Wastewater Treatment Works Research Articles

Application of the DIY carbon footprint calculator to a wastewater treatment works

The provision of water and wastewater treatment services exerts a huge operational cost on public financial resources. A substantial portion of the operational budget is made up of carbon-intensive energy costs. Energy is consumed in this sector in pumping, aeration, motor drives, administration, transportation and in the manufacture of chemicals such as polyelectrolyte, chlorine and ozone. The high electrical power consumption exerts added pressure on the environment in terms of greenhouse gas emissions. In order to manage the energy budget and develop climate-friendly technological options, Royal HaskoningDHV (RHDHV) has developed a do-it-yourself (DIY) Excel-based carbon footprint calculator to estimate the carbon equivalent emissions for a waterworks, a wastewater treatment works or a pumping station. The DIY carbon calculator computes Scope 1, Scope 2 and Scope 3 emissions. The DIY calculator starts with establishing the baseline carbon footprint of a works and shows the relative carbon equivalent emissions for different treatment stages. The next step involves the development of strategies to reduce the carbon footprint. Inherent within a wastewater treatment works is its ability to potentially generate its own ‘green’ energy by using anaerobically produced methane gas as a green energy alternative. This investigation demonstrates how the baseline carbon footprint of a wastewater treatment works can be reduced by considering viable options such as biogas to power generation, process re-design and drives to improve energy efficiency. Results show that the carbon calculator was able to demonstrate the effectiveness of carbon-reducing strategies in this energy-intensive sector. This further implies that the carbon calculator can be used as an additional management and decision support tool to assist an organisation towards a low carbon footprint. Keywords : carbon footprint calculator, carbon equivalent emissions, greenhouse gas, green energy, Scope 1, 2 and 3 emissions, emission factor, sustainability, energy factory

Evolutionary Multi-Objective Optimal Control of Combined Sewer Overflows

This paper presents a novel multi-objective evolutionary optimization approach for the active control of intermittent unsatisfactory discharges from combined sewer systems. The procedure proposed considers the unsteady flows and water quality in the sewers together with the wastewater treatment costs. The distinction between the portion of wastewater that receives full secondary treatment and the overall capacity of the wastewater treatment works (including storm overflow tanks) is addressed. Temporal and spatial variations in the concentrations of the primary contaminants are incorporated also. The formulation is different from previous approaches in the literature in that in addition to the wastewater treatment cost we consider at once the relative polluting effects of the various primary contaminants in wastewater. This is achieved by incorporating a measure of the overall pollution called the effluent quality index. The differences between two diametrically opposed control objectives are illustrated, i.e. the minimization of the pollution of the receiving water or, alternatively, the minimization of the wastewater treatment cost. Results are included for a realistic interceptor sewer system that show that the combination of a multi-objective genetic algorithm and a stormwater management model is effective. The genetic algorithm achieved consistently the frontier optimal control settings that, in turn, revealed the trade-offs between the wastewater treatment cost and pollution of the receiving water.

Assessing the water quality response to an alternative sewage disposal strategy at bathing sites on the east coast of Ireland

A three-dimensional model is used to assess the bathing water quality of Bray and Killiney bathing sites in Ireland following changes to the sewage management system. The model, firstly calibrated to hydrodynamic and water quality data from the period prior to the upgrade of the Wastewater Treatment Works (WwTW), was then used to simulate Escherichia coli (E. coli) distributions for discharge scenarios of the periods prior to and following the upgrade of the WwTW under dry and wet weather conditions. E. coli distributions under dry weather conditions demonstrate that the upgrade in the WwTW has remarkably improved the bathing water quality to a Blue Flag status.The new discharge strategy is expected to drastically reduce the rainfall-related incidents in which environmental limits of the Bathing Water Directive are breached. However, exceedances to these limits may still occur under wet weather conditions at Bray bathing site due to storm overflows that may still be discharged through two sea outfalls offshore of Bray bathing site.

