An anaerobic-anoxic/oxic (A2/O) multi-phased biological process called "phased isolation tank step feed technology (PITSF)" was developed to force the oscillation of organic and nutrient concentrations in process reactors. PITSF can be operated safely with a limited carbon source in terms of low carbon requirements and aeration costs whereas NAR was achieved over 95% in the last aerobic zone through a combination of short HRT and low DO levels. PCR assay was used for XAB quantification to correlate XAB numbers with nutrient removal. PCR assays showed, high NAR was achieved at XAB population 5.2 × 10(8) cells/g MLVSS in response to complete and partial nitrification process. It was exhibited that low DO with short HRT promoted XAB growth. Simultaneous nitrification and denitrification (SND) via nitrate were observed obviously, SND rate was between 69-72%, at a low DO level of 0.5 mg/l in the first aerobic tank during main phases and the removal efficiency of TN, [Formula: see text], COD, TP was 84.7 .97, 88.3 and 96% respectively. The removal efficiencies of TN, [Formula: see text], and TP at low C/N ratio and DO level were 84.2, 98.5 and 96.9% respectively which were approximately equal to the complete nitrification-denitrification with the addition of external carbon sources at a normal DO level of (1.5-2.5 mg/l).

No abstract

Problem statement: The wastewater from petrochemical complex is varying in flow, organic contaminant loading and composition due to various operating condition of the petrochemical complex. This study is demonstration case of petrochemical wastewater treatment plant. Approach: This study is demonstration case on Basrah petrochemical wastewater treatment plant whereas the description of wastewater composition and system of treatment had reviewed and the experimental work on the most important control parameters (F/M ratio and MCRT) had implemented. Results: The experimental results showed that (i) The optimum rate of BOD removal could be obtained at food to microorganism ratio between 0.1-0.15 where this optimum ratio exists at the maximum zone settling velocity (ii) The design effluent BOD5 could be obtained at a MLSS concentration of 6000 mg L^-1 and in about 26-30 day of mean cell residence time Conclusion: The experimental data from petrochemical wastewater treatment plant in Basra City (south of Iraq) showed that the extended Aeration offers the most desirable features for the treatment of petrochemical wastewater where the specification of this method apply with experimental results as well as that the study show that control parameters (F/M ratio and MCRT) is a good tool to control the effluent wastewater quality of petrochemical wastewater treatment plant

Removal efficiency of COD, NH4-N and PO4-P and NO3-N in five step SBR processes is widely influenced by hydraulic retention time of Anaerobic/Anoxic/Aerobic/Anoxic/Aerobic step of this system where the hydraulic retention time in each step is influence directly on removal efficiency of this system therefore the operator of this system cannot control on this system without experience or a control model. The major objective of this paper is develop a control model (Fuzzy Logic Control Model) based on fuzzy logic rule to predict the maximum removal efficiency of COD,NH4-N,PO4-P and NO3-N and minimize hydraulic retention time in each step of SBR process where the controlled variables was the hydraulic retention times in the An-aerobic/Anoxic/Aerobic/Anoxic/Aerobic step respectively and the output variables was the COD, NH4-N, PO4-P and NO3-N removal efficiency at constant ratio of C/N/P and sludge age. As a results Fuzzy logic if-then rules were used and MIMO Model was built to control COD, NH4-Nand PO4-P and NO3-N removal efficiency based on hydraulic retention time in each tank of five step SBR process where the three dimension results show that the influence of hydraulic residence time at each step of SBR system on removal efficiency COD, NH4-N, PO4-P and NO3-N. Fuzzy control model provide a suitable tool for control and fast predict of Hydraulic residence time effects on biological nutrient removal efficiency in five-step sequencing batch reactor .