Evolution site selection by using an analytical hierarchy process for decentralized wastewater treatment plants in the city of QOM, IRAN

Introduction: Decentralized wastewater treatment facilities are an expensive approach for developing countries. Decentralized wastewater treatment plants [DWWTP[s] are a flexible technology. They have low construction and operational costs. Site selection is the most significant stage in the implementation of a DWWTP[s]

Therefore, the present study aimed to perform a site selection among the proposed locations for a DWWTP[s] in Qom

Materials and Methods: In this experimental study, the criteria of DWWTP[s] site selection were determined, judged by interview experts, and analyzed by the analytic hierarchy process [AHP] using the Expert Choice 11 software. Finally, according to the performed judgments, the proposed locations [sites] were ranked in order of preference

Results: The slope of the land held maximum importance, while the density of the population had minimum importance in the site selection process. The southern and north-eastern regions of Qom had appropriate sites

Conclusion: The AHP is a decision analysis method that considers both the qualitative and quantitative information applicable for the various subjects, especially site selection. In this study, according to the expert's notices, the AHP technique could determine an appropriate site among the proposed locations for the construction of DWWTP[s]

Evaluation of trends for iron and manganese concentrations in wells, reservoirs, and water distribution networks, Qom city, Iran

Background: This study aimed to evaluated trends for iron and manganese concentrations in wells, reservoirs, and water distribution networks in Qom city during the summer of 2012

Methods: This was a cross-sectional study. The studied scopes consisted of groundwater [60 wells], reservoirs [10 tanks], and water distribution network [33 points]. One sample was taken from each source monthly. Statistical tests used included post hoc tests [Tukey HSD]. Finally, the results were compared with drinking water standards

Results: The average concentrations of iron in groundwater, reservoirs, and distribution networks were 0.09, 0.07, and 0.07 mg/l, respectively. The average concentrations of manganese in groundwater, reservoirs, and distribution networks were 0.15, 0.09, and 0.1 mg/l, respectively. The turbidity averages in groundwater, reservoirs, and distribution networks were 0.58, 0.6, and 0.52 NTU, respectively. The average concentrations of free chlorine residual in water reservoirs and distribution networks were 1.74 and 1.06 mg/l, respectively. The pH averages in groundwater, reservoirs, and distribution networks were 7.4, 7.7, and 7.5, respectively. The amounts of iron, manganese, turbidity, free chlorine residual, and pH in the investigated resources had no significant differences [P > 0.05]

Conclusion: The amounts of iron, manganese, turbidity, free chlorine residual and pH in groundwater, reservoirs, and water distribution networks of Qom are within permissible limits of national standards and EPA guidelines. Only the amount of manganese was higher than the Environmental Protection Agency [EPA] permissible limit

Efficiency of horizontal roughing filter in removing nitrate, phosphate and chemical oxygen demand from effluent of waste stabilization pond

Background: The effective size of the end grain of horizontal roughing filters [HRFs] is larger than 2 mm. This study aimed to examine the efficiency of HRFs in removing nitrate, phosphate, and chemical oxygen demand [COD] from effluent of a wastewater stabilization pond

Methods: This experimental study was conducted in 2013. The pilot project was transferred to the Karaj wastewater treatment plant [stabilization pond], and the installation, equipping, and start-up of the system began using an effluent treatment plant. Sampling was done from March to August in 3 rates, 0.5, 1 and 1.5 m/h, and included simultaneous sampling from inlet and outlet filtering to determine the concentrations of nitrate, phosphate, and COD

Results: At filtration rates of 0.5, 1, and 1.5 m/h, the average nitrate removal equaled 25%, 32%, and 34%, respectively, average phosphate removal equaled 29%, 26%, and 28%, respectively, and the average COD removal at filtration rates of 0.5, 1, and 1.5 m/h equaled 62%, 66%, and 68%, respectively. Outlet values of phosphate and nitrate were lower than the standards set by the Environmental Standards Organization [ESO] [P < 0.05]

Conclusion: According to the results of this study, the HRF function was approximately adequate in COD removal, but its efficiency in nitrate and phosphate removal was lower