To What Extent Can Full-Scale Wastewater Treatment Plant Effluent Influence the Occurrence of Silver-Based Nanoparticles in Surface Waters?

Silver-based nanoparticles (Ag-b-NPs) emitted by wastewater treatment plants (WWTPs) are considered to be widely present in the natural environment. However, there is much that is unknown about the effect of WWTP effluent on the occurrence of Ag-b-NPs in surface waters. On the basis of field analysis of representative WWTPs in Germany, we demonstrate that more than 96.4% of Ag-b-NPs from wastewater influent are removed through WWTPs, even though influent contains Ag-b-NP concentrations of tens to hundreds ng L(-1), resulting in effluent Ag-b-NP concentrations of 0.7-11.1 ng L(-1) over the seasons. The estimated flux of Ag-b-NPs associated with WWTPs effluent discharge is ∼33 kg y(-1) in Germany. WWTPs effluent increases Ag-b-NP levels of the River Isar to 2.0-8.6 ng L(-1), while remarkable decreases are observed at sites ∼1.5 km downstream of each discharge point, and Ag-b-NP levels then keep stable (0.9-2.3 ng L(-1)) until the next discharge point, showing subtle differences in Ag-b-NP levels between the river and reference lakes without industrial sources and WWTPs effluent discharge. Our results demonstrate that WWTPs effluent can exert a clear influence on the occurrence of Ag-b-NPs in surface waters.

A novel test method to determine the filter material service life of decentralized systems treating runoff from traffic areas.

In recent years, there has been a significant increase in the development and application of technical decentralized filter systems for the treatment of runoff from traffic areas. However, there are still many uncertainties regarding the service life and the performance of filter materials that are employed in decentralized treatment systems. These filter media are designed to prevent the transport of pollutants into the environment. A novel pilot-scale test method was developed to determine - within a few days - the service lives and long-term removal efficiencies for dissolved heavy metals in stormwater treatment systems. The proposed method consists of several steps including preloading the filter media in a pilot-scale model with copper and zinc by a load of n-1 years of the estimated service life (n). Subsequently, three representative rain events are simulated to evaluate the long-term performance by dissolved copper and zinc during the last year of application. The presented results, which verified the applicability of this method, were obtained for three filter channel systems and six filter shaft systems. The performance of the evaluated systems varied largely for both tested heavy metals and during all three simulated rain events. A validation of the pilot-scale assessment method with field measurements was also performed for two systems. Findings of this study suggest that this novel method does provide a standardized and accurate estimation of service intervals of decentralized treatment systems employing various filter materials. The method also provides regulatory authorities, designers, and operators with an objective basis for performance assessment and supports stormwater managers to make decisions for the installation of such decentralized treatment systems.

Removal of hydrocarbons from synthetic road runoff through adsorptive filters.

Compact filter systems, which are installed to significantly reduce the load of pollutants from road runoff, are very promising treatments for urban runoff. The objective of this research was to evaluate the effectiveness of activated carbon, activated lignite, zero valent iron, exfoliated graphite, amorphous ferric hydroxide, and activated alumina at removing petrol hydrocarbons from synthetic road runoff. Therefore, the kinetics and the equilibrium adsorption of petrol hydrocarbons onto these adsorbents were investigated using column adsorption experiments at levels ranging from 100 to 42 g L(-1). Of the tested adsorbents, exfoliated graphite is the most effective with a maximum adsorption capacity for petrol hydrocarbons of 3,850 mg g(-1). The experimental equilibrium data are fitted to the Freundlich and Langmuir models.

Monitoring benzotriazoles: a 1 year study on concentrations and removal efficiencies in three different wastewater treatment plants.

