Study On Treatment Of Stillage By Microbial Consortium RXS Associated With Anaerobic Activated Sludge

A system of integrated ethanol-biogas dual fermentation was introduced in our previousstudies. No wastewater was discharged in this system. However, large amounts oflignocellulose existing in cassava stillage was difficult to be degraded effectively in anaerobicdigestion due to the particular structure and properties of lignocellulose. A new system ofintegrated ethanol-biogas dual fermentation with microbial consortium RXS pretreatment wasintroduced in this paper to solve the pollution of wastewater and augment the anaerobicdigestion rate and biogas yield to realize the goal of “low energy consumption” in alcoholmanufacturing industries based on cassava.In this paper, the nitrogen sources correlated with cultivation of microbial consortiumRXS was optimized. And then the microbial consortium RXS associated with anaerobicacivated sludge was applied in treatment of stillage. The experimental results were shown asfollows:1. Sterilization of thermophllic effluent had negative effects on microbial consortiumRXS. The optimum nitrogen sources were fishermeal and corn steep liquor. The optimumnitrogen mixing ratio between fishermeal and corn steep liquor was48:28. Components of themedium consisted of: cassava residue10g·L-1, filter paper5g·L-1, fishermeal4g·L-1, cornsteep liquor3.5g·L-1and thermophillic effluent1L.Cost of PCS medium was approximately10times higher than that of cost-effective medium. Degradation performance for cassavaresidues in cost-effective medium increased by37%compared with that in PCS medium.Microbial consortium RXS had the good passage stabilities in cost-effective medium.2. Ethanol yield, starch utilization ratio, fermentation time and residual total sugar duringeach recycling batches stablized at12.6%,88~92%,48h and less than1%, respectively. Itwas proved that reuse of anaerobic effluent was feasible in this new system. pH inthermophillic and mesophillic reactors was stable during each recycling batches and thereactors run in good conditions. Alkalinity, COD, nitrogen material (total nitrogen, totalsoluble nitrogen and ammonia nitrogen), volatile acid, conductivity and SO24-reach balancedstates through2~7recycling batches. Total methane yield, methane producing velocity andrelative methane yield increased by15~33%,17~38%and25%, respectively, andcorresponded with the first stage. Results in biogas fermentation showed that the system ofintegrated ethanol-biogas dual fermentation was superior to the original system.