Chemical Oxygen Demand (COD)
A test commonly used to indirectly measure the amount of organic compounds in water.
Compounds formed by the reaction of hypochlorous acid (or aqueous chlorine) with ammonia.
Chloride, in the form of Cl-, is one of the major inorganic ions in water and wastewater. The salty taste produced by chloride concentrations is variable and depends on the chemical composition of the water. Some waters containing 250 mg Cl-/L may have a detectable salty taste if the cation present is sodium. But when the predominant cations are calcium and magnesium, the salty taste may be absent in water containing as much as 1,000 mg/L.
City of Gardens and Water
By integrating the streams, rivers and lakes with the parks and gardens in a holistic way, new community spaces can be created. These will be bustling with life and activities, and transform Singapore into a City of Gardens and Water, a vision outlined by Singapore’s Prime Minister Lee Hsien Loong in 2007.
Chemicals that cause very fine particles to clump (floc) together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.
The clumping together of very fine particles into larger particles (floc) caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles, allowing them to come closer and form larger clumps. This clumping together makes it easier to separate the solids from the water, by settling, skimming, draining or filtering.
A group of bacteria commonly found in the intestines of animals and humans beings. Coliform count is used as a hygiene indicator. The test is performed via membrane filtration, and filters placed onto selective agar. After incubation, plates are counted and suspect colonies confirmed with confirmation tests (lactose fermentation)
Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a liquid for a long time due to their small size and electrical charge. When most of the particles in the water have negative electrical charge, they tend to repel each other. This repulsion prevents the particles from clumping together, becoming heavier, and settling out.
A measure of the ability of an aqueous solution to carry an electric current. This phenomenon is not only shown in metals such as iron but also in water. The conductivity value of water depends on the presence of ions, total concentration, mobility of ions and valence, and also the water temperature during measurement. Ion concentration and temperature have a proportional effect on water conductivity. Solutions of most inorganic compounds are relatively good conductors, whereas molecules of organic compounds that do not dissociate in aqueous solution show poor conductivity.
Securing an adequate supply is only half of the water equation – managing the demand side is just as crucial. PUB has a wide-ranging water conservation plan that encourages customers to use water wisely. Singapore’s per capita domestic water consumption has been brought down from 165 litres per day in 2003 to the current 155 litres. The target is to lower it to 140 litres by 2030.