Occurrence patterns of pharmaceutical residues in wastewater, surface water and groundwater of Nairobi and Kisumu city, Kenya.

Emerging organic contaminants have not received a lot of attention in developing countries, particularly Africa, although problems regarding water quantity and quality are often even more severe than in more developed regions. This study presents general water quality parameters as well as unique data on concentrations and loads of 24 pharmaceuticals including antibiotic, anti(retro)viral, analgesic, anti-inflammatory and psychiatric drugs in three wastewater treatment plants, three rivers and three groundwater wells in Nairobi and Kisumu. This allowed studying removal efficiencies in wastewater treatment, identifying important sources of pharmaceutical pollution and distinguishing dilution effects from natural attenuation in rivers. In general, antiretrovirals and antibiotics, being important in the treatment of common African diseases such as HIV and malaria, were in all matrices more prevalent as compared to the Western world. Wastewater stabilization ponds removed pharmaceuticals with an efficiency between 11 and 99%. Despite this large range, a different removal is observed for a number of compounds, as compared to more conventional activated sludge systems. Total concentrations in river water (up to 320 µg L(-1)) were similar or exceeded concentrations in untreated wastewater, with domestic discharges from slums, wastewater treatment plant effluent and waste dumpsites identified as important sources. In shallow wells situated next to pit latrines and used for drinking water, the recalcitrant antiretroviral nevirapine was measured at concentrations as high as 1-2 µg L(-1). Overall, distinct pharmaceutical contamination patterns as compared to the Western world can be concluded, which might be a trigger for further research in developing regions.

High-resolution time-of-flight mass spectrometry for suspect screening and target quantification of pharmaceuticals in river water.

The growing interest in screening and quantification of potential harmful pharmaceuticals in the environment requests multi-residue analytical techniques. Large-volume injection ultra performance liquid chromatography (LVI-UPLC) in combination with full-spectrum high-resolution mass spectrometry (HRMS) is a promising alternative for the state-of-the-art MS/MS instruments, because of its ability to analyse a virtually unlimited number of analytes thereby avoiding the time-consuming sample enrichment steps. We developed and fully validated an innovative analytical method for suspect screening and target quantification of a set of 69 pharmaceutical compounds in surface water based on LVI-UPLC coupled to a quadrupole time-of-flight (QTOF) MS. In a systematic research, we showed that optimal mass accuracy was obtained after centroiding the spectra. A novel suspect screening strategy was developed, assuring the detection of 95% of the pharmaceuticals spiked in surface water by modelling the variability of the signal intensity-dependent accurate mass error. A first screening of five Belgian river water samples revealed the occurrence of 30 pharmaceuticals (antibiotics, analgesics, antidepressants, alkylating agents, antiinflammatories, etc.). Concentrations between 17 ng/L up to 3.3 microg/L were subsequently measured by the validated target quantification.

Modelling pathogen fate in stormwaters by a particle-pathogen interaction model using population balances.

Stormwater is polluted by various contaminants affecting the quality of receiving water bodies. Pathogens are one of these contaminants, which have a critical effect on water use in rivers. Increasing the retention time of water in stormwater basins can lead to reduced loads of pathogens released to the rivers. In this paper a model describing the behaviour of pathogens in stormwater basins is presented including different fate processes such as decay, adsorption/desorption, settling and solar disinfection. By considering the settling velocity distribution of particles and a layered approach, this model is able to create a light intensity, and particle and pathogen concentration profile along the water depth in the basin. A strong effect of solar disinfection is discerned. The model has been used to evaluate pathogen removal efficiencies in stormwater basins. It includes a population of particle classes characterized by a distribution of settling velocities in order to be able to reproduce stormwater quality and treatment in a realistic way.