The impact of climate change on the treatability of dissolved organic matter (DOM) in upland water supplies: A UK perspective

Abstract

Climate change in the UK is expected to cause increases in temperatures, altered precipitation patterns and more frequent and extreme weather events. In this review we discuss climate effects on dissolved organic matter (DOM), how altered DOM and water physico-chemical properties will affect treatment processes and assess the utility of techniques used to remove DOM and monitor water quality. A critical analysis of the literature has been undertaken with a focus on catchment drivers of DOM character, removal of DOM via coagulation and the formation of disinfectant by-products (DBPs). We suggest that: (1) upland catchments recovering from acidification will continue to produce more DOM with a greater hydrophobic fraction as solubility controls decrease; (2) greater seasonality in DOM export is likely in future due to altered precipitation patterns; (3) changes in species diversity and water properties could encourage algal blooms; and (4) that land management and vegetative changes may have significant effects on DOM export and treatability but require further research. Increases in DBPs may occur where catchments have high influence from peatlands or where algal blooms become an issue. To increase resilience to variable DOM quantity and character we suggest that one or more of the following steps are undertaken at the treatment works: a) 'enhanced coagulation' optimised for DOM removal; b) switching from aluminium to ferric coagulants and/or incorporating coagulant aids; c) use of magnetic ion-exchange (MIEX) pre-coagulation; and d) activated carbon filtration post-coagulation. Fluorescence and UV absorbance techniques are highlighted as potential methods for low-cost, rapid on-line process optimisation to improve DOM removal and minimise DBPs.

Characterisation of algogenic organic matter during an algal bloom and its implications for trihalomethane formation

“…In addition, 304 algogenic DOC is reported to be associated with higher nitrogenous DBP (NDBP) production than 305 humic DOC (Bond et al 2011;Ritson et al 2014). Thus the relationship between DOC origin and THM 306 yield in drinking water is not straightforward.…”

“…Some species of algae also produce toxic metabolites which present a public 36 health risk (Žegura et al 2011). The frequency and duration of algal blooms is predicted to increase 37 as a result of climate change (Ritson et al 2014). Thus, developing a better understanding of the 38 hydrophilic neutral (HPIN) according to their sequential adsorption onto macroporous resins; 130 Superlite™ DAX-8™ resin and Amberlite™ XAD-4™ resin (Sigma-Aldrich, Dorset, UK).…”

High‐frequency monitoring of catchment nutrient exports reveals highly variable storm event responses and dynamic source zone activation

“…In addition to ecological impacts, high riverine nutrient concentrations can cause significant socio-economic implications by impairing freshwater ecosystem services including drinking water supply, recreational opportunities, and aesthetic qualities such as taste or odor [Millennium Ecosystem Assessment, 2005;Bennett et al, 2009]. Moreover, drinking water supplies with high concentrations of nitrate and disinfectant by-products (associated with the removal of aromatic dissolved organic matter) have been linked to adverse public health impacts including cancer, diabetes, and mutagenic diseases [Ward et al, 2005;Carpenter et al, 2013;Ritson et al, 2014]. Given the global relevance of increasing river nutrient concentrations, there is a critical need to develop a thorough mechanistic understanding of the variability and controls on nutrient mobilization and export from river catchments.…”

Characterization of dissolved organic matter for prediction of trihalomethane formation potential in surface and sub-surface waters

“…Chow et al [19] reported that significant amounts of DBP precursors in sub-surface waters can be attributed to the leaching of organics from deciduous litter of surrounding vegetation, emphasizing the influence of catchment sub-surface water on reservoir water quality and consequently on DBP formation. The concentration and character of DOM significantly influences raw and treated water quality and DBP formation [9,20,22].…”