---

Research Feature

Wildfire resilience for small drinking water systems with nature-based treatment  

Key messages

• Nature-based drinking water treatment technologies, such as biological filtration, can be an attractive alternative to conventional treatment, especially for small systems, since they are less operationally demanding and more cost-effective compared to conventional treatment technologies. 
  
  
• Small systems are particularly vulnerable to the impacts of climate change-exacerbated landscape disturbances such as wildfire—biological filtration shows promise to increase resilience of these systems to the effects of wildfires since it can degrade elevated and altered organic matter in source waters post-wildfire. However, some types of organic matter remain recalcitrant to removal by biodegradation.
  
  
• Although technologies that are nature-based can offer key benefits, especially for small systems, they often do not offer as much operational control as more conventional treatment systems and may be less able to respond to sudden changes in source water quality, despite evidence that biological filtration can buffer organic matter-related shifts in source water.
  
  
• This highlights that nature-based technologies are not a silver bullet for resilience and that the trade offs between valuable aspects of these technologies and their operational control should be assessed on a case-by-case basis.

Water Treatment Costs Reduced by

per cent

Summary

 Wildfires are recognized globally as a threat to water quality and drinking water treatment. Although most climate change-exacerbated landscape disturbances can pose challenges for drinking water treatment, wildfires can be especially concerning because they can episodically increase turbidity and alter dissolved organic matter (DOM)—key drivers of the design and optimization of drinking water treatment processes—in receiving source waters. Shifts in DOM concentration and character can be especially difficult to remove with conventional treatment technologies, as they can exert significant oxidant demand and increase disinfection by-product formation if not removed prior to disinfection. These impacts can challenge treatment plants beyond their design or operational capacity, ultimately resulting in increased infrastructure and operating costs, service disruptions or even service outages. Small systems are particularly vulnerable to the impacts of climate change-exacerbated landscape disturbances, including wildfires, since they experience disproportionately higher health risks associated with the provision of safe drinking than do larger systems—largely due to the structures that govern them. Thus, these threats to drinking water security emphasize the need for cost-effective and resilient solutions that are appropriate for all systems.

Nature-based solutions can be promising since they take advantage of natural processes to achieve intended goals. However, drinking water must be adequately protective of public health and therefore some level of engineering is required—techno-ecological nature-based solutions (TE-NBS) are more appropriate. An example of an underutilized TE-NBS for drinking water treatment is biological filtration, which takes advantage of

naturally occurring microorganisms in either engineered or natural systems to achieve treatment targets. Biological filtration may also be appropriate to address some challenges that are faced by small systems since they are relatively low cost and require less operational demand than do more conventional drinking water treatment technologies, thus matching the operational capacity of many small systems. Biological filtration may be especially promising for regions prone to wildfire since it can degrade DOM, which has been shown to be altered and elevated in source waters after wildfire. For the first time, resilience of biological filtration was demonstrated in a proof-of-concept bench-scale experiment with synthetically created wildfire-impacted water. It was found that the biodegradation capacity of the biofilters were not significantly impacted by wildfire ash. However, some fractions of DOM were less well-removed by the biofilters than others—this underscores that operational resilience may be compromised if the balance between readily removed and recalcitrant fractions of DOM change. It also underscores that some key trade-offs exist between TE-NBS and operational control. Although technologies that are nature-based can offer benefits such as cost effectiveness or ease of operation, they often do not offer as much operational control as more conventional treatment systems because of factors such as the lack of design and operational (i.e., typically mechanical) controls over system components. As such, some TE-NBS may be less able to respond to sudden changes in source water quality—this issue requires further investigation to ensure resilient treatment, especially in environments vulnerable to climate change-exacerbated landscape disturbances such as wildfires.

Publications

Advancing on the Promises of Techno-Ecological Nature-Based Solutions: A Framework for Green Technology in Water Supply and Treatment

Biological Filtration is Resilient to Wildfire Ash-Associated Organic Carbon Threats to Drinking Water Treatment

Needs standard format and hyperlink

Photo: Working onsite with partner X.

Contributors

Blackburn EAJ
Emelko MB
Dickson-Anderson S
Anderson WB
Stone M