Water Treatment & Supply

Chlorine is the most widely used disinfectant in municipal water treatment worldwide. It effectively kills bacteria, viruses, and other pathogens, and provides residual protection as water travels through the distribution system.

Desalination is the process of removing dissolved salts and minerals from seawater or brackish water to produce fresh water. The two main methods are reverse osmosis and thermal distillation.

Sedimentation is a physical process where gravity causes suspended particles and floc to settle to the bottom of a tank. The clear water above is then drawn off for further treatment, while the settled material (sludge) is removed.

The Pont du Gard is a Roman aqueduct bridge built in the 1st century AD near Nimes, France. Standing 49 meters high with three tiers of arches, it is one of the best-preserved Roman aqueducts and a UNESCO World Heritage Site.

Reverse osmosis forces water under high pressure through a semi-permeable membrane that blocks most dissolved salts, organics, bacteria, and pyrogens. It is widely used in desalination and water purification systems.

Saudi Arabia is the world's largest producer of desalinated water, producing approximately 22% of the world's desalinated water. The country relies heavily on desalination due to its arid climate and limited freshwater resources.

Fluoride is added to drinking water (fluoridation) primarily to prevent tooth decay. The practice began in the United States in 1945 and has been credited with significantly reducing dental cavities in communities that practice it.

Coagulation involves adding chemicals (coagulants) like aluminum sulfate to raw water. These chemicals neutralize the electrical charges on fine particles, causing them to clump together into larger particles called 'floc' that can be removed.

The Croton Aqueduct brought clean water from the Croton River in Westchester County to New York City, covering 41 miles. It was built in response to a devastating cholera epidemic and water shortages in the growing city.

The activated sludge process uses microorganisms to biologically break down organic matter in wastewater. Air is pumped into tanks to support the microorganisms, which consume organic pollutants and form settleable floc.

Dr. John Snow traced a cholera outbreak in London's Soho district to the Broad Street water pump. His work was pioneering in epidemiology and helped establish the connection between contaminated water and disease.

UV disinfection uses ultraviolet light (specifically UV-C at 254 nanometers) to inactivate microorganisms by damaging their DNA, preventing them from reproducing. It is chemical-free and increasingly used in water treatment.

The water table is the upper surface of the zone where soil and rock are fully saturated with groundwater. Its depth varies by location, season, and precipitation, and it is crucial for well placement and water supply planning.

Singapore's NEWater uses a multi-barrier approach: microfiltration removes particles, reverse osmosis removes dissolved salts and contaminants, and UV disinfection provides final sterilization. It meets up to 40% of Singapore's water demand.

The Great Stink of 1858, caused by raw sewage in the River Thames during a hot summer, made Parliament nearly uninhabitable and prompted the construction of London's modern sewer system, engineered by Joseph Bazalgette.