우리나라 공공하수처리시설의 TOC 배출특성 및 관리방안 연구

Under Korea`s Enforcement Decree of the Framework Act on Environmental Policy amended in 2013, total organic carbon (TOC) is newly added as water quality parameter to assess organic pollution in water and aquatic ecosystem. To meet the TOC requirement and improve quality of effluent discharged into public watershed, it is also necessary to develop standards for TOC in effluent from public sewage treatment works (PSTWs). In this study, we reviewed the characteristics and removal efficiency of TOC in influent and effluent of PSTWs. The study found that phosphorus treatment process removed not only soluble phosphorus but also a portion of TOC remaining after the secondary treatment process. TOC concentration in effluent from PSTWs operated in tandem with industrial wastewater treatment work was higher due to influx of insoluble substances from the industrial wastewater treatment work. In order to lay a foundation for the management of TOC from PSTWs, it is necessary to carry out research on TOC from different perspectives. For example, studies on the generation mechanism of TOC and the impact of TOC on drinking water resources, assessment of effluent qualities through monitoring, and development of measures to control TOC for the preservation of aquatic ecosystem are needed.

Filament identification and dominance of Eikelboom Type 0092 in activated sludge from wastewater treatment facilities in Cape Town, South Africa

Routine characterisation of activated sludge and identification of the filamentous population by microscopic and/or other non-culture dependent techniques can assist in diagnosing the aetiology of poor performance of wastewater treatment works (WWTWs). In South Africa, most facilities rely solely on physicochemical indicators, treating reactors as ‘black-boxes’, with the result that process adjustments are often delayed, to the detriment of the environment. This study was performed in order to gain insight into the filamentous population found in activated sludge in Cape Town WWTWs, to compare these with other global and local literature findings, and to build capacity in this science. Physicochemical and plant performance parameters, in terms of nutrient removal and settling, were obtained from routine operational data and assessed in conjunction with the microscopic analyses of activated sludge samples taken over a 6-month period. Hypotheses on the links between filament types and/or plant configurations and/or operational parameters were formulated using existing literature. In order of prevalence, the five most common dominant filament species in 96 activated sludge samples were: Eikelboom Type 0092, Eikelboom Type 1851, nocardioforms, Microthrix parvicella and Eikelboom Type 021N. In order to compile a statistically significant database, it is recommended that an extensive nationwide study is conducted to link filament types with plant configurations, operational parameters and geographical locations. Keywords : activated sludge, bulking, identification, filament, Type 0092

Sustainable wastewater treatment – ways to achieve energy neutrality

Increasing emission of greenhouse gases intensifies global warming. To tackle the problem, major economies in the world need to implement policy on energy saving. The wastewater treatment industry, being one of the energy consumers, has developed various technologies to improve energy efficiency and has started to use renewable energy with the aim of achieving energy neutrality in the wastewater treatment process. A literature review found that there is a series of energy-saving methods that can reduce the electricity consumption by 20% in wastewater treatment. Majority of the energy saving comes from energy conservation measures in pumping and aeration systems. In wastewater treatment works, two kinds of renewable energy are usually available, namely solar energy and biogas. The recent development of photovoltaic cells makes it a more practical and financially viable energy source which may cover 40% of the electricity consumption of a wastewater treatment works. Biogas, a by-product generated from the anaerobic digestion process in a wastewater treatment works, can also generate 40% of the electricity required. To achieve energy neutrality, the remaining electricity consumption can be generated through co-digestion of wastewater sludge and organic fraction in municipal solid waste.

Integrated water quality modelling: Application to the Ribble Basin, U.K.

This paper reviews the traditional approach of linking models to cover integrated water management from the upper reaches of catchments through river basins, into estuaries and to the coastal/marine environment. It highlights some of the deficiencies in the approaches currently being adopted in many non-integrated studies, where artificial boundaries are included in the system, and then highlights the need for a more integrated conceptual approach. A case study is discussed, namely the non-compliance of bathing waters along the Fylde Coast and Ribble Basin (U.K.) from riverine inputs, with the inputs arising from Waste water Treatment Works (WwTW), outfalls and drainage systems. A more integrated approach was applied to this estuary, with refinements to the artificial boundaries. Both hydrodynamic and solute transport processes in 1-D and 2-D domains of this estuary were modelled for a wet event in June 1999. The bio-kinetic decay process representation included the impacts of salinity, solar irradiation, turbidity and water temperature on the decay rate. Solutes modelled included faecal coliform, water temperature and salinity. This paper demonstrates that a similar or better accuracy of the coliform concentrations can be achieved using an integrated model based on a realistic representation of physical and biochemical processes. This is significant because the integrated model does not need extensive calibration to give good results. This is therefore a much more robust model which is not influenced significantly by the position of boundaries. The robustness of the model gives increased confidence in predicted results for new scenarios where measured data is not available. This is particularly important for all types of real time water quality prediction (e.g. toxic spills) including bathing water quality. Hence better decisions can be made when considering investment strategies, appropriate for various treatment options and catchment management solutions in the river basin upstream.