Benzotriazole (BTri), 4- and 5-tolyltriazole (4-TTri, 5-TTri) were monitored over 1 year in three wastewater treatment plants (WWTPs) with a membrane bioreactor (MBR-MH) and two conventional activated sludge systems (CAS-E, CAS-M). The influent/effluent concentrations and treatment stages removal efficiencies were monitored. 5-TTri was removed best (mean removal 80%) in the WWTP mainly by biodegradation followed by BTri (mean removal 45%) and 4-TTri (mean removal 15%) that showed a significant lower elimination. High removal fluctuations for all three benzotriazoles occurred over the four seasons with lowest removal during winter. All three WWTPs constituted a point source for BTs in the aquatic environment as concentration measurements in the receiving rivers upstream and downstream of the WWTP proved. While MBR-MH and CAS-M significantly increased the downstream concentrations, CAS-E only slightly increased the downstream concentrations as the receiving river was already contaminated with benzotriazoles from hydropower. 5-TTri was detected in lowest concentrations due to its good removal compared to BTri and 4-TTri that contribute to high effluent concentrations with the potential to accumulate due to insufficient self-purification.

Perovskite Oxides: Syntheses and Perspectives on Their Application for Nitrate Reduction.

Over the decades, the rise in nitrate levels in the ecosystem has posed a serious threat to the continuous existence of humans, fauna, and flora. The deleterious effects of increasing levels of nitrates in the ecosystem have led to adverse health and environmental implications in the form of methemoglobinemia and eutrophication, respectively. Different pathways/routes for the syntheses of perovskites and their oxides were presented in this review. In recent times, electrocatalytic reduction has emerged as the most utilized technique for the conversion of nitrates into ammonia, an industrial feedstock. According to published papers, the efficiency of various perovskites and their oxides used for the electrocatalytic reduction of nitrate achieved a high Faradaic efficiency of 98%. Furthermore, studies published have shown that there is a need to improve the chemical stability of perovskites and their oxides during scale-up applications, as well as their scalability for industrial applications.

Serial coupling of RP and zwitterionic hydrophilic interaction LC-MS: suspects screening of diclofenac transformation products by oxidation with a boron-doped diamond electrode.

The presence of pollutants and their transformation products (TPs) in the water system is a big concern because of possible adverse effects on the aquatic environment. Their identification is still a challenge that requires the combination of different chromatographic techniques. In the current research, serial coupling of RPLC and zwitterionic hydrophilic interaction LC with TOF-MS was investigated as a single separation technique for the screening of suspected TPs from electrochemical oxidation of diclofenac using a boron-doped diamond electrode. Diclofenac oxidation was performed in three water matrices in order to study its transformation in different chemical contexts. 47 TPs resulting from similar oxidation methods were selected from the literature. As in most cases standards were not available, an identification procedure based on accurate mass data and chromatographic behavior was proposed. According to this procedure, 11 suspected TPs, previously analyzed by LC, GC, or ion chromatography, were detected in a single injection. The method was proved to be reliable and versatile and it could be efficiently employed as a comprehensive analytical tool for the simultaneous analysis of compounds in a wide polarity range.

A three-stage treatment system for highly polluted urban road runoff.

A three-stage treatment device for polluted urban road runoff was installed and tested at a highly trafficked urban road over a period of one year. In the first stage coarse material and particles from the runoff are removed by a special gutter system. The second stage eliminates particles using a hydrodynamic separator. In the third stage dissolved pollutants are adsorbed in a filter unit with lignite as filter material. Twenty-four rain events were sampled over the one year period and analyzed for dissolved and particulate copper (Cu), zinc (Zn), lead (Pb), suspended solids (SS), total organic carbon (TOC), sodium (Na), and pH value. The treatment system was able to safely retain all relevant pollutants during the investigated period, except Na. In the effluent of the treatment device Pb could never be detected, values measured for Zn were in the range of the detection limit. Cu, the element most frequently detected in the effluent, never exceeded the critical value of 50 µg/L set by the German Federal Soil Protection Act and Ordinance. The median Cu concentration in the effluent of the treatment system was 8.13 µg/L. The treatment system proved to be very effective. Highly polluted road runoff can be purified by the system to an extent that no contamination risk for soil and groundwater remains when infiltrated into the soil.

Biomass-Tuned Reduced Graphene Oxide@Zn/Cu: Benign Materials for the Cleanup of Selected Nonsteroidal Anti-inflammatory Drugs in Water.

