Abstract of PhD Thesis

Assessment of pharmaceutical residue levels in three Irish sewage treatment plants

Clair Lacey, Dublin City University (2008)

Pharmaceutical and metabolite residues have been reported in European aquatic matrices since the 1980s. Discharges from municipal sewage treatment facilities have been identified as the primary source of these residues in the environment. Reported removal rates from wastewater treatment plants are low and residues are found to be persistent in the environment.

The extent of pharmaceutical pollution in Irish waters is currently unknown. Therefore, the aims of this work were to develop an LC-MS/MS method for the simultaneous detection and identification of twenty pharmaceutical compounds commonly used in Ireland and to establish their influent and effluent concentrations in three wastewater treatment plants (WWTP) in the greater Dublin region. Results of a twelve month sampling programme, from the three plants, were then used to determine any seasonal variability in the occurrence of pharmaceutical contamination.

A combined SPE-LC-MS/MS method using Strata-X cartridges for sample preconcentration was developed to investigate the occurrence of the twenty pharmaceuticals in WWTP streams. Analytical separation was achieved using a reversed phase Sunfire column with gradient elution. Fourteen of the twenty analytes investigated were found in the wastewater treatment plants. Concentrations determined in the effluent streams were in the low mg/L range and consistent with those reported in previous studies. These concentrations are below known toxicity levels however the cumulative effect of discharged residues may impart a negative ecotoxicological effect. No correlation between flowrate, BOD, COD or suspended solids and WWTP effluent concentration was observed for the analytes. Seasonal variation of effluent concentration was investigated with respect to rainfall, temperature and sunlight hours. Again, no relationship was identified. Correlations were difficult to determine due to suppression of the analyte ions in influent samples and the potential for conjugated metabolites to deconjugated over the course of treatment. This work has established an insight into the level of pharmaceutical residues present in Irish wastewater treatment plant effluents and can be used as a baseline for future work in this area.