Source apportionment of trace contaminants in urban sewer catchments

Sampling and analysis of Water Framework Directive priority chemicals were undertaken in nine urban catchments across the UK. Over 9000 samples were collected from a number of different catchment sources including tap water, domestic waste water, surface water runoff, trade discharges, town centre and light industrial estate wastewaters. Determinands included trace metals, polyaromatic hydrocarbons (PAHs), persistent organic pollutants and a number of common pharmaceuticals. Loads of the chemicals from each catchment entering the local wastewater treatment works (WwTW) were estimated and were shown to be relatively consistent between different catchments, after taking population into account. A Monte Carlo mixing model was used to combine the concentrations and flows from the different catchment sources and to predict concentrations and loads entering the WwTW. Based on the model output, the significance of the different sources could be evaluated. The study highlighted the importance of domestic wastewater as a source of contaminants, including metals and trace organic substances (such as ethylenediaminetetraacetic acid (EDTA), bisphenol A, nonylphenol and tributyl tin (TBT)). Concentrations in trade discharges were important in some locations in the case of nonylphenol, EDTA, TBT, as well as for some metals such as copper, zinc and nickel. Contributions to the total load from town centre and light industrial estate sources were generally less than 10% of the total.

A review on emerging contaminants in wastewaters and the environment: Current knowledge, understudied areas and recommendations for future monitoring

This review identifies understudied areas of emerging contaminant (EC) research in wastewaters and the environment, and recommends direction for future monitoring. Non-regulated trace organic ECs including pharmaceuticals, illicit drugs and personal care products are focused on due to ongoing policy initiatives and the expectant broadening of environmental legislation. These ECs are ubiquitous in the aquatic environment, mainly derived from the discharge of municipal wastewater effluents. Their presence is of concern due to the possible ecological impact (e.g., endocrine disruption) to biota within the environment. To better understand their fate in wastewaters and in the environment, a standardised approach to sampling is needed. This ensures representative data is attained and facilitates a better understanding of spatial and temporal trends of EC occurrence. During wastewater treatment, there is a lack of suspended particulate matter analysis due to further preparation requirements and a lack of good analytical approaches. This results in the under-reporting of several ECs entering wastewater treatment works (WwTWs) and the aquatic environment. Also, sludge can act as a concentrating medium for some chemicals during wastewater treatment. The majority of treated sludge is applied directly to agricultural land without analysis for ECs. As a result there is a paucity of information on the fate of ECs in soils and consequently, there has been no driver to investigate the toxicity to exposed terrestrial organisms. Therefore a more holistic approach to environmental monitoring is required, such that the fate and impact of ECs in all exposed environmental compartments are studied. The traditional analytical approach of applying targeted screening with low resolution mass spectrometry (e.g., triple quadrupoles) results in numerous chemicals such as transformation products going undetected. These can exhibit similar toxicity to the parent EC, demonstrating the necessity of using an integrated analytical approach which compliments targeted and non-targeted screening with biological assays to measure ecological impact. With respect to current toxicity testing protocols, failure to consider the enantiomeric distribution of chiral compounds found in the environment, and the possible toxicological differences between enantiomers is concerning. Such information is essential for the development of more accurate environmental risk assessment.

