Abstract
This study presents the potential of combining anaerobic grey water sludge treatment with black water in an up-flow anaerobic sludge blanket (UASB) reactor to improve energy recovery within source-separated sanitation concepts. Black water and the mixture of black water and grey water sludge were compared in terms of biochemical methane potential (BMP), UASB reactor performance, chemical oxygen demand (COD) mass balance and methanization. Grey water sludge treatment with black water increased the energy recovery by 23% in the UASB reactor compared to black water treatment. The increase in the energy recovery can cover the increased heat demand of the UASB reactor and the electricity demand of the grey water bioflocculation system with a surplus of 0.7 kWh/cap/y electricity and 14 MJ/cap/y heat. However, grey water sludge introduced more heavy metals in the excess sludge of the UASB reactor and might therefore hinder its soil application.
Highlights
Biogas as a renewable energy source is increasing its energy market share with the enforced regulation of organic waste treatment and recycling in the European Union (EU) [1]
This study presents the potential of grey water sludge treatment with black water in batch experiments by determining the biochemical methane potential (BMP) of black water, grey water sludge from an A-trap and their mixture
Is the amount of CH4 –chemical oxygen demand (COD) produced in the reactor, “effluent” is the amount of total COD discharged with effluent, “sludge wasted” is the amount of COD wasted as excess sludge, including sludge bed samples, and “sludge reactor” is the amount of COD accumulated in the sludge bed
Summary
Biogas as a renewable energy source is increasing its energy market share with the enforced regulation of organic waste treatment and recycling in the European Union (EU) [1]. Grey water originating from washing activities in the household, contributes a significant fraction of the organic load present in domestic wastewater. This fraction is lost either by using a constructed wetland or a sequencing batch reactor (SBR) [12], where the organic matter is oxidized instead of utilizing it as an energy source. The organic fraction can be concentrated in a bioflocculation unit, such as the membrane bioreactor (MBR) or the A-trap of the Adsorption-Belebung (AB)-process [13] and subsequently treated with black water in an up-flow anaerobic sludge blanket (UASB) reactor for improved energy recovery. The influence of grey water sludge addition on the quality of UASB reactor excess sludge in terms of heavy metals is examined to evaluate its application in soil improvement
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