1. Sewage is the muncipal waster water generated in cities and towns everyday, which contains large amount of organic matter and pathogenic microbes.
2. Biological Oxygen Demand (B.O.D) refers to the amount of O2 that would be consumed, if all the organic matter in one litre of water were oxidized by bacteria.
3. Floes are masses of bacteria associated with fungal laments to form mesh like structures.
