The correct choice is (c) Roughing filter
To explain: Roughing filter is used to pretreat water by removing suspended solids from the water that might clog the passage through bio filters, high rate bio filters usually constructed as tower models treating food waste which has considerable potential to rough high strength industrial effluents prior to sewage discharge, Conventional bio filters are also called as Percolating filters in which the waste trickles and is oxidized and hence removed by biological degradation, Filter cake is the by-products of filtration left on the surface forming cakes.