Effects Of Several Condition Factors On The Bioflocs Cultivation In Sequencing Batch Reactor

Biofloc technology(BFT) was an effective method to convert residual and fecesinto heterotrophic bacteria biomass. Bioflocs could be fed to filter feeders fish or addedto the aquatic feed instead of fish meal and soybean, it was an effective way to solve theenvironment restriction and resource utilization promblem which were sustainabledevelopment of the aquaculture industry faced. Culturing bioflocs by using sequencingbatch reactors(SBRs)was not only solved the problems of gill jam and oxygen deficit,but also the reaction system was operable and controllability. Based on the influencefactors to produce bioflocs, effects of aeration mode, pH, alkalinity, carbon sourcecontent on the bioflocs cultivation in sequencing batch reactors were studied.1. Effects of aeration mode on the activity and nutritional component of bioflocs insequencing batch reactors(SBRs)Aquaculture solid waste was used to culture bio-flocs in SBRs. Continuousaeration and intermittent aeration modes were set up to study effects of aeration modeon the activity and nutritional component of bioflocs SBRs. Results showed thatintermittent aeration tended to inhibit the nitrification process with average nitriteconcentration of0.93±0.26mg/L and nitrate concentration of0.90±0.21mg/Lthroughout the experimental period. In continuous aeration treatments, highaccumulation of nitrite and nitrate were observed during the trial. At the end ofexperiment, the concentration of nitrite and nitrate were8.68mg/L and20.78mg/L,respectively. The percentage of organic nitrogen to total nitrogen (TON/TN) ofbio-flocs increased gradually in intermittent aeration SBRs with an average of81.85±1.27%, while a decreasing treand was observed in the continuous aerationtreatment with an average of61.11±4.30%during the study. In intermittent aeration treatments, the maximum concentration of protein content was34.38±0.15%and incontinuous aeration SBRs, was28.59±3.50%. Average protein content of bio-flocs was5.85±0.26%higher in the intermittent aeration group than continuous aerationtreatment.2. Effects of pH levels on the activity and nutrition component of bioflocs insequencing batch reactors(SBRs)Study on the effects of different pH levels on the activity and nutrition componentof bioflocs by using SBRs to culture bioflocs. Results indicated that nitrite and nitratehad no accumulation,dissolved active phosphorus had a better removal efficiency, buttotal ammonia nitrogen accumulation was higher when pH levels ranged from6.5~8.5,especially,the concentration of total ammonia nitrogen reached37.71mg/Lwhen pH was6.5;conversion efficiency of inorganic nitrogen into organic nitrogen washighest when pH levels ranged from7.5~8.5in SBRs. The microbial activity in bioflocswas less influenced by pH, the activity of total microorganism,heterotrophic bacteriaand nitrifying bacteria had no significant differences; dominant bacterial community inbioflocs was heterotrophic bacteria during the experiment. From the concentration ofEPS(Extacellular Polymeric Substances，EPS）in bioflocs of view, the concentrationof exopolysaccharide was higer than extracellular protein in the components of EPScontent. Weak acid environment with pH6.5was beneficial to bioflocs to synthetizeextracellular protein and exopolysaccharide. Furthermore, bioflocs had bettersettleability and highest crude protein content when pH level was6.5.3. Effects of alkalinity on the activity and nutrition component of bioflocs insequencing batch reactors(SBRs)Study on the effects of different alkalinity on the activity and nutrition componentof bioflocs by using SBRs to culture bioflocs.Results indicated that nitrite and nitratehad no accumulation, total ammonia nitrogen had a better removal efficiency whenalkalinity were800mg/L,4000mg/L and8000mg/L.The microbial activity in bioflocswas less influenced by different alkalinity levels,the activity of total microorganism,heterotrophic bacteria and nitrifying bacteria had no significant differences; dominantbacterial community in bioflocs was heterotrophic bacteria during the experiment. Itwas benifical to heterotrophic bacteria growth and bioflocs formation.From bioflocssettleability of view,bioflocs had highest biomass,best settleability, lower EPS and extracelluar protein when alkalinity was8000mg/L. From the EPS of bioflocs,it wasbenificial to synthetize extracellular protein and exopolysaccharide when alkalinity was4000mg/L. Organic ingredients and crude protein content were highest when alkalinitywas800mg/L.4. Effects of carbon sources addtion on the activity and nutrition component ofbioflocs in sequencing batch reactors(SBRs)Study on the effects of carbon sources addtionon the formation,activity, nutritioncomponent of bioflocs and aquaculture water treatment by using SBRs to culturebioflocs with glucose as carbon source. Results indicated that biflocs were all loose instructure, lower content and adverse to bioflocs formation when carbon sources addtionwere1.25times,1times,0.75times and0.5times than aquaculture waste solids.Compared with carbon sources addtion1times,0.5times thanaquaculture waste solid,the cultivation effects of bioflos were better when carbon sources addtionwere1.25times,0.75times than aquaculture waste solids.Nitrite and nitrate had no accumulation,conversion efficiency of inorganic nitrogen into organic nitrogen was higher, crudeprotein content was highest and bioflocs quantity was higher whencarbon sourcesaddtionwere1.25times,0.75times than aquaculture waste solidin reactors.