Laboratory simulation of postfire effects on conventional drinking water treatment and disinfection byproduct formation

Abstract

What is the present research focus of your group?My research group evaluates the effects of extreme events and watershed disturbances on the resilience of drinking water systems. We study how events such as wildfire, floods, and droughts affect source water quality and treatment process performance, and how utilities can best adapt to address these disruptions in water quality. What motivated the research behind your recent article in AWWA Water Science-that is, what problems are you trying to solve?Our research was motivated by the needs of water utilities across North America, but especially utilities in the West that have experienced wildfires or are concerned about the risk of future wildfires to their water treatment system. The rise in wildfire 24 JOURNAL AWWA T h e o r y a n d P r a c t i c e o f S a f e , S u s t a i n a b l e W a t e r www.awwawaterscience.com Amanda (Mandi) collects water samples from the Naches River in central Washington during a day trip with her research group. The Naches River supplies drinking water to the City of Yakima; upstream drainage areas were burned in 2017 by the Norse Peak fire in the Cascade Mountains.

A review of simulation experiment techniques used to analyze wildfire effects on water quality and supply

“…However, isolating wildfire-driven DOM response is challenging because of natural background sources of DOM, contributed by other hydrological, topographical, physicochemical, and microbiological processes 2,56 . DOM levels monotonically decrease 89 or remain the same 61 with increasing burn severity in some studies, while others report peak DOM concentrations under moderate burn severity conditions 5,26,30,83,90 . Lower DOM concentrations are frequently reported at high burn intensities, likely due to DOM vaporization (transformation of organic material into carbon dioxide and water vapor) at extreme temperatures 6,43,89 .…”

“…Laboratory-scale experiments typically use excavated, intact soil cores or homogenized samples which have low spatial variability, due in part to their smaller size 54,67,76,89,103 . Samples are typically excavated by hammering lysimeter boxes or PVC cylinders into soil 89,90 or collected from loose soil and litter on the ground-often homogenized to minimize variability 26,54,102,104 . Laboratory-scale samples are often less representative of natural conditions in terms of wildfire intensity, erosional processes, vegetation type, and soil structure, but allow for precise control over experimental factors.…”

“…Prescribed and slash burns, propane torches and heat lamps, litter burns, and muffle furnaces have all been used to study the effects of burning on soil and runoff physical and chemical properties 22,26,54,67,83,90,103 . The key features which differ across these techniques are the range of simulated wildfire intensities, ARTICLE Please do not adjust margins Please do not adjust margins Table 1 Comparison of pros and cons of plot-and laboratory-scale simulation experiments based on the following factors: spatial and temporal variability, control over environmental factors, representation of the natural environment, edge effects, and subsurface flows.…”

“…Muffle furnaces are a laboratory-scale wildfire simulation technique typically used to analyze burn impacts on soil chemical composition 26,52,113,123 . Samples are placed in an oven which is typically raised to temperatures between 100-570°C for as little as 65 seconds up to 2 hours to simulate a range of burn intensities 26,52,83,113 .…”

“…Limited information exists about post-wildfire water quality response, in particular, with most studies primarily focusing on DOM and nutrients-leaving the responses of microbial constituents and more novel contaminants largely unknown 23 . Laboratory-and plot-scale simulation experiments which replicate burning and combustion mechanisms present in natural wildfires, as well as raindrop kinetic energies and leaching effects similar to post-wildfire precipitation, offer an alternative analytical technique for estimating wildfire effects on water quality and supply 2,7,[24][25][26][27][28] . Hereafter, these two types of simulation experiments will be referred to as wildfire and rainfall simulators, respectively.…”