Preparation Of Bioflocculant Using Straw And Glutamate Wastewater And Research On Its Water Purification Efficacy

The bioflocculant (BF) is one of most potential research and development direction of flocculants because of its many advantages such as high efficiency, nontoxicity, easy biodegradability and healthy security. However, the high cost and narrow application fields of BF fermentation are the bottleneck problems limiting the industrial production and application of bioflocculant. Consequently, concentrating on on the resource utilization of multivariate biomass wastes, research on the preparation of compound bioflocculant (CBF) using glutamate wastewater and its production process were conducted.Based on the optimization of fermentation conditions, effects of fed-batch fermentation on the bacterium F2-F6 were investigated. The optimal parameters of the carbon source fed were as follows:lOg/L of the initial glucose concentration, glucose fed-types,15h of the best fed-batch fermentation time,0.1% of the concentration of fed-batch, one time fed-batch mode. There were no need for nitrogen addition as the nitrogen addition did not ehance the production of (CBF). The two types of fermentation methods, the batch fermentation and fed-batch fermentation, had been compared. After feeding, the biomass, BF production, sugar utilization and the output rata of BF had increased 37.04%,40.90%,5.51%,28.15%, respectively compared that of the fermentation without feeding. The production of (CBF) by feeding mode was greater than that of batch mode fermentation.The fermentation process of bioflocculant producing bacteria was studied in batch system. Based on the equations of "Logistic equation" and "Luedeking-Piret equation", the kinetic models reflecting its fermentation features of strain growth, substrate consumption and product generation were constructed respectively. The experimental data were processed with the Origin 7.5 software and the batch fermentation kinetics model parameter was obtained. The good agreement of predicted values with the experimental results showed that the kinetic models were applicable for predicting the actual fermentation process.Rice straw pretreatment process was optimized by orthogonal experiment. The optimal condition of NaOH- pretreated rice straw was temperature 80℃concentration of NaOH solution 1.0%, reaction time 90min, suitable smashed rice straw 40 mesh. Pretreated rice straws were degraded by cellulose degradation bacterium. The degradation rate and reduced sugar yield are 70.3% and 10.6%. Flocculation producing bacteria could utilize the saccharifyed liquid of rice straw and produce bioflocculant. The flocculation rate of bioflocculant can reach 94%. Pretreated rice straws were hydrolyzed by cellulase. The hydrolysis yield rate was 49.65% when the rice straw concentration was 50g/L, the cellulase dosage was 0.2g/g substrate. Flocculation rate of enzymatic hydrolysate was 96.5%. It illuminated that the pretreated rice straw could completely substitute glucose as substrate for (CBF) production. The maximum production was 87kg (CBF) per ton rice straws.Monosodium glutamate wastewater was applied as substitutive medium with gradient concentration. The optimum medium compositions was feeding 8 g/L of glucose into 20% glutamate fermentation wastewater without adding additional nitrogen source. This mudium could replace bioflocculant medium for producing bioflocculant and the flocculation rate can reach 95.4%. The optimal (CBF) fermentation conditions for flocculant-producing bacteria F2-F6 by wastewater medium were as follows:fermentation temperature 30℃, initial pH 7.0, rotation speed 140 r/min, seed inoculation concentration 8%, fermentation time 20h. Per litre glutamate wastewater produce 8.5g compound bioflocculant. During fermentation process, there were differences of DO requirement between the growth of flocculent-production bacteria and production of flocculation. Therefore, combined with the step wise oxygen supply strategy, the time of supply high concentrations of oxygen during the glutamate wastewater fermentation process was only 8h, while in the bioflocculant medium process was 21h. Obviously, using glutamate fermentation wastewater for (CBF) production was more energy saving.Production process of (CBF) was constructed and the main operating conditions and control strategies during the production process were confirmed. And product quality standard of (CBF) production was established. Technical and economic index, social and environmental benefit were briefly analyzed.Based on drinking source water and oily sewage, complex formulation flocculation tests and the effects of additives were carried out for (CBF) to find out the optimal addition method and dosage of flocculant. The results showed that the simultaneous application of (CBF) and its additives could reach the best results, which met the requirements of effluent quality and greatly reduced the total dosage.