Haematological and genotoxic responses in an urban adapter, the banana bat, foraging at wastewater treatment works

Wastewater Treatment Works (WWTWs) are a ubiquitous feature of the urban landscape. The Banana Bat, Neoromicia nana specifically exploits the high abundance of chironomid midge prey available at WWTWs but these populations also have higher levels of non-essential metals (Cd, Cr and Ni) in their tissues than bats foraging at unpolluted sites. Pollutant exposure may elicit primary physiological responses such as DNA damage and haematological changes. We investigated whether pollutant exposure from foraging at WWTWs impacts haematological and genotoxic parameters in N. nana. We compared four measures of haematological/genotoxic damage between N. nana foraging at three WWTWs and two unpolluted sites located in KwaZulu-Natal, South Africa: DNA damage measured by the Comet assay, total antioxidant capacity as indicated by the FRAP assay, chromosomal aberration indicated by micronuclei formation and blood oxygen capacity based on haematocrits. There was significantly higher DNA damage in N. nana at WWTWs than in bats from unpolluted sites, suggesting inadequate repair to double stranded DNA breaks. In addition, WWTW bats had a significantly lower antioxidant capacity than bats from unpolluted sites. This suggests that bats at WWTWs may have a diminished capacity to cope with the excess reactive oxidative species (ROS) produced from pollutants such as metals. There was no increase in micronucleus frequency in WWTW bats, indicating that cellular functioning has not yet been disrupted by chemical exposure. Haematocrits, however, were significantly higher in WWTW bats, possibly due to erythrocyte production in response to certain pollutants. Thus, effects of pollutant exposure in bats foraging at WWTWs elicit sub-lethal haematological and genotoxic responses which may pose serious long-term risks. This provides evidence that WWTWs, that are aimed to remove pollutants from the environment, can themselves act as a source of contamination and pose a threat to animals exploiting these habitats.

Concentrations of trace substances in sewage sludge from 28 wastewater treatment works in the UK

Concentrations of trace substances in sewage sludge have been measured in a survey of 28 wastewater treatment works (WwTWs) in the UK carried out over a period of 12months. Approximately 250 samples were analysed for more than 40 trace contaminants, including trace metals, pharmaceuticals, polycyclic aromatic hydrocarbons (PAHs), ‘emerging’ and regulated organic pollutants. All substances investigated were found to be present in at least some of the sludges sampled. Concentrations were relatively homogenous across all the WwTWs, irrespective of the treatment process, influent and effluent concentrations, and the location of the sludge sampling point within each works. Analysis of the results against existing regulatory and proposed thresholds suggested that levels are mostly below the limits set in the Sewage Sludge Directive, and proposed new limits for sludge used in agriculture. Predicted soil concentrations after application of sewage sludge to land were below the predicted no effect concentrations (PNEC) for all determinands. Predicted concentrations of pharmaceuticals in soil were also below thresholds deemed to indicate negligible environmental risk.

Bioavailability of the imidazole antifungal agent clotrimazole and its effects on key biotransformation genes in the common carp (Cyprinus carpio)

Clotrimazole (CTZ) is a persistent imidazole antifungal agent which is frequently detected in the aquatic environment and predicted to bio-concentrate in fish. Common carp (Cyprinus carpio) were exposed to mean measured concentrations of either 1.02 or 14.63μgl−1 CTZ for 4 and 10 days, followed by a depuration period of 4 days in a further group of animals. Following each exposure regimen, plasma and liver CTZ concentrations were measured. Mean measured plasma concentrations of CTZ in animals exposed to the lower concentration of CTZ were 30 and 44μgl−1 on days 4 and 10, respectively, and in the higher concentration were 318 and 336μgl−1. Mean measured liver levels in the same animals were 514, 1725, 2111 and 7017μgl−1 suggesting progressive hepatic accumulation. Measurement of CTZ in plasma after depuration suggested efficient elimination within 4 days, but appreciable levels of CTZ remained in the liver after depuration suggesting a degree of persistence in this tissue. In addition we measured responses of a number of key hepatic detoxification gene targets in the liver associated with the transcription factor pregnane X receptor (PXR); namely cyp450s 2k and 3a, glutathione-S-transferases a and p (gsta and p), and drug transporters multidrug resistance protein1 (mdr1), and MDR-related protein2 (mrp2). CTZ is a potent ligand of the PXR in humans and there is some evidence of PXR activation following exposure to CTZ in fish. The highest concentration of CTZ was adopted to explore the potential for alterations to detoxification gene expression in fish at a pharmacologically relevant dose level, and the lower concentration is within the range reported in effluents from waste water treatment works (WWTW). The genes for all biotransformation enzymes were up-regulated after exposure to the higher concentration of CTZ for 10 days, and alterations in expression occurred for the drug transporter genes mdr1 and mrp2 following exposure to the lower concentration of 1.02μgl−1 CTZ (mean measured concentration). These data support the potential for CTZ to induce alterations in biotransformation and drug transporter genes associated with PXR in fish at concentrations measured in some WWTW effluents.

