Domestic sewage-Domestic sewage consists of human faeces, urine and the dirty used-up water in houses. It contains a large number of pathogenic bacteria and virus.

Industrial Effluents- The industrial wastes includeing heavy metals (Hg, Cu, lead, zinc, etc.), detergents petroleum, acids, alkalies, phenols, carbonates, alcohol, cyanides, arsenic, chlorine, etc.
Thermal pollution - Many industries use water for cooling. The resultant warm water is discharged into rivers. This brings about thermal pollution.

Fertilizers- The fertilizers used for crops are washed into ponds and rivers.
Pesticides- Pesticides are used to control pests in fields and houses. They include DDT, BHC, endrin, etc.
Radioactive wastes- Liquid radioactive wastes are released into the sea around nuclear installations. The oceanic currents carry the radioactive contaminants everywhere.
Oil pollution- Oil pollution is due to ship accidents, loading and discharging of oil at the harbour, oil refineries and offshore oil production.
Retting- The process of decaying coconut husk to get fibre for making coir is called retting. Retting releases H2S. It makes water polluted.