Downstream Wastewater Treatment Plant Research Articles

Integrated urban wastewater management through on-site generation and application of ferrous carbonate

Integrated urban water management is an increasingly popular concept that cost-effectively maximizes system-wide performance by holistically considering all aspects of water and wastewater sectors. An innovative technology enabling production of high-quality bioenergy and an iron salt, ferrous carbonate (FeCO3), represents a significant opportunity for integrated urban water management. This study experimentally evaluates the effect of in-sewer FeCO3 dosing on the performance of sewers and the downstream wastewater treatment plants. Two continuous-flow laboratory-scale urban wastewater systems, each consisting of sewer reactors, a sequencing batch wastewater treatment reactor, and an anaerobic digester, were operated in parallel. After establishing comparable performance, one served as the control without any chemical dosing, while the other received a dosing of 10mgFe/L of FeCO3 in its sewer reactors. Compared to the control, the FeCO3-dosed experimental system reduced dissolved sulfide concentrations by 32.2±3.3% (at 0.58±0.05mgS/mgFe, or 1.0molFe/molS) in sewer reactors, decreased phosphate concentrations by 38.3%±3.2% (at 0.37±0.04mgP/mgFe, or 1.5molFe/molP) in sequencing batch reactors, and lowered dissolved sulfide concentrations by 72.0±4.2% (18.9±2.4mgS/L) in the anaerobic sludge digester. Iron accumulated in the sludge and improved sludge settleability by 33.9±5.5% and enhanced dewaterability of anaerobically digested sludge by 15.9±2.0%. The findings indicate multiple benefits from the integrated use of FeCO3, potentially being as a substitute for the currently used iron salts in urban wastewater systems.

Techno-economic analysis of nutrient recovery from urine: Centralized treatment of hydrolyzed urine vs. decentralized treatment of fresh urine

The centralized process integrating “Thermal NH3 stripping → Na-chabazite adsorption → Struvite precipitation” has been proposed for nutrient recovery from hydrolyzed urine. Meanwhile, a decentralized approach involving Na-chabazite and biochar adsorption has been suggested for fresh urine, followed by urea hydrolysis and the subsequent centralized integration of struvite precipitation and thermal stripping. However, a systematic comparison of nutrient recovery processes for fresh and hydrolyzed urine, evaluating both technical viability and financial feasibility, is lacking. This study addresses the gap by thoroughly examining both scenarios over a 30-year project, using Université Laval as a case study. It provides a comprehensive roadmap for techno-economic assessment, offering guidance for evaluating nutrient recovery processes prior to scaling up. The decentralized process achieved higher recovery efficiencies for nitrogen and phosphorus, at 89.4 % and 98.7 %, respectively. Financially, the decentralized scenario demonstrated its advantage in the lower initial investment requirement, thereby generating higher gross profits compared to the centralized scenario. As a result, it is projected to reach the break-even point in the 21st year, demonstrating its potential economic feasibility. Sensitivity analysis indicated that a 20 % increase in urine inflow rate and the price of urea-enriched biochar could further enhance the economic viability of both processes. Beyond financial considerations, both scenarios have the potential to reducing the contaminant loading rate in the downstream wastewater treatment plants and promote nutrient recovery and recycling.

Pretreatment for potable reuse: Enhancing the biological removal of 1,4-dioxane from landfill leachate through cometabolism with tetrahydrofuran.

1,4-Dioxane is a probable human carcinogen and a persistent aquatic contaminant. Cometabolic biodegradation of 1,4-dioxane is a promising low-cost and effective treatment technology; however, further demonstration is needed for treating landfill leachate. This technology was tested in two full-scale moving bed biofilm reactors (MBBRs) treating raw landfill leachate with tetrahydrofuran selected as the cometabolite. The raw leachate contained on average 82 μg/L of 1,4-dioxane and before testing the MBBRs removed an average of 38% and 42% of 1,4-dioxane, respectively. First, tetrahydrofuran was added to MBBR 1, and 1,4-dioxane removal was improved to an average of 73%, with the control MBBR removing an average of 37% of 1,4-dioxane. During this period, an optimal dose of 2mg/L of tetrahydrofuran was identified. Tetrahydrofuran was then fed to both MBBRs, where the 1,4-dioxane removal was on average 73% and 80%. Cometabolic treatment at the landfill significantly reduced the concentration of 1,4-dioxane received from the landfill at a downstream wastewater treatment and indirect potable reuse facility, reducing the load of 1,4-dioxane from 44% to 24% after the study. PRACTITIONER POINTS: Cometabolic degradation of leachate 1,4-dioxane with THF in MBBRs is a feasible treatment technology and a low-cost technique when retrofitting existing biological treatment facilities. The MBBRs can be operated at a range of temperatures, require no operational changes beyond THF addition, and operate best at a mass ratio of THF to 1,4-dioxane of 24. Source control of 1,4-dioxane significantly reduces the concentration of 1,4-dioxane in downstream wastewater treatment plants and potable reuse facilities.

