Development of high-throughput biosensors for multi-sample determination of biochemical oxygen demand (BOD) based on optical detection of oxygen

Biochemical oxygen demand (BOD) is one of the most important and frequently used parameters for estimating the level of organic pollutants in water. Microbial BOD sensors have received much attention as they provide fast, portable and cost-effective methods for environmental monitoring and rapid determination of wastewater quality in wastewater treatment plants. In this project, we aim at developing a high-throughput multi-sample BOD sensor for BOD determination of a large number of wastewater samples based on the optical sensing of dissolved oxygen concentration.; Two prototype optical biosensors for multi-sample BOD determination have been constructed based upon the optical sensing of change in dissolved oxygen concentration by the luminescent metal complex Ru[(dpp)3] 2+ (dpp = 4,7-diphenyl-1,10-phenanthroline). In the first prototype BOD sensor, activated sludge and Bacillus subtilis strain 1A304 (&phis;105MU331) were immobilized on oxygen sensing films on the bottom of glass sample vials. This BOD biosensor was found to retain about 77% of its initial activity for activated sludge and 88% for B. subtilis after stored at 4°C for 30 days. Good agreement was achieved between the results of the BOD measurement by the activated sludge biosensor and those obtained from conventional BOD5 method for water samples. However, only fairly good agreement was obtained by the B. subtilis biosensor. The results show that the B. subtilis biosensor may be suitable for wastewater with low BOD levels, as the microbes cannot assimilate a wide enough range of organic substrates.; The second prototype BOD biosensor was constructed using ormosil oxygen sensing films and Stenotrophomonas maltophilia immobilized in an ormosil polymer hybrid material of tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS) and poly(vinyl alcohol) (PVA).{09}This BOD biosensor has a wide range of BOD loading (linearly up to about 60 mg l-1 GGA standard), longer lifetime, higher stability and better correlation of low BOD5 values (especially for GGA solutions) as compared to the first prototype biosensor. Good agreement was achieved between the results of the BOD measurement by the immobilized Stenotrophomonas maltophilia biosensor and those obtained from conventional BOD5 method for water samples. The particular strain Stenotrophomonas maltophilia isolated from activated sludge is shown to be suitable for BOD biosensor fabrication. (Abstract shortened by UMI.)...