A&B Test Questions - Florida Rural Water Association

11. You are considering the addition of alum to your up-flow clarifier. You determine that 12mg/l of alum is correct. The raw pH is 8.0 and the alkalinity is 230 mg/l. You know that ittakes an excess of 21 mg/l of alkalinity per mg/l of alum for precipitation to occur. Whatwould be the best selection in this situation?a. Go ahead and slowly start adding the Alumb. Add additional alum to increase the alkalinityc. Add lime or soda ash to increase the alkalinityd. Add carbon dioxide to decrease the alkalinitye. Adjust the mixing intensity of the flocculator12. You use alum as a coagulant. Here would it be best to take a sample of the water for a jartest in order to set a target pH?a. Between the flocculation and the sedimentation basinb. Before chlorination of the finished waterc. Just past the raw water inlet gated. After the flash mixere. In the mixing zone of the sediment basin13. You raw water alkalinity increased from 230 mg/l to 235 mg/l and the pH to 7.9. Yourchlorine residual then dropped below acceptable limits. What is the most likely cause ofthis condition?a. Excess alkalinity reacted with the chlorineb. Chlorine has been converted to hypochlorous acidc. Chlorine has reacted with mineral compounds that raised the pHd. There has been an increase in hypochlorite14. Alum usuallyTROUBLESHOOTINGa. has an optimum PH of 5.5 to 6.8GUIDE SECTIONb. is effective on highly colored waters at pH’s below 5.5c. effective with high mineral waters at PH as high as 7.5d. all of the above15. Sodium Aluminate TROUBLESHOOTINGGUIDE SECTIONa. acidicb. very corrosivec. reduces both carbonate and noncarbonate hardnessd. all of the aboveTROUBLESHOOTINGGUIDE SECTION44