Partial degradation of organic materials presented in sewage water had been conducted in the current research in a simulated sewer system. The process had been improved by aeration and seeding with activated sludge to reveal the effect of increasing the amount of biomass in the system. Three ambient temperatures were conducted as 10, 20, and 30 OC to display the influence of temperature on the degradation process. The results revealed that adding activated sludge to the system in a ratio of 50/50 (v/v) had a significant influence on the degradation as more microorganisms required more organic nutrients. In the other hand, increasing the operating temperature indicated positive influence in terms of soluble chemical oxygen demand (SCOD) removal as temperature motivated the living biomass towards severe degradation.
Activated sludge process is considered one of the most common and highly effective methods used in aerobically biological treatment systems. The design of such systems is usually based on the biological kinetic approach considerations. The present study is concerned in determining the biological kinetic of the last part of Diyala River at AL-Rustimiyah WWTP's, Baghdad, Iraq. A completely mixed continuous flow lab-scale reactor without recycling was used for this purpose. Various detention times were adopted during the experimental work ranging from 0.723 to 3.809 days. Influent and effluent BOD5, MLVSS and MLSS for the aeration tank, among other tests were performed at different detention times, after reaching the steady state conditions, in order to generate the required data for bio-kinetic coefficients. The biological kinetics k, Y, Kd, and Ks for the last part of Diyala River at AL-Rustimiyah WWTP's were found to be 5.68 d-1, 0.75, 0.06 d-1, and 70 mg/l, respectively. These values were compared with the bio-kinetics of different types of wastes and were found to be within the typical ranges of bio-kinetic parameters for activated sludge process treating domestic wastewater, which indicates that the water at the river reach of interest is rather wastewater than pure river water.
Secondary clarifiers form a crucial component in gravity separation processes mainly in solid-liquid separation. They perform the crucial process of separating the activated sludge from the clarified effluent and also to concentrate the settled sludge. As treatment plants receive increasingly high wastewater flow, conventional sedimentation tanks suffer from overloading problems which result in poor performance. Inlet baffle modification by using an energy dissipating inlet (EDI) was proposed to enhance the performance in the circular clarifiers in Al-Dewanyia wastewater treatment plant. A 3-Dimensional fully mass conservative clarifier model was applied to evaluate proposed tank modification and to estimate the maximum capacity of the existing and modified clarifiers. A Computational Fluid Dynamics (CFD) model was formulated to describe tank performance and design parameters were obtained based on the experimental results. The study revealed that velocity and SS are better parameters than TS, BOD5, and COD to evaluate the performance of sedimentation tanks. Removal efficiencies of suspended solids, biochemical oxygen demand, and chemical oxygen demand were higher in the EDI (Baffle).