Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2021

Lessons learnt from assessing sewage pollution for catchment management and intervention programs in Sydney’s Drinking Water Catchment. (#13)

Lisa Hamilton 1 , Ann-Marie Rohlfs 1 , Julia Barnes 1 , Alan Benson 1
  1. WaterNSW, Parramatta1, NSW, Australia

The success of sewage monitoring programs is contingent on understanding the nature of the environment in which the indicators are to be applied. Over the last few years, WaterNSW has collaborated with research partners to deploy numerous different sewage detection methods across a range of contamination pathways and environments. Indicator technologies used include pharmaceuticals and personal care products (PPCPs), genomic faecal source tracking and ammonia passive samplers. These techniques have been applied to provide evidence of cumulative impacts of onsite sewage systems failures across a locality, assess water quality improvements after onsite sewage systems removal, investigate faecal pollution in routine monitoring samples and locate contaminant sources entering stormwater systems. A number of lessons have been learnt from these studies.  Being clear about what you are monitoring for and whether there is potential for other environmental sources of that indicator to affect the interpretation of results is important. PPCP monitoring suites may include substances that could also originate from non-sewage sources like greywater or refuse leachate or easily be introduced from field and laboratory staff and sampling and analysis consumables. Narrowing PPCP monitoring to synthetic prescription pharmaceuticals can improve certainty that sewage is present in the environment. Additionally, the use of passive samplers can increase the likelihood of detecting what could be sporadic contamination events. Genomic markers for specific host species of gut microbiota can sometimes produce unclear and conflicting results. In multiple situations, we have detected PPCPs or human genomic sewage markers in control and reference samples. The complexity of using novel, research-based methods requires good collaboration partnerships to ensure success of a long-term monitoring program. Our experiences highlight that there are no ‘silver bullet’ sewage indicator. The strongest inferences are from multiple lines of evidence that have been carefully matched to clear monitoring objectives and a well-understood deployment environment.