interesting opm article

Brisbane Water – optimising investment using risk assessment
The lower Brisbane River catchment in South-East Queensland, Australia, is highly modified, with 52% of the catchment occupied by urban areas. The health of the ecosystem in the Brisbane River estuary, like most urban rivers, is generally poor. The concentrations of nutrients and suspended solids are far greater in the Brisbane River than in any other major tributary flowing into Moreton Bay, due to large sewage and stormwater inputs. However, significant investment from Brisbane City Council is starting to show dividends, with the water quality of the estuary recently upgraded from a grade F to a grade D, and nutrient inputs from sewage treatment plants halved.

Brisbane Water manages Brisbane’s wastewater treatment plants, including Luggage Point and Gibson Island. Brisbane Water recently commissioned NIWA Australia to help determine what was required to assess the public health risk from the discharge of bacteria and viruses in the treated effluent from the two plants. The study is intended to help with strategies and infrastructure investment decisions for wastewater treatment based on risk.

The lower Brisbane River is used mainly for ‘secondary’ contact (e.g., boating, jet skiing) rather than primary contact (e.g., swimming, wading), says NIWA Australia scientist Jamie Corfield. ‘People are reluctant to swim or wade in this area because of the highly turbid water, threat of shark attacks, and proximity to sewage outfalls. However, after consultation, the Brisbane River Estuary has now been proposed as a primary contact region based on ‘aspired to’ environmental values rather than existing values’, says Dr Corfield. ‘Consequently, efforts are being made to ensure that poor water quality doesn’t prevent primary contact in the future.’ The classification is tentative, and further work may help clarify ‘zone boundaries’ for safe primary and secondary contact.

The driving force behind the study is to determine whether Brisbane Water needs to undertake disinfection treatment to reduce the public health risk. ‘We wanted to be proactive about understanding the risks,’ says Brisbane Water’s Steve Kenway, ‘and we wanted to have the best science to help with our investment decisions. Our licences for Luggage Point and Gibson Island don’t require us to disinfect because of their location, but we want to try to provide a wastewater transport and treatment service that will be of maximum benefit to the community.’

Together with team members Graham McBride from NIWA and Andrew Ball from ESR, NIWA Australia firstly assessed the water quality and notifiable disease information that had already been collected. ‘There was a definite lack of information on microbial organisms for the Brisbane River’, says Dr Corfield. ‘In our risk assessment we recommended that Brisbane Water go beyond just assessing indicator organisms like E. coli and monitor a range of harmful microorganisms, particularly those identified by the Queensland Department of Health as being a potential threat or which have been linked with previous outbreaks of disease in Brisbane.’

Mr Kenway says Brisbane City Council plans to invest $180 million over the next three years to reduce nutrient loads into the lower Brisbane River catchment. ‘To date, nutrient levels have been the major issue for the treatment plants, and there has been a gap along the microbiological side of things. This study will help us to address that gap.’

NIWA Australia has also just completed a benchmarking review of large coastal wastewater treatment plants to enable Brisbane Water to see how their monitoring and management practices compare with other plants in Australia and overseas. The results of this review will be used to decide whether a full-scale microbiological risk assessment is warranted for the Luggage Point and Gibson Island plants.

‘We’ve now got a logical process to work through to understand our risk,’ says Mr Kenway, ‘although there are still a number of things we need to know. We’re hoping to work through all the recommendations in the study.’

NIWA Australia contact:
Jamie Corfield [ [email protected] ]

Brisbane Water contact:
Steve Kenway [ [email protected] ]

For more information on the waterways and catchments of South-East Queensland, see: www.healthywaterways.env.qld.gov.au