Powering up sewage monitoring

South Korean researchers have developed the bacterial equivalent of a miner's canary to monitor sewage processing.

Safe and effective treatment of sewage relies on the use of microbes to break down the organic matter in the waste water so that it can safely be discharged into rivers. But if effluent loaded with toxins enters a processing facility it can kill off the microbial community, affecting the efficiency with which the plant can handle waste. As a result inadequately treatment water can be discharged from the plant, with serious environmental and health implications. To avoid this problem sewage farms have monitoring systems in place, but they can be slow off the mark and might not pick up a problem sufficiently quickly. So researcher Hyung Joo Kim, from Konkuk University in Seoul, has developed a rapid read-out bacterial fuel cell to do the job more quickly.

Plant bacteria are grown in the cell and fed with waste from the plant. As they break down the organic material present in the waste the cell generates electricity. The more the bugs thrive the more current the generate, which can be picked up with a potentiometer. But if toxins levels in the water rise and begin to compromise the bacteria then their generating capacity drops, which is immediately detectable. The results are very encouraging but Kim and his team need to do more work to test the concept before their method can replace existing systems. In particular they need to ascertain the detection limits and specificity for various toxins and also check that the microbial community won't adapt to changes in pollution levels, which would make them less sensitive as indicators over time.