Presentation on theme: "Slow Sand Filter Amendments for Clay Removal and Corrosion Control Stephen J. Rooklidge Bioengineering Department Oregon State University June 23, 2003."— Presentation transcript:
Slow Sand Filter Amendments for Clay Removal and Corrosion Control Stephen J. Rooklidge Bioengineering Department Oregon State University June 23, 2003
Slow Sand and Roughing Filters “Passive” treatment method RF/SSF - physical and biological processes Appropriate for rural regions and developing nations
Limestone Amendments Two experimental and one EPA-approved limestone amendment positions to alter filter performance and effluent corrosion control Research filter media materials are basalt, calcite, and dolomite limestone
Research Origins Slow sand filters of the City of Salem, OR provide drinking water for 155,000 residents from the Santiam River
Research Origins Santiam River produces filter effluent with pH < 7 SSF were unable to treat water with > 140 ntu clay turbidity during the flood of 1996 turbidity during the flood of 1996
Research Questions Will roughing filters amended with limestone enhance clay removal? Will a SSF amended with limestone enhance effluent corrosion control?
Laboratory Experiments Bench-scale RF clay turbidity challenge tests: Compared clay removal of basalt and calcite media Calcium Dissolution 48-minute Detention Ca 2+ (mg/L) BASALT1.55 CALCITE8.42
X-Ray Diffraction Qualitatively examined clay removal using changes in kaolinite and montmorillonite XRD peak area ratios (K/M) Kaolinite ~ 25 o / Montmorillonite ~ 27 o
SSF Corrosion Control Effluent pH decreased by: Microbial activity Microbial activity CO 2 conversion CO 2 conversion Increase effluent pH by: Installing dolomite layer 48 cm from schmutzdecke
Corrosion Control Results Effluent met OHD pH requirements for majority of 60- day study Saturation Index, alkalinity, and hardness raised
Mineral Service Life Calculation Constant flow rate Filter area Range of dolomite packed density Assumption of stoichiometric dissolution CaMg(CO 3 ) 2 Ca 2+ + Mg 2+ + 2CO 3 Verified by: EDTA titration hardness EDTA titration hardness vs. vs. Hardness by Calculation Hardness by Calculation (P > 0.12) (P > 0.12)
Effluent Limestone Contactor Research study limestone media acquired from: Ashgrove Rivergate Lime Plant, Portland, Oregon
Contactor Feasibility Decision Tree Design contactor length using EPA DESCON program Parameters needed: pH pH Alkalinity (DIC) Alkalinity (DIC) Calcium Calcium Iron Iron Manganese Manganese Available at Raymond Letterman’s website http://web.syr.edu/~rdletter/
Research Results Slow sand filters pretreated by calcite-amended roughing filters comply with regulatory requirements for raw water clay turbidity <1 to 150 NTU, while enhancing effluent corrosion control characteristics. Dolomite-amended slow sand filters enhance effluent corrosion control, and amendment layer service life appears acceptable for engineering applications. Limestone contactors are an applicable corrosion control engineering design for surface waters of the Pacific Northwest.
Acknowledgements Environmental & Water Resources Institute (ASCE) Oregon State University, Dr. J. Ronald Miner University of Notre Dame, Dr. Lloyd H. Ketchum, Jr. City of Salem water operations and engineering staff Publications: Rooklidge, S., Ketchum, L., Burns, P. 2002. Clay Removal in Basaltic and Limestone Horizontal Roughing Filters. Advances in Environmental Research, 7/1, 231-237. Rooklidge, S., Ketchum, L. 2002. Corrosion Control Enhancement from a Dolomite-amended Slow Sand Filter. Water Research, 36/11, 2689-2694. Rooklidge, S., Ketchum, L. 2002. Calcite-Amended Roughing Filtration for Clay Turbidity Removal. Journal of Water Supply: Research and Technology- Aqua, 51/6, 333-343.