Soil-Based Onsite Wastewater Treatment and the Challenges of Climate Change.

A quarter of the U.S. population relies on onsite wastewater treatment systems (OWTS) to provide soil-based dispersal and treatment of domestic wastewater.  The current state of knowledge indicates that the presence of oxygen and optimal soil moisture conditions will enhance treatment mechanisms in the vadose zones beneath OWTS soil treatment areas.  Regulatory codes are predicated on this basic understanding, and many OWTS are already installed under this long-standing paradigm.  Climate change is real and here to stay – predicted warmer, and wetter or drier, climatic conditions will pose challenges to system treatment performance and longevity.  The potential impact of climate change on OWTS may include elevated sea level and water tables, compromised separation distances, wetter/saturated soil pore space, lower O₂ solubility, higher soil microbial O₂ consumption due to higher soil temperatures, further reduction in levels of O₂ available for wastewater treatment – all of which can contribute to diminishing the infiltrative and water quality functions of OWTS.  We need to recognize climate change as real and imminent challenge, begin to understand these impacts more fully, and develop mitigation and adaptation measures that are sustainable and protective of public and environmental health.