Regulation 17: the way forward to meet requirements

Regulation 17 from the Water Services Act 108 (1997) is currently being implemented for the classification of wastewater treatment facilities and process controllers in South Africa. Green Drop Assessments (an incentive-based programme for wastewater treatment works) place a large focus on Regulation 17 compliance, which replaces Regulation 2834. Over the years, a lack of enforcement of Regulation 2834 has resulted in the incorrect appointment of staff. Many municipalities are therefore struggling to meet the Regulation, which requires appointment of the correct skill level staff to corresponding treatment facilities. The purpose of this paper is to identify the common problems experienced by municipalities, more specifically by the eThekwini Metro Municipality, and to identify possible solutions for closing the gaps. The four key problem areas identified were: imbalanced staff allocation, lack of education amongst staff, lack of experience amongst staff and the need for grandparenting assessments. The solution began with the correct classification of plants and staff, and included education drives and training programmes in addition to staff reallocation methods. These initiatives form part of both a short-term gap-closing strategy and a broader long-term sustainable plan for compliance with Regulation 17, enhanced process control at a plant level and ultimately the acquisition of Greens Drops, as part of the Green Drop Assessments.

Biofilm Responses to Toxic Shocks in Closed Pipes: Using Nitrous Oxide Emissions as an Early Warning of Toxicity Ahead of a Wastewater Treatment Works

Wastewater treatment works can receive toxic substances that can kill microorganisms responsible for waste degradation. Implementation of toxicity monitors in-sewer, as part of an early warning system to help prevent toxic substances entering treatment works, is, however, very rare. This work presents results from a pilot-scale study using an in-sewer early warning system based on detection of nitrous oxide (N2O) gas emitted by nitrifying bacteria naturally present in sewer biofilm. Nitrous oxide has potential to be an indicator of nitrification inhibition as it is typically emitted when nitrifiers are under stress. The biofilm was allowed to develop over 14 days under fixed wastewater flow and level. Presence of nitrifying bacteria was verified on day 13 followed by a 90 min toxic shock on day 14 by four different known nitrification inhibitors. Pre-shock nitrification rates averaged 0.78 mg-NH4 +-N mg-VS−1 d−1 and were significantly reduced post shock to <0.2 mg-NH4 +-N mg-VS−1 d−1. Nitrous oxide emissions were found to vary with influent wastewater quality, suggesting a more complex data processing algorithm is needed instead of a simple threshold emission value. The extent of nitrification inhibition differed from the recorded response for suspended growth biomass with allylthiourea resulting in a 77 and 81 % nitrification inhibition for literature suspended growth EC50 and EC75 concentrations, respectively. Results from this study suggest nitrifying biofilms in closed pipes can be used as part of an early warning system but will likely require amplification of the response to be of practical use. Further research is required to better understand the biofilm response and calibrate the early warning system for differentiating its unique baseline from true toxicity events.

Populations of a cyprinid fish are self-sustaining despite widespread feminization of males.

