Humans and Water Pollution Through Detergents: Though wastewater is treated before being discharged, small amounts of detergents still end up in the water supply, contaminating it with phosphates. Phosphates from detergents, like nutrients from fertilizers, contribute to the growth of algae. This can affect the oxygen levels in bodies of water and harm plant and animals living in the body of water. Today, many detergents low in phosphates are available for purchase.