Iranian Journal of

Backgrounds and Objectives:Total and Fecal coliforms (TC and FC), heterotrophic plate count (HPC), were counted by microbiological method and E.coli O157:H7 were detected through immunological and Real time PCRmethods inwater intake and all of units of Isfahanwater treatment plant (IWTP).
Materials and Methods: The microbial profile including TC, FC, and HPC, were monitored and turbidity and total organic carbon were analyzed in 8 locations of water intake, and unit operation and processes of IWTP, including, inlet, sedimentation, ozonation, and filtration and finished water. Immunological method through anti-serum kits and molecular method of RT-PCR were used to detect E.coli O157:H7 in the 8 locations and also the sludge of the sedimentation basin and filters backwash water of IWTP.
Results: Survival of E.coli O157:H7 in sludge sample of sedimentation basin was indicated by formation of agglutination particles in immunological method and through indicator probes in the RT-PCR method. However, E.coli O157:H7 was not detected in water samples of other units of IWTP. The removal percent of TC, FC, and HPC were: 59.5, 49, and 54.8 % in sedimentation basin 66, 45.8, and 57 % in ozonation: 98.8, 98, and 78.8 in the filtration and 96, 100, 91% in disinfection, respectively.
Conclusion: This study approved the existence of the pathogenic coliform, E.coli O157:H7 in the
sludge of sedimentation basin. Absent of E.coli O157:H7 in the finished water indicates that the existing units of IWTP could eliminate these pathogenic bacteria, before reaching the final units of the plant, including the filters and disinfection.

Background & Objectives: Listeria bacterium resists to the sludge digestion conditions and Listeria monocytogenes is the most important of them. Sludge produced in the north Isfahan wastewater treatment plant is stabilized by anaerobic digesters and is used for fertilizing agricultural lands after drying in the sludge drying beds. Based on the importance of the subject, the objective of this study was evaluation of sludge processing units efficiency, particularly anaerobic sludge digestion for reduction or removal of Listeria. Materials and Methods: In this descriptive study, samples were collected weekly from sludge processing units 13 times in north Isfahan wastewater treatment plant according to standard methods over three months. Listeria bacteria were enumerated and isolated by triple-tube fermentation method and U.S Department of Agriculture method respectively. Isolated Listeria were confirmed by phenotypic method and then bacterial species were diagnosed differentially by biochemical carbohydrate fermentation and CAMP test. Results: Contamination of raw, stabilized and dried sludge at least to one of L. Monocytogenes, L. Innocua and L. Seeligeri species was 100, 92.3 and 53.8 percent respectively. Anaerobic sludge digesters efficiency to remove L. Monocytogenes, L. Innocua and L. Seeligeri species was determined 64.7, 39.72, and 100 percent while the efficiency of drying sludge beds for L. monocytogenes and L.innocua species removal was 73.4 and 96.68 percent respectively. Conclusion: Listeria monocytogenes is more resistant than other identified species against the sludge processing conditions. Thus, the use of sludge as fertilizer can cause the spread of this bacterium in the environment and agricultural products pollution.

Background and Objective: Silver is a toxic heavy metal that is used in various industries and has adverse effects on both human health and the environment. In this respect its determination with sensitive and economic analytical methods is of great importance.
Materials and Methods: In this research, a novel ion selective electrode based on perphenazine as an ionophore was developed for determination of Ag+. The optimum composition that showed the highest sensitivity was constructed by mixing 9% ionophore, 2% NaTPB as ionic additive, 59% DOP as the plasticizer and 30% PVC.
Results: The designed sensor showed a linear response over the concentration range of 1×10-6-1×10-2 M with the slope of 60.3 mV/Decade. The detection limit of the electrode was obtained 9×10-7 M. The response time and lifetime of the proposed sensor were 5 seconds and 10 weeks, respectively. The selectivity of electrode was evaluated by matched potential method and no serious interference was observed.
Conclusion: In the end, the sensor applicability in determination of Ag+ in three waste water specimens as real samples was evaluated and the good agreement between the results of sensor and the results of flame atomic absorption spectroscopy showed the designed electrode has enough accuracy and it can be used for determination of Ag (I) in the aqueous environmental samples. In conclusion, finally the performance of the prepared sensor in determining the amount of silver ions in three effluent samples was evaluated as the real samples. The results were in good agreement with those obtained by flame atomic absorption method which indicates that the designed sensor can be successfully employed in the accurate determination of silver (I) in environmental aqueous samples.