ICSE Class 9 Answered

Contamination of drinking water can occur in the following ways:
(1) Sewage, if not disposed off properly can leak into sub-soil and may contaminate water supplies.
(2) People defecating or urinating near lakes, rivers or ponds may contribute to contamination of water.
(3) Animal wastes and washing from dairies and poultries, etc. may also be drained into water bodies.