Coagulant-assisted filtration through a dual-media filter, with pH adjusted to 5.5-6, gave an average effluent turbidity of less than 0.5 mg/L at a filtration rate of 120 m/day. The dual-media filter has a coarse medium bed at the upper part and a sand bed at the lower part. The removal efficiency was almost 100% for turbidity and 50-60% for color. Though 80% of the removed flocs were in the coarse medium, the head loss in that part was less than 20% that of the total head loss. The coagulant dosage of 4 mg Al3+/L was the optimum for filtration.
Removing Color and Turbidity from Secondary Wastewater Effluent by Direct Filtration in a Dual Media Filter
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