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)0-V - Kennedy/Jenks Consultants Memorandum John Marlow, Owner 1 April 2009 Page 3 It should be recognized that the WTP backwash was conducted manually at 8 AM during last Fall's pilot tests, and that operation may have caused the water hammer pressure surge, which did not occur when the system had its normal off peak. Considering the very unusual requirement for a storage tank and booster pump for trains of pyrolusite filters, and the likelihood it would not increase system reliability at all, rather complicate it, we are opposed to do that, unless it is demonstrated as a necessity based upon sustained operation. Chlorine Residual: The maintenance of a filtered water chlorine residual over 1 mg/I to maintain the effectiveness of pyrolusite media for iron ad manganese removal is neither necessary or desirable. Data on pyrolusite media was provided in our report of 5 December 2007, with attachments specifically the AWWA Iron and Manganese Removal Handbook as stated in page 85, "Where possible sufficient chlorine is fed ahead of the filter to keep the pyrolusite in a regenerated condition. Where formation is unwanted chlorine byproducts is a concern, chlorine is used intermittently to regenerate the bed following backwash." Data also was provided in that report on the Adedge Technologies recommendations for chlorine dosage. As is stated: "Oxidant- Hypochlorite feed for best results Typically Oxidant Dosage 0.5-2 ppm. A low hypochlorite dose is recommended for optimal performance it enhances the removal process improves longevity and keeps the surface of the media oxidized to prevent the build up of solids." The installed hypochlorite pump will deliver a dosage of as much as 5 mg/I at 90 gpm with a 6% (1/2 strength) solution concentration; it has a 100:1 turn down ratio, and can be adjusted for stroke and speed to provide a desired chlorine concentration. Typically chlorine dosages range from 1 to 3 mg/I during the pilot and demonstration tests, so there was a sufficient chlorine dosage for media regeneration. The chlorine chart during demonstration operation showed residual concentrates in the range of 0 to 2.5 mg/I with an average of 0.25 mg/I and during the previous pilot plant operation showed in the last month of operation residuals from 0 to 0.79 mg/I with a median of 0.30 mg/I Furthermore no coliform organisms have been found in the wells or treated water, so continuous chlorination is not needed for this ground water supply. In summary there is no justifiable reason to operate the WTP to provide a minimum of 1 mg/I of residual chlorine. u::�n.�!.vR'+*"sa*^�?:w_�J101u@ii�isl;ntlenreti!tYgnuy�ltti�:wrstntl'te:i,ry z;menraarMvmjohn marbw 040lA9 tlec ®Y.en,cetlY+��s^uns,s:ans.l,c.