Secondary sedimentation is one of the most commonly used unit operations in wastewater treatment plants. It is customarily designed to achieve solids separation from biologically treated effluent through clarification of biological solids and thickening of sludge. As treatment plants receive increasingly high wastewater flow, conventional sedimentation tanks suffer from overloading problems which result in poor performance. Inclined plate settlers, a form of tube settlers, may have good potential in upgrading sedimentation tanks. This study was conducted to examine the possibility of applying inclined plate settlers in secondary sedimentation in order to upgrade conventional rectangular sedimentation tanks and improve their performance. Experiments were carried out at Al-Awir sewage treatment plant in Dubai using a pilot-scale inclined plate settler which received a mixed liquor stream from the high-rate activated sludge aeration tank. The results showed that inclined plate settlers perform slightly better than conventional type settlers during normal operation of plants, but during peak flows the inclined plate settlers showed much better performance than conventional settlers. The inclined plate settlers are less affected by overloading in comparison to conventional settlers. The solids removal efficiency increased as the hydraulic residence time was increased or as the surface loading rate was decreased. Application of these plates will not cause any interruption of daily operation of treatment plants and could be achieved at minimal cost when compared with other methods such as addition of chemicals, application of deep tanks, … etc. The study revealed that SS is a better parameter than TS, BOD, COD to evaluate the performance of sedimentation tanks. A statistical model was formulated to describe tank performance and design parameters were obtained based on the experimental results.

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The current study included a study of the microfacies and sequence stratigraphy of Saadi Formation in two subsurface sections within the Balad and Tikrit oilfields, the first represented (Ba-5) with a thickness of (120) m, and the second section (TK-6) the thickness of this formation (270))m. The formation under study consisted of chalk limestone sequences with the layers of marley limestone, the study showed that the lower bounder is compatible with the of Tanuma Formation in both sections, while the upper bounder is conformable with the Mashura Formation within well (Ba-5) and is unconformable with the Hartha Formation in a well (TK-6). Petrographic study showed the presence of many microfacies at divided into five main microfacies and six submicrofacies Lime mudstone microfacies, Lime wackstone microfacies divided to (Calcispheres lime wackestone and Rotalid lime wackestone submicrofacies), Lime packestone microfacies divided to (keeled planktonic foraminiferal lime packstone, Hedbergella lime packstone, Calcispheres lime packstone and Rotalid lime packstone submicrofacies), lime grainstone microfacies and crystalline microfacies. Depending on microfacise the paleoenvironment of formation extended from slope, open marina, deep shelf and deep sea. The sequence stratigraphy defined of study divide to the sequences into sets, and each sets represents a sedimentary cycle that event a rise and fall in sea level during a certain period of time, the formation in well (Ba-5) compound one sequence and well (TK-6) consist three sequence, the sequence begins with the sequence boundary of (Type-2) and after the transgression system tract (TST) it deposit by Retrogadation and the upper surface of this tract represented by the Maximum Flood Surface (MFS), followed high stand system tract (HST) deposited in progradation pattern, which is characterized by a gradual decrease in sea level and a shallowing sedimentary environment. The presence of three sequence cycles through the Tk-6 well is due to the fact that the Tikrit field is shallower than the Balad field of sedimentation and is located at the edges of the deeper part of the sedimentary basin and the beginning of the shallowing, which is affected more The processes of marine Transgression, where the final report of the well (Tk-6) showed that the succession of shallow sedimentary facies with deep facies as shown, indicating the instability of the substratum and its significant impact on tectonic movements.