Author(s)

A. Abusam, H. Al-Naser & A. Shahalam

Abstract

The wastewater treatment plant (WWTP) located in Riqqa, Kuwait, has shown signs of instability. The chemical oxygen demand (COD) in the secondary effluent COD was found to be particularly unstable (fluctuating sharply between 30 and 200 mg/l). This paper presents the performance evaluation conducted by the Kuwait Institute for Scientific Research (KISR) of the activated sludge system, at Riqqa plant. Probable causes are indentified, and a mathematical model is developed. In addition to the system performance records for 2004– 2007, the results of a sampling campaign conducted from March 2009 to March 2010 were also used in the evaluation of the activated sludge system, based on influent and effluent qualities and common operating variables, e.g., hydraulic retention time (HRT), solids retention time (SRT), volumetric organic load (Lv) and food-to-microorganism ratio (F/M). The system was then modeled in a SIMBA platform, using Activated Sludge Model No. 1 (ASM1). The results obtained results indicated that the quantity and degree of biodegradability, i.e. biological oxygen demand-to-chemical oxygen demand ration (BOD/COD) of the wastewater being treated fluctuated greatly, probably due to the illegal discharge of industrial wastewaters or septage. The system, which is controlled manually, was repeatedly being operated outside optimal ranges. To maintain a high quality of treatment, it is recommended that automatic flow controllers be installed in recirculated activated sludge (RAS) and wasted activated sludge (WAS) streams, and that protective strategies be implemented to prevent the discharge of industrial and other toxic or inhibitory substances into the system. The developed model can be used to control and optimize the performance of the system. Keywords: activated sludge, performance evaluation, operating variables, activated sludge modeling, ASM1.

Keywords

activated sludge, performance evaluation, operating variables, activated sludge modeling, ASM1