BOD sensors using multi-species living or thermally killed cells of a BODSEED microbial culture

Abstract

A biochemical oxygen demand (BOD) biosensor installed with a biofilm containing immobilized thermally killed cells of a BODSEED (Cole-Palmer E-05466-00) microbial culture gave BOD sensing sensitivity comparable with that of a biosensor using the same population of the immobilized living cells of the same culture. The thermally killed cell sensor showed better response and storage stability but slightly longer response and recovery times than the living cell sensor. Both the living and thermally killed cell sensors generally underestimated the BOD 5 of wastewater differing by about −21–28.4% from the values obtained by the conventional APHA method of 5-day BOD measurement using the same BODSEED for seeding. The poor response of both the BOD biosensors to dairy wastewater and industrial organic waste and zero response to lactose compared with the conventional APHA method of 5-day BOD measurement could be attributed to the mass transfer resistance of the membranes in the sensor but more significantly to the slow assimilation and bio-oxidation rates of these components by the BODSEED microbial system. Unlike the living cell BOD sensor which requires periodic additions of nutrients and minerals to keep the microorganisms alive and viable, the thermally killed cell BOD sensor can be stored in phosphate buffer at room temperature over long idling period without such periodic additions. More significantly with respect to commercialization of these biosensors, the thermally killed cells can be prepared in bulk and stored in dry sealed container over long period.