Occurrence and suitability of sucralose as an indicator compound of wastewater loading to surface waters in urbanized regions

Urban watersheds are susceptible to numerous pollutant sources and the identification of source-specific indicators can provide a beneficial tool in the identification and control of input loads, often times needed for a water body to achieve designated beneficial uses. Differentiation of wastewater flows from other urban wet weather flows is needed in order to more adequately address such environmental concerns as water body nutrient impairment and potable source water contamination. Anthropogenic compounds previously suggested as potential wastewater indicators include caffeine, carbamazepine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, primidone, sulfamethoxazole, and TCEP. This paper compares the suitability of a variety of anthropogenic compounds to sucralose, an artificial sweetener, as wastewater indicators by examining occurrence data for 85 trace organic compounds in samples of wastewater effluents, source waters with known wastewater point source inputs, and sources without known wastewater point source inputs. The findings statistically demonstrate the superior performance of sucralose as a potential indicator of domestic wastewater input in the U.S. While several compounds were detected in all of the wastewater effluent samples, only sucralose was consistently detected in the source waters with known wastewater discharges, absent in the sources without wastewater influence, and consistently present in septic samples. All of the other compounds were prone to either false negatives or false positives in the environment.     

Heavy metals in domestic wastewater with respect to urban population in Ostrava,Czech Republic

During dry weather periods, domestic wastewater is a major component of urban wastewater influent to a wastewater treatment plant (WWTP). For this reason, the quantity and quality of domestic wastewater have a considerable effect on the resultant contamination of urban wastewater and on the subsequent selection of appropriate WWTP technology. The aim of this study was to quantify the amount of hazardous elements in domestic wastewater to determine the average daily production of domestic wastewater and risk elements per inhabitant and quantify the proportion of households in the total load of urban wastewater. Wastewater samples were collected from nine local sewer systems in Ostrava, the Kravare WWTP and the Central Wastewater Treatment Plant of Ostrava (Czech Republic). We found that the average production of wastewater from households is approximately 135 L per person per day. The results also show that the share of households in urban wastewater is approximately 60% in the case of Cd, 35–21% in the case of Zn, Cu, As and less than 15% for Pb, Cr, Fe, Ni and Mn.     

Nitrous oxide emissions from the oxidation tank of a pilot activated sludge plant

This study discusses the results of the continuous monitoring of nitrous oxide emissions from the oxidation tank of a pilot conventional wastewater treatment plant. Nitrous oxide emissions from biological processes for nitrogen removal in wastewater treatment plants have drawn great attention over the last years, due to the high greenhouse effect. However, even if several studies have been carried out to quantify nitrous oxide emission rates from different types of treatment, quite wide ranges have been reported. Only grab samples or continuous measurements over limited periods were considered in previous studies, which can account for the wide variability of the obtained results. Through continuous monitoring over several months, our work tries to fill this gap of knowledge and get a deeper insight into nitrous oxide daily and weekly emission dynamics. Moreover, the influence of some operating conditions (sludge age, dissolved oxygen concentration in the oxidation tank, nitrogen load) was studied to determine good practices for wastewater treatment plant operation aiming at the reduction of nitrous oxide emissions. The dissolved oxygen set-point is shown to play a major role in nitrous oxide emissions. Low sludge ages and high nitrogen loads are responsible for higher emissions as well. An interesting pattern has been observed, with quite negligible emissions during most of the day and a peak with a bell-like shape in the morning in the hours of maximum nitrogen load in the plant, correlated to the ammonia and nitrite peaks in the tank.     

Sources of heavy metals in urban wastewater in Stockholm

The sources of heavy metals to a wastewater treatment plant was investigated. Sources can be actual goods, e.g. runoff from roofs, wear of tires, food, or activities, e.g. large enterprises, car washes. The sources were identified by knowing the metals content in various goods and the emissions from goods to sewage or stormwater. The sources of sewage water and stormwater were categorized to enable comparison with other research and measurements. The categories were households, drainage water, businesses, pipe sediment (all transported in sewage water), atmospheric deposition, traffic, building materials and pipe sediment (transported in stormwater). Results show that it was possible to track the sources of heavy metals for some metals such as Cu and Zn (110 and 100% found, respectively) as well as Ni and Hg (70% found). Other metals sources are still poorly understood or underestimated (Cd 60%, Pb 50%, Cr 20% known). The largest sources of Cu were tap water and roofs. For Zn the largest sources were galvanized material and car washes. In the case of Ni, the largest sources were chemicals used in the WTP and drinking water itself. And finally, for Hg the most dominant emission source was the amalgam in teeth. For Pb, Cr and Cd, where sources were more poorly understood, the largest contributors for all were car washes. Estimated results of sources from this study were compared with previously done measurements. The comparison shows that measured contribution from households is higher than that estimated (except Hg), leading to the conclusion that the sources of sewage water from households are still poorly understood or that known sources are underestimated. In the case of stormwater, the estimated contributions are rather well in agreement with measured contributions, although uncertainties are large for both estimations and measurements. Existing pipe sediments in the plumbing system, which release Hg and Pb, could be one explanation for the missing amount of these metals. Large enterprises were found to make a very small contribution, 4% or less for all metals studied. Smaller enterprises (with the exception of car washes) have been shown to make a small contribution in another city; the contribution in this case study is still unknown.     

