TANGENTIAL FLOW ULTRAFILTRATION AS AN ANTIFOULING STRATEGY FOR WATER QUALITY SENSORS

Abstract

Water quality monitoring is important for water treatment facilities, food processing industry, aquaculture and in geological surveys. Gathering reliable measurements from sensors can be challenging over extended periods of time in conditions where the biological growth occurs. This is due to biofouling, the growth of biotic matter, on the sensor surface. This deteriorates the quality of measurements from the sensors over time. In this thesis, membrane technology was implemented to prevent the biofouling on the sensor surface by filtering out the bacteria from the water sample. The effects of accelerated biofouling on the microfabricated pH and DO sensors were studied. A decrease of 21% in the sensitivity value is observed for the pH sensor and a decrease of 66% in the sensitivity value is noted for the DO sensor. Next, the sensors were integrated in a customized flat sheet Tangential Flow Filtration (TFF) device with an ultrafiltration membrane and placed on the permeate side of the filtration device. The decrease in the sensitivity noted for the pH and DO sensors used with TFF were 5 times lower as compared to when used without the TFF device. In summary, the device proposed in this thesis was shown to successfully prevent the deterioration of sensitivity of the microfabricated pH & DO water monitoring sensors by preventing the formation of biofilm on the sensor surface and the grooved spacers used in the TFF helped in mitigating membrane fouling.