Feature of slow filter (w.r.t. Faster filter) is/are:

Slow sand filters occupy more space, require less skilled operators and gives good bacterial quality when compared to rapid sand filters. But it takes more time for the operation. Rate of filtration is 200 m.g.a.d in the rapid sand filter but only 2-3m.g.a.d. in the slow sand filter (PARK TB 25th edition pg 773)