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Secondary clarifier is one of the most commonly used unit operations in wastewater treatment plants. It is customarily designed to achieve the separation of solids from biologically treated effluents through the clarification of biological solids and the thickening of sludge. As treatment plants receive increasingly high wastewater flows, conventional sedimentation tanks suffer from overloading problems, which result in poor performance. Modification of inlet baffles through the use of an energy dissipating inlet (EDI) was proposed to enhance the performance in the circular clarifiers at the Al-Dewanyia wastewater treatment plant. A 3-dimensional fully mass conservative clarifier model, based on modern computational fluid dynamics theory, was applied to evaluate the 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 the tank is performance, and design parameters were obtained based on the experimental results. The study revealed that velocity and (suspended solids) SS is a better parameter than TS (total solids), (Biochemical Oxygen Demand) BOD, (Chemical Oxygen Demand) COD to evaluate the performance of sedimentation tanks and that the removal efficiencies of the suspended solids, biochemical oxygen demand, and chemical oxygen demand were higher in the baffle.

Several modifications with different construction costs were proposed to enhance the performance in large rectangular sedimentation tanks. A two-dimensional fully mass conservative sedimentation model, based on modern computational fluid dynamics theory, was applied to evaluate proposed tank modifications of the existing and modified sedimentation tanks. The usually unknown and difficult to be measured particle density is found by matching the theoretical to the easily measured experimental total settling efficiency. The proposed strategy is computationally much more efficient than the corresponding strategies used for the simulation of wastewater treatment. It is noteworthy that even small differences in the particle velocity can cause large changes in the percent of settled particles; in this work, the overall solids removal efficiency increased when using the modifications from 84.4 and 98.8%, leading to a reduction of the effluent solids concentration of approximately 85%. The comparison of model predicted results with the field data collected in tanks before and after modifications shows very good agreement.

External corrosion, which depends on environmental and operating conditions, is the main cause of structural deterioration of all metallic mains. Internal corrosion, on the other hand, can cause significant functional (hydraulic, water quality) deterioration within a distribution system. This work deals with the corrosion of water pipes which greatly affects the durability and failure rate of water systems. The test is evaluated in accordance with STN 75 7151 and ASTM D2688-11. The corrosion tests were carried out on raw and treated water at the water treatment plant in Jakubany.

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