Identifying key sources of uncertainty in the modelling of greenhouse gas emissions from wastewater treatment

This study investigates sources of uncertainty in the modelling of greenhouse gas emissions from wastewater treatment, through the use of local and global sensitivity analysis tools, and contributes to an in-depth understanding of wastewater treatment modelling by revealing critical parameters and parameter interactions. One-factor-at-a-time sensitivity analysis is used to screen model parameters and identify those with significant individual effects on three performance indicators: total greenhouse gas emissions, effluent quality and operational cost. Sobol's method enables identification of parameters with significant higher order effects and of particular parameter pairs to which model outputs are sensitive. Use of a variance-based global sensitivity analysis tool to investigate parameter interactions enables identification of important parameters not revealed in one-factor-at-a-time sensitivity analysis. These interaction effects have not been considered in previous studies and thus provide a better understanding wastewater treatment plant model characterisation. It was found that uncertainty in modelled nitrous oxide emissions is the primary contributor to uncertainty in total greenhouse gas emissions, due largely to the interaction effects of three nitrogen conversion modelling parameters. The higher order effects of these parameters are also shown to be a key source of uncertainty in effluent quality.     

Evaluation of Po River water quality in Torino (Italy): Effects of diffuse and local point loads

The aim of this paper is to examine the Po River water quality in a small stretch in Piedmont (northern Italy). In this stretch a large pollution load, derived from the wastewater treatment plant of Torino area (more than 2 million inhabitants), is discharged and diluted in the water. In this study this load has been quantified and modeled in order to understand the sources, destinations and effects of the emitted pollutants. The objective was to determine the impact produced by the Torino Wastewater Treatment Plant on the quality of the water, based on various hydrological conditions and the possible intervention on the point and diffuse loads.     

Pollution loads in urban runoff and sanitary wastewater

While more attention has been paid in recent years to urban point source pollution control through the establishment of wastewater treatment plants in many developing countries, no considerable planning nor any serious measures have been taken to control urban non-point source pollution (urban stormwater runoff). The present study is a screening analysis to investigate the pollution loads in urban runoff compared to point source loads as a first prerequisite for planning and management of receiving water quality. To compare pollutant loads from point and non-point urban sources, the pollutant load is expressed as the weight of pollutant per hectare area per year (kg/ha.year). Unit loads were estimated in stormwater runoff, raw sanitary wastewater and secondary treatment effluents in Isfahan, Iran. Results indicate that the annual pollution load in urban runoff is lower than the annual pollution load in sanitary wastewater in areas with low precipitation but it is higher in areas with high precipitation. Two options, namely, advanced treatment (in lieu of secondary treatment) of sanitary wastewater and urban runoff quality control systems (such as detention ponds) were investigated as controlling systems for pollution discharges into receiving waters. The results revealed that for Isfahan, as a low precipitation urban area, advanced treatment is a more suitable option, but for high precipitation urban areas, urban surface runoff quality control installations were more effective for suspended solids and oxygen-demanding matter controls, and that advanced treatment is the more effective option for nutrient control.     

Evaluation of management strategies for reducing nitrogen loadings to four US estuaries

In this study we used the Watershed Assessment Tool for Evaluating Reduction Strategies for Nitrogen (WATERSN) model to evaluate a variety of management strategies for reducing nitrogen (N) loads to four US east coast estuaries: Casco Bay, Long Island Sound, Chesapeake Bay and Pamlico Sound. These management strategies encompass reductions in atmospheric emissions and deposition of N from sources including, fossil fuel burning utility emissions and mobile NO(x) emissions, N treatment in wastewater and controls on agricultural N inputs. We find that in primarily urban watersheds biological removal of N in wastewater treatment produces the greatest reduction in N loading (32-57% reductions), while in less urban watersheds, reductions in agricultural loading are more effective (5-56% reductions) in decreasing N loads to coastal ecosystems. Because anthropogenic N inputs are derived from a variety of sources, we also examined an integrated scenario targeting all major N sources; this resulted in 35-58% reductions in N loading. Nitrogen pollution originates from multiple sources and is transported through several media (air, soil, water); a major challenge of the development of N management strategies will be the control of multiple sources to effectively reduce N loads to estuaries.     

