ABSTRACT
BACKGROUND: Using treated wastewater in agriculture irrigation could be a realistic solution for the shortage of fresh water in Iran, however, it is associated with environmental and health threats; therefore, effluent quality assessment is quite necessary before use. The present study aimed to evaluate the physicochemical and microbial quality of Shiraz wastewater treatment plant effluent for being used in agricultural irrigation. In this study, 20 physicochemical and 3 microbial parameters were measured during warm (April to September) and cold months (October to march). Using the measured parameters and the Canadian Water Quality Index, the quality of the effluent was determined in both warm and cold seasons and in all the seasons together. RESULTS: The calculated index for the physicochemical parameters in the effluent was equal (87) in warm and cold months and it was obtained as 85 for the seasons all together. When the microbial parameters were used in order to calculate the index, it declined to 67 in warm and cold seasons and 64 in all the seasons together. Also, it was found that three physicochemical parameters (TDS, EC, and NO3) and three microbial parameters (Fecal coliform, Helminthes egg, and Total coliform) had the most contribution to the reduction of the index value. CONCLUSIONS: The results showed that the physicochemical quality of Shiraz Wastewater Treatment Plant Effluent was good for irrigation in the warm, cold, and total of the two kinds of seasons. However, by applying the microbial parameter, the index value declined dramatically and the quality of the effluent was marginal.
ABSTRACT
The aims of this study were to evaluate the SCOD removal efficiency in submerged biological aerated filters (BAFs) and subsequently to assess the relationship between the specific surface area (Ss) and Excess Sludge Production (ESP) rate in such filters. Accordingly, four filters with different porosity and specific surface (647, 295, 175 and 136 m2 m(-3)) have been loaded with synthetic wastewater based on low fat dry milk powder with COD of 1500 mg L(-1) in different hydraulic retention time (8, 4, 2, 1 and 0.5 h). In this study, it was shown that specific surface increase of the filters initially increases the efficiency of the filters and after a certain value, the filter efficiency remains uncharged or decreases, as in HRT of 8 h the SCOD removal efficiency of filters 1 and 2 (Ss = 647 m2 m(-3) and Ss = 295 m2 m(-3)) were 89.8 and 91% at VOL of 3.195 and 3.727 kg COD m(-3) d(-1), respectively. Also, the results showed that in all the filters, the production rate of suspended sludge increases inversely with the hydraulic retention time and the media with higher porosity (90.5%) produced less suspended sludge (8-57 g m(-3)) despite having lower efficiency in the SCOD removal.
