Qom University of Medical Sciences Journal

Background and Objectives: Horizontal roughing filters (HRF) can properly remove suspended solids and microorganisms from surface water resources, especially on filtration rates less than 1.5 m/h. This research was aimed at suspended solid removal efficiency of HRF during secondary wastewater effluent filtration.

Methods: This experimental study was conducted by installing an HRF pilot system on effluent pumping station of Qom wastewater treatment plant based on aerated lagoon process. The pilot was a horizontal cylindrical column consisting of three compartments filled with river gravels in various sizes. Grab samples were simultaneously taken from HRF inlet and outlet in three filtration rates: 0.5, 1, and 1.5m/h

Results: The results indicated that filtration rate had a significant effect on the amount of total suspended solids in HRF effluent. During optimum operation of HRF, removal efficiencies of three filtration rates (0.5, 1, and 1.5 m/h) were 78.5, 63.1, and 66.9, respectively.

Conclusion: T-test analysis indicated that with a significance difference, outlet effluent from HRF in all three flow rates met the standard requirements of Iran Environmental Protection Agency for irrigation and discharge to surface water.