Visualisation and quantification of geogrid reinforcing effects under strip footing loads using discrete element method

Geogrids have been commonly used in reinforced soil structures to improve their performance. To investigate the geogrid reinforcement mechanisms, discrete element modelling of unreinforced and geogrid reinforced soil foundations and slopes was conducted under surface strip footing loads in this study. For unreinforced and reinforced soil foundations, the numerically obtained footing pressure-settlement relationships were validated by experimental results from the literature. In the numerical modelling of unreinforced and reinforced soil slopes, identical models and micro input parameters to those used in the numerical modelling of unreinforced and reinforced soil foundations were used. The geogrid reinforcing effects under strip footing loads were visualised by the qualitative contact force distributions in the soil structures, as well as the qualitative and quantitative tensile force distributions along the geogrids. In addition, the qualitative displacement distributions of soil particles in the soil structures and the quantitative vertical displacement distributions along soil layers/geogrids also indicated the geogrid reinforcing effects in such practical reinforced soil structures. The discrete element modelling results visualise and quantify the load transfer and spreading behavior in geogrid reinforced soil structures, and it provides researchers with an improved understanding of geogrid reinforcing effects at microscopic scale under strip footing loads.     

基于流量调查的分流制雨水系统诊断研究

分流制雨水系统的非雨水入流不但影响其正常的排涝功能，而且混接污水的直接排放还易导致受纳水体的严重污染。为了制定合理的系统改造方案，首先需要对系统状况进行分析诊断。为此，结合上海市早期建造的某分流制雨水系统改造工程，进行了以流量调查为基础的系统分析诊断研究，掌握了该系统同时存在雨污混接、与河道直接连通等复杂水力情况，为进行系统改造方案决策提供了依据。研究成果与方法对其他雨水系统的分析诊断有参考价值。     

关于钢铁企业给排水总体设计的思考

作为耗水大户，如何实现污水排放量的减少与节约用水，是钢铁企业排水系统的目标。本文以钢铁企业给排水总体设计的意义作为切入点，介绍了给排水总体设计可在钢铁企业中发挥的功能。并根据其特征，提出了几条与设计相关的建议，以期在工程实践中起到参考作用。     

The Indoor Chemical Human Emissions and Reactivity (ICHEAR) project: Overview of experimental methodology and preliminary results

With the gradual reduction of emissions from building products, emissions from human occupants become more dominant indoors. The impact of human emissions on indoor air quality is inadequately understood. The aim of the Indoor Chemical Human Emissions and Reactivity (ICHEAR) project was to examine the impact on indoor air chemistry of whole-body, exhaled, and dermally emitted human bioeffluents under different conditions comprising human factors (t-shirts/shorts vs long-sleeve shirts/pants; age: teenagers, young adults, and seniors) and a variety of environmental factors (moderate vs high air temperature; low vs high relative humidity; presence vs absence of ozone). A series of human subject experiments were performed in a well-controlled stainless steel climate chamber. State-of-the-art measurement technologies were used to quantify the volatile organic compounds emitted by humans and their total OH reactivity; ammonia, nanoparticle, fluorescent biological aerosol particle (FBAP), and microbial emissions; and skin surface chemistry. This paper presents the design of the project, its methodologies, and preliminary results, comparing identical measurements performed with five groups, each composed of 4 volunteers (2 males and 2 females). The volunteers wore identical laundered new clothes and were asked to use the same set of fragrance-free personal care products. They occupied the ozone-free (<2 ppb) chamber for 3 hours (morning) and then left for a 10-min lunch break. Ozone (target concentration in occupied chamber ~35 ppb) was introduced 10 minutes after the volunteers returned to the chamber, and the measurements continued for another 2.5 hours. Under a given ozone condition, relatively small differences were observed in the steady-state concentrations of geranyl acetone, 6MHO, and 4OPA between the five groups. Larger variability was observed for acetone and isoprene. The absence or presence of ozone significantly influenced the steady-state concentrations of acetone, geranyl acetone, 6MHO, and 4OPA. Results of replicate experiments demonstrate the robustness of the experiments. Higher repeatability was achieved for dermally emitted compounds and their reaction products than for constituents of exhaled breath.     

