In the present research, the effect of different coagulants in conditioning of digested sludge in Qods wastewater plant, have been investigated. In order to accomplish such investigation, coagulants including cationic polyelectrolyte, feeric chloride, quicklime and alum, with different concentrations, were added to the sludge samples. Jar test, then specific resistance of sludge with respect to dewatering, TSS and VSS on sludge samples before and after dewatering were performed. In addition, TSS and VSS, COD, BOD5 and turbidity were performed on supernatant in order to determine the optimized concentration of.The value of specific resistance of sludge to the dewatering process for raw sludge and conditioned sludge with cationic polyelectrolyte, ferric chloride, ferric chloride with lime, lime and alum are as follows: 7.68*1013, 0.347*1013, 0.839*10113, 0.89*1013, 2.36*1013 and 2.52*1013 m/kg. Since my decrease in specific resistance of sludge facilities the dewatering process, it could be concluded that the most suitable for fludge conditioning are, cationic polyelectrolyte, ferric chloride, ferric chloride with lime, lime and alum respectively.By considering the results of this investigations and comparing economic factors and supplier availability, ferric chloride as pilot sludge conditioner substance was preferred. By adding ferric with concentration of 440 mg/l to the outgoing sludge from aerobic digester, the required time for drying sludge (production of sludge with DS=45%) in drying beds, is reduced from 9 days to 4 days. In other word, if input sludge to drying beds in conditioned, the required bed area, is reduced considerably (at least 50%).

Background: Application of some materials, in order to increase raw water turbidity and to enhance the efficiency of coagulation process is usual. SFBW recycling due to its relatively high volume (4% of total water production) is usual too. In the USA usually in about 30% of water treatment plants SFBW is recycled directly to the inlet of treatment plant line. This study was achieved in order to determine the influence of SFBW recycling on coagulants reduction in Jalalieh   water treatment plant. Materials and Methods: In this study the samples were taken from raw water and filter wash water effluent. At the first step, the parameters of pH, turbidity, TDS, EC and temperature were examined for both raw water and SFBW. Then the optimum coagulant dosages for raw were determined by Jar test. The optimum coagulant dosages for raw water and the mixture of 4% SFBW and raw water were determined at the next stage. Finally the data was analyzed by SPSS software.  Results: The results of this study showed that the mean values of pH for raw water and SFBW were 8.1 and 7.73 respectively. The mean values of raw water and SFBW turbidity were 7.7 and 237 NTU respectively. The mean values of EC for these two conditions were 253.2 and 240.7 μs/cm respectively. Conclusion: Although it was observed that by recycling 4% of filter wash water there was a 0.72 mg/l reduction in ferric chloride, but the difference was not statistically significant in the range of analyzed turbidity (3.77 25 NTU…)

Background: Pending solids concentration and turbidity are the main drawbacks of waste water stabilization ponds used in hot climates for sewage treatment to reuse effluent. The effectiveness of chemical coagulation and lime addition in upgrading the ponds effluent quality is the purpose of this study.Materials and Methods: The effects of three coagulants including Alum, Ferric sulfate, and Ferric chloride and Lime with variable dosages on suspended solid and turbidity were studied in Kashan University of Medical Sciences living compounds stabilization ponds during the summer 2005. Data analyzed using Jar test.Results: Ferric sulfate 20 mg/l dosage reduced suspended soil concentration from 215 to 11.8 mg/ l and turbidity from 189 to 14.9 NTU (Nephelometric Turbidity Unit). Maximum TSS (Total Suspended Solid) and turbidity removal was 94.5 % and 92.1 %, respectively.Conclusion: Chemical coagulation can efficiently upgrade the ponds effluent quality compared with Iranian organization of environmental health standards (TSS and turbidity less than 100 mg/l and 50 NTU).

Background: Since Coagulation and flocculation are essential processes for turbidity removal from drinking water, many studies have been conducted on different coagulant.Materials and Methods: The present study - a pilot scale experiment- was conducted in the laboratory of water and wastewater chemistry of Zahedan public health school in 2007 to compare the efficiency of PAC, Ferric chloride and aluminum sulfate as coagulants. To do so, lab experiments were performed using distilled water containing synthetic Caoline. Eight turbidity levels (10-80 NTU), five pH levels (5.5, 6.0, 6.5, 7.0 and 7.5) and five coagulants doses (5, 10, 20, 30 and 40 mg/l) were used for the jar test. Rapid mixing for all experiments was 380 rpm for one minute and slow mixing was 30 rpm for 20 minutes. Finally, at the end of every experiment, residual turbidity was measured by turbidity meter; in addition, removal efficiency for various conditions was determined by covariance and regression analysis.Results: The results showed that an increase of aluminum sulfate dose up to 40 mg/l can increase removal efficiency to 99.9%. The highest removal efficiency for ferric chloride occurred at feed dose of 20 mg/l and primary turbidity of 10 NTU, while for PAC the highest removal efficiency (99%) occurred at 40 mg/l. Effect of pH in turbidity removal for all experiments was similar.Discussion: Finally, it can be concluded that the best coagulant for turbidity removal (pH=5.5-7.5) is aluminum sulfate, because as the coagulant dose rises up the removal efficiency increases significantly. Efficiency removal, also, depends on the initial turbidity.

