Production And Application Of Compound Bioflocculant Using Piggery Wastewater As Nutrilite

This study focused on bioflocculant whose medium cost was too expensive andindustrialization was blocked, using piggery wastewater as a cheaper alternativemedium for bioflocculant-producing bacteria, then the bioflocculant produced was usedfor tannery wastewater treatment, which was treating wastewater with wastes.Piggery wastewater was used as a cheaper alternative medium for abioflocculant-producing bacteria flora B-737. According to the nutrient, energy andadaptability to the environment of B-737, the best culture medium and culturingconditions was studied, fermentation kinetics including producing, production ofbioflocclant and substrate consuming were studied under the optimal culture media.Meanwhile, the chemical structure and characteristics of MBF-737was analysed, thenthe bioflocculant was used to treat tannery wastewater and the flocculating mechanismswas discussed.The results showed that, the best culture medium and culturing conditions for floraB-737were the piggery wastewater(COD is about2500~5000mg/L, TN is about150~300mg/L) with1.6g/LK2HPO4,0.8g/L KH2PO4added, no need to add any carbon ornitrogen source, natural pH, inoculation was2%, cultivated for18~24h in shaker whenthe temperature was30℃, rotating speed was160r/min, the bioflocculant yieldreached to1.5g/L as well as COD and TN of the wastewater was reduced by61.9%and53.6%. Not only the medium cost reduced over99%, but the bioflocculant yield andflocculating properties was maintaining well.Based on the optimum fermentation conditions, kinetics model containing theproducing of B-737, MBF-737production and COD consumption were establishedusing mathematical modeling, the experiment data could be well fitted with the modeldata, average error were below5%, and these models contributed to large scaleproduction of the bioflocculant for controlling and forecasting.Bioflocculant MBF-737contained83.07%polysaccharide as its main component,infrared spectra showed the presence of hydroxyl, carboxyl and amino groups in itsmolecules. It was soluble in water but not in organic solvent such as ethanol, acetone.MBF-737had the characteristics of high thermo-stability between20~100℃and pH stability between5~10, fermentation liquid stored in refrigerator and dry powder storedat room temperature could keep high flocculating activities more than5months.Bioflocculant MBF-737could well cooperate with Fe2+, Ca2+, Al3+, Fe3+, the amount ofMBF-737for treating kaolin suspension was only0.2mL and it had the characteristicsof lower dosage, better flocculation efficiency.The optimum flocculating conditions for treating wastewater was adding0.01125g/L MBF-737at first, then0.25g/L CaCl2,and then0.25g/L NaOH, mixingconditions was320r/min,2min;80r/min,7.5min, it was still effective when enlarged15times. The sedimentation kinetics analysis showed that the flocs formed afterflocculating could well settlement at only30s. The flocculating mechanism of MBF-737was that surface electric charge of particles in wastewater reduced and repelling forcebetween particles weakened because of NaOH, bioflocculant and particles aborbedthrough electric-attraction and ion-bond, and settlemented down through bridging ofCa2+. hydroxyl and carboxyl of the bioflocculant extend the molecule and the chains hadlonger useful length and promoted the bridging.