Model-based assessment of in-sewer heat recovery potentials considering wastewater treatment-specific temperature limits

ABSTRACT Due to the ongoing climate and energy crisis, wastewater is becoming increasingly important as a source of renewable energy. In urban areas, heat recovery from the sewer is considered a promising approach, as the locations of supply and demand are close to each other. In this context, it is crucial that negative impacts on temperature-sensitive processes in the downstream wastewater treatment plant are strictly avoided. To support the necessary planning and authorization, this paper presents a model-based approach to assess the thermal energy level of the wastewater at any given location in the sewer, taking into account the influent temperature constraints of the wastewater treatment plant. The entire modelling is based on the open-source software SWMM 5, which was extended by a temperature model. The concept showed its practicability and informative value during a full-scale field application in the sewer systems of the Austrian city of Graz. All modelling is based on freely available software, which makes the approach easy transferable to other cities with comparable infrastructural boundary conditions.

Design Issue Analysis and Operation Effect Evaluation of Large-Scale Storage Tank

In order to address the issue of combined sewer overflows (CSOs), W city has constructed a large-scale storage tank with a volume of 220,000 m3. The storage tank is planned for CSO control in the near term and stormwater runoff pollution control in the long term. However, the actual operation of the storage tank is unsatisfactory. This paper elucidates the design scheme and operation mode of the tank and analyzes the challenges encountered during its design and operation. A storm water management model (SWMM) model was constructed to simulate the effect of the storage tank working in a combined sewer system (CSS), a separate sewer system (SSS) and a decentralized storage situation. This study determined that during the 2022 rainy season, the actual reduction in pollutants by the storage tank was only about 60% of the designed value. As a result, the inadequate treatment capacity of the downstream wastewater treatment plant (WWTP) resulted in the water being retained in the tank for a long time, leading to unsatisfactory operation outcomes. If the storage tank works in SSS and the problem of water retention can be solved, it could reduce the total runoff volume by 30% and the total amount of pollutants by 40% during the same rainy season. At the same time, under the premise of constant total storage volume, if decentralized storage tanks were used to control runoff pollution, the reduction effect can be increased by up to 11.6% compared with that of the centralized storage.

Online trend estimation and detection of trend deviations in sub-sewershed time series of SARS-CoV-2 RNA measured in wastewater

Wastewater surveillance has proven a cost-effective key public health tool to understand a wide range of community health diseases and has been a strong source of information on community levels and spread for health departments throughout the SARS- CoV-2 pandemic. Studies spanning the globe demonstrate the strong association between virus levels observed in wastewater and quality clinical case information of the population served by the sewershed. Few of these studies incorporate the temporal dependence present in sampling over time, which can lead to estimation issues which in turn impact conclusions. We contribute to the literature for this important public health science by putting forward time series methods coupled with statistical process control that (1) capture the evolving trend of a disease in the population; (2) separate the uncertainty in the population disease trend from the uncertainty due to sampling and measurement; and (3) support comparison of sub-sewershed population disease dynamics with those of the population represented by the larger downstream treatment plant. Our statistical methods incorporate the fact that measurements are over time, ensuring correct statistical conclusions. We provide a retrospective example of how sub-sewersheds virus levels compare to the upstream wastewater treatment plant virus levels. An on-line algorithm supports real-time statistical assessment of deviations of virus level in a population represented by a sub-sewershed to the virus level in the corresponding larger downstream wastewater treatment plant. This information supports public health decisions by spotlighting segments of the population where outbreaks may be occurring.

Multifaceted benefits of magnesium hydroxide dosing in sewer systems: Impacts on downstream wastewater treatment processes

Magnesium hydroxide [Mg(OH)2] is a non-hazardous chemical widely applied in sewer systems for managing odour and corrosion. Despite its proven effectiveness in mitigating these issues, the impacts of dosing Mg(OH)2 in sewers on downstream wastewater treatment plants have not been comprehensively investigated. Through a one-year operation of laboratory-scale urban wastewater systems, including sewer reactors, sequencing batch reactors, and anaerobic sludge digesters, the findings indicated that Mg(OH)2 dosing in sewer systems had multifaceted benefits on downstream treatment processes. Compared to the control, the Mg(OH)2-dosed experimental system displayed elevated sewage pH (8.8±0.1vs 7.1±0.1), reduced sulfide concentration by 35.1%±4.9% (6.7±0.9mgSL−1), and lower methane concentration by 58.0%±4.9% (19.1±3.6mgCODL−1). Additionally, it increased alkalinity by 16.3%±2.2% (51.9±5.4mgCaCO3L−1), and volatile fatty acids concentration by 207.4%±22.2% (56.6±9.0mgCODL−1) in sewer effluent. While these changes offered limited advantages for downstream nitrogen removal in systems with sufficient alkalinity and carbon sources, significant improvements in ammonium oxidation rate and NOx reduction rