Effects of Untreated Sewage and Fertilisers

Untreated sewage and fertilisers both contribute to the problem of nutrient pollution in water bodies. This is when excess nutrients, such as nitrogen and phosphorus, cause a rapid growth of plants and algae in lakes and ponds.
The rapid growth of these organisms is known as an algal bloom. While some algal blooms are harmless, others can be toxic to animals and humans.
When the plants and algae die off they decompose, a process which uses up oxygen in the water. This can create ‘dead zones’ where the lack of oxygen makes life untenable for other organisms.
When oxygen levels in water are depleted, it can lead to the death of aquatic animals such as fish and invertebrates. This not only disrupts the food chain but also reduces the biodiversity of aquatic ecosystems.
The leaching of nutrients from fertilisers into water bodies can also affect the balance of nutrients in soil. This can lead to decreased soil fertility, affecting plant growth and agriculture.
Untreated sewage is also a public health concern as it contains harmful microorganisms. These can contaminate drinking water supplies and cause a range of illnesses, including diarrhoea, dysentery, and cholera.
Both untreated sewage and fertilisers have indirect impacts on the climate as well. Decomposing organic matter releases greenhouse gases like methane, contributing to global warming.
Solutions to these problems involve improving sewage treatment to ensure harmful substances and excess nutrients are removed before the wastewater is released. Similarly, more sustainable farming practises can reduce the usage of synthetic fertilisers.