Combining environmental isotopes with Contaminants of Emerging Concern (CECs) to characterise wastewater derived impacts on groundwater quality.

The potential for Wastewater Treatment Plants (WWTPs) to cause adverse impacts to groundwater quality is a major global environmental challenge. Robust and sensitive techniques are required to characterise these impacts, particularly in settings with multiple potential contaminant sources (e.g. agricultural vs. site-derived). Stable (δ2HH2O, δ18OH2O, δ15NNO3, δ18ONO3 and δ13CDIC) and radioactive (3H and 14C) isotopes were used in conjunction with three Contaminants of Emerging Concern (CECs) - carbamazepine, simazine and sulfamethoxazole - to discriminate between multiple potential contamination sources at an Australian WWTP. The radioactive isotope tritium provided a sensitive indicator of recent (post-1990s) leakage, with groundwater activities between 0.68 and 1.83 TU, suggesting WWTP infrastructure (activities between 1.65 and 2.41) acted as a recharge 'window', inputting treated or partially treated effluent to the underlying groundwater system. This was corroborated by water stable isotopes, which showed clear demarcation between δ18OH2O and δ2HH2O in background groundwater (δ18OH2O and δ2HH2O values of approximately -5 and -28‰, respectively) and those associated with on-site wastewater (median δ18OH2O and δ2HH2O values of -1.2 and -7.6‰, respectively), with groundwater down-gradient of the plant plotting on a mixing line between these values. The CECs, particularly the carbamazepine:simazine ratio, provided a means to further distinguish wastewater impacts from other sources, with groundwater down-gradient of the plant reporting elevated ratios (median of 0.98) compared to those up-gradient (median of 0.11). Distinctive CEC ratios in impacted groundwater close to the WWTP (∼3.0) and further down-gradient (2.7-9.3) are interpreted to represent a change in composition over time (i.e., recent vs. legacy contamination), consistent with the site development timeline and possible changes in effluent composition resulting from infrastructure upgrades over time. The data indicate a complex set of co-mingled plumes, reflecting different inputs (in terms of both quantity and concentration) over time. Our approach provides a means to better characterise the nature and timing of wastewater derived impacts on groundwater systems, with significant global implications for site management, potentially allowing more targeted monitoring, management and remedial actions to be undertaken.

Contaminants of Emerging Concern as novel groundwater tracers for delineating wastewater impacts in urban and peri-urban areas.

Management and treatment of environmental impacts from wastewater treatment plants (WWTPs) is a major, worldwide, sustainability challenge. One issue associated with WWTP operation is the potential for groundwater contamination via leaking or infiltration of wastewater, particularly with inorganic nutrients (ammonia and nitrate) as well as persistent organic compounds. Despite the potential for such contamination to create environmental and health risks, conventional methods, such as the assessment of major ions, nutrients, bacteriological indicators and conventional tracers (such as stable and radiogenic isotopes) are often unable to provide accurate delineation of multiple potential sources of contamination. This is particularly important for WWTPs which often occur in urban, peri-urban or intensively farmed agricultural areas where multiple potential sources (such as livestock, fertilisers, wastewater irrigation, and domestic septic systems) may contribute similar contaminants. This review explores the applicability of promising novel groundwater tracers, such as Contaminants of Emerging Concern (CECs) and isotopic tracers, which can be used in conjunction with conventional tracers (i.e. 'co-tracers') to provide a more definitive assessment of contaminant sources, plume delineation and even (potentially) indicating the age of contamination (e.g., recent vs. legacy). The suitability of the novel groundwater tracers is evaluated according to four key criteria: (i). sufficient presence in raw wastewater and/or treated effluents; (ii) diagnostic of WWTP impacts as opposed to other potential off-site contamination sources; (iii) persistence in the subsurface environment; and (iv) amenable to rapid and sensitive analysis. Further analysis of various classes of CECs along with improved detection limits associated with improvements in analytical methodologies should allow for future application of promising groundwater tracers, providing WWTP operators and regulatory authorities a more definitive toolbox with which to assess groundwater contamination associated with site operations. These include: persistent pharmaceuticals and personal care products (carbamazepine, crotamiton, primidone, atenolol and sulfamethoxazole), artificial sweeteners (acesulfame, sucralose, saccharin and cyclamate) and potentially, certain pesticides (atrazine and simazine).

A metabolomics based test of independent action and concentration addition using the earthworm Lumbricus rubellus.

