Clean water supply is essential in establishing and maintaining a healthy community. There are two sources of water supply which are the surface water and ground water. Most natural waters are not suitable for consumption as it is contaminated by pathogens and also natural chemicals and minerals. In addition, as a city grew, wastes from human activities contaminate most of the water supplies. Water treatment plays an important role to properly treat a contaminated source of water supply in order to protect the health of consumers. Water treatment process is defined as a process of eliminating pollutants from untreated water to produce a biologically and chemically risk-free water, which is both potable and palatable for human consumption (SAJ Holdings Sdn Bhd., n.d.). There are six important steps in water treatment process, namely screening, aeration, coagulation and flocculation, sedimentation, filtration and lastly, disinfection (refer to Figure 1 in Appendix 1).
The first step in water treatment process is screening. Raw water undergoes physical screening to remove coarse material and debris as it comes to the water treatment plant. Screening separates particles according to their size alone. As mentioned by Hendricks (2006),
the objective of the screen is to accept a feed containing a mixture of particles of various sizes and separate it into two fractions, an underflow that is passed through the screen and an overflow that is rejected by the screen. (p. 121)
Screening is further divided into coarse and fine screens. Raw water undergoes coarse screen to eliminate floating material of fairly large size as preliminary treatment for the next step. These floating or submerged debris would damage pumps or block inlets, hence it is prudent to provide coarse screens (Binnie & Kimber, 2009). Fine screen removes waterweed, filamentous algae, small wastes, and the larger dwellers of raw water, which is typically the first stage of water treatment.
The second step of water treatment process is aeration. At the aerator, raw water is mixed with air. The aeration process helps to provide oxygen to the raw water which is needed for the oxidation process of dissolved iron and manganese in order for it to precipitate and therefore enables its removal through filtration (SAJ Holdings Sdn Bhd., n.d.). Wormleaton and Tsang (2000) stated that for water treatment process and also natural streams, it is essential to maintain a high amount of dissolved oxygen. Aeration also provides the escape of dissolved gases, such as carbon dioxide and hydrogen sulphide to reduce the corrosiveness of water, thus controls the tastes and odors of the water (Shun, 2007). Groundwater with high dissolved carbon dioxide levels or high concentrations of iron and manganese commonly require aeration as well as water drawn from reservoirs that is low in dissolved oxygen.
Thirdly, the proceeding water treatment step involves coagulation and flocculation. The objective of this step is to...