The sanitation services provided by the Municipality entail the collection, removal, disposal or purification [treatment] of human excreta, domestic waste-water, sewage and effluent resulting from the use of water for commercial purposes. The Regulations Relating to Compulsory National Standards and Measures to Conserve Water require that the Municipality must every month measure the quantity of effluent received at each sewage [waste-water] treatment plant and determine the quantity of water supplied but not discharged to sewage treatment plants by comparing the measured quantity of effluent received at all sewage treatment plants with the total measured quantity of water provided to all user connections. There are waste water treatment works in Zastron and Rouxville as well as oxidation ponds in Smithfield.