Sedimentation and Infiltration on the Hope Valley Water Treatment Plant and Barker Inlet Wetlands - Case Study Example

Report of Field Trips to Barker Inlet Wetlands and Hope Valley Water Treatment Plant Singapore NEWater: Singapore NEWater is the result of the attempts of the Singapore government to augment its water resources. This initiative was started in 2002 and uses the most efficient technologies available to treat domestic waste water from kitchens and bathrooms to make available water initially for industrial purposes and then gradually as potable water. The first plant went on stream in 2003 and it is estimated that Singapore NEWater will meet 15-20% of Singapore’s water requirements by 2010. (1). The domestic waste water goes through intensive purification processes that consist of four stages. In the first stage the collected domestic waste water goes through a conventional water treatment process. (2). The objectives in this initial process is the removal of heavy solids and floatable materials present in the water, through settling. The waste sludge obtained from sedimentation is used drawn off. (3). The second stage in the water purification process consists of micro-filtration or ultra-filtration to remove any remaining suspended solid material, colloidal particles, bacteria, viruses and cysts of protozoa. This process makes use of membranes from Canada. These membranes contain very fine pores of about 0.04 micron through which the water is filtered. The water that comes out from after this process are likely to contain only dissolved salts and organic material. Reverse osmosis is used in a third process to remove these dissolved heavy metals, nitrates, chlorides, sulphates, organic molecules that include aromatic hydrocarbons, disinfectant by-products and pesticides. The reverse osmosis membranes have been sourced from the United States of America and have a pore size 0.0001 microns. Pressure is used to force the water through these membranes to give water that exceeds the guidelines of the World Health Organization. The final process is disinfection using ultra violet rays. The ultraviolet disinfectant unit comes from the United Kingdom. Sodium hydroxide is finally added to this water raise the pH levels that would have dropped from all these processes to give NEWater. (4). Prospect Water Treatment Plant in Sydney: The Prospect water treatment plant was set up at a cost of about $ 200 million to provide drinking water for Sydney. Water from the huge Warragamba Dam is brought to the Prospect water treatment plant through a canal. The Prospect water treatment plant is a filtration plant and is among the largest of these types of plants in the world. The water entering the filtration plant is initially screened to provide data for the coagulation process involved in the filtration. The sediment that is collected from the coagulation process is backwashed and taken away to lagoons at the rear of the filtration plant for disposal. (5). Two main processes of removal of particles of matter and inactivation of present in the raw water and inactivation of micro-organisms present in the raw water along with two minor processes of flouridisation and adjusting the pH of the treated water make up the processes involved in providing safe and healthy drinking water to the residents of Sydney. Screening of the raw water provides the input on the coagulants to be used and the dosage rate of the coagulants in the initial process of removing particulate matter from the raw water, as several coagulants are used in for this process. The main coagulant involved in this process is ferric chloride, which overcomes the. Based on the screening of the raw water the dosage rate of ferric chloride is adjusted to flocculate the water. Flocculation is the process by which ferric chloride neutralises the surface charge of the particles in the water causing them to precipitate as flocs. A secondary coagulant in the form of a polyelectrolyte or long chain polymer is employed to assist in the flocculation by ferric chloride and to assist in the removal of the flocs by the filters. Adjustment of the pH levels of the water may be required to assist in the coagulation and flocculation process and this is done through the addition of lime or caustic soda. In case of heavy presence of dissolved metals like manganese, iron or aluminium and dissolved organic material pre-oxidation is done through the addition of potassium permanganate or chlorine. This coagulated water is then filtered to remove all the solid material in the water. The second major treatment process at the water treatment plant is the destruction of micro-organisms, which include pathogens. Chlorine is the disinfectant uses at this plant in several forms, which include chlorine gas, liquid sodium hypochlorite and calcium hypochlorite tablets. The quantum of disinfectant used is so adjusted as to leave residual action that prevents recontamination as the water moves along the water distribution system of Sydney Water. Fluoride is added to meet the requirements of the Fluoridation of Public Water Supplies Act, 1957. For this purpose sodium silicofluoride or hydrofluorosilicic acid is added so that there is a fluoride content of one milligram per litre present in the treated water. To increase the hardness of the water and to adjust and buffer the pH of the treated water Lime and carbon dioxide may be added. Alternatively sodium hydroxide or sulphuric acid is added for adjustment of the pH levels of the treated water. In this manner the raw water received is treated at the Prospect water treatment plant of Sydney to give safe drinking water. (6). Barker Inlet Wetlands: The Barker Inlet Wetlands is one of the constituents of constructed wetlands in Australia, which were constructed with several objectives in mind. These objectives include improving the quality of storm and urban discharge water that flows into the Barker Inlet Aquatic Reserve; storm water retention, pollution management and flood control; water re-use source; providing a habitat for plants, birds and animals; ecotourism and providing educational opportunities. (7). Storm water that emerges from urban and industrial areas is allowed to find its way into Wetlands via four storm water drains. In the Wetlands the flow of water is such that it takes more than ten days for the water to drain into the Barker Inlet to allow for the natural processes that enhance the quality of water to occur before the water flows into the Barker Inlet. (7). Sedimentation is the main natural process involved in enhancing the quality of water, which may be assisted by naturally occurring filtration, adsorption, biological assimilation, and decomposition. (8). A special feature of the Barker Inlet Wetlands is the use of different species of plant in enhancing the quality of water. Around fifty different species of terrestrial and aquatic plants from the Adelaide plains region have been planted in the wetlands and they play a vital role in enhancing the quality of the water. (9). It is this use of different species of terrestrial and aquatic plants that differentiates the Barker Inlet Wetlands from the Range Wetlands. Sedimentation and filtration are two of the processes observed that enhance the quality of water. In the sedimentation process, the solid particles in the water are caused to be precipitated out of the water and are removed, while in filtration the filtration process filters are employed to remove solid and colloidal particles in the water. Works Cited 1. “Reclaimed Water: Singapore Introduces NEWater”. 2002. IRC. 12 June 2008. . 2. Pikul, Corrie. “Would you drink this water?” 2004. 12 June 2008. . 3. Qin, Jian-Jun., Wai, Nyunt, Maung., Oo, Htun, Maung., Kekere, Arun, Kiran & Seah, Harry. “Feasibility study for reclamation of a secondary treated sewage effluent mainly from industrial sources using a dual membrane process”. Separation and Purification Technology 50.3(2006): 380-387. 4. “Radio Feature 4: Singapore: NEWater”. 12 June 2008. . 5. “Sydney's Cryptic Water Crisis”. 1998. Radio National. ABC. 12 June 2008. . 6. “Prospect water filtration plant”. Water Quality. 12 June 2008. . 7. “Barker Inlet Wetlands”. Waterwatch Central Adelaide. Government of South Australia. 12 June 2008. . 8. Walker, J. David & Hurl, Sigrid. “The reduction of heavy metals in a stormwater wetland”. Ecological Engineering 18.4 (2004): 407-414. 9. “Wetlands”. Port Adelaide Enfield. 12 June 2008. . Read More