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Anaerobic co-digestion of sewage sludge and organic fraction of
municipal solid wastes
Technical University of Lodz, Department of Bioprocess Engineering, Wolczanska 213, 93-005 Lodz, Poland
Abstract
The paper presents the results of investigation of methane fermentation of sewage sludge and organic fraction of
municipal solid wastes (OFMSW) as well as the cofermentation of both substrates under thermophilic and mesophilic
conditions.In the first experiment the primary sludge and thickened excess activated sludge were fed into a 40 dm3
bioreactor operated thermophilically.The second co-fermentation experiment was conducted with the mixture of
sewage sludge (75%) and OFMSW (25%) in the same bioreactor arrangement.The other three experiments (III and
IV, V) were carried out in quasi-continuous mode in two separated stages: acidogenic digestion in the continuous
stirred tank bioreactor under thermophilic conditions (56 8C) and mesopholic methane fermentation (36 8C).The
third experiment was conducted with the substrate-OFMSW only, in the fourth run sewage sludge from a municipal
water treatment plant was used.In the fifth experiment a mixture of sewage sludge and OFMSW was used. In all
experiments the following data were determined: biogas content and productivity, pH, total suspended and volatile
solids, elemental content (C, H, N, S) of sludge, OFMSW and inoculum, total organic carbon, total alkalinity and
volatile fatty acid content.Comparing the elemental analysis of sewage sludge and OFMSW it is evident that N
content is higher in the sludge than in the OFMSW, however, the carbon content relation is the opposite, which may
be beneficial to methane yield of co-digestion.Methane concentration in the biogas was above 60% in all cases.
Biogas productivity varied between 0.4 and 0.6 dm3yg VSS depending on substrate added to the digester.The
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obtained results are generally consistent with literature data.

2002 Elsevier Science Ltd.All rights reserved.
Keywords: Anaerobic digestion; Mesophilic; Thermophilic; Sewage sludge; Organic fraction of municipal solid wastes (OFMSW);
Biogas; Elemental analysis; Mass and energy balance
1. Introduction
Sewage sludge is characterized by a high content of
organic compounds and this is the cause of its putrescibility.
Ther efore, sludge before landfill disposal or
agricultural application should undergo chemical and
hygienic stabilization.One possible method of stabilization
and hygienization involves methane fermentation.
Municipal solid wastes (MSW) contains an easily biodegradable
organic fraction (OF) of up to 40%.Con-
*Corresponding author.T el.: q48-42-631-3715; fax: q48-
42-636-5663.
E-mail address: stanleda@ck-sg.p.lodz.pl (S.Ledakowicz ).
ventional MSW management has been primarily
disposal by landfilling.The anaerobic co-digestion of
sewage sludge with organic fraction of municipal solid
waste (OFMSW) seems to be especially attractive
(Hamzawi et al., 1998).The feasibility of anaerobic codigestion
of waste activated sludge and a simulated
OFMSW was examined by Poggi-Varaldo and Oleszkiewicz
(1992).The benefits of the co-digestion
include: dilution of potential toxic compounds,
improved balance of nutrients, synergistic effects of
microorganisms, increased load of biodegradable organic
matter and better biogas yield.Additional advantages
include hygienic stabilization, increased digestion本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。