Electronic nose for water monitoring: The relationship between wastewater quality indicators and odor

An electronic nose (e-nose) comprising a nonspecific sensor array based on metal oxide semiconductors was employed to monitor wastewater samples, collected various sources in Bangkok, i.e., Samsen canal, Nanglerng canal, Praemprachakorn canal and Sanseab canal for 6 weeks (from the end of March to the first week of July), and compared with the fresh water supply. It was found that our electronic nose can classify odor of wastewater and fresh water. Moreover the relationship between wastewater quality indicators, including BOD₅, DO and pH, with odor measured by the e-nose was observed. The results have shown that BOD increases with the increasing ammonia concentration according to the oxygen demand for oxidization of ammonia. In addition, nitric acid that was produced by oxidization of ammonia leads to acidic water. Although more experiments to prove correlation between electronic nose sensor response and BOD₅ value are required, this preliminary study has offered a new alternative for cheap and real-time water monitoring.