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Background and Objective: Raw water is one of the main sources of water supply in some communities. Filteration of surface water resources is a challenging point in the rainy seasons due to the highly turbidity. This study was done to evaluate the removal of turbidity in raw water using chitosan in electrocoagulation process using aluminum electrodes. Methods: In this the descriptive –analytical study, a Plexiglas electrocoagulation reactor in a lab scale to an approximate volume of 6 liter which was equipped with four aluminum electrodes having dimension of 200×20×2 mm was proposed. The effects of operating parameters including pH (5 to 9), applied voltage (10 to 30 V), the initial turbidity (100-600 NTU), initial chitosan concentration (0.5-2 mg/L) and contact time (5 to 30 min) were evaluated. Results: Turbidity removal efficiency was over 100% (pH=7, applied voltage=30 V and initial turbidity concentration of 100NTU) in the application of electrocoagulation with chitosan but in the application of electrocoagulation without chitosan removed 87% of turbidity in the same condition. Conclusion: Chitosan as coagulant aid in low amount can increase turbidity removal efficiency rather than application of electrocoagulation alone.

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Background and Objective: Water resident bacteria are potentially important reservoir of antibiotic resistance genes. This study was performed to evaluate the antibiotic resistance in Escherichia coli strains isolated from raw waters of Golestan province, northern Iran.

Methods: In this descriptive study, 26 samples from Ziarat river water (13 samples pre & 13 samples post treatment) and 36 samples from Azadshahr area springs water (18 samples pre & 18 samples post treatment) were collected. 75 numbers of Escherichia coli bacterium samples (50 isolated from river and 25 isolated from springs) identified and isolated from raw waters of Golestan province, northern Iran by MPN method via differential tests. Susceptibility of Escherichia coli strains to 11 antibiotics (Amoxicillin / Clavulanic acid, Ampicillin, Imipenem, Cefalotin, Cefotaxime, Gentamicin, Amikacin, Tetracycline, Nalidixic acid, Ciprofloxacin and Trimethoprim / Sulfamethoxazole) was assayed by disk diffusion Kirby & Bauer’s method.

Results: 14 spring's raw water samples and 12 river raw water samples contained Escherichia coli. All of the river and springs samples assayed free from Escherichia coli post treatment. All of the Escherichia coli strains isolated from samples showed the similar phenotypical resistance against to surveyed 11 antibiotics. The most significance resistance to Ampicillin (river 94% & springs 88%), Amoxicillin / Clavulanic acid (river 76% & springs 80%), Tetracycline (river 14% & springs 16%) and Cefalotin (river 8% & springs 16%) viewed. Resistance to Trimethoprim / Sulfamethoxazole (8%), Nalidixic acid (2%) and Ciprofloxacin (2%) just viewed in river samples. All of the river and spring isolates were sensitive to Imipenem, Cefotaxime, Gentamicin and Amikacin and demonstrated intermediate resistance to others antibiotics.

Conclusion: Treatment of raw water from springs and rivers caused the eradication of Escherichia coli. As regard to observed phenotypical resistance in springs’ raw waters, presumably with lack of treatment springs’ raw water can be caused the transmission of antibiotic resistance to human body.