Sewerage Contamination of Water, Groundwater and Sediments

Identification of faecal sterols in water, groundwater and sediment samples can be useful in identifying the presence of sewage contamination and sometimes for the identification of other pollutants. For example a leaking sewer can sometimes impact an aquifer with industrial pollutants such as chlorinated solvents. Faecal sterols as biomarkers provide a valuable tool in the investigation of the sources and fate of faecal contamination in the environment. Identification of faecal contamination in waterways, marine environment and groundwater may be an indicator of run-off, leaking septic tanks and/or leaking sewers. The data obtained can be useful in pin pointing source/s of faecal pollution in our environment.

Faecal Sterols
Faecal sterols are excreted by animals and humans as by-products of digestion of dietary sterols. The particular distribution of sterols found in faecal matter is influenced by factors such as diet, intestinal microflora and the animal’s ability to synthesise its own sterols. The combination of these factors determines ‘the sterol fingerprint’. The most commonly known faecal sterol, coprostanol, is produced in the digestive tract of humans by microbial hydrogenation of cholesterol. By drawing on the differences in the sterol profile of humans and animals, it is possible identify to the presence of and also distinguish the source of faecal contamination. Many compounds ingested, including pharmaceutical’s in our diet are excreted in addition to the sterol profile compounds such as caffeine, isobuprofen, trichlosan and aspirin (acetylsalicylic acid) are also examined for as an indication of sewerage input.

Methodology
Water samples and soil samples are solvent extracted. The solvent extracts are then concentrated and derivatised. The extracts are then analysed by high resolution capillary gas chromatography-mass spectrometry (GC/MS) to identify and quantitate the target compounds. The relative ratio of the sterols is calculated and the presence of target compounds is used to determine the presence and source of faecal contamination. Leeder Analytical have developed a sensitive method that is able to detect these compounds at ng/L (ppt) level.

Sample Requirement
Two 500ml brown glass bottles are required for each sample location. The samples should be acid preserved, chilled on ice and shipped to Leeder Analytical for analysis.