Ch2 overview of wate treatment

Ch2 overview of wate treatment - Chapter 2. Introduction to...

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Unformatted text preview: Chapter 2. Introduction to Water Treatment Dr. G.H. Chen Department of Civil Engineering HKUST Water Engineering (review) Objective: To provide chemically and microbiologically safe, and pleasant (free from apparent turbidity, color, odor and objectionable taste) water for human consumption. Tasks:- Removal of particles- Removal of pathogen to prevent waterborne diseases.- Removal of chemical contaminants.- Control of taste and odor. Management of Water Resources (Review) Source selections: high quality raw water and sufficient quantity. Major Sources for Water Supply (*) River water Lake/reservoir water Groundwater Sea water } Surface water Which one is the major source of water in Hong Kong? Which one is the major source of water in Hong Kong? Acceptable Raw Water Quality for Water Supply What are meant by mg N/L and mg P/L? What are meant by mg N/L and mg P/L? River Water The major water source for Hong Kong water supply. Quality 1) fluctuates in time and location; 2) usually has a high turbidity, large number of bacteria, and a low hardness; 3) may have overgrowth of algae generating unpleasant flavors (smells & tastes) and color. Overgrowth of algae is the consequence of excessive discharge of nitrogen and phosphorous, which is called eutrophication (nutrients in excess), indicating a serious pollution of water body. Eutrophication often occurs in closed water bodies such as shallow tidal rivers, lakes, reservoirs, sea bays because of limited dilution capacity resulting in nutrients accumulation in the mud. Eutrophication will cause: 1) death of fishes due to release of toxicants from algae; 2) shortage of dissolved oxygen during night-time as algae consume a great deal of oxygen by algal respiration; 3) unpleasant flavors such as bad taste and smell and high turbidity. To prevent water bodies from eutrophication, nitrogen and phosphorus in water should be controlled below 1 mg N/L and 0.5 mg P/L. Do we need to control both? Do we need to control both? Quantity River flow rate usually changes from season to season and from year to year. In order to secure an adequate intake of raw water for a water supply system over a long period (e.g., 20 yrs) with a 90% confidence, a 7-day minimal flow rate for 10 yrs is practically used in evaluating the supply capacity of a river of interest. The 7-day minimal flow rate for 10 yrs means that a mean minimal flow rate in a week over a 10-yr period.over a 10-yr period....
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Ch2 overview of wate treatment - Chapter 2. Introduction to...

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