Assessing environmental impacts of treated wastewater through monitoring of fecal indicator bacteria and salinity in irrigated soils

Abstract

To assess the potential for treated wastewater irrigation to impact levels of fecal indicator bacteria (FIB) and salinity in irrigated soils, levels of Escherichia coli, Enterococcus, and environmental covariates were measured in a treated wastewater holding pond (irrigation source water), water leaving the irrigation system, and in irrigated soils over 2 years in a municipal parkland in Arizona. Higher E. coli levels were measured in the pond in winter (56 CFU 100 mL(-1)) than in summer (17 CFU 100 mL(-1)); however, in the irrigation system, levels of FIB decreased from summer (26 CFU 100 mL(-1)) to winter (4 CFU 100 mL(-1)), possibly related to low winter water use and corresponding death of residual bacteria within the system. For over 2 years, no increase in FIB was found in irrigated soils, though highest E. coli levels (700 CFU g(-1) soil) were measured in deeper (20-25 cm) soils during summer. Measurements of water inputs vs. potential evapotranspiration indicate that irrigation levels may have been sufficient to generate bacterial percolation to deeper soil layers during summer. No overall increase in soil salinity resulting from treated wastewater irrigation was detected, but distinct seasonal peaks as high as 4 ds m(-1) occurred during both summers. The peaks significantly declined in winter when surface ET abated and more favorable water balances could be maintained. Monitoring of seasonal shifts in irrigation water quality and/or factors correlated with increases and decreases in FIB will aid in identification of any public health or environmental risks that could arise from the use of treated wastewater for irrigation.

Bacteriological Quality of Reclaimed Wastewater Used for Irrigation of Public Parks in the United Arab Emirates

“…Microbiological quality guidelines for treated wastewater use for irrigation are generally based on total coliforms, fecal coliforms, and/or Escherichia coli [13]. However, bacterial species such as Salmonella, Shigella and Enterobacter are not routinely monitored in the raw and treated wastewater.…”

“…E. coli is one of the total coliform group members and its presence indicates the general bacteriological quality of water [11]. Several studies have indicated the survival of human pathogens in soils irrigated with recycled water [8], [12], [13]. The presence of pathogenic microorganisms in recycled water used for irrigation creates potential health hazards for the exposed human population [6], [14].…”

Reclaimed water as a reservoir of antibiotic resistance genes: distribution system and irrigation implications

“…While WWTPs are now well-established as a reservoir of ARGs (Auerbach et al, 2007; Kim et al, 2010; Czekalski et al, 2012), and some have considered effect of irrigation with reclaimed water (McLain and Williams, 2012; Negreanu et al, 2012), there is a void of studies focused on the potential for re-growth in treated wastewater distribution systems (“purple” pipes). In one study examining soil irrigated with treated wastewater, no differences in the microbiome or ARG levels were observed compared to soil irrigated with fresh water (Negreanu et al, 2012).…”

Fate of carbamazepine and anthracene in soils watered with UV-LED treated wastewaters

“…This implies that soil has a very high buffering capacity, which makes pH remaining constant. The influence of watering on soil EC depends on the water quality as shown by McLain and Williams (2012), who found that watering with tertiary treated wastewaters, did not lead to changes in EC after 2-year experiments. Mosse et al (2012) have also shown that irrigation with untreated wastewater from wineries affected various physico-chemical characteristics of soil (including pH and EC) and soil bacterial community structure which was not observed when irrigated with treated wastewater from wineries.…”