Elsevier

Environmental Research

Volume 155, May 2017, Pages 249-260
Environmental Research

Anaerobic digestion of sewage sludge with grease trap sludge and municipal solid waste as co-substrates

Highlights

Addition of two waste into the sewage sludge digester improves process efficiency.

Co-digestion of 3-component mixtures increases VS removal up to 29%.

While, methane yield increased up to and 82% relative to the control digester.

Effectiveness of the process depends on OLR and the content of waste in the feedstock.

Abstract

The feasibility of simultaneous treatment of multiple wastes via co-digestion was studied in semi-continuous mode at mesophilic conditions. The obtained results indicated that sewage sludge, organic fraction of municipal waste (OFMSW) and grease trap sludge (GTS) possess complementary properties that can be combined for successful anaerobic digestion. During the co-digestion period, methane yield and VS removal were significantly higher in comparison to digestion of sewage sludge alone. Addition of GTS to digesters treating sewage sludge resulted in increased VS removal and methane yield up to 13% (from 50 to 56.4) and 52% (from 300 to 456,547 m3/Mg VSadd), respectively. While the use of OFMSW as the next co-substrate in the feedstock, can boost methane yield and VS removal up to 82% (300–547 m3/Mg VSadd) and approximately 29% (from 50% to 64.7%), respectively. Moreover, the results of the present laboratory study revealed that the addition of co-substrates to the feedstock had a significant influence on biogas composition. During the experiment methane content in biogas ranged from 67% to 69%. While, the concentration of LCFAs was increasing with the gradual increase in the share of co-substrates in the mixtures, wherein only the oleic acid was higher than some inhibition concentrations which have been reported in the literature. However, it did not significantly affect the efficiency of the co-digestion process.

Keywords

Co-digestion
Sewage sludge
Co-substrate
Methane yield
Long chain fatty acids

This work was supported by Norway Grants in the Polish-Norwegian Research Programme operated by the National Centre for Research and Development "Innovation in recycling technologies of sewage sludge and other biowaste - energy and matter recovery" [POL-NOR/201734/76/13].

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