The potential effects of climate change on water quality and disinfection by-products (DBPs) formation based on laboratory simulations

Water resource is one of the essential natural resources which are vulnerable to climate change. Increased frequency and severity of extreme weather events (i.e. floods and droughts) combined with elevated temperature are considered as the consequences of climate change. These extreme weather events will cause potential threats to the surface water quality and the downstream drinking water productions.
Many studies have found that the concentrations of dissolved organic matter (DOM) have increased in surface waters over the past decades. Studies also indicated that DOM is an important precursor of various disinfection by-products (DBPs). Several climate-related factors are considered as the potential drivers of DOM changes, especially temperatures and rainfall patterns. The rising DOM, after reactions with various disinfectants, may results in the increasing concentrations of DBPs with different toxicities or carcinogenesis during water treatment processes.
The objective of this study is to characterize the DOM and DBPs formation under different simulated weather conditions. The effects of temperature, drought, rainfall intensity, sea level rising, and acid deposition were considered in the laboratory simulated systems. After simulated treatments, the DBP formation potentials (DBPFPs) were measured to assess the impacts of climate change on DBPs formation and drinking water quality.
After ten various laboratory simulations, it was found that there is an increasing trend on dissolved organic carbon (DOC) and C-DBPFP levels with increasing temperature and dry scenarios. Br-THMFP levels were increased when bromide was presented during rewetting processes that represents the impact of sea level rise on drinking water quality. As a comparison, when bromide was presented before chlorination, only the proportion of Br-DBPFP increased. Besides, acid deposition had a two-side effect under different weather conditions. Also, the matrix of soil sources and change of the land uses may influence the DOM concentrations and the following DBPs formation.
The results of the rainfall simulations suggested that the deterioration of the water quality was observed in the beginning period of extreme rainfalls. Abundant DOM was flushed out from the soil, and led to a high peak of DBPFPs. If the rainfall was happened after a long drought, accompanying with the drought-rewetting cycle effects, the situation would become much more severe.