| Summary, etc. |
Abstract:<br/><br/>The feasibility of ozone treatment of secondary wastewater effluent in arid climets was studied, using continuous flow and batch ozonation systems. Raw and secondary treated (prior to chlorination) wastewater was collected from “Al-Khomra ‘ sewage treatment plant in Jeddah, Saudi Arabia. A U-tube system of ozone contactor which was the most effective ozone absorption system was indicated in the literature was used in this study.<br/>Optimization of ozone dosages was carried out using different ozone dosages ranged from 4.8 to 10.55 mg/L, during batch ozonation. The optimum ozone dosage of 10.55 mg/L was used to study the ozone treatment efficiencies for different wastewater temperatures ranged from 20 to 42° C and different ozone contact times ranged from 0 to 100 minutes. <br/>The ozone treatment efficiencies were measured in terms of BOD, COD, Tss, T. Coliform, and Ammonia, pH values, residual ozone, and dissolved oxygen changes during the experiments The ranges of the removal efficiencies of the BOD5, COD, TSS, T. Coliform and ammonia, at 10.55 mg/L ozone dosage, wastewater temperature range from 20 to 42° C and at 100 minutes batch P ozonation, were 59 to 84.7%, 50 to 78%, 25.1 to 75.1%, 81.4 to 100%, and -18 to 39 % respectively. The higher the wastewater temperature the lower BOD, COD, T. Coliform removal efficiencies, and the higher TSS and ammonia<br/>removal efficiencies. The higher ozone dosage and/or ozone contact time the higher removal efficiencies. Tracer tests were carried out to find out the dispersion numbers of the ozone contactor (ranged from 0.521 to 1.186).<br/>Mathematical equations were determined by applying linear, multi linear, and polynomial regression analysis (using computer programs) to the experimental data to show the relationship between the main parameters (BOD5, COD, TSS, T. Col. Ammonia and pH) and wastewater temperatures, ozone dosages, and ozone contact time. The goodness of fit for the equations of wastewater temperature, ozone dosage, and ozone contact time, with BOD, COD, T. Col. and TSS were high was very low (less than 0.6) for ammonia. The higher correlation coefficients were reported in this study, and the lower coefficients were neglected. <br/>The effect of batch ozonation on the reduction of various metals such as Fe, Mn, Ca, Mg, Na, K, Cu, Cd, Pb, and Zn was also studied, at different wastewater temperatures and ozone dosages. The metals analyzed during the experiments were Fe, Mn, Ca, Mg, Na, K, Cu, Cd, Pb, and Zn.<br/>Batch ozonation reduced the metal concentration from the wastewater Ozonation helps to release heavy metals from wastewater due to leaching action. The flocs formed by organic matter during batch ozonation, absorb or adsorb metal particles which settled after ozonation Cd, and pb could not be detected during this study because the concentration of these metals were very small or undetectable.<br/>The quality of the ozonated wastewater effluents was not high because of the poor quality of the unozonated effluents which can be considered as a primary treated effluents. The quality of the ozonated wastewater, by considering all parameters does not meet the Saudi standards without any farther treatment. But if the ozonation followed by filtration or carbon adsorption the quality of the wastewater will be better and it will meet the Saudi standards for direct discharge.<br/> |
