Technological feasibility of biodiesel production from bioaugmented hydrolysate of waste sludge in a municipal wastewater treatment plant

Abstract

The hydrolysate of waste sludge was used as the feedstock of biodiesel production, and its technological feasibility was investigated. Waste sludge, collected from No.3 Municipal Wastewater Treatment Plant of Xi’an, was hydrolyzed in two parallel reactors firstly. Yeast was added into one reactor for bioaugmentation, and the other reactor without yeast was used as a control. Then an acid-catalyzed in situ esterification process was carried out to convert the hydrolysate to biodiesel. The results of hydrolysis showed that the reactor bioaugmented with yeast could promote hydrolysis compared with the control one because of an obvious variance in total suspended solid(TSS), volatile suspended solid(VSS) and soluble chemical oxygen demand (SCOD). Furthermore, gas chromatography (GC) analysis exhibited that the total volatile fatty acid (VFA) was low in the hydrolysate of bioaugmentation reactor; however, its yield of the fatty acid methyl esters (FAMEs) by in situ esterification was obviously higher when compared with the control one. Therefore, it may be inferred that the hydrolysate of bioaugmentation was mainly inclined to longer-chain fatty acid rather than to VFA. Anyway, an FAMEs yield of 9.24% (wt%) from dried sludge was attained after the 12-d bioaugmentation hydrolysis and succedent esterification. This value was not only higher than that of the control one but also higher than that reported in previous literature. The above results illuminated that it was feasible to produce biodiesel from the bioaugmented hydrolysate of waste sludge.

Keywords

waste sludge / hydrolysis / bioaugmentation / biodiesel production / feasibility

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