Science dives into dirty issue
Sewage may seem an unlikely conversation starter. But the issue recently grabbed the media spotlight after a Swedish study, which surveyed 71 stations around Antarctica, found that more than half lack any kind of sewage treatment.
Australia's Casey and Mawson stations have functioning secondary treatment plants, which remove biodegradable organic material before discharging liquid waste to the ocean (sludge is returned to Australia). The secondary wastewater treatment system at Davis, however, failed several years ago, and sewage has since been macerated and discharged to the ocean. This practice meets the minimum requirements set out by the Protocol on environmental protection to the Antarctic Treaty, provided conditions exist for the outflow's rapid dilution and dispersal.This season, to meet the needs of the Australian Antarctic Division's managers, Antarctic Division scientists will lead a number of studies assessing the biological, physico-chemical and ecotoxicological impacts of the sewage to answer three questions:
- How well does the sewage disperse in the vicinity of the outfall and are there better, alternative locations for the outfall?
- What are the nature and extent of the impacts of the present sewage outfall?
- How toxic is the sewage effluent to local species?
Their findings, in addition to operational and policy requirements, will help managers determine what level of treatment is appropriate; whether the existing treatment is suitable or if moving the outfall to another site is a viable option; or whether a new treatment system (and what type of system) is required. Regardless of the scientific results, any treatment system will need to be easily maintained, cost effective, capable of coping with seasonal variations in the station population, able to meet the expectations of the Australian and Antarctic communities and fulfil Australia's obligations under the Environmental Protocol to the Antarctic Treaty.
The scientific work will see seven divers and 11 associated support and research personnel immerse themselves in the waters around the outfall area over the summer season. For the biological survey, divers will compare fish and organisms from microbial and soft sediment communities (such as invertebrates and algae) living in the outfall zone, with organisms living in 'reference' sites away from the outfall area. This comparison will allow scientists to understand the natural variation in communities away from the outfall, and to detect any difference, beyond natural variation, at the outfall site.
'Sewage contamination can cause changes in soft sediment communities, resulting in a loss of biodiversity and the domination of these communities by one or two species, such as opportunistic polychaete worms,' says benthic (sea-bed) ecologist and dive team leader, Dr Jonny Stark.
'The abundance of nutrients could also lead to algal blooms or, alternatively, the sediments could become anoxic and uninhabitable for anything except specialised microbes.'During the physico-chemical studies, the team will collect up to 300 sediment cores for analysis of sediment grain size and the presence of metals and sewage 'biomarkers' – such as particular organisms and nitrogen and sulphur isotopes associated with sewage. They will also look for the presence of pharmaceutical markers from medicines and personal care products, such as shampoos.
The ecotoxicology work will examine the impact of different concentrations of effluent on invertebrates (such as worms, crustaceans and molluscs), which will be collected and housed in a specially designed field aquarium.
'We'll look at the uptake of sewage nutrients, such as the sewage-specific sulphur and nitrogen isotopes, in the tissues of invertebrates, and at the effect of sewage on local food webs,' Dr Stark says.
'We'll also examine fish collected for the biological survey, to see what they've been eating and to look for any pathology in their gills and gonads, which may provide an early warning of sewage-related problems.'A number of other scientific projects involving researchers from the University of New England, Macquarie University, University of New South Wales, CSIRO and Deakin University, will also feed into the environmental assessment work. These include:
- Investigating the distribution of antibiotic resistance genes from sewage through the Antarctic environment.
- Studying the effects of sewage on the food web near the outfall site, in comparison to sites away from the outfall.
- Developing water quality guidelines for Antarctica.
- Looking at the growth, survival and recruitment of marine plants and animals living on hard substrates (particularly boulders) in the sediment at Davis.
The work will provide the first comprehensive environmental assessment of sewage impacts in Antarctica and may help inform wastewater disposal practices amongst other nations active in Antarctica. For Australia's purposes, it will assist in identifying the best engineering solution and the most suitable discharge site for the treated wastewater. An appropriate wastewater treatment solution is expected to be in place at Davis by 2012. The studies will also contribute to research on biodiversity for the 2010 International Year of Biodiversity, and will provide an important baseline assessment of benthic ecosystems against which future changes can be measured.
Corporate Communications, AAD
Gröndahl F, Sidenmark J and Thomsen A. Survey of waste water disposal practices at Antarctic research stations. Polar Research 28: 298-306, 2009.