Climate Change Impacts on Wastewater Treatment

So much of climate change is about the distribution and redistribution of water: sea-level, rainfall patterns, frequency and intensity of storms, and accumulation — or not — of snow (OECD, 2013; Singh & Tiwari, 2019). When snow fails to form or melts earlier, river flows are altered, and both drought and flooding are more likely. Such changes impact wastewater systems in a number of ways.

Nitrification-Denitrification Process
Nitrification-Denitrification Process (Source: AboutCivil)

Wastewater treatment plants are designed to handle a certain volume of water on a daily basis. When a plant receives too much stormwater too quickly, it releases wastewater into the environment untreated to avoid overwhelming the system. As climate change brings about more frequent rainstorms, more high-volume days will likely mean more frequent discharges of untreated wastewater.

Superstorm Sandy (October 2012) provides an example of the havoc that can result from extreme weather events interacting with storage challenges in wastewater treatment. For example, heavy rainfall from Sandy caused approximately 776 million gallons of wastewater spills in the U.S. Mid-Atlantic. In Washington alone, more than five inches of rain in 24 hours led to a sewage overflow of 475 million gallons (Kenward et al., 2013). In other areas, record storm surges overwhelmed treatment facilities. In the eight states most damaged by the storm, a total of 11 billion gallons of untreated or partially treated wastewater flowed into rivers, bays, canals and streets due to plant failures (Kenward et al., 2013). New York’s Bay Park Sewage Treatment Plant, on Long Island, was one of them. Hit by a tidal surge on October 29th, the plant flooded residents’ yards and homes with raw sewage and spilled 2 billion gallons of partially or untreated wastewater into coastal waters (Kenward et al., 2013). The result has been the destruction of coastal marshlands – the very habitat that protects these communities from flooding.

Septic systems, especially cesspools, are also highly vulnerable to the impacts of climate change. Septic systems rely on the surrounding soil (the drain field) to remove bacteria, phosphorus, carbon, and nitrogen from effluent. As sea-level rise pushes up groundwater in coastal areas, the distance between septic systems and water can shrink, resulting in environmental contamination (Cooper et al., 2016).

Septic systems around the world are compromised. In the U.S. alone, sea-level rise could affect the septic systems of 60 million Americans (EPA, 2014). With one in five American homes on the coast using septic, this problem will only get worse. Places like New England, with half of households on septic systems, and Florida, with 12% of the country’s septic systems, will be hit especially hard. In Miami-Dade County, for example, approximately 56% of households are already experiencing problems with their septic systems, and that number is projected to rise to 64% by 2040 (Miami-Dade County DERM, 2018).