Survival of pathogenic and indicator organisms in groundwater and landfill leachate through coupling bacterial enumeration with tracer tests Elise Grisey a , Emilien Belle a , James Dat b , Jacques Mudry a , Lotfi Aleya a, ⁎ a Université de Franche-Comté, Chrono-Environnement UMR CNRS 6249, 1 place Leclerc, 25030 Besançon cedex, France b Université d'Angers/INRA, rue Georges Morel, BP 57, 49071 Beaucouze Cedex, France abstract article info Article history: Received 21 January 2010 Received in revised form 4 May 2010 Accepted 4 May 2010 Available online 9 June 2010 Keywords: Leachate Septic tank Bacteria Tracer test Groundwater contamination We reported on the transit and survival of 6 potentially pathogenic bacterial populations in a schist aquifer beneath the Etueffont landfill (France). Total coliforms, Escherichia coli, Enterococci, Pseudomonas aeruginosa, Salmonella and Staphylococcus aureus were monitored for 15 months in groundwater and leachate and coupled to tracer tests in an attempt to identify the source of contamination. The results showed the absence of S. aureus and Salmonella. The monitoring of piezometer 30 (PZ30) located downstream from the landfill highlighted leachate infiltrations into the substrate. Groundwater analysis showed high levels of faecal bacteria in the underground environment (20,000 CFU 100 mL -1 for total coliforms, 15,199 CFU 100 mL -1 for E. coli and 3290 CFU 100 mL -1 for Enterococci). Data from tracer tests indicated that bacteria originated from the septic tank of the transfer station and part of these bacteria transited through waste. Bacterial density was lower in leachates than in groundwater sampled from PZ30, except for P. aeruginosa which seemed to take advantage of adverse environmental conditions. The landfill, closed since 2002, was not a source of faecal bacteria which appeared to be able to survive in the schist substrate, and may be considered as good markers of recent faecal contamination. © 2010 Elsevier B.V. All rights reserved. 1. Introduction According to the French law 92-646 of July 13th 1992 [1], municipal solid waste disposal in landfill sites is no longer allowed in France since 2002. This legislation also requires continued monitoring of the environmental impact of landfills over a 30-year period after landfill closure. While most studies on leachate have focused on the physical and chemical sources of the pollutant and its impact on groundwater quality [2–4], little is known about the composition of pathogenic bacterial populations in landfill leachate. Yet, pathogenic bacteria may contaminate drinking water and their presence must thus be controlled in order to avoid potential health hazards. This is even more important since the new active waste treatment centers are generally located in the vicinity of old landfills. The purpose of this work is to identify the origin of pathogenic bacteria found in the Etueffont (northeastern France) landfill leachates and groundwater by means of bacterial analysis and dye tracer test experiments. Seasonal variations in abundance of total coliforms, Escherichia coli, Enterococci, Salmonella, Pseudomonas aeruginosa, and Staphylococcus aureus which may develop in leachate are investigated. The presence of the latter two bacterial populations is not considered a public health issue, but rather an indication of the presence of wastewater. Total coliforms are frequently measured as an indicator of contamination. Among total coliforms, non- faecal coliforms are capable of proliferation under normal environmen- tal conditions. On the other hand, the presence of total coliforms may indicate the presence of faecal coliforms, common indicators of faecal pollution [5]. The other bacteria are more systematically involved in sanitary problems. E. coli, commensal of numerous animal digestive tracts, is not a saprophyte in temperate climate and is the most appropriate coliform bacteria to indicate warm blooded animal faecal pollution [6–8]. Enterococci bacteria are found under a variety of environmental conditions, especially in wastewater. Their life span is longer than coliforms [5,9–11] and may be equivalent to viruses [12] but they can not multiply [13]. These features make them not only excellent indicators of faecal contamination but also indicators of the presence of viruses. P. aeruginosa is the bacterial species with the widest range of habitats; it lives and proliferates as a saprophyte in water and humid soils. Its presence is generally abundant in wastewater [14] but it is not a specific indicator of recent faecal contamination. Salmonella sp. are widespread in the environment and they can survive for several weeks in dry conditions and up to several months in water. S. aureus is a skin commensal of human and animal mucous. It may survive for long periods under a wide range of environmental conditions and, it is resistant to antibiotics. The Etueffont landfill is surrounded by a moderate urban activity which may exacerbate bacterial contamination of groundwater Desalination 261 (2010) 162–168 Abbreviations: E, Eosin; FL, Former landfill; N, Naphthionate; NC, New cell; PZ30, Piezometer 30; SWTS, Selective waste collection facility and transfer station; UC, Under cell. ⁎ Corresponding author. E-mail address: lotfi.aleya@univ-fcomte.fr (L. Aleya). 0011-9164/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2010.05.007 Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal