Lismore gets raw deal on sewage
By Tessa Hoffman
RAW sewage is contaminating Lismore's stormwater during high-rain periods, a new study has found.
In the study, Southern Cross University environmental science honours student Louissa Rogers discovered that not only did faecal coliform levels in stormwater grossly exceed environmental guidelines, most of it was coming from humans.
The study, partly funded by a Lismore City Council research grant, was based on water testing during three days of heavy rain in February and last November at four sites around the city.
At one site upstream from the CBD, faecal coliforms exceeded Environment Conservation Council (ANZECC) guidelines for swimming, while water tested within the CBD exceeded those recommended even for boating.
Results from a February test show faecal coliforms in water at Fawcetts Bridge, downstream from stormwater discharge, were 540 times higher than the recommended level for boating.
Ms Rogers said the tests were a 'snapshot' and did not represent the river's every day state.
The results were, however, still 'disturbing'.
"Human faecal coliforms are the most dangerous type because they can carry diseases harmful to us," she said.
The source of the human contamination has not been determined, however, Ms Rogers suspects rain entering sewerage pipes, causing them to overflow.
"Lismore's sewerage system is designed to overflow into the drains in times of high flow through the pipes", she said
The pipes then release water into the drains at various overflow points around the city.
Lismore City Council's Stormwater Management Plan states the city has an estimated 57 such overflow points.
Ms Rogers, who presented her study findings to Lismore City Council last week, made several recommendations to solve the problem. These included retro-fitting the sewerage system; providing constructed wetlands to treat stormwater; and catching and treating the sewage at overflow points.
Scott Turner, council's manager of assets and support services, who jointly manages sewerage infrastructure, said faecal contamination in the Wilson River was no surprise.
"However, while previous studies had 'lumped all faecal contamination together'," Ms Rogers had used a new scientific process to determine the quantity that was human," Mr Turner said.