Behaviour of selected emerging pollutants in stormwater best management practices (BMPs)

A range of emerging pollutants (EPs) are now being considered for regulatory designation as potentially hazardous or as priority substances. These EPs occur ubiquitously in urban receiving waters and have both point and non-point sources. The occurrence and likely sources of four selected EPs (diclofenac, perfluoro-octane sulphonic acid; PFOS, hexabromocyclododecane; HBCD and dichlorvos; DDVP) found in urban surface water discharges are discussed with reference to extreme events and CSO discharges. A unit operating process (UoP) methodology is utilised to evaluate primary BMP removal mechanisms and the susceptibility of the individual EPs to be removed by these processes based on their physico-chemical properties. Despite the prevailing low level concentrations encountered in urban runoff, the methodology provides a scientifically underpinned screening framework to identify the most appropriate BMP controls for the pollutant(s) under consideration. True source control approaches such as direct infiltration, green roofs, rain gardens and porous paving would appear to the moist effective management measures

Factors influencing the infiltration of pharmaceuticals through soils

Pharmaceuticals and personal care products (PPCPs) are emerging environmental contaminants but studies of their environmental fate have focused on their behaviour during wastewater treatment processes. Little is known about the behaviour of PPCPs in soils and this is important to provide an understanding of how these compounds will be distributed during the infiltration processes which occur both naturally and under a number of treatment procedures. In this study four PPCP compounds (bezafibrate, carbamazepine, chloramphenicol and diclofenac) have been selected for investigation to determine their mobility and leaching behaviour in two types of soils. Under experimental conditions, chloramphenicol showed the highest potential to leach through the soils followed by carbamazepine, bezafibrate and diclofenac, which mirrors the order of their increasing organic carbon adsorption coefficients (Koc). The results suggest that ionic strength, pH and soil organic matter (SOM) are notable factors affecting the sorption and therefore the overall fate of pharmaceutical compounds in the soil environment

Guidance manual for constructed wetlands.

This Guidance Manual was produced to provide up to date information on the design, costs, construction, operation and maintenance of constructed wetlands used for the treatment of highway runoff. Information is provided on the different types of wetlands and their mode of operation, the design and planting of a wetland system and the retrofitting of treatment structures, the performance and costs of wetlands and their operation and maintenance requirements. The benefits of wetlands in encouraging wildlife and improving the landscape are discussed. The implementation of Sustainable Drainage systems (SuDS) and the use of decision support approaches for selecting SuDS systems are considered. Recommendations are made for future research

An investigation of urban water and sediment ecotoxicity in relation to metal concentrations

The majority of urban rivers and watercourses routinely receive pollution inputs from a wide variety of sources such as separately sewered stormwater and combined surface water outfalls (CSOs). Although the physico-chemical characteristics of urban runoff have been widely reported, the ecotoxicological impacts of these discharges are less certain. Implemen-tation of the EU Water Framework Directive, with its over-arching aim of protecting, restor-ing and enhancing the ecological status of aquatic ecosystems and its specific reference to the need to control diffuse pollution, has refocused attention on the impact of non-point source discharges on receiving water bodies. However, the implementation of this Directive has also raised several key and complex questions such as how should the ecological status of various water body types be determined. Should the proposed all-encompassing Environmental Qual-ity Standards (EQS) be developed in relation to water, sediment or biotic components? And, once determined, how should compliance with EQS be assessed? In order to contribute to the current and considerable debate surrounding these issues, the ecotoxicity of urban water and sediments was investigated in relation to concentrations of se-lected heavy metals in these environments. The Microtox test was used to evaluate the eco-toxicity of urban stream water, sediment porewater and water samples produced by resus-pending urban sediments to simulate the impact of storm event conditions. Total concentrations of Zn, Cu and Cd were then determined in these same water fractions, as well as in whole sediment samples. The results of this monitoring programme provide an insight into the metal pathways in urban rivers during different conditions and are interpreted in terms of the usefulness of this approach in contributing to the evaluation of the overall eco-logical status of urban water bodies

The role of stormwater in the urban water cycle

The potential contributions of impermeable surface water discharges to urban water resource management strategies are considered through the development and analysis of an urban water cycle (UWC) study approach. The structure, outputs and benefits of a UWC study are described and a test application of the methodological approach is made to the Eastside development area within the city of Birmingham, UK. Water demand and usage rates for the proposed 170ha regeneration area are quantified and potentially significant savings identified assuming re-use of stormwater runoff which would considerably facilitate a more sustainable future urban water cycle strategy

Heavy metal concentrations and toxicity in water and sediment from stormwater ponds and sedimentation tanks

