Anaerobic co-digestion of brown water with kitchen waste in decentralized, source-separation-based sanitation concepts

Current centralized sanitation systems adopted by many developed and developing countries minimize the exposure of wastewater to citizens by flushing them away from households. However, the transportation process consumes large amounts of energy and water and gives rise to diluted sewage. In contrast, decentralized sanitation systems that treat source separated wastewaters would encourage the recycling of nutrients for agriculture, reduce household water consumption significantly and generate a source of clean energy. This study is initiated by an attempt to redefine urban communities as renewable resource recovery centres through the adaptation of “decentralized and source-separationbased sanitation concepts.

Further Authors:
R. Rajinikanth - Nanyang Technological University, Singapore
Y. Mao - Nanyang Technological University, Singapore
I. Ho - Nanyang Technological University, Singapore
A. Ahamed - Nanyang Technological University, Singapore
J. Y. Wang - Nanyang Technological University, Singapore

In this concept, the wastes are separated into various streams. A source separation toilet would be used to separate urine and feces from the souce. Other waste streams include grey water (from showers and cleaning) and kitchen waste. Among the various household wastes, brown water and kitchen waste which are high in organic matter are suitable for energy recovery by anaerobic digestion. This study presented the potential of using brown water and kitchen waste as feed sources for energy production. Mesophilic anaerobic co-digestion of brown water with kitchen waste in benchscale (5 L) and lab-scale (30 L) reactors were carried out. The objective was to compare the performance between single-stage and two-phase systems, and between continuous stirred tank reactors (CSTR) and sequencing batch reactor (SeqBR) for the initial 110 days of operation. Monitoring parameters like reactor pH, COD, biogas volume and composition, VS, TS and VFA were analyzed twice a week. The kitchen waste/ brown water mixture was prepared daily and fed to the reactors in a semi continuous mode. All the reactors were operated in parallel and had an initial organic loading rate (OLR) of about 1 g COD/L.d. For the first 40 days of operation (i.e. OLR of 1 g COD/L.d), the effluent quality in terms of organic fraction was almost similar in all the configurations, with COD, TS and VS removal efficiencies of about 80, 55 and 65%, respectively. However, SeqBR was found to have higher organic removal efficiencies as compared to CSTR after the OLR increased to 2-3 g COD/L.d. Based on the bench-scale study, subsequent scaling up to 30 L lab-scale adopted the two-phase CSTR/ SeqBR digester configuration with similar operating conditions. During the initial 75 days of operation, the lab-scale two-phase CSTR/SeqBR digester showed better performance, as illustrated by the higher TS, VS, total COD and soluble COD removal efficiencies than the bench-scale reactors.

Copyright: © European Compost Network ECN e.V.
Quelle: Orbit 2012 (Juni 2012)
Seiten: 7
Preis inkl. MwSt.: € 7,00
Autor: Jun Wei Lim

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