Impact of rainfall on microbial contamination of surface water

Abstract

Purpose -Increased annual precipitation and more frequent episodes with heavy precipitation are expected in Norway due to climate change. The purpose of this paper is to use two case studies to investigate effects of precipitation on the amounts of faecal indicator bacteria and parasitic protozoa (Cryptosporidium and Giardia) loaded to surface waters from catchment areas exposed to different faecal sources. Design/methodology/approach -In the first case study, the loads of faecal indicator bacteria and Cryptosporidium and Giardia, were investigated in relation to precipitation in a stream from a small valley where cattle and sheep are grazed. In the second case study, historical data (monthly values from 2004-2009) regarding faecal coliforms and water flow in five tributaries (urban and rural) of a lake used as a drinking water source, were used for calculating loads of faecal indicator bacteria. These loads were evaluated in relation to historical data on precipitation. Additional sampling during/after rainfall, including analysis of samples for Cryptosporidium and Giardia, was performed. Findings -The study visualises how heavy rainfall may increase the load of faecal microorganisms and potential pathogens in Norwegian water sources. Originality/value -This study provides supplementary information about microbial contamination (including by parasites) of Norwegian surface waters during or after rainfall. This is useful input for decision making regarding protection of vulnerable water sources and for risk assessments. Data are also provided for evaluation of water treatment needs for Norwegian municipalities and waterworks responsible for providing safe drinking water under future climatic conditions.

Changes in Microbial Quality of Irrigation Water Under Different Weather Conditions in Southeast Norway

“…Although neither FIB nor intestinal protozoa were detected in water samples collected from the ground well, faecal contamination was detected in all surface water samples. This is unsurprising as it is widely accepted that surface water bodies are more vulnerable to contamination than groundwater reservoirs due to the lack of natural soil protection (Kistemann et al 2002;Tryland et al 2011).…”

“…Although in Norway the potential for waterborne transmission of the protozoan parasites, Cryptosporidium and Giardia, has been considered of minor significance, contamination of water and food by protozoan cysts and oocysts had also been reported (Robertson and Gjerde 2001a, b). Moreover, an extensive outbreak of waterborne giardiasis occurred during 2004/ 2005 in Bergen, the second largest city in Norway (Robertson et al 2006), and this has resulted in an increased focus on the contamination of Norwegian water sources with these parasites (Gaut et al 2008;Robertson et al 2009;Tryland et al 2011). Furthermore, there have been various outbreaks of waterborne and foodborne cryptosporidiosis in other countries in Scandinavia, particularly Sweden (Robertson and Chalmers 2013).…”

“…In Norway, over 90 % of water consumed is obtained from surface water, and this is highly affected by warmer climatic conditions, with shorter periods of ice cover and longer periods with water circulation, resulting in a reduction in the efficacy of some hygienic barriers against pathogenic microorganisms (Tryland et al 2011). Furthermore, extreme precipitation and runoff will cause an increased risk of microbial pathogen contamination of water sources.…”

“…Furthermore, extreme precipitation and runoff will cause an increased risk of microbial pathogen contamination of water sources. This may develop into a spiral of more infections, greater contamination, and thus further increases in the risk of infection with waterborne diseases (Tryland et al 2011).…”

“…Therefore, in order to protect human and environmental health, the faecal contamination of water sources, especially those used for drinking water and for the irrigation of fruits and vegetables commonly consumed as fresh produce, should be regularly monitored (Tryland et al 2011). For agricultural practices, this is particularly important during the relatively dry and short growing season, when the higher water demands for irrigation last until sufficient precipitation occurs.…”