The impact of new developments on river water quality from an integrated system modelling perspective

New housing areas are a ubiquitous feature of modern life in the developing and developed world alike built in response to rising social, demographic and economic pressures. Inevitably, these new developments will have an impact on the environment around them. Empirical evidence confirms the close relationship between urbanisation and ambient water quality. However, what is lacking so far is a detailed and more generalised analysis of environmental impact at a relatively small scale. The aim of this paper is to quantify the impact of new developments on river water quality within an integrated system modelling perspective. To conduct the impact analyses, an existing integrated urban wastewater model was used to predict water flow and quality in the sewer system, treatment plant and receiving water body. The impact on combined sewer overflow (CSO) discharges, treatment plant effluent, and within the river at various reaches is analysed by ‘locating’ a new development on a semi-hypothetical urban catchment. River water quality is used as feedback to constrain the scale of the new development within different thresholds in compliance with water quality standards. Further, the regional sensitivity analysis (RSA) method is applied to reveal the parameters with the greatest impact on water quality. These analyses will help to inform town planners and water specialists who advise them, how to minimise the impact of such developments given the specific context.     

On-road vehicle emission inventory and its uncertainty analysis for Shanghai, China

As vehicle population and activity increase, vehicle emissions are becoming the most predominant source of air pollution in Shanghai, China. It has become important to accurately estimate the traffic emissions in this city. This paper presents a bottom-up approach based on the International Vehicle Emission (IVE) model to develop the vehicle emission inventory for Shanghai. The results show that the total emissions of CO, VOC, NO(X) and PM from vehicles in Shanghai in 2004 were 57.06 x 10(4) t, 7.75 x 10(4) t, 9.20 x 10(4) t and 0.26 x 10(4) t, respectively. About 20% of the total emissions were emitted during the cold start period. Heavy-duty vehicles such as trucks and buses contributed over half of NO(X) and PM. Motorcycles and mopeds provided 45.0% of VOC and 36.3% of PM. Light-duty vehicles are the main source of CO emissions. An assessment of vehicle emissions by time of day and road type was also discussed. The three peak emission periods accounted for 54% to 56% of the total emissions during the day and more than 50% of the total emissions were emitted on the arterial roads. Finally, the study focused on the uncertainty analysis of two critical factors: emission factors and the estimate of the total Vehicle Kilometers Traveled (VKT). The analysis indicates that the emission factors calculated in this paper are close to those factors measured during on-road testing, and the difference between the VKT used in this paper and other calculations is less than 10%.     

Hydraulic Performance of Completely Mixed Tanks in Series under Unsteady Flow

Completely mixed tanks in series are often used in water and wastewater treatment processes and surface-water quality modelling. Hydraulic retention time, which describes the overall hydraulic performance of the tanks, is one of the main parameters in the design and operation of treatment processes and modelling of the surface-water quality. Differential equations to calculate the hydraulic retention time of completely mixed tanks in series under unsteady flow were derived in this study, and the equations were subsequently used to evaluate the hydraulic performance of tanks under a step change inflow rate and a cyclical flow rate, respectively. For a step change in flow rate, the differential equations were solved analytically using a recursive method. For a cyclical hydraulic loading, computer simulation was carried out using the Runge-Kutta method with adaptive stepsize control.     

Nitrous oxide emission during wastewater treatment

Nitrous oxide (N₂O), a potent greenhouse gas, can be emitted during wastewater treatment, significantly contributing to the greenhouse gas footprint. Measurements at lab-scale and full-scale wastewater treatment plants (WWTPs) have demonstrated that N₂O can be emitted in substantial amounts during nitrogen removal in WWTPs, however, a large variation in reported emission values exists. Analysis of literature data enabled the identification of the most important operational parameters leading to N₂O emission in WWTPs: (i) low dissolved oxygen concentration in the nitrification and denitrification stages, (ii) increased nitrite concentrations in both nitrification and denitrification stages, and (iii) low COD/N ratio in the denitrification stage. From the literature it remains unclear whether nitrifying or denitrifying microorganisms are the main source of N₂O emissions. Operational strategies to prevent N₂O emission from WWTPs are discussed and areas in which further research is urgently required are identified.     

