Full Description

The disposal of membrane concentrate and other residuals from membrane watertreatment plants is becoming increasingly difficult, especially in inland areas. The Citiesof Tipp City and Vandalia, Ohio formed a joint venture to provide nanofiltrationsoftening for its residents. The disposal of the treatment plant residuals were asignificant driver in the ultimate water process decisions.The regulations in some states, including Ohio, require that the discharge of dissolvedsolids, iron, manganese, dissolved oxygen and other constituents meet a certain standard.These limits, while not especially stringent, caused a significant change in process designfor this 7.7 mgd nanofiltration membrane water treatment plant.The process was piloted not only for the typical RO membrane parameters of flux,recovery, pressures, and permeate water quality, but also for the ability of the concentratedischarge to be treated before discharge to the Great Miami River, a scenic river inwestern Ohio. The original process decision to utilize well water in the anaerobic statewas changed when the difficulty of settling iron and manganese from membraneconcentrate was encountered.Jar testing of membrane concentrate proved ineffective in the removal of iron andmanganese below the regulatory limits of 1 mg/l. The subsequent decision to oxidize theiron and manganese upfront was not taken lightly as there are disadvantages with thisapproach on the RO process. The ultimate process resulted in three waste streams, two ofwhich have been permitted for discharge to the Great Miami River. The concentratestream, virtually free of iron and manganese, is directly discharged to the river afteraeration along with the decant of the filter backwash holding tank to meet regulatorylimits with a unique blended waste stream.

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Edition: Vol. - No. Published: 06/01/2007 Number of Pages: 44File Size: 1 file , 2.5 MB