Environmental forensics: sewage

Sampling sediment

Sewage contamination is a major cause of poor water quality in rivers and lakes within the UK and throughout the world. High concentration of human and animal sewage in the water and sediments in shallow lakes is of widespread concern for two reasons:

  1. The complex chemical mixture causes nutrient enrichment, eutrophication, toxic algal blooms and water column anoxia which in turn can lead to a reduction in species diversity and ecosystem stability.
  2. Untreated sewage can, under specific conditions, provide a home for bacterial and viral pathogens that, if swallowed, can lead to diseases such as Salmonella, cholera, diarrhoea, typhoid, gastroenteritis and hepatitis A.

Research at Attenborough Nature Reserve

Attenborough Nature Reserve

Attenborough Nature Reserve is located near Nottingham in the UK and is a site of special scientific interest (SSSI) primarily because of the wide diversity of birds. The ponds are a series of ex-gravel pits excavated between 1939 and 1968 covering an area of about 1.67 km2. Their location, similar size (0.49 to 0.1 km2), depth (~3m) and mode of formation make them ideally suited to ecosystem-scale comparisons.

The ponds (including Church, Clifton and Coneries Ponds) have varying histories of connectivity to the polluted River Erewash, which drains a heavily urbanised catchment and receives effluent from seven sewage treatment plants.

In 1972, the course of the River Erewash was diverted directly into Coneries Pond, which was then connected to Church and Clifton Pond during periods of high water level. In 1981, engineering works completely isolated Clifton from Coneries Pond, resulting in the system that exists today where Church and Clifton Pond are isolated from the River Erewash and Coneries Pond system in all but the most extreme flood events. As a result, Coneries waters are enriched in phosphorus and dissolved inorganic nitrogen and are turbid whereas Clifton and Church ponds have lower concentrations and clear water.

BGS scientists have been carrying out research in this area to:

  1. establish whether historical river diversion could be tracked using sewage as a biomarker
  2. find out whether the ponds were ever truly isolated from each other and the adjacent rivers Erewash and Trent
  3. test that different sources of faecal matter (sewage from either human or animal) within the sediments could be distinguished

5B-coprostanol
5B-epicoprostanol

Results

Sediment cores were collected at several locations in the nature reserve (pictured below). These were then taken to the laboratory for analysis. Results showed that Coneries Pond had received a greater input of sewage than Church or Clifton Ponds. This result was not unexpected given that the River Erewash has a number of sewage works along its banks and discharges directly into Coneries Pond. In general only the uppermost sediment intervals of Church or Clifton Ponds showed high concentrations of sewage. It was also possible to distinguish sewage from human and animal sources.

Overall, the extraction and analysis of sewage biomarkers in sediments provides environmental forensic information that complements and supplements traditional microbiological methods and may potentially be used to infer the palaeoenvironment at recharge and the extent of biological activity.

Further information

Vane, C H, Kim, A W, McGowan, S, Leng, M J, Heaton, T H E, Coombs, P, Kendrick, C P, Yang, H and Swann, G E A. 2010. Sedimentary record of sewage pollution using faecal marker compounds in contrasting peri-urban shallow lakes. Science of the Total Environment 409, 345–356.

Contact

Contact Dr Christopher Vane for more information.