Water Supply

Slow Sand Filter Area

Filter bed area for a slow sand filter (SSF) given design flow and filtration rate. Recommends two or more beds for continuity during cleaning.

Formula
A = Q / v

Typical SSF rate: 0.1–0.2 m/hr (i.e. 0.1–0.2 m³/m²/hr).

Resultlive
Total filter area, A
166.67
Area per bed (n beds)
83.333
Width of each bed
6.455m
Length of each bed
12.91m
Reference: WHO / IRC guidelines for slow sand filters. Sand: ES 0.15–0.35 mm, UC ≤ 3; bed depth 0.8–1.2 m; under-drain layer 0.3 m.