AWWA WQTC62387

The primary goal of this AwwaRF funded research was to investigate the impact and contribution of natural organic matter (NOM) fouling using vendor-supplied proprietary units from membrane manufacturers on specific natural water supplies. Interactions between water quality, pretreatment chemicals, membrane materials, and membrane configurations were tested at pilot-scale with various operating conditions. Pilot studies were conducted with Zenon's Zee-Weed 1000 pilot unit with immersed membranes at the Tampa Bay Regional Water Treatment Plant, utilizing raw and coagulated waters as feed. The unit was equipped with 0.02 µm PVD hollow fiber membranes. The pilot testing program was designed to distinguish between three types of NOM-based fouling: hydraulically reversible fouling, chemically reversible fouling, and irreversible fouling. Membrane filtration cycle was evaluated through quantification of membrane flux decline rates. Chlorine oxidation was more effective in reversing the effect of NOM fouling of the Zeeweed PVDF membrane compared with the acid and caustic. Runs that utilized lowered recovery or phosphoric acid chemical wash showed a reduction in membrane fouling compared to coagulated water baseline runs. HPSEC analyses revealed that high molecular weight compounds (10k-30k Daltons) were rejected or adsorbed by the ZeeWeed 1000 PVDF membrane as indicated by the decreased concentration of these compounds in the permeate. Backwash samples showed an elevated response of the high molecular weight compounds, indicating that these compounds were hydraulically displaced from the membrane or with the foulant layer. Data from 3-D fluorescence excitation emission matrices supported this trend. Includes 6 references, tables, figures.