Background & Objectives: Several methods are available for cleaning ammonia gas from the air stream. It seems that acid scrubbing by packed column is more successful than other methods. In this study, the possibility of removal of ammonia gas with sulfuric acid scrubbing liquid by a packed column was investigated. Methods: A packed column with 20 cm diameter was randomly packed in 30 cm with ceramic raschig rings. Acidic scrubbing liquid in three liquid flow rates and three pH of scrubbing liquid including 5, 6, and 7 were used to scrub the gas with three concentrations as well as three air flow rates. The pH values of scrubbing liquid were controlled by using sulfuric acid and monitored with a pH meter. Ammonia gas was measured by using a direct reading sampler. All measuring instruments were calibrated by the researcher or local manufactures representative. The results were analyzed by SPSS version 16 software package. Results: The findings of this study showed that with decreasing the pH of scrubbing liquid from 7 to 6theremoval efficiency of column increased but it was not significant. Also with decreasing the pH of scrubbing liquid from 6 to 5theremoval efficiency of column increased but it was not significant. However, the removal efficiency of column increased significantly (p<0.01) as the pH of scrubbing liquid was reduced from 7 to 5. Conclusion: Chemical absorption was increased the removal efficiency of ammonia gas significantly. Gas removal efficiency was increased with the decreasing of scrubbing liquid pH values.

Background & Objectives: Rapid sand filter backwashing water typically consists of 2-5% of the total treated water and it has high turbidity. Therefore, effluent treatment of rapid sand filter backwashing is essential. This research aimed to survey turbidity removal from filtration effluent of Tehranpars water treatment plant using Electrocoagulation (EC)/Electroflotation (EF) process.

Methods: This practical study was done in a continuous system at laboratory scale. An electrocoagulation tank with the dimensions of 24×17×18 cm and volume of 7.35 l from plexiglass was used in this work. Inside the tank 4 Al or Fe plates (15×22×0.1cm) were used as cathode and anode. Each electrode was immersed up to 16 cm in effluent of electrocoagulation tank. 126 samples with turbidities of 320, 350, and 400 NTU were taken from effluent of rapid sand filter backwashing and the removal efficiency was tested at current densities of 4.16, 5.83, 7.5, 10, 11.66, and 13.33 mA cm^-2 in detention times ranging from10 to 30 min. The space of electrodes is fixed at 1.5cm and pH at 8.2.  Data analyzed by excel software.

Results: The optimum pH of 8.2 was determined for this process. The optimum current density and detention time for both electrodes were the same and equal to 13.33 mA cm^-2 and 30 min, respectively. At optimum conditions the respective highest turbidity removal by Al and Fe electrodes were 95.13 and 4.87%.

Conclusion: Regarding the results, using electro coagulation-electro floatation processes has an appropriate efficiency in turbidity removal. One can say that aluminum electrode has higher efficiency than iron electrode to remove turbidity.