Evaluating ‎Filters Operation after Backwash by Examining Turbidity Decrease and Counting Zooplanktons in Isfahan Water Treatment Plant

Document Type : Research Paper


1 PhD student of Microbiology, Lab. Expert of Isfahan Water and Wastewater Company, Isfahan, Iran

2 Prof. of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran

3 PhD Student of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran

4 Water Treatment Plant Manager, Isfahan Water and Wastewater Company, Isfahan, Iran


One of the reasons for poor performance of filters is their being backwashed. The purpose of this study is to evaluate filtration process and sand filters operation after being backwashed through examining turbidity and zooplanktons in Esfahan water treatment plant. This study was conducted during 4 months in the sand filters (phase 1 & 2) of the treatment plant. Turbidity and microscopic counting were studied to assess the performance after filtration. The average for turbidity variations and nematodes & rotifers counting were evaluated in different times after backwash. Turbidity break point and zooplanktons reduction occurred after 15-20 minutes of backwash. The number of nematodes and rotifers in phase 1 after 10 minutes increased respectively by 13 and 12 numbers per liter and within 20 minutes, it reduced to 7 and 9 numbers, respectively. Also after 20 minutes in phase 2, the number of nematodes and rotifers decreased respectively by 8 and 6 per liter. This changes were significant based on t-test (p <0.001). Also after 15-20 minutes, filters effluent turbidity reduced to less than 0.2 NTU. It is better to put filters in the circuit 20 minutes after being backwashed in order to restrict the number of suspended particles and organisms inside the effluent.


Main Subjects

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