| Bioethanol is a kind of clean and renewable bioenergy. Cellulose can be used as materials for ethanol fermentation;however it could not be wildly used because of the complex pretreatment.Cellulose is ubiquitous in industrial wastewater especially in agriculture products processing plants,and is hard to be treated using conventional methods.This study,therefore,combined the wastewater treatment and ethanol fermentation processes in one unit in order to investigate the feasibility and operation conditions of ethanol fermentation in a wastewater treatment unit.The scope of this study included three aspects:(ⅰ)to determine the cultivation conditions of fungus,(ⅱ)to find out the microbiological properties of fungi in wastewater treatment process and (ⅲ)to analysize metabolic network for ethanol fermentation.It has been investigated on detection approaches of species distribution of bacterial and fungus in mixed community by adopting selective inhibition technique.Activated sludge and supernatant of soil liquor from grass ground were used as seed fungus in a sequence batch reactor (SBR).It showed that selective inhibition technique could be used to quantify the activity distribution of sludge.However,in some cases,imcomplete or failture inhibition effect of antibiotics could also happen.Moreover,the accuracy of results was not high and could only be applied for estimating the ratio of fungal and bacterial activity of a certain kind of activated sludge.It was suggested that this method should combine with other methods to define the accuracy of results,e.g.,microscope and analysis of cellular composition.Using different aeration conditions,the operation conditions for fungus concentration were investigated.By analysis of microbiological properties,metabolic products such as organic acids were measured,and process propeties of wastwater treatment system were examined as well as the microbiological properties of fungus in wastewater treatment process.The following results was obtained:(ⅰ)under short-time aeration condition,the number of fungus increased continuously,reached to 1.62x106cfu/mL at 85 day and was stable afterwards.After canceled the aeration phase in the SBR sequences and extended oxygen-limiting reaction time,a large number of fungus died off.It was suggested that some amounts of dissolved oxygen was important for fungal survival;(ii)the efficiency of degradation of cellulose for ethanol fermentation was not satisfied by fungal mixed species.The degradation of cellulose was limited,and the total organic carbon(TOC) removal was only 20～30%.Propionic acid type fermentation occurred which indicates that ethanol fermentation was inhabited.It was presumed that the low temperature in the reactor caused a low utilization rate of cellulose as high ORP (oxidation-reduction potential) brought about excessively propionic acid accumulation.In order to find or optimize the control conditions of coupling wastewater treatment and ethanol fermentation,the theoretical analysis of metabolism network model of ethanol fermentation by yeast was also performed in this study.The preliminary analysis has been carried on metabolism way and flux distribution under anaerobic condition using element mode analysis and flux balanced analysis respectively.And the compatibility of wastewater treatment with ethanol fermentation was analylized theoretically from the model.It was believed that G6P(glucose-6-phosphate),GAP (glyceraldehyde-3-phosphate) and ACET(cetaldehyde) were main nodes which influenced the model flux distribution;The glycerine was main by-products affecting ethanol production rate;The reduction of glycerine flux could cause distinct enhancement of ethanol production rate,when reduced by 43.2%,the flux of EMP (Embdem-Meyerhof-Parnas) increased 120% and the carbon flux which was carried by ethanol increased 135.8%;Under anaerobic condition,ethanol fermentation wouldn't affect the efficiency of wastewater treatment,which were compatible theoretically and might be carried in the same system.The results in this research provided a new perspective for solving industrial wastewater which consisting of cellulose richly in Shanxi province,and provided a basic theoretical understanding for discussing new crafts which could recycle new energy in the process of wastewater disposal.It was of value theoretically and practically. |
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