The persistent increase in the amount of nonsteroidal anti-inflammatory drugs such as ibuprofen (IBP) and diclofenac (DCF) in water bodies is alarming, thereby calling for a need to be addressed. To address this challenge, a bimetallic (copper and zinc) plantain-based adsorbent (CZPP) and reduced graphene oxide modified form (CZPPrgo) was prepared by facile synthesis for the removal of ibuprofen (IBP) and diclofenac (DCF) in water. Both the CZPP and CZPPrgo were characterized by different techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and pHpzc analysis. FTIR and XRD confirmed the successful synthesis of the CZPP and CZPPrgo. The adsorption of the contaminants was carried out in a batch system, and several operational variables were optimized. The adsorption is affected by the initial concentration of the pollutants (5-30 mg·L-1), the adsorbent dose (0.05-0.20 g), and pH (2.0-12.0). The CZPPrgo has the best performance with maximum adsorption capacities of 148 and 146 mg·g-1 for removing IBP and DCF from water, respectively. The experimental data were fitted into different kinetic and isotherm models; the removal of IBP and DCF follows the pseudo-second order, which can be best explained by the Freundlich isotherm model. The reuse efficiency was above 80% even after four adsorption cycles. This shows that the CZPPrgo is a promising adsorbent for removing IBP and DCF in water.

Interaction of heavy metals and biocide/herbicide from stormwater runoff of buildings with dissolved organic matter.

Stormwater runoff from roofs and façades can be contaminated by heavy metals and biocides/herbicides. High efficiency on-site treatment methods are now urgently needed to safeguard the ecosystem. The basis for developing such treatment facilities is an in-depth understanding of their interactions with dissolved organic matter (DOM), as this affects their migration in the environment. Hence, the interactions between copper (Cu), zinc (Zn), benzyl-dimethyl-tetradecylammonium chloride dihydrate (BAC), mecoprop-P (MCPP) and DOM at pH 5 to 9 were investigated separately in this study. The evaluation of the interaction processes was achieved by applying excitation emission matrix and parallel factor analysis (EEM-PARAFAC) to titration samples; obtained data were fitted by two different models. Mechanisms involved in BAC/MCPP-DOM interactions were revealed by Fourier-transform infrared spectroscopy (FTIR) and two-dimensional correlation spectrum (2D-COS) analysis. Results showed that the applied DOM was composed of the two different fluorescent components C1 and C2. More interaction with C1 than with C2 was observed for both Cu/Zn and BAC/MCPP. Increasing the pH enhanced the interactions between Cu/Zn and DOM. At pH 5 with a maximum quencher addition, the remaining fluorescence of CuC1 and ZnC1 were 15.7% and 87.1%, respectively. Corresponding data at pH 9 decreased to 3% and 69.5%. Contrarily, interactions between BAC/MCPP and DOM were impaired by high pH conditions. The increase of pH from 5 to 9 with maximum BAC and MCPP added raised the remaining fluorescence of BAC-C1 and MCPP-C1 by 15.9% and 21.3% separately. The fitting outcomes from the Ryan-Weber equation (Cu/Zn titration) and the Stern-Volmer equation (BAC/MCPP titration) corresponded well with the titration studies. FTIR coupled with 2D-COS analysis revealed that mechanisms involved in BAC/MCPP titration include hydrogen bonding, π-π interaction, and electrostatic effect. The order of mechanisms taking effect during the interaction with DOM is affected by the molecular structure of BAC and MCPP.

Groundwater risk assessment of leached inorganic substances from façades coated with plasters and mortars.

A requirement of the Construction Products Regulation (CPR) in the European Union states that construction materials and works must be designed in a way that throughout their entire life cycle, they have no exceedingly high impact on the environment. The objective of the current work was to evaluate the environmental risk of stormwater runoff from plasters and mortars using the Groundwater Risk Assessment (GRA). The source term eluates are based on the results obtained by a model for leaching prediction of inorganic substances for vertical test panels (VTPs) coated with plasters and mortars. During the evaluation, it was determined that vanadium, chromium, lead and zinc are relevant substances leached by plasters and mortars during rain events due to the high magnitude of concentrations, which can lead to a significant alteration in the chemical status of groundwater. The evaluation showed that chromium is the only leached substance that invalidates the applicability of one of the materials for a particular scenario of a selected technical construction application.