This study aims to investigate the performance of polyaluminum chloride (PAC) as a coagulant to remove Acid blue 292 (AB292), which is used widely in textile industry in Iran. The effect of pH, coagulant dosage, kaolinite (as a natural coagulant aid), and initial dye concentration were examined in the coagulation process with PAC. Results showed that the optimum pH range to remove AB292 was 6-8. In such conditions, the dye removal using 40mg/L of PAC was more than 83%. This dosage (40mg/L) was considered as the optimum dosage of PAC to remove AB292. Addition of kaolinite as a coagulant aid increased the efficiency of the process. With the aid of 40 mg/L kaolinite, dye removal efficiency increased by 30% when the coagulant dosage was 30mg/L. As the initial dye concentration increased, the dye removal efficiency decreased, so that the efficiency for dye concentrations of 25 and 250 mg/L was 95% and 21%, respectively.

Today, coagulants used for water treatment in Iran are predominantly inorganic salts of iron and aluminum while in many countries like Canada, Italy, U.S., China, France and England, and newly in Iran, In Baba Sheikh Ali Water Treatment Plant in Isfahan, a new coagulant named Polyaluminum Chloride (PACl) is used as the alternative coagulant. The present investigation mainly aims to evaluate: (1) the use of Polyaluminum Chloride in place of Ferric Chloride and Alum used as coagulants, (2) the effect of temperature conditions, and (3) the effectiveness of using PACl doubled with starch as a coagulant aid, for turbidity removal of a simulated turbid water with Kaolin. The results showed the trend of floc settlement and higher settling velocity for PACl flocs as well. Coagulation efficiency of PACl proved not to be sensitive to temperature changes, while Ferric Chloride and Alum did. Starch showed to be an effective coagulant aid only at low doses of PACl.

Mixing the wastewater of Industries with natural water has caused environmental pollution. So researcher tries to obtain methods and optimum conditions for wastewater treatment. One of Important stage in wastewater treatment is dissolved air flotation. DAF is used for the removal of suspended solids and oils from wastewater. In this paper, the effect of several parameters on flotation efficiency with Cationic Polyacrylamide as flocculants, was examined, namely, (a) concentration of cationic flocculants, (b) pH (c) fast mixing time, (d) fast mixing speed, (e) slow mixing time, (f) retention time and temperature. After dwesign of experiment, in each trial turbidity of wastewater was measured by spectrophotometer. Results show that contribution of pH and concentration of flocculants on flotation efficiency are 75 % and 9 % respectively. Cationic polyacrylamide led to a significant increase in the settling speed and effect of temperature is negligible. In the optimum condition, the outcome of the DAF unit is increased and amount of suspended solid and oil in wastewater is decreased effectively.

Background and Aim: The fluoride ions are commonly found in water resources. These ions should be in optimum levels for prevention of dental caries. However, the excess value can cause such health problems as fluorosis. The aim of the present study was to investigate the removal of excess fluoride ions by using poly aluminum chloride as a new coagulant that is used in water treatment plants.Materials and Methods: All experiments were conducted in batch system. Several combinations of parameters such as initial fluoride concentration (1.4, 2 and 2.4 mg/L), pH of solution (3, 7, 9), poly aluminum concentration (10, 20, 30, 40 mg/L), and exposure time (30, 60, 90 minute) were investigated. Various concentrations of poly aluminum chloride solution at different pH levels were added into 200 ml of fluoride solution, and samples were taken in predetermined time intervals and the final concentration of fluoride was determined by spectrophotometer at 570 nm.Results: The results showed that, the highest removal was obtained at pH=7. In addition, it was observed that fluoride removal efficiency was higher in pH=5 than in pH=9. Also the results showed that, removal efficacy can be increased by increasing the poly aluminum chloride and the exposure-time.Conclusion: This study denoted that removal of high levels of fluoride ions can effectively be done by using poly aluminum chloride as a new coagulant. Its use is possible in water treatment facilities without any need for modification in water treatment plans.