B Hozzar - PhD student of mathematics, Region five Water & Wastewater Company
S Mohammadi - PhD student of mathematics, Bestsun Group
B Pirouz - M.Sc. Civil-Water Engineering, ADP Company
H Javadinejad - M.Sc. Environmental Engineering, Bestsun Group

In many countries especially in developing countries, the natural ways for wastewatertreatment like wastewater stabilization ponds (WSPs) are so popular because good efficiency and noneeds to high technology. Furthermore the WSPs are suitable for wastewater treatment in smallsocieties and some special industries namely slaughterhouse, dairy products, meat products and etc.The advantages of this method are high efficiency in treatment of pathogens, toxic and organicmaterials. But there are some problems and issues in using them. Inappropriate design can leads todead space and short-circuiting and Etc in the ponds and will reduce the efficiency. In this regard, in thispaper the hydraulic design of WSPs have been considered and the CFD method used for modeling.Therefore a WSP pond modeled with Fluent software and some parameters like different inlets andoutlets length and situation and also different numbers of inlet structures modeled and analyzed tooptimum the efficiency. The model is calibrated with field data of previous Tehran WSP. The results ofCFD modeling show the numbers of inlet and outlet structures change the spatial distribution of thevelocity and with increasing the number of structures, more uniform flow and cross sectional velocityprofile occurs. With increasing in the length of the inlet structures the dead space increase andtherefore the retention time decrease so the efficiency of the WSP operation reduce. The models withinlet structure in the bed also have more uniform flow profile in comparison with inlet structure in thewall. For other parameters and conditions the papers, manuals and documents about the WSPs checkedand analyzed and at the end some methods and tips presented to improve the efficiency of WSP ponds.In conclusion, it can be seen that the CFD models are needful to optimum the efficiency of WSP ponds.

WSPs, CFD modeling, waste water treatment, Hydraulic design