A major challenge in ecotoxicology is to understand the effects of multiple toxicants on organisms. Here we assess the effects on survival, weight change, cocoon production and metabolism caused by exposure to two similarly acting (imidacloprid/thiacloprid) and two dissimilarly acting (chlorpyrifos/Nickel) chemicals on the earthworm Lumbricus rubellus. We assessed the standard models of concentration addition (CA) and independent action (IA), in conjunction with a metabolomics based approach to elucidate mechanisms of effect. For imidacloprid and thiacloprid the reproductive effects indicated probable additivity. Although this suggests joint effects through a similar mechanism, metabolite changes for each pesticide actually indicated distinct effects. Further, earthworms exposed to a 0.5 toxic unit equitoxic mixture demonstrated metabolic effects intermediate between those for each pesticide, indicating a non-interactive, independent joint effect. For higher effect level mixtures (1 and 1.5 toxic units), metabolite changes associated with thiacloprid exposure began to dominate. The metabolomic effects of the two dissimilarly acting chemicals were distinct, confirming separate modes of action and both proved more toxic than anticipated from previous studies. In the mixtures, phenotypic effects were in accordance with IA estimates, while metabolite changes were dominated by Ni effects, even though chlorpyrifos contributed most to reproductive toxicity. This could be attributed to the greater systematic effect of Ni when compared to the more specifically acting chlorpyrifos.

The occurrence and removal of selected pharmaceutical compounds in a sewage treatment works utilising activated sludge treatment.

Pharmaceutical substances have been detected in sewage effluents as well as receiving waters in many parts of the world. In this study, the occurrence and removal of a number of drug compounds were studied within a large sewage treatment plant in the south of England. Samples were processed using solid phase extraction and analysed using gas chromatography-mass spectrometry (GC-MS). The results demonstrate that ibuprofen, paracetamol, salbutamol and mefenamic acid were present in both the influent and effluent of the works while propranolol-HCl was not found above the limit of quantification in any sample. Elimination rates were circa 90% for each compound but several hundred nanograms per litre were still present in the final effluent.

Partitioning behavior of five pharmaceutical compounds to activated sludge and river sediment.

Pharmaceutical substances have been detected in sewage effluents as well as receiving waters in many parts of the world. To assess the fate and removal of these compounds within sewage treatment plants, an understanding of their partitioning behavior between the solid and aqueous phases is critical. Therefore, a preliminary study was conducted to ascertain an understanding of the binding behavior of five drug substances sorbing to the solid phase in a laboratory scale-activated sludge plant (Husmann unit). For comparison, uncontaminated river sediment was also used as a substrate. All of the compounds tested partitioned more readily to the sludge than the sediment, likely because of the former's higher organic carbon content. Partitioning to the solid phase correlated roughly with predicted log Kow values. A period of initial sorption was followed by a phase of desorption, and net absorption of the selected drugs (with the exception of mefenamic acid) after 5 hours of mixing was minimal.

Potential ecological and human health risks associated with the presence of pharmaceutically active compounds in the aquatic environment.

Recently, considerable interest has developed regarding the presence of pharmaceuticals in the environment, but as yet the potential ecological effects associated with the presence of these compounds have been largely ignored. In this review, laboratory-based acute and chronic toxicity data, as well as studies concerned with the effects of pharmaceuticals on a variety of different organisms, are examined, along with the reported environmental concentrations of pharmaceuticals in aquatic systems. The possible sources and pathways of these compounds to the environment and the effects of a variety of medicines on a range of organisms are also highlighted, and recommendations are made for further research.

Aquatic environmental assessment of the top 25 English prescription pharmaceuticals.

An environmental assessment is presented for the 25 most used pharmaceuticals in the National Health Service (NHS) in England in 2000. Predicted environmental concentrations (PECs) for the aquatic environment were calculated using conservative assumptions and all PECs exceeded 1 ng 1 (-1). The calculation of predicted no-effect concentration (PNEC) based on aquatic toxicity data from the literature was possible for eleven of the pharmaceuticals. PNECs were predicted with ECOSAR for 12 of the remaining 14 but no data was available for two of the compounds. The PEC/ PNEC ratio exceeded one for Paracetamol, Amoxycillin, Oxytetracycline and Mefenamic acid. Comparisons of the predicted concentrations of the compounds in sewage sludge based on either calculated sludge-water coefficients (Kd), octanol water coefficients (K(ow)), acid base constants (pKa) or environmental modelling revealed large variations. No toxicity data was available for the terrestrial environment and no assessment was made.