BIO 2008: Sensing the sewage assassin

Cleaning slime out of sewage pipes is a dirty job but, as the saying goes, somebody's got to do it. That somebody is Australian environmental scientist Ross Chandler, but thankfully the biochemical solution he has developed to reduce the level of harmful bacteria in Australia's sewage treatment systems means nobody has to get their hands dirty.

Chandler is the creator of Biosol, a liquid product made up of naturally occurring chemicals that is injected into sewage systems to control the behaviour of corrosion-inducing bacteria. The product was featured in an episode of The New Inventors on the ABC in February of this year, where it was received enthusiastically and awarded best invention by the show's panel of expert judges.

Wastewater is rife with bacteria, which gather at bends in the thousands of kilometres of pipes leading to water treatment plants. These collections of bacteria eventually form slimes, known as biofilms, which generate poisonous gas and corrosive acid that cause millions of dollars worth of damage to sewerage infrastructure every year.

It's no surprise to anyone that sewers smell bad. But the source of that odour, hydrogen sulphide gas (H2S), is also responsible for the corrosion of sewage pipes - and worse. Hydrogen sulphide gas is also one of the chief threats facing sewer maintenance workers, many of whom are injured or even killed by the gas every year. Chandler says developing nations with less-advanced sewage treatment systems lose three to five people a year "just from opening manhole covers".

Hydrogen sulphide gas arises from the breakdown of organic and inorganic sulphates made possible by the anaerobic conditions that exist in sewage pipes. This hydrogen sulphide gas is later oxidised by other bacteria to form sulphuric acid, the main culprit behind pipe corrosion.

Recent research in the US places the cost of sulphuric acid-induced corrosion in the area of $US14 billion a year, and Chandler estimates the damage to Australian wastewater infrastructure alone is in the order of $1.1 billion a year.

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