BackgroundTreated effluents from wastewater treatment works can comprise a large proportion of the flow of rivers in the developed world. Exposure to these effluents, or the steroidal estrogens they contain, feminizes wild male fish and can reduce their reproductive fitness. Long-term experimental exposures have resulted in skewed sex ratios, reproductive failures in breeding colonies, and population collapse. This suggests that environmental estrogens could threaten the sustainability of wild fish populations.ResultsHere we tested this hypothesis by examining population genetic structures and effective population sizes (Ne) of wild roach (Rutilus rutilus L.) living in English rivers contaminated with estrogenic effluents. Ne was estimated from DNA microsatellite genotypes using approximate Bayesian computation and sibling assignment methods. We found no significant negative correlation between Ne and the predicted estrogen exposure at 28 sample sites. Furthermore, examination of the population genetic structure of roach in the region showed that some populations have been confined to stretches of river with a high proportion of estrogenic effluent for multiple generations and have survived, apparently without reliance on immigration of fish from less polluted sites.ConclusionsThese results demonstrate that roach populations living in some effluent-contaminated river stretches, where feminization is widespread, are self-sustaining. Although we found no evidence to suggest that exposure to estrogenic effluents is a significant driving factor in determining the size of roach breeding populations, a reduction in Ne of up to 65% is still possible for the most contaminated sites because of the wide confidence intervals associated with the statistical model.

Determination of changes in wastewater quality through a treatment works using fluorescence spectroscopy

Fluorescence spectroscopy was used to characterize municipal wastewater at various stages of treatment in order to understand how its fluorescence signature changes with treatment and how the signal relates to biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The impact of size fractionation on the fluorescence signal was also investigated. Fluorescence measurements were taken for unfiltered and filtered (0.45 and 0.20 μm) samples of crude, settled and secondary treated wastewater (activated sludge and trickling filter), and final effluent. Good correlations were observed for unfiltered, diluted wastewater samples between BOD and fluorescence intensity at excitation 280 nm, emission 350 nm (Peak T1) (r=0.92) and between COD and Peak T1 intensity (r=0.85). The majority of the T1 and T2 signal was found to be derived from the<0.20 μm fraction. Initial results indicate that fluorescence spectroscopy, and changes in Peak T1 intensity in particular, could be used for continuous, real-time wastewater quality assessment and process control of wastewater treatment works.

Mapping species distributions in one dimension by non-homogeneous hidden Markov models: the case of freshwater pearl mussels in the River Dee

The investigation of species distributions in rivers involves data which are inherently sequential and unlikely to be fully independent. To take these characteristics into account, we develop a Bayesian hierarchical model for mapping the distribution of freshwater pearl mussels in the River Dee (Scotland). At the top of the hierarchy the likelihood is used to describe the sequence of sites in which mussels were observed or not. Given that false observations can occur, and that “not observed” means both that the species was not present and that it was not observed, a Markov prior is introduced at the second level of the hierarchy to represent the sequence of sites in which mussels are estimated to occur. The Markov prior allows modelling the spatial dependency between neighbouring sites. A third level in the hierarchy is given by the representation of the transition probabilities of the Markov chain in terms of site-specific explanatory variables, through a logistic regression. The selection of the explanatory variables which influence the Markov process is performed by means of a simulation-based procedure, in the complex case of association between covariates. Four features were found to be associated with reduced chance of finding a local mussel population: tributaries, bridges, dredging, and waste water treatment works. These results complement the results of a previous study, providing new evidence for the causes of the deterioration of a highly threatened species.

An assessment of the impact of different land use activities on water quality in the upper Olifants River catchment

Routine sampling of water quality was conducted at sites along a longitudinal gradient from upstream to downstream in the Olifants River to determine spatial trends in nutrient and metal concentrations and to relate these trends to changes in land use activities in the catchment. In addition, once-off sampling was conducted at a number of sites located downstream of current mining, abandoned mining, agriculture, wastewater treatment works (WWTWs) and industry. Nutrient concentrations were relatively high and a number of sites within the catchment had average N:P ratios that were indicative of eutrophic to hypertrophic conditions. Routine and once-off sampling indicated that wastewater treatment works contribute high nutrient loads to the system. Trend analysis of Department of Water Affairs (DWA) data indicated significant positive trends in ortho-phosphate at 12 of 14 stations in the catchment. An increase in sulphate concentrations from upstream to downstream indicates that mining activities have a progressively greater impact on water quality with increasing distance downstream. While dissolved metal concentrations frequently exceeded chronic and acute effect aquatic ecosystem health guidelines (particularly aluminium, copper and zinc), there was no observable trend from upstream to downstream. Once-off sampling showed high variability in water quality parameters downstream of current mining activities, and some sites showed higher metal concentrations in comparison to other land use activities. However, the contribution of current mining activities to metals is low in comparison to the contribution from abandoned mines. Hydrological data showed that acidic rivers contribute proportionally higher flow volumes in comparison to neutral rivers during the drier winter months, which may significantly impact on the lower stretches of the upper Olifants River and into Loskop Dam. A prolonged drought period will most likely result in severe impacts to the lower reaches of the Olifants River and to Loskop Dam. Improved management and maintenance of wastewater treatment works and rehabilitation and/or treatment of abandoned mines and associated acid mine drainage are crucial. Proper rehabilitation of current mining activities is essential to avoid or minimise acid mine drainage related impacts in the future. Keywords: acid mine drainage, land use, metals, nutrients, Olifants River

