Propose a drinking-water treatment scheme for a community that can effectively r

Question

Propose a drinking-water treatment scheme for a community that can effectively remove turbid articles, natural organic matter pathogens and herbicides from water. Please note that the community cannot afford to use membrane filtration and reverse osmosis. For the proposed treatment system, please name the chemicals to be used and comment on how to determine the doses the chemicals. Please discuss the general mechanisms of each treatment unit you have proposed. (one sentence each treatment points) Define break-point disinfection in one sentence. The disinfection byproducts (DBPs) of drinking water of another community is elevated. Please propose three solutions for the community to lower the concentrations of DBPs. (short answers in three sentences; 10 points) In addition to the disinfection unit within the water treatment plant, can DBPs also be formed in the distribution system? (short answers; 5 points)

Explanation / Answer

1) SEDIMENTATION WITH COAGULATION is the best method for a drinking water scheme for a community that can effectively remove turbidity particles,natural organic matter, pathogens and herbicides from water.

2) The common coagulant chemicals to be used are: a) aluminium sulphate or alum b)chlorinated copper c)ferrous sulphate and lime d) magnesium carbonate e) poly electrolytes and f) sodium aluminate.

a) alum is found to be effective when PH of water ranges between 6.5 to 8.5. its dose depends upon turbidity ,colour ,taste, PH value and temperature of water. the dose of alum varies between 10 and 30 MILLIGRAMS PER LITRE OF WATERR.

b) when chlorine is used independently it is effective over a PH range of 3.5 to 6.5 and above 8.5.

c)the effective PH range for this coagulant is 8.5 and above.

d) magensium carbonate and e) polyelectrolytes are not commonly used. the ususal dosage is less than 1ppm.

f) sodium aluminate is effective for a PH range of 6 to 8.5.

3) sedimentation is the removal of particles by gravitational settling.these are designed to reduce the velocity of flow of water so as to permit the suspended solids to settle out water by gravity.

4) disinfection means killing the bacteria potentially present in the water . BREAK DOWN POINT means at the point where all the microrganisms are killed .

5) solutions for the community to lower the concentrations of disinfectioon by products are boiling method,excess lime treatment method,silver treatment,ultra violet ray treatment and potassium permangante treatments.

6) disinfection by products can also be used besides disinfection unit but DBP are timetaking methods . as the disinfection treatment plant is more the DBPs are not commonly used.

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