Leaching prediction for vertical test panels coated with plaster and mortars exposed under real conditions by a PHREEQC leaching model.

A requirement of the Construction Products Regulation (CPR) in the European Union states that construction works must be designed in such a way that throughout their entire life cycle, they have no exceedingly high environmental impact. The objective of the current work was to simulate the leaching of selected metals and sulfate in vertical test panels (VTPs) covered by plaster and mortar. The investigation is based on 18-month leaching outdoor tests (LOT) under real weather conditions. A leaching model was developed using the geochemical model PHREEQC with the Lawrence Livermore National Laboratory (LLNL) thermodynamic data base and coupled with MATLAB in order to optimize the run-off and weather parameters. The model was calibrated by comparing the data from laboratory Dynamic Surface Leaching Tests (DSLT) with simulation results up to an acceptable fit. The parameters obtained were then used in the LOT simulations and validated. The model allows predictions on the substance discharge from various plasters and mortars under real weather conditions. Physical characteristics of the material (e.g., thickness and absorption capacity) play an important role in the leaching of substances in façades covered with plaster and mortar. The lower the thickness and absorption capacity of the material applied, the greater the run-off and discharge of leached substances.

Microbial retention and resistances in stormwater quality improvement devices treating road runoff.

Current knowledge about the microbial communities that occur in urban road runoff is scarce. Road runoff of trafficked roads can be heavily polluted and is treated by stormwater quality improvement devices (SQIDs). However, microbes may influence the treatment process of these devices or could lead to stress resistant opportunistic microbial strains. In this study, the microbial community in the influent, effluent and the filter materials used to remove dissolved heavy metals from two different SQIDs were analyzed to determine microbial load, retention, composition, and mobile resistance genes. Although the microbes were replaced by new taxa in the effluent, there was no major retention of microbial genera. Further, the bacterial abundance of the SQIDs effluent was relatively stable over time. The heavy metal content correlated with intl1 and with microbial genera. The filter media itself was enriched with Intl1 gene cassettes, carrying several heavy metal and multidrug resistance genes (e.g. czrA, czcA, silP, mexW and mexI), indicating that this is a hot spot for horizontal gene transfer. Overall, the results shed light on road runoff microbial communities, and pointed to distinct bacterial communities within the SQIDs, which subsequently influence the microbial community and the genes released with the treated water.

Influence of façade orientation on the leaching of biocides from building façades covered with mortars and plasters.

Biocides used in building façades to prevent potential growth of algae, fungi and bacteria are of major concern regarding the quality of stormwater runoff. The aim of the study was to analyze the influence of the façade orientation on the biocide release under real weather conditions to gain information for the development of on-site treatment systems. Field tests with model houses containing two different plaster compositions were carried out over a period of 18 months. The results of the analyzed rain events demonstrate that façade orientation plays an important role in the leaching loads of biocides. Biocide loads in the runoff decreased corresponding to the wind direction. High cumulated active substance discharges of diuron (149 mg/m2), carbendazim (43.5 mg/m2), terbutryn (9.3 mg/m2) and octylisothiazolinone (OIT) (31.9 mg/m2) were found in the runoff of the façades facing the predominant weather orientation. Meanwhile, the highest concentrations of diuron (2.8 mg/L) and OIT (0.7 mg/L) were observed in the runoff from façades with smaller runoff volumes. The obtained results demonstrate that treatment facilities have to be installed at all building sides. The hydraulic and the substance load is highest at the weather side, which has a strong influence on the dimension and the lifetime of the treatment system.

Spatial distribution of zinc in the topsoil of four vegetated infiltration swales treating zinc roof runoff.

