Pilot Study of a Surface Water with Low pH, Low Alkalinity, and Iron Using Silicon Carbide Membranes

Pilot Study of a Surface Water with Low pH, Low Alkalinity, and Iron Using Silicon Carbide Membranes Mike Snodgrass, Ovivo USA, LLC. PILOT SITE Test site had ZERO existing infrastructure All pilot supplies had to be brought in No existing water supply, chemicals, etc. Power supplied by onsite generator PILOT STUDY Flat plate SiC and pressurized alumina membranes Test flux rates of 100, 150, and 200 gfd (per test plan) Coagulant is added to aide filtration process Membranes periodically backwashed with cleaning chemicals 10 PILOT UNIT Submerged SiC flat plate configuration 0.1 micron pore size Air scour, backwash, and chemical cleaning capabilities 25 gpm capacity Daily CEBs (chlorine or acid) PILOT TEST PLAN Phase Description Flux (gfd) Coagulant pH Permeate Adjustment Flow (gpm) – Mobilization – – Start-up ACH Caustic 11. I Coagulant/pH ACH Caustic 11. Optimization II Low Flux Run ACH Caustic 11. III Higher Flux Run ACH Caustic 17. IV Maximum Flux Run ACH Caustic 23. V Maximum flux Optimal ACH Caustic TBD SOURCE WATER CHARACTERISTICS Very low turbidity (i.e. solids) <1. NTU Iron is present, but at low levels <0.1 mg/L pH is low 6-7 Low alkalinity <20 mg/L 10 INITIAL OBSERVATION Originally started pilot adding ACH No visible floc being formed TMP increased rapidly Membranes had slimy layer indicating ACH fouling Observed iron staining 10 IRON FOULING Combination of iron, low pH, and low alkalinity was leading to higher than expected plugging of membranes due to formation of iron + organic complexes Due to the type of fouling, looked into different coagulant options as a potential solution as original approach with ACH may not be the right fit for this water source. 10 ALUM Less aggressive than ACH, less likely to plug membranes Very acidic, so pH adjustment is needed due to low alkalinity water Optimized alum addition and caustic addition for pH Started alum dosing May 9th 10 TMP PROFILE W/O ALUM 150 gfd Steep increase in pressure 10 TMP PROFILE W/ ALUM 150 gfd Pressure profile is flat 10 DESIGN FLUX SELECTION Net/Instantaneous Flux (gfd) Flow (MGD) No. KEY TAKEAWAYS Surface water treatment is often a chemistry problem that needs to be solved Raw water source has a unique water chemistry that wasn’t fully understood until testing began Chemical pre-treatment is critical for membrane performance Collaborative team effort design build team was essential for solving pilot challenges Project is now moving to 100% design 10.