Sources, dispersal and impacts of wastewater in Antarctica

The Protocol on Environmental Protection to the Antarctic Treaty permits the discharge of sewage and wastewater (hereafter referred to as wastewater) from Antarctic stations into the sea or into deep ice pits in non-coastal areas, when its removal from the region is not practically achievable (Annex III – Waste Disposal and Management). Wastewater has also been previously disposed of in inland areas, including burial in snow, discharged into inland streams and lakes and onto ice-free land^{1, 2}, none of which now meet the requirements of the Protocol. In accordance with the Protocol, discharge into the sea must take into account the “assimilative capacity of the receiving marine environment”, and must be located, wherever practicable, where conditions exist for “initial dilution and rapid dispersal”, but these terms are not currently defined. The minimum level of treatment required is maceration, but only where station summer populations exceed c. 30. In practice a wide range of treatment technologies are used^{1, 3, 4}, ranging from no treatment (e.g. at many smaller or seasonal stations) to advanced tertiary systems.

Wastewater on Antarctic stations includes domestic (kitchens, showers, toilets) and light industrial sources wastewater from laboratories and mechanical workshops. Station wastewater has some similarities to standard municipal wastewater, for example, high microbiological loads⁵, however, several properties can differ: wastewater may be more concentrated (as there is no stormwater or runoff inputs and water use is generally restricted) while nutrients, Biological Oxygen Demand (BOD) and settleable solid levels may be higher⁵ and environmental degradation rates lower³. Wastewater quantity may also be highly variable due to seasonal cycles in station populations; however, volumes are generally small in comparison to domestic outfalls, ranging from several hundred to tens of thousands of litres per day, with notably higher volumes at larger stations (e.g. McMurdo Station⁶). The large variability in wastewater parameters may cause technical difficulties for those operating treatment plants year-round.  Contaminants detected in wastewater and around Antarctic stations include metals, persistent organic compounds (POPs), (such as polybrominated diphenyl ethers (PBDEs)^{7, 8}) surfactants, hydrocarbons, endocrine disrupting compounds³, pharmaceutical compounds⁹ and microplastics¹⁰.

Antarctic wastewater studies have focused on measuring the distribution and extent of wastewater discharged into the marine environment. Five categories of wastewater dispersal tracers have been identified: human-associated enteric bacteria e.g. Escherichia coli, Enterococci, Clostridum perfringens and total coliforms^{3, 11-13}; human biomarkers e.g. faecal sterols^14-16; contaminants and sewage molecular markers e.g. hydrocarbons¹², linear alkylbenzenes¹⁵, trace metals¹², polybrominated diphenyl ethers (PBDEs)^{7, 8, 12}; stable isotopes⁶; and pharmaceutical compounds and drugs^{9, 10}. Wastewater tracers have been detected in seawater, marine sediments and biota, including fish and invertebrates¹⁶, up to 2 km from stations. Studies have been undertaken predominantly during the summer; however, during winter when coastal areas are covered by sea ice the dispersal conditions may be different¹³. In general, wastewater discharged from Antarctic outfalls predominantly flows along the shore, with less evidence for dispersal out to sea^{12, 17}. Exceptions are for offshore disposal sites on ice shelves or permanent sea ice such as the airfields at McMurdo Station¹⁸.The detection of tracers in the environment, however, does not indicate whether any environmental impacts result from the discharge.

The Protocol states that precautions should be taken to prevent the introduction of non-native micro-organisms to Antarctica, although it does not specifically mention risks posed by wastewater. Wastewater discharge results in the release of large numbers of non-native micro-organisms, viruses and pathogens³ to the environment that may remain viable for extended periods^{2, 19}, and may also present a substantial threat to indigenous microbial and macrofaunal species²⁰. Wastewater may also contain mobile genetic elements, such as those encoding for antibiotic resistance^{21, 22}, which have been found established in local bacterial and animal populations^{20, 21} and have been termed “genetic pollution”. Beyond establishing the presence of non-native microorganisms, there has been little research to determine their potential impacts. There are many records of disease associated pathogens (e.g. Salmonella) present in Antarctic wildlife including Adélie and macaroni penguins, skuas, fur seals, albatross and gulls³, although evidence of an anthropogenic source or any subsequent disease outbreaks is lacking. Human faecal bacteria have been found in Antarctic wildlife, (e.g. clams, fish, sea urchins and starfish) with a higher incidence closer to outfalls, indicating ingestion of wastewater, further confirmed by stable isotopes⁶. No disease symptoms have been reported³ but an increased incidence of internal organ abnormalities were reported for fish around an outfall²³.

Our understanding of the environmental impacts of wastewater discharged into Antarctic ecosystems is relatively limited, but a comprehensive study at Australia’s Davis Station indicated a potentially wide range of significant impacts resulting from practices currently regarded as acceptable under the Protocol²⁴. Marine benthic communities have been studied at McMurdo, Casey and Davis Stations as indicators of wastewater pollution. In general, impacts on the communities were correlated with scale of the wastewater discharge, with reduced species diversity and abundance and dominance by some opportunistic species^{25, 26}. Ecotoxicological studies of wastewater are rare but indicate toxicity to Antarctic marine invertebrates at low concentrations, over exposures of several weeks⁵. Very little is known regarding the impacts of wastewater disposed to inland areas such as ice pits, freshwater lakes and streams or ice-free areas. Extremely low degradation rates and recent climate change may lead to exposure of historical wastes and long term pollution problems².

The effectiveness of wastewater treatment facilities depends on the type and level of treatment. Traditional wastewater treatment removes nutrients (to prevent eutrophication) and reduces microorganism/pathogen concentrations. Antarctic marine waters are generally not nutrient limited but significant risks to the environment may be caused by contaminants and microorganisms⁵. Most station treatment systems remove nutrients and lower BOD, thereby reflecting secondary treatment processes described in the Protocol, (i.e. Rotary Biological Contactors). However, the removal of sewage microorganisms becomes more effective when employing more sophisticated treatment processes, with advanced tertiary treatment almost eliminating micro-organism/pathogen release and removing all contaminants^{3, 5}.