Water Supply & Treatment Water Treatment Plant 'Water Treatment Works, Kaituna, Masterton' Located about 10 km west of Masterton, on the north side of the Waingawa River, from which water is extracted for town supply. The water treatment plant was opened in September 1983, and supplies a population of almost 20,000 mainly residential consumers. Daily consumption varies from about 9 million litres per day during winter, to a high of 25 million in summer. Syphon Water is extracted from the river by syphon to draw the flow into a concrete main. This feeds the Water Treatment Plant 5 kms downstream. The flow is gravity assisted as it goes, with air being taken out of the pipe at several points along the line, to help maintain a full pipe. Storage Ponds At the treatment plant, raw (river) water is stored in three holding ponds until required. In the event of flooding and dirty river water, the flow can be shut off and the plant can run on its stored capacity for 3-4 days. Touring the Water Treatment plant Coagulation From the ponds, water is let into a large concrete vessel or clarifier, where the chemical coagulants PAC (poly aluminium chloride) and polyelectrolite are added to form small floc particles, which attract the fine suspended silt and clays present in the water. These drop to the bottom of the clarifier as sludge. Filtration Five sand filters are used to "polish" the water to a high degree of clarity and remove any residual floc particles. The filtered water is then piped to a covered clear water pond. Chlorine, Fluoride & Lime Metered dosing is carried out at the clear water pond, using chlorine (disinfectant to give protection from micro-organisms which may enter the distribution system), fluoride (prevention of dental cavities in children), and lime (to raise the pH of the water making corrosion of pipes less likely). Reservoirs The last storage point before water enters the town mains is the Upper Plain Reservoir, supplemented by smaller reservoirs on Lansdowne hill. The supply is almost all gravity fed from our reservoirs, with only a limited amount needing to be pumped to the highest point.