water ratio there were some difference in the pollutants removalration for MBBR. As the condition of gas-water ratio changes, the removal rate ofmoving bed biological filter for ammonia firstly decreases and then increases. Thegas-water ratio in this experimental phase are6:1,10:1,15:1,20:1and30:1. When thegas-water ratio is6:1, the removal rate of biological filter is the maximum, and whenthe gas-water ratio is20:1, the removal rate is the minimum. Under the condition ofdifferent gas-water ratio, the accumulative degree of filter effluent nitrogen is varying.As the gas-water ratio increases, the accumulative concentration of nitrous decreasesat first and then it increases. When gas-water ratio is6:1, the nitrous accumulation isthe most serious and the fluctuation is larger. When gas-water ratio is20:1, theaccumulation is the smallest, and the concentration of effluent nitrogen is theminimum. When the gas-water ratio is6:1, the removal rate of filter on COD is thehighest, with the average up to16.63%, when gas-water ratio is20:1; the removal rate of filter on COD is the lowest, with the average of only8.35%. Therefore, in the studyof influence of gas-water ratio on treatment efficiency of moving bed biological filter,select6:1as the best gas-water ratio.3. Select the gas-water ratio of6:1, hydraulic retention time at this experimentalstage is40min,60min,80min,100min and120min. At different hydraulic retentiontime, there is significant difference for removal rate of moving bed biological filter forammonia. The overall trend is, as hydraulic retention time increases, the removal rateof biological filter for ammonia increases correspondingly. When HRT is40min, theremoval rate of filter for ammonia is the minimum. The removal rate of HRT of80min is higher than that of HRT of100min. When HRT is120min, the removal rateof filter for ammonia is the maximum, with the average removal rate of16.69%. Theaccumulation of nitrogen concentration increases as hydraulic retention time increases.The removal rate of filter for COD is, when HRT is the maximum of60min, theaverage removal rate is31.47%. When HRT is40min, the removal rate is the lowest.When HRT is100min and120min, the removal rate is without significant difference.There is little difference between the removal rate of HRT of80min and the removalrate of HRT of120min. Integrated study, HRT of80min is the best under thecondition of gas-water ratio of6:1.The study of influence factors for moving bed in this thesis provides a referenceand basis for further study, as well as contributing to enhancing the applicableprecision of moving bed biological filter in the actual production, optimizingproduction management of recalculating aquaculture system and promoting andenhancing the refinement and standardization of business management.