Investigating the Effect of Different Substrates of Pressurized Sand Filters on the Water Quality of Moallemkola Refinery in Sari City

Due to lack of water resources and per capita consumption in Iran, conservation of water resources is one of the most important and basic priorities. Drinking water in Sari city and its dependent villages are provided with groundwater resource. The poor quality of the outlet water especially the high amount of iron after the pressurized sand filters in the refinery of Moallemkola led to investigate the effective factors on the efficiency of the above filters. The purpose of this study is to investigate groundwater resource by changing the bed and surface load of pressurized sand filters to improve the removal of physical and chemical parameters of the water refinery.

In this research investigated the physical and chemical parameters of pressurized sand filters with the change in filter granulation using a pressurized sand filter model and using different substrates (silica, silica-anthracite and leca-anthracite). Samples were taken after treatment at three points in the refinery (at the beginning of the filter operation, at the end of the filter operation and after chlorination) after 4 months. The measured parameters included determination of suspended solids, turbidity, total soluble solids, hardness, calcium, magnesium and iron. The experiments were carried out in factorial and completely randomized design with three replications. Statistical analysis of data was done using SAS software and comparison of means was done by Duncan method at 5 percent probability level.

The results showed that the effect of substrates materials on TSS, Tu, TDS, Ca and Fe parameters was significant at 1% probability level. The effect of sampling point on all parameters was significant different at 1% probability level. The silica-anthracite bed had the greatest effect on the reduction of all parameters, especially the reduction of turbidity and iron content. So that the reduction of turbidity and iron content in the silica-anthracite bed was close to 70% relative to the silica bed. The leca-anthracite bed was better than the silica substrate. The best reduction in chemical parameters of water was related to silica-anthracite in pressurized sand filters with a surface load of 54 cubic meters per hour. The interaction effect of different materials inside the filter and sampling point was also significant at 1% probability level on TSS, TDS and Fe parameters. The results of the comparison of the average of the physical and chemical parameters of the water studied at different points of sampling showed that the output water at the end of the disinfection had the lowest values relative to the water outflow from the filter at the beginning of the operation and the outlet water from the filter at the end of the operation.

The option of using silica-anthracite in pressurized sand filters in addition to improving the water quality, will reduce the cost of operating (maintenance and repair) of the filters.