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Title: Biological treatment of a pharmaceutical wastewater
Authors: Ng, W.J. 
Yap, M.G.S. 
Sivadas, M.
Issue Date: 1989
Citation: Ng, W.J.,Yap, M.G.S.,Sivadas, M. (1989). Biological treatment of a pharmaceutical wastewater. Biological Wastes 29 (4) : 299-311. ScholarBank@NUS Repository.
Abstract: The treatability of a pharmaceutical wastewater using a two-stage biological system was investigated. The system consisted of two reactors operated in a batchwise mode with the effluent of reactor A becoming the feed for reactor B. During a cycle of operation each reactor served, in turn, as the aeration basin and then clarifier. Reactor A was supplied with sufficient air to maintain good mixing of the reactor's mixed liquor. Attempts were made to keep the dissolved oxygen (DO) below 0.3 mg litre-1 and at hydraulic retention times (HRT) below 6.6 days the DO was 0 mg litre-1. Reactor B was operated under aerobic conditions during the REACT phase but DO levels dropped to 0 mg litre-1 during SETTLE when the reactor was most heavily loaded. Results indicated that a wastewater with a chemical oxygen demand (COD) and 5-day biological oxygen demand (BOD5) of about 26,500 mg litre-1 and 12,500 mg litre-1 respectively could be treated with the system. COD removal by reactor A ranged from 96 to 63% while system COD removal ranged from 99 to 86% as various loading conditions were investigated. It was initially thought that the 2-ethylhexanoic acid present in the wastewater at a concentration of 2500 mg litre-1 might prove inhibitory to the biological process and adversely affect treatment performance. The system, however, adapted well and the 2-ethylhexanoic acid was effectively removed. Gas chromatographic analysis of reactor A's effluent suggested the occurrence of fermentation. Ethanoic, propanoic, butanoic and, on one occasion, pentanoic acids were detected. These were originally absent in the wastewater. The results suggested that the system might be further developed on the lines of the sequencing batch reactor (SBR) concept. In comparison to the conventional effluent treatment plant configuration comprising of trickling biofilters, activated sludge basins, secondary clarifiers and sludge return, the two-stage batch system would probably be simpler in terms of construction, operation and maintenance.
Source Title: Biological Wastes
ISSN: 02697483
Appears in Collections:Staff Publications

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