Public Health

Sewage Treatment and Disposal

The Use of Water In Our Cities

Water supplied to households is used for many purposes, other than drinking and food preparation, notably bathing and showering, toilet flushing and the washing of utensils, dishes and clothes. Except where main drainage is not installed, the used water gravitates to the local sewer and becomes ‘sewage’.

Domestic waste water will contain both solid and dissolved pollutants including fecal matter, paper, urine, sanitary items, food residues and a variety of other contaminants. The sewer network will usually also receive waste waters from office and commercial properties and from industrial premises. Rainwater from roofs and roads may also drain into the sewer network.

Preventing Disease with Clean Water

  • The impact of clean water technologies on public health in the U.S is estimated to have had a rate of return of 23 to 1 for investments in water filtration and chlorination during the first half of the 20th century.
  • Community water fluoridation prevents tooth decay safely and effectively. Water fluoridation has been named one of 10 great public health achievements of the 20th century.

Why Is It So Important?

Treatment of sewage is essential to ensure that the receiving water into which the effluent is ultimately discharged is not significantly polluted. However, the degree of treatment required will vary according to the type of receiving water. Thus, a very high degree of treatment will be required if the effluent discharges to a fishery or upstream of an abstraction point for water supply. A lower level of treatment may be acceptable for discharges to coastal waters where there is rapid dilution and dispersion.