Water Treatment <ul><li>Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the concentration of such contaminants so the water becomes fit for its desired end-use. One such use is returning water that has been used back into the natural environment without adverse ecological impact. </li></ul><ul><li>The processes involved in treating water for drinking purpose may be solids separation using physical such as settling and filtration, chemical such as disinfection and coagulation. </li></ul><ul><li>Biological processes are also employed in the treatment of wastewater and these processes may include, for example, aerated lagoons, activated sludge or slow sand filters. </li></ul>
Objectives for the Developments of a Water Treatment System <ul><li>Production of Safe Drinking Water </li></ul><ul><li>Minimize the cost of supply of safe drinking water </li></ul><ul><li>Bring water to rural communities </li></ul>
Factors considered at the treatment process selection <ul><li>Quality of raw water </li></ul><ul><li>Use for the processed water </li></ul><ul><li>Treatment and quality desired for the water </li></ul><ul><li>Size and capacity of the system </li></ul><ul><li>Cost of processes </li></ul>
Processes for Water Treatment <ul><li>Pretreatment: consists of storage, screening, and presedimentation. </li></ul><ul><li>Chemical coagulation: is the destabilization of a colloidal suspension by adding chemical species to absorb colloids in water. The coagulants used must be effective, non-toxic, and insoluble. The most widely used coagulants are aluminum and iron salts: aluminum sulfate (alum), ferric sulfate and ferric chloride </li></ul>
<ul><li>Rapid Mixing: process where chemicals are added to the water. It can significantly enhance coagulation by facilitating contact between the hydrolysis products and the colloids in water. Chemicals are commonly added during rapid mixing, including: </li></ul><ul><li>• Chloride (for disinfection) </li></ul><ul><li>• Powdered activated carbon (for taste and odor control) </li></ul><ul><li>• Potassium permanganate for taste odor and Fe Mn removal), and </li></ul><ul><li>• Acid or base (for pH control). </li></ul><ul><li>Rapid mixing is not necessary for these chemicals to be effective, but it is good for them be well dispersed in the water and to have an adequate time to react. </li></ul>
<ul><li>Flocculation: causes coagulated particles to collide with one another and aggregate into larger particles called “flocs”. </li></ul><ul><li>Sedimentation: water is placed in a tank for 2-4 hours so settlement of floc particles can take place. </li></ul><ul><li>Filtration: water is filtered so its turbidity level decreases, does not guarantees a particle free water. The types of filtration are: slow sand filters and rapid sand filters. This is determines by the size of the sand grains used in the filters. </li></ul>
<ul><li>Disinfection: This process kills bacteria escaping filtration or to make them inactive. This keeps water safe from bacterial-growth. Chemicals most commonly used for disinfection in the US are chlorine and monochloramine. The degree of disinfection actually achieved in practice depends not only on the type and dosage of disinfectant and the types of organism present, but also on temperature, pH, time, mixing, and the presence of interfering substances such as particles or chemical that react with the disinfectant. </li></ul>
<ul><li>Softening: is used in place of ( sometimes ahead of) coagulation when removal of hardness is desired to decrease scale formation and soap use. </li></ul><ul><li>This process of softening is a very wide process because it includes the removal of metals of water, therefore hardness, the removal of odor, tastes, organic contaminants, the stabilization of pH of water, fluoridation and defluoridation. </li></ul>
Conclusion <ul><li>These processes help the sanity of public health but it is up to people to make consciousness of the importance of avoiding contamination and pollution of our water streams. These processes cost more money day by day as water pollution increases. </li></ul>
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