Since stormwater runoff from zinc roofs is polluted with high concentrations of zinc (Zn), runoff treatment is recommended in order to avoid harmful influences to the ecosystem. For the retention of Zn, vegetated infiltration swales with a topsoil layer are often used as decentralized Sustainable Urban Drainage Systems (SUDS). The aim of this study was to assess the risks of groundwater contamination due to infiltration of stormwater runoff of a Zn roof using infiltration swales. The spatial horizontal and vertical distribution of Zn content in four 15 year old vegetated infiltration swales at a zinc roof was analyzed and evaluated. High Zn contents (up to 27.9 g/kg dry mass) have been measured only for spatially limited areas at the inflow zones of each infiltration swale. Zn content decreased significantly with increasing distance from inflow and with increasing topsoil depth. Because the topsoil is still contaminated in deeper layers and because the soil's sorption potential is locally exceeded, the risk of groundwater contamination was expected to be high. Possible optimization of the hydraulic functioning and regular maintenance of the swales is recommended as well as a regular topsoil exchange of highly polluted areas.

On-site infiltration of a copper roof runoff: role of clinoptilolite as an artificial barrier material.

On-site infiltration may be considered as a promising way of managing rainwater runoffs in urban areas, provided the hydrological and ecological conditions allow infiltration, and provided there is adequate treatment of the contaminants to avoid a risk of soil and groundwater pollution. The aim of this study was to evaluate the feasibility of the application of a new technical infiltration system equipped with clinoptilolite as an artificial barrier material for the treatment of the copper roof runoff of the Academy of Fine Arts in Munich, Germany. During the 2-yr sampling period, 30 rain events were examined. The cover material of the roof and the drainage system was responsible for the high copper concentrations in the roof runoff. The rain height and the rain intensity were of great significance regarding the establishment of the copper runoff rate. The technical infiltration system applied was able to reduce the copper from the roof runoff by a factor up to 96%. The mean measured copper concentration in percolation water was lower than the critical value of 50 microg/l set by the German Federal Soil Protection Act and Ordinance, indicating no risk for soil and groundwater contamination.

Critical review of heavy metal pollution of traffic area runoff: Occurrence, influencing factors, and partitioning.

A dataset of 294 monitored sites from six continents (Africa, Asia, Australia, Europe, North and South America) was compiled and evaluated to characterize the occurrence and fate of heavy metals in eight traffic area categories (parking lots, bridges, and three types each of both roads and highways). In addition, site-specific (fixed and climatic) and method-specific (related to sample collection, preparation, and analysis) factors that influence the results of the studies are summarized. These factors should be considered in site descriptions, conducting monitoring programs, and implementing a database for further research. Historical trends for Pb show a sharp decrease during recent decades, and the median total Pb concentrations of the 21st century for North America and Europe are approximately 15 µg/L. No historical trend is detected for Zn. Zn concentrations are very variable in traffic area runoff compared with other heavy metals because of its presence in galvanized structures and crumbs of car tire rubber. Heavy metal runoff concentrations of parking lots differ widely according to their use (e.g., employee, supermarket, rest areas for trucks). Bridge deck runoff can contain high Zn concentrations from safety fences and galvanizing elements. Roads with more than 5000 vehicles per day are often more polluted than highways because of other site-specific factors such as traffic signals. Four relevant heavy metals (Zn, Cu, Ni, and Cd) can occur in the dissolved phase. Knowledge of metal partitioning is important to optimize stormwater treatment strategies and prevent toxic effects to organisms in receiving waters.

Evaluation of site-specific factors influencing heavy metal contents in the topsoil of vegetated infiltration swales.

