Anaerobic co-digestion of source segregated brown water (feces-without-urine) and food waste: For Singapore context

• Published in: The Science of the total environment 2013-01, Vol.443, p.877-886
• Main Authors: Rajagopal, Rajinikanth, Lim, Jun Wei, Mao, Yu, Chen, Chia-Lung, Wang, Jing-Yuan
• Format: Article
• Language: English
• Subjects: Anaerobic co-digestion; Anaerobiosis; Applied sciences; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biological treatment of waters; Bioreactors; Biotechnology; Brown water; Decentralized; Environment and pollution; Exact sciences and technology; Flushing; Food; Food waste; Foods; Fundamental and applied biological sciences. Psychology; General purification processes; Humans; Hydrogen-Ion Concentration; In Situ Hybridization, Fluorescence; Industrial applications and implications. Economical aspects; Marine; Methane; Pollution; Reactors; Sanitation; Sewage; Singapore; Source separation; Urban and domestic wastes; Urbanization; Volatile fatty acids (VFAs); Wastes; Wastewaters; Water Pollutants - metabolism; Water treatment and pollution
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2012.11.016

The objective of this study was to evaluate the feasibility of anaerobic co-digestion of brown water (BW) [feces-without-urine] and food waste (FW) in decentralized, source-separation-based sanitation concept. An effort has been made to separate the yellow water (urine) and brown water from the source (using no-mix toilet) primarily to facilitate further treatment, resource recovery and utilization. Batch assay analytical results indicated that anaerobic co-digestion [BW+FW] showed higher methane yield (0.54–0.59L CH4/gVSadded) than BW or FW as a sole substrate. Anaerobic co-digestion was performed in the semi-continuously fed laboratory scale reactors viz. two-phase continuous stirred-tank reactor (CSTR) and single-stage sequencing-batch operational mode reactor (SeqBR). Initial 120d of operation shows that SeqBR performed better in terms of organic matter removal and maximum methane production. At steady-state, CODs, CODt, VS removals of 92.0±3.0, 76.7±5.1 and 75.7±6.6% were achieved for SeqBR at 16d HRT, respectively. This corresponds to an OLR of 2–3gCOD/Ld and methane yield of about 0.41L CH4/gVSadded. Good buffering capacity did not lead to accumulation of VFA, showing better process stability of SeqBR at higher loading rates. The positive findings show the great potential of applying anaerobic co-digestion of BW+FW for energy production and waste management. In addition, daily flush water consumption is reduced up to 80%. Decentralized, source-separation-based sanitation concept is expected to provide a practical solution for those countries experiencing rapid urbanization and water shortage issues, for instance Singapore. ► Source separation of organic waste/wastewater streams on household level was done. ► Brown water (BW) was collected from a specially designed no-mix toilet. ► BW and food waste codigestion proved as a potential substrate for biogas production. ► A distinct improvement in methane yield was observed. ► This concept is vital for countries facing rapid urbanization and water shortage.