The past decade of sustainability, monitoring, research and innovation in Australia's on-site water treatment industry was summed up recently by CQUniversity Senior Research Fellow Ted Gardner...

Professor Gardner was addressing the Australian Water Association conference in Newcastle, where he covered auditing and monitoring, risk assessment methods, off-site impacts and microbial source tracking, septic trench hydraulics, greywater reuse, source separation (of urine) for fertiliser, and cluster-scale recycled water systems.

Senior Research Fellow Ted Gardner presents at the conference

"Cluster-scale developments with a strong water re-use component are going gang busters in Australia," he said.

"But we need to be careful in assuming that decentralised systems will be more sustainable and robust than centralised solutions, unless the technology is radically different.

"The question remains whether decentralised systems will fiscally outcompete centralised systems on a level 'paying field'. There's a strong niche market for decentralised systems in remoter urban communities and CBD buildings aspiring to greenstar status.

"Greywater reuse is likely to largely remain an opportunistic response to drought-induced water restrictions in water reticulated areas.

"Resource recovery is the next big idea in sewage treatment but source separation in domestic dwellings is unlikely to be economic due to urine collection difficulties. However this is not necessarily a limitation in high-rise commercial and residential buildings."

Among his other conclusions was that risk assessment models are critically dependent on GIS tools and geo-referenced on-site systems.

He also said that nutrient export from on-site systems was very difficult to detect against export from the background land uses.

"Chemical and microbiological tracers are the most useful for detecting off-site export," Professor Gardner said.

"Off-site impacts are likely to be pathogen rather than nutrient dominated. Molecular microbiology tools are well suited to quantify human sewage contamination of creeks and waterways."

Professor Gardner said the popularity of greywater irrigation varied with the severity of potable water restrictions.

"Sophisticated greywater systems are probably more in the domain of boutique developments and buildings chasing a Green Star rating!

"Research funding for on-site systems has dried up; we need another crisis!"