Stormwater runoff of traffic areas is usually polluted by organic and inorganic substances and must be treated prior to discharge into groundwater. One widely used treatment method is infiltrating the runoff over the topsoil of vegetated swales. The aim of this study was to evaluate the factors influencing the heavy metal contents in such topsoil layers of vegetated infiltration swales near highways, roads, and parking lots. In total, 262 topsoil samples were taken from 35 sampling sites, which varied in age, traffic volume, road design, driving style, and site-specific conditions. In the evaluation of all soil samples, the median heavy metal values of cadmium, chromium, copper, lead, and zinc were yielding 0.36 (mean: 1.21) mg/kg DM, 37.0 (mean: 44.5) mg/kg DM, 28.0 (mean: 61.5) mg/kg DM, 27.0 (mean: 71.9) mg/kg DM, and 120 (mean: 257) mg/kg DM, respectively. The main purpose was to evaluate the site-specific data (i.e., surrounding land use characteristics, traffic area site data, and operational characteristics). In general, heavy metal contents increased with increasing traffic volumes. However, other factors also had a notable impact. Factors such as road design (e.g., curves, crossings, and roundabouts) and grade of congestion significantly influenced the heavy metal contents. High heavy metal contents were detected for stop-and-go areas, roundabouts, crossings, and sites with traffic lights, signs, and guardrails. Findings of this study can be used to identify highly polluted traffic areas and to verify or improve standards regarding the treatment of runoff from traffic areas.

Co-digestion of food waste in a municipal wastewater treatment plant: Comparison of batch tests and full-scale experiences.

The effects of co-digestion of food waste in a municipal wastewater treatment plant (WWTP) were studied in batch tests. The results obtained were compared with the mass balance of a digester at a full-scale WWTP for a one-year period without and with the addition of co-substrate. The specific methane yield calculated from the balance was 18% higher than the one in the batch tests, suggesting a stimulation of methane generation by co-digestion. It was hypothesized that this increase was caused by shifting the C/N ratio of raw sludge (8.8) to a more favourable ratio of the added food waste (17.7). In addition, potential benefits by adding food waste for energy autarky was investigated. While just 25% of the total energy demand of the plant could be recovered by biogas generation when no co-substrate was fed, this percentage has more than doubled when food waste was added at a ratio of 10% (w/w).

Heavy metal removal mechanisms of sorptive filter materials for road runoff treatment and remobilization under de-icing salt applications.

The objective of this research study was to elucidate the removal and remobilization behaviors of five heavy metals (i.e., Cd, Cu, Ni, Pb, and Zn) that had been fixed onto sorptive filter materials used in decentralized stormwater treatment systems receiving traffic area runoff. Six filter materials (i.e., granular activated carbon, a mixture of granular activated alumina and porous concrete, granular activated lignite, half-burnt dolomite, and two granular ferric hydroxides) were evaluated in column experiments. First, a simultaneous preloading with the heavy metals was performed for each filter material. Subsequently, the remobilization effect was tested by three de-icing salt experiments in duplicate using pure NaCl, a mixture of NaCl and CaCl2, and a mixture of NaCl and MgCl2. Three layers of each column were separated to specify the attenuation of heavy metals as a function of depth. Cu and Pb were retained best by most of the selected filter materials, and Cu was often released the least of all metals by the three de-icing salts. The mixture of NaCl and CaCl2 resulted in a stronger effect upon remobilization than the other two de-icing salts. For the material with the highest retention, the effect of the preloading level upon remobilization was measured. The removal mechanisms of all filter materials were determined by advanced laboratory methods. For example, the different intrusions of heavy metals into the particles were determined. Findings of this study can result in improved filter materials used in decentralized stormwater treatment systems.

Influence of chemical conditioning on the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite.

Aim of this study was to evaluate the feasibility of the use of clinoptilolite as a barrier material to eliminate heavy metals from roof runoff. The effect of chemical conditioning with 1 M NaCl solution upon the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite has been investigated. According to the batch experiments the modified clinoptilolite has up to 100% higher sorption capacity, regarding Zn than the natural material. The pre-treatment of clinoptilolite results in an acceleration of the ion exchange process up to 40% regarding zinc. In order to define the reasons of this behaviour, both materials, modified and natural, were analysed for: (i) chemical composition, (ii) density, (iii) pore size distribution and (iv) zeta potential. The clogging of the pores, the charge of the grain surface, the pH of the initial metal solution and the ion metal concentration are the factors which are mainly affecting the ion exchange capacity and the rate of zinc uptake by clinoptilolite.