AWWA WQTC58835

The North Texas Municipal District (NTMWD) experiences seasonal taste and odor(T&O) problems caused by the algal metabolites, geosmin and MIB. As part of acomprehensive T&O study, bench- and full-scale tests were performed to evaluate theeffectiveness of powdered activated carbon (PAC) in removing geosmin and MIB from the NTMWD source water,Lake Lavon. The results of the bench- and full-scale tests are reported in this paper.NTMWD operates three conventional surface water treatment plants with a combinedcapacity of over 600-mgd. Each plant has its own raw water intake and pumping stationon Lake Lavon. Ferric sulfate is used for enhanced coagulation at each plant. Jar testingwas performed at Texas A&M University with four PAC brands. The sample water fromLake Lavon was spiked with a Carbon 14 radiolabeled MIB (14C-MIB), and MIBconcentrations in the spiked and treated water were measured with a scintillation counter.The bench-scale testingobjectives were as follows:develop dose-response curves for MIB removal specific to the NTMWD source;compare the treatment efficiencies for PAC addition at the raw water intake andrapid mix basin; and, evaluate the cost-effectiveness of the four PAC brands.Several researchers have demonstrated that geosmin is more readily removed by PACadsorption than MIB 2, 3, 4. Consequently, MIB was selected for testing to provide aconservative representation of treatment requirements for geosmin removal. The jartesting protocol was designed to simulate contact time and chemical additions at the fullscaleplants.Following jar testing, full-scale tests were conducted at one of the NTMWD watertreatment plants. The objectives of the full-scale tests were to: verify bench-scale testresults and calibrate the bench-scale dose-response curves to full-scale conditions; and,test the effects of sufficient PAC doses on filter headloss. PAC addition was tested at therapid mix basin and with 30 minutes of PCT to simulate addition at the raw water intake.During full-scale testing, filter headloss was measured every two hours to evaluate theimpact of the PAC doses on filter run times. Includes 5 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/02/2003

Number of Pages:

14

File Size:

1 file , 1.5 MB