Journal of Environmental Biology

Treating restaurant wastewater using a combined activated sludge-contact aeration system

 

Chih-Kuei Chen and Shang-Lien Lo

Graduate Institute of Environmental Engineering,

National Taiwan University, 71, Chou-Shan Rd., Taipei, 106, Taiwan, R. O. C.

 

(Received: 16 October, 2004 ; Accepted: 8 August, 2005)

 

Abstract: The combined activated sludge/contact aeration (AS/CA) system proposed herein involves both suspended and attached microorganisms. In an experiment over 7 days, and at 8 hr hydraulic retention time (HRT), the AS/CA system was able to treat restaurant wastewater of fluctuating quantity and quality, and reduce the standard deviations of COD and BOD₅ from 115.8 and 158 to 40.5 and 8.8mg/l, respectively. In a twenty-four hour experiment, the standard deviation of COD fell from 188.9 to 23.8mg/l, showing a strong tolerance of environmental changes. In an analysis of composite samples collected over 1 day, the AS/CA effluent had 57.8mg/l COD (84% removal rate), 21mg/l BOD₅ (87% removal rate), 12mg/l SS (86% removal rate), 6mg/l oil and grease (O and G) (90% removal rate), and a true color of 1 (80% removal rate). Denaturing Gradient Gel Electrophoresis (DGGE) analysis was performed on sludge samples taken from three treatment systems: the activated sludge system, the contact aeration system and the AS/CA system for comparison. The results showed that the AS/CA system contained higher microbe quantity and diversity.

 

Key words: Oil and grease, Combined activated sludge, Contact aeration system, Spike loading, DGGE

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