Sedimentation is a widely used technique in structural best management practices to remove pollutants from stormwater. However, concerns have been expressed about the environmental impacts that may be exerted by the trapped pollutants. This study has concentrated on stormwater ponds and sedimentation tanks and reports on the accumulated metal concentrations (Cd, Cr, Ni, Pb, and Zn) and the associated toxicity to the bacteria Vibrio fischeri. The metal concentrations are compared with guidelines and the toxicity results are assessed in relation to samples for which metal concentrations either exceed or conform to these values. The water phase metal concentrations were highest in the ponds whereas the sedimentation tanks exhibited a distinct decrease towards the outlet. However, none of the water samples demonstrated toxicity even though the concentrations of Cu, Pb, and Zn exceeded the threshold values for the compared guidelines. The facilities with higher traffic intensities had elevated sediment concentrations of Cr, Cu, Ni, and Zn which increased towards the outlet for the sedimentation tanks in agreement with the highest percentage of fine particles. The sediments in both treatment facilities exhibited the expected toxic responses in line with their affinity for heavy metals but the role of organic carbon content is highlighted

Sources and pathways for pharmaceuticals in the urban water environment

The progress of five pharmaceutical compounds (bezafibrate, carbamazepine, diclofenac, ibuprofen and sulfasalazine) and one antibacterial agent (triclosan) were monitored through the treatment stages of a large sewage treatment works (STW) using activated sludge as well as in the receiving water both upstream and downstream of the effluent discharge. All except sulfasalazine were detected in the influent at concentrations ranging from 1.44-3.75 µg/L. The analysis of prescription data has been used as a tool to predict the amount of pharmaceuticals potentially released into the catchment of the investigated sewage treatment works and the results compared with the measured influent concentrations. A reduction in concentration between influent and final effluent samples (51-97%) indicates the variable removal of these compounds and therefore their potential to be discharged into receiving surface waters. The analysis of primary and final effluents highlight the important processes involved in the removal of pharmaceuticals and indicate that sorption processes are important for bezafibrate, carbamazepine and diclofenac. These three PPCPs were observed at higher concentrations (0.07-0.35 µg/L) downstream of the discharged effluent compared to upstream (0.02-0.04 µg/L) although the risks that these compounds pose in the environment are not yet fully understood

Urban wastewater system management and risk assessment under catastrophic antiviral pandemic conditions

There are considerable concerns that wastewater treatment processes will be unable to effectively remove elevated antiviral Oseltamivir carboxylate (OC) concentrations during a pandemic wave and that toxic exposures might result in urban receiving waters. A risk management framework for the wastewater system under such catastrophic stress conditions is outlined with the main focus being on the protection of critical functions, services and workforce operations. A generic risk assessment approach for predicting OC removal rates in sewage treatment works (STWr) and receiving surface water concentrations (PECSW) is examined. The wide range of predicted daily concentrations values varying between 20 and– 10310µg L-1 d-1 resulting from the application of the modelling approach and this confers little confidence in the risk methodology and argues that toxicological risk for OC pandemics remains insufficiently characterised. The operation of STW unit treatment process however, would appear to be relatively robust under predicted pandemic stress conditions in terms of functional performance although system management difficulties might predicate optimal removal rates

Sorption behaviours and transport potentials for selected pharmaceuticals and triclosan in two sterilised soils

Purpose: Pharmaceuticals and personal care products (PPCPs) are emerging environmental pollutants, which in addition to direct deposition processes, can find their way into surface soils through the agricultural application of sewage sludge and irrigation practices using contaminated wastewater. Therefore, it is important to assess the extent to which soils are able to retain PPCPs and to prevent their downward migration towards groundwaters. Materials and methods: To further our understanding in this area, batch sorption experiments and artificial rainwater leaching experiments have been performed using five compounds (bezafibrate, carbamazepine, chloramphenicol, diclofenac and triclosan) possessing a range of physicochemical properties in two soils with differing acidities and organic carbon contents. Results and discussion: The determined Koc values for triclosan and diclofenac consistently demonstrated their lower potential mobilities in both soils. The predicted high mobility of chloramphenicol is supported by its efficient leaching potential (89-100%) in both soils whereas bezafibrate, diclofenac and carbamazepine demonstrate slightly lower affinities for the leachate (61-96%) for soil A and are strongly retained (>99%) by soil B. The amount of PPCP in the leachate, the rate of leaching and the depth of soil penetration are explained in terms of the soil characteristics and the properties of the individual PPCPs (such as solubility and pKa) with soil organic content being shown to be a critical factor controlling the ability of a soil to retain a PPCP in the surface layers. Conclusions: The findings contribute to the scientific knowledge required by practitioners and regulators as they consider future sub-soil contamination by PPCPs and subsequent possible threats to groundwater resources and surface water habitats