Fate of β-blocker human pharmaceuticals in surface water: Comparison of measured and simulated concentrations in the Glatt Valley Watershed, Switzerland

This study focused on the occurrence and fate of four β-blockers (atenolol, sotalol, metoprolol, propranolol) in wastewater and surface water. Measured concentrations were compared with predicted concentrations using an implementation of the geo-referenced model GREAT-ER for the Glatt Valley Watershed (Switzerland). Particularly, the question was addressed how measured and simulated data could complement each other for the exposure assessment of human pharmaceuticals and other micropollutants entering surface water through wastewater treatment plants (WWTP).Concentrations in the Glatt River ranged from <LOQ to 83 ng L⁻¹ with the highest concentrations found for atenolol. Higher loads were measured on days with combined sewer overflow events during high flow conditions.GREAT-ER was able to predict spatially resolved river concentrations based on average consumption and excretion data, removal in wastewater treatment plants (WWTPs) and dissipation and degradation processes in surface water within a factor of 2. These results indicate that modelling might be sufficient to estimate daily average exposure concentrations for compounds that are either recalcitrant or whose degradation and sorption behaviour can be predicted with confidence based on laboratory experiments. Chemical measurements, in contrast, should be reserved for assessing point sources, investigating mechanisms which lead to short-term temporal fluctuations in compound loads, and determining in-situ degradation rates in conjunction with modelling.     

High mercury emissions from dental clinics despite amalgam separators

Mercury (Hg) as amalgam has been used as a dental filling material for more than 150 years. Thereby, dentists and their patients have been directly exposed to Hg, and the public and the environment indirectly exposed via Hg emissions from incinerators and Hg in waste water from households and dental clinics. Due to the toxic properties of Hg and bioaccumulation in biota of Hg emitted via dental clinic waste water, amalgam separators were introduced in Sweden in the 1980s. Although these amalgam separators in the certification process are required to remove at least 95% of incoming Hg in a standardized laboratory test, their efficiency in practical use has not been properly investigated. Here we present actual Hg emissions via waste water from 12 dental clinics equipped with the same type of amalgam separator based on sedimentation. All waste water was collected for four consecutive working days, initially at ordinary operating conditions and a second time after a thorough revision and cleaning of the discharge system. The results indicate that mercury emissions from dental clinics can be reduced by an improved design of the discharge system, a sensible use of high pressure water cleaning, and regular maintenance, including replacement of amalgam separators and filters at certain intervals. The study also indicates that banning Hg in dentistry is the one long-term way to stop Hg emissions from dental amalgam.     

Urine separation as part of a real-time control strategy

Considering wastewater from household sources, urine accounts for approximately 80% of the ammonia loads but for only 1% of the hydraulic load. Where classical urine separation deals with the separation and subsequent removal of urine from the wastewater stream, the method promoted here (urine separation for waste design) aims to (1) separate urine from the wastewater stream, (2) store it at the household and (3) release it in a controlled manner into the drainage system. The ultimate goal is on the one hand to average the daily dynamics in the ammonia load to the wastewater treatment plant (WWTP) and on the other hand to reduce ammonia emissions towards receiving waters. All process steps from urine production, separation, harvesting and controlled release of urine have been modelled on a micro-level where all toilets in the system are balanced separately. As a case study the integrated urban drainage system of Vils/Reutte in Tyrol was used where a total of 11 different control strategies – ranging from simple to highly complex real-time control (RTC) applications – have been developed and tested. The evaluation (taking into account both aims as expressed above) showed that the simplest RTC applications are the most effective. The optimal performance achieved in the case study resulted in an ammonia reduction of 62% (load based) compared to the status quo. As such a method would require considerable systems changes, an incremental implementation of associated improvements were also tested in this work. An important outcome was that a large proportion of the final improvement is gained already with the first 25% of installed separation toilets.     

Temperature as an alternative tracer for the determination of the mixing characteristics in wastewater treatment plants

The hydraulic characteristics, i.e. the residence time distributions, of wastewater treatment plant reactors are usually determined using conventional tracers. This paper aims to present an alternative approach based on wastewater temperature. The step in temperature change, e.g. from stormwater events with cold rainwater, is used as a tracer signal. The method was verified using lab- and pilot-scale tests that showed very good agreement of the time series estimated both with conventional and temperature tracer methods. Results from lab-scale tests exhibit a zone with a minor water exchange of about 10% of the volume of all reactors, while the respective zone in the pilot-scale tests was estimated at about 30% of the total volume. The short-circuit flow was more than 50% of the inflow resulting from gaps between the walls inside the reactor cascade. An application example shows the importance of reliable residence time distribution underlying activated sludge modelling and the uncertainty associated with neglecting the determination of appropriate flow-through characteristics.