Introduction of human pharmaceuticals from wastewater treatment plants into the aquatic environment: a rural perspective.

Incomplete removal of pharmaceuticals during wastewater treatment can result in their discharge into the aquatic environment. The discharge of pharmaceuticals in wastewater treatment plant (WWTP) effluents into rivers, lakes and the oceans has led to detectable concentrations of pharmaceuticals in the aquatic environment in many countries. However, to date studies of WWTP discharges into the aquatic environment have largely been confined to areas of relatively high population density, industrial activity or systems impacted on by such areas. In this work, two sites in the far north of Scotland were used to assess whether, and which, pharmaceuticals were being introduced into natural waters in a rural environment with low population density. Samples from two WWTPs (with differing modes of operation), and one receiving water, the River Thurso, were analysed for the presence of 12 pharmaceuticals (diclofenac, clofibric acid, erythromycin, ibuprofen, mefenamic acid, paracetamol, propranolol, sulfamethoxazole, tamoxifen, trimethoprim and dextropropoxyphene). Ten of the 12 pharmaceuticals investigated were detected in at least one of the 40 WWTP effluent samples. Maximum concentrations ranged from 7 ng L(-1) (sulfamethoxazole) to 22.8 µg L(-1) (paracetamol) with diclofenac and mefenamic acid being present in all of samples analysed at concentrations between 24.2 and 927 ng L(-1) and 11.5 and 22.8 µg L(-1), respectively. Additionally, the presence of four pharmaceuticals at ng L(-1) levels in the River Thurso, into which one of the WWTPs discharges, shows that such discharges result in measurable levels of pharmaceuticals in the environment. This provides direct evidence that, even in rural areas with low population densities, effluents from WWTPs can produce quantifiable levels of human pharmaceutical in the natural aquatic environment. These observations indicate that human pharmaceuticals may be considered as contaminants, with potential to influence water quality, management and conservation not only in urban and industrial regions but also those more rural in nature.

Measurement of cyclic volatile methylsiloxanes in the aquatic environment using low-density polyethylene passive sampling devices using an in-field calibration study--challenges and guidance.

Cyclic volatile methylsiloxanes (cVMS) are used in personal care products and are hydrophobic, volatile and persistent. Their environmental water concentrations are low and are difficult to detect using conventional sampling methods. This study shows the potential of passive sampling for cVMS. We used low-density polyethylene (LDPE) samplers and in-field calibration methods for octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5). (13)C-D4 and (13)C-D5, methyltris(trimethylsiloxy)silane (MT), tetrakis(trimethylsiloxy)silane (TK), and five deuterated polycyclic aromatic hydrocarbons (PAHs) were used as performance reference compounds (PRCs). Samplers were calibrated (7-d) using effluent at a treatment plant, with uptake of cVMS and losses of the PRCs measured at 12 time-points. Concentrations of D4 (53ngL(-1)) and D5 (1838ngL(-1)) were stable in the effluent. Uptake of D4 and loss of (13)C-D4 were isotropic and equilibrium was approached by 7-d. Two estimates of sampler uptake rate (Rs) were 2.1Ld(-1) and 2.5Ld(-1). The estimated log LDPE/water partition coefficient was 4.4. The uptake of D5 was slower (Rs=0.32Ld(-1)) and equilibrium was not reached. Offloading of (13)C-D5, MT and TK were slow, and isotropic behaviour was not demonstrated for D5. Offloading of PAHs followed the predicted pattern for LDPE. Uptake of cVMS appeared to be under membrane control, due to low diffusion coefficients in LDPE. Samplers can monitor time-weighted average concentrations of D4 for less than a week, and D5 for longer periods. LDPE samplers allow cVMS to be determined at lower concentrations than by spot sampling methods.