A substance flow analysis of phosphorus in the UK food production and consumption system

Phosphorus (P) is both an essential resource, required for plant growth and food production, and a costly pollutant, capable of causing eutrophication in water courses. The possibility of future phosphorus scarcity and the requirement to improve the quality of UK waters necessitates the development of a UK phosphorus management system, which increases use efficiency, reduces losses and recycles wastes more effectively. A vital first step towards creating such a system is to conduct a substance flow analysis (SFA), which maps and quantifies the relevant stocks and flows, allowing specific measures to be implemented that target identified losses and areas of inefficient resource use. This paper presents the results of a SFA for phosphorus in the UK, focussing in particular on the food production and consumption system for the year 2009. The SFA results suggest that the UK population consumed around 31.0kt P in 2009, which was largely achieved by importing food, feed and fertilisers, with net imports totalling 113.5kt P. Imported fertilisers accounted for 56% of the total imports, containing 77.5kt P. The largest losses within the systems were those to water, estimated at around 41.5kt P/yr, and soil accumulations are estimated at 37.5kt P/yr. The efficiency of UK crop production is estimated at 81%, whereas the efficiency of producing animal products is only 16.5%. Wastewater treatment works (WwTW) received around 55.0kt P within wastewater, with 57% being removed in sewage sludge. The 23.5kt P discharged within final effluent represented the largest loss to UK waters. Around 71% of the sludge was recycled to land, containing 22.5kt P, although the rate of application was around 5× higher than the uptake rate for crops, demonstrating the challenges of effectively recycling bulky wastes. Existing measures aimed at tackling water pollution and climate change have acted to improve P management in the UK, although additional measures focussing particularly on P as a resource are required. The results from this analysis suggest focussing on P removal and recovery at WwTW, as well as developing more effective methods for recycling bulky wastes such as animal manure, food waste and sewage sludge in order to reduce soil accumulations and replace imported fertilisers. Conducting additional SFAs at smaller scales may be necessary in order to develop more specific measures, such as regional recycling strategies.

Foraging at wastewater treatment works increases the potential for metal accumulation in an urban adapter, the banana bat (Neoromicia nana)

Wastewater treatment works (WWTWs) are known to provide profitable foraging areas for insectivorous bats in Europe and the New World because of their association with high abundance of pollution-tolerant midges (Diptera). However, bats that feed on these insects may also accumulate metal pollutants such as cadmium and copper in their tissues, with acute or chronic effects on their health. Using a time expansion bat detector, the activity (number of passes and feeding buzzes) of Neoromicia nana (family Vespertilionidae) was quantified at threeWWTWpoints – upstream, the point of wastewater effluent discharge, and downstream – along three urban rivers in South Africa. In addition, metal concentrations in the kidney, liver and muscle tissue of N. nana caught at the sites were quantified. The diversity of aerial insects, sampled over the same period as the bat surveys, was measured using a black light trap and sweep-netting. Relative abundance and feeding activity of N. nana were higher at wastewater-polluted sites than at upstream sites. The most abundant insect order at wastewater-polluted sites and in the diet of resident bats was Diptera. Essential metals (copper, zinc and iron) were detected in all N. nana tissue samples, but the toxic metals cadmium, chromium and nickel were mostly present in tissue of bats at wastewater-polluted sites. Thus, although WWTWs provide an optimal food resource to bats in the short-term, it may pose serious long-term health risks for these top predators.