Jar Test, Continued

coagulant selected for trial by adding 10 grams of coagulant to 1 liter of distilled water. 2. Correct the pH of a sample of raw water to within the optimum range for the coagulant being tested (only if the pH is to be adjusted to the same extent in actual plant operation). Divide the raw water into six 1 liter samples, 3 . Add 0.5 ml of standard coagulant solution to one sample of raw water, 1.0 ml to the second sample, 2.0 ml to the third sample, 3.0 ml to the fourth sample, 4.0 ml to the fifth sample, and 5.0 ml to the sixth sample. The result is a dosage of 5, 10, 20, 30, 40, and 50 mg/1, respectively. 4. Agitate samples in the jar test apparatus at a velocity about equal to the treatment equipment you are using and for the same length of time as the treatment equipment mixing time. 5. Keep the samples at the same temperature as water passing through your treatment equipment. 6. After stirring, let the samples settle for 30 minutes. 7. Siphon off a sample of the supematant and determine the turbidity by using a turbidimeter. 8. The smallest amount of coagulant that produces the lowest turbidity represents the optimum dosage. Multiply the coagulant dosage in mg/1 ( step 5 above) by 8.33 to get the correct chemical feed in pounds per million gallons. 9. Repeat the steps for each chemical used until satisfactory results are obtained. As to acceptability, the taste and odor of water must be considered from the user’s point of view. Tastes and odors of water are m o s t c o m m o n l y c a u s e d b y a l g a e, decomposing organic material, dissolved gases, or industrial wastes. Potability is not fleeted by the presence of odors and tastes. On the other hand, palatability is frequently affected, particularly when a substance such as bone or fish oil is present. Tastes and odors that make water unpalatable must be removed. Use of free available chlorine, aeration, and activated carbon can do much to prevent or remove unacceptable tastes and odors from treated water. The use of free available chlorine is advantageous because most odors and tastes are removed and rigorous disinfection is assured. Activated carbon is the most widely used single process for taste and odor removal. Aeration and copper sulfate treatment are also used. All three methods are described below. The method used depends upon the substance or substances to be removed and the equipment available. l Activated carbon is an excellent absorbing agent to use in ridding water of unpleasant tastes and odors. It is also an effective agent for removal of organic color. It is insoluble and tends to float unless all particles are wetted thoroughly by being made into a slurry before being added to the water. When continuous flow equipment is being used, the activated carbon should be added to the limestone feeder and added to the water with the limestone slurry. When the batch type of equipment is being used, the activated carbon can be added along with other chemicals in the coagulation tank. Being 9-15-A