Performance evaluation of a cloth-media disk filter for wastewater reclamation

A cloth-media disk filter (CMDF) was evaluated as an alternative to granular-medium filtration for use in wastewater recycling applications. The CMDF was effective for filtration of effluent from an activated-sludge treatment process. Effluent turbidity values from the CMDF were consistently less than California's wastewater recycling application limit of 2 nephelometric turbidity units (NTU) for influent turbidity values of up to 25 NTU at hydraulic loading rates varying between 7 and 15 m/h (2.86 and 6.1 gpm/sq ft). The filter produced 154 m/d (3781 gpd/sq ft) at a hydraulic loading rate of 7 m/h (2.86 gpm/sq ft) with high turbidity (6 to 25 NTU) and 330 m/d (8102 gpd/sq ft) at a hydraulic loading rate of 15 m/h (6.1 gpm/sq ft) with low influent turbidity (< or = 6 NTU/m2 [6 NTU/sq ft] of filter cloth). The backwash water required by the CMDF at HLRs between 7 and 15 m/h (2.86 and 6.1 gpm/sq ft) and corresponding solids loading rates between 5 and 32 kg/(m2 x d) (0.21 and 1.35 lb/d/sq ft) varied from 2 to 10% of the total influent flow. Thus, the CMDF could consistently meet the recycling requirements of a turbidity less than 2 NTU over a broad range of influent turbidity values and hydraulic loading rates.