Effects of Organic Load, pH, and EC Variations of Raw Wastewater and Weather Condition on the Efficiency of Yazd Stabilization Ponds

Document Type : Research Paper


1 Faculty Member of Civil Engineering Dept., Islamic Azad University, Yazd branch, Yazd

2 Water and Wastewater Laboratory Expert, Yazd Water and Wastewater Company, Yazd

3 Faculty Member of Yazd University of Medical Sciences, Dept. of Environmental Health, Yazd

4 Member of Statistics and Information Office in Yazd Provincial Government, Yazd


This study investigates the effects of organic load, pH, and EC variations of raw wastewater as well as the effect of weather condition on organic removal in Yazd wastewater Stabilization Ponds (2007). During the course of this study, composite samples were collected from the inlet and outlet of the anaerobic pond and the final effluent to measure such quality parameters as BOD5, COD, TSS, EC, and pH.  BOD5, COD, TSS, and Fecal coliform removal efficiencies in the final effluent were found to be 64.9%, 44.9 %, 62.6 %, and 99.96%, respectively. No intestinal nematode egg was observed. Comparison of BOD5 and COD concentrations in the filtered and non-filtered samples showed that 52% of the BOD5 and 57% of the COD in the final effluent, respectively, were due to the presence of algal mass and organic suspended solids in the non-filtered samples. The results showed that variations in organic load, pH, EC as well as seasonal weather variations had no effects on organic removal and that the removal of BOD5 was almost constant. Effluent EC was higher than influent EC. This phenomenon can be related to the evaporation rate in wastewater stabilization ponds. The survey of algae in the final effluent showed that the major species of algae were Phytoconis, Chlorella, and Anabaena.


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