Microbiological Condition of Urban Groundwater in the Vicinity of Leaky Sewer Systems

Abstract

The possible deterioration of the microbiological quality of groundwater due to leaky sewer systems was investigated in a medium‐sized city (Rastatt) in SW‐Germany. Specially constructed focus observation wells drilled close to leaky sewers have been compared with the background observation wells in urban and rural areas. The sampling was performed in March (shallow depth of groundwater) and in July and October (deep groundwater table). It included the measurement of ammonium ions, temperature, electric conductivity, oxygen, and the depth of the groundwater table. Coliforms, Escherichia coli, and enterococci were enumerated as indicator organisms for wastewater contamination. In addition, the total number of colony forming units was determined. Bacterial counts of coliforms and E. coli generally increased during the course of the investigation (March to October). This may have been caused either by a slightly increased groundwater temperature (higher activity rates) or by a higher proportion of sewage in the urban groundwater system as a result of the dry season (summer). The contamination with faecal indicator bacteria was greater adjacent to leakage locations. In addition, elevated concentrations of ammonium ions were observed at these areas. The results provide evidence that leaky sewer systems elevate faecal indicator concentrations in groundwater with associated potential health risk where such waters are used for potable water supply.

Pesticide Health Risk Mapping and Sensitivity Analysis of Parameters in Groundwater Vulnerability Assessment

“…The acifluorfen relative leaching ranks were developed by applying ArcPRZM-3 for 25 monitored well sites (i.e., 6, 7, 9, 10, 11 (6,23,36, and 43) was rice while it was soybean for all the others. The daily average dissolved acifluorfen concentrations were modeled at soil depth of 1.8 m for 25 well sites during the period of interest.…”

“…The application of pesticides increases the crop productivity but it can also contaminate the groundwater sources [2][3][4][5][6][7][8]. Groundwater vulnerability assessment can be obtained by analyzing the pesticides leaching toward groundwater using the simulation models, e.g., depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity (DRASTIC) [9], groundwater loading effects of agricultural management systems (GLEAMS) [10], HYDRUS-1D [11], leaching estimation and chemistry model (LEACHM) [12], PRZM [13], root zone water quality model (RZWQM) [14], hierarchical cluster analysis (HCA) [15], and groundwater modeling tool for grass (GMTG) [16].…”

An approach to identify urban groundwater recharge

“…Microbiological tracers have been proposed to assess recharge by contaminated waters related to sewer water, landfills, runoff, etc. Powel et al, 2003;Paul et al, 2004;Vertraeten et al, 2005;Morris et al, 2006). Contaminated waters can also be identified by means of organic compounds, BTEX, PAH, metabolites, pharmaceuticals, etc.…”

Impacts of Sewer Leakage on Urban Groundwater

“…Microbiological indicators Several groundwater observation wells in the urban area revealed coliforms, E. coli and enterococci as indicators for faecal contamination (Paul et al, 2004). Regarding the coliforms and E. coli the bacterial counts showed a strong correlation with the distance to the leakage, all three bacteria were found in highest concentrations in the focus observation wells close to major sewer leaks.…”

“…Table 5. Bacterial counts in groundwater samples according to the location of the groundwater monitoring well (Paul et al, 2004 As no obvious originator could be identified and the plumes extend along one of the main sewers it was considered that the contamination results from sewer leakage. Furthermore, trans-DCE in groundwater is only stable for a very short time as it is further degraded to vinylchloride so findings of trans-DCE in groundwater suggest a recent or permanent entry.…”