a b s t r a c tBiosand filters can be amended with activated carbon and zeolite in order to improve their efficiency at removing micropollutants. The tested pollutants here include ammonia (5 mg/L), lead (210 µg/L), phosphate (12 mg/L), COD (400 mg/L), and iron (0.4 mg/L). The response surface methodology (RSM) is used to evaluate the influence of the adsorbents' column heights (H) and lead ([Pb]) on system efficiency. The results show that (i) increased H values enhanced filter efficiency; (ii) increased [Pb] values only influenced the lead concentration of the effluent; (iii) there was a higher removal of ammonium, COD, and phosphate; and (iv) the removal of iron was below the allowable level. The RSM results suggest that heights of 33 cm and 26 cm could be considered optimal for zeolite and activated carbon, respectively. The optimized filter quantitatively removed biological pollutants and was capable of removing ammonium, lead, COD, and phosphate pollutants at upto 98, 98, 97, and 87%, respectively. Amending biosand filters with efficient adsorbents enables them to be used to remove micropollutants.

Clarifying is one of the most crucial stages in water treatment at water treatment plants. Determining the type of the clarifier in water treatment plants and using it efficiently is necessary. In this study, a pilot is designed and constructed in which the pulsator, the superpulsator and the accelerator are simulated. For each system, turbidity removal efficiency for different influent turbidities and flow rates were studied and the optimum condition was obtained. The results showed that the superpulsator has a superior performance compared to the pulsator, and the pulsator has a superior performance compared to the accelerator and these differences are more sensible at higher flow rates. Also, the best condition for achieving the highest efficiency for the pulsator and the superpulsator is determined to be at flow rate 3 lit/min for an initial turbidity of 2,500 NTU with alum as the coagulant and the highest efficiency for the accelerator is determined to be at flow rate 3 lit/min for an initial turbidity of 2,500 NTU with ferric chloride as the coagulant. Comparing the turbidity removal efficiency shows that for 67% of the cases, ferric chloride has a better performance as the coagulant compared to alum and increasing the influent turbidity leads to an increase in the removal efficiency. Furthermore, three water treatment plants located in Tehran were studied and their characteristics were compared and suggestions were made to enhance their qualities.