Importance and objectives of wastewater disposal

Necessity (importance) of wastewater management

Wastewater produced by a community contains pathogens, organic matter, nutrients and toxic substances. If it is left on the street or let into rivers without treatment, it:

• spreads waterborne diseases (cholera, typhoid, dysentery, hepatitis, diarrhoea),
• pollutes surface water and groundwater that people use for drinking, bathing and irrigation,
• kills fish and aquatic life by depleting oxygen, and causes eutrophication,
• gives bad smell, mosquitoes and flies, and spoils the look of the city,
• blocks the drains and causes flooding, and
• reduces land value and tourism.

So scientific management (collection, treatment and safe disposal) is necessary for public health, protection of the environment and economic development, and is required by law (Environment Protection Act 2076 and Environment Protection Rules 2077, which replaced the Act 2053 and Rules 2054).

Objectives of sewage (wastewater) disposal

1. To protect public health by preventing contact of people with pathogens and by controlling disease carriers.
2. To prevent pollution of water sources: streams, lakes and groundwater, so that the quality of the water supply remains safe.
3. To protect aquatic life and the ecological balance of the receiving water (by maintaining dissolved oxygen).
4. To avoid nuisance: bad smell, flies, mosquitoes, and unsightly conditions.
5. To meet the legal standards for effluent (Nepal's generic standards).
6. To recover resources: reuse of treated water for irrigation and industry, biogas from sludge, and sludge as manure.
7. To protect the soil and crops from clogging and contamination.
8. To dispose of the wastewater in the cheapest and safest way, with the least treatment that meets the above aims.