Climate’s toll on wastewater
As the climate changes, coastal communities feel the heavy burden of sea level rise and intense rainfall during storms, with flooding a primary issue. The encroaching water also has consequences for rising groundwater levels, with offsite wastewater management, such as septic systems, a cause for concern.
In the Carolinas, USA, millions of homes and businesses rely on decentralised wastewater infrastructure to drain into the surrounding soils towards the coast, and this region is the focus of new research into groundwater levels in the subsurface aquifer and their management. Specifically, a team of researchers from East Carolina University and North Carolina Sea Grant, USA, use a multidisciplinary approach that involves interviewing wastewater operators, installers and health regulators across the region, as well as evaluation of the temporal variations in groundwater levels in the tourist town of Nags Head in Dare County, North Carolina.
The team shows that as soils saturate, the capacity of the vadose zone (the subsurface down to groundwater table) to drain wastewater away reduces; when this vertical separation is below 30 cm, any septic system in the area located at less than 2.6 m above sea level could experience inefficiency.
Insufficient cleansing of wastewater through unsaturated soil poses a health hazard as bacteria and viruses would not be effectively filtered from the wastewater and could rise to the surface, backing up into homes. This also risks ecosystem damage and economic instability, given the area relies upon water-based activities for industry and tourism.
While those with financial means may be able to install aerobic treatment units or effluent pumps to transfer wastewater to higher ground for drainage, for many people this is not a practical solution. One alternative is to build an artificial buffer of mounded sand to increase the volume of unsaturated soil. Even so, managers of offsite wastewater systems concede that greater regulations are required to mitigate climatic impacts when deciding on the locations of future sites, both in the Carolinas and coastal locations across the globe.
Weather, Climate and Society, 14(4), 1287-1305; https://doi.org/10.1175/WCAS-D-21-0192.1
Geological Society of America Abstracts with Programs 54, No. 5 (2022); doi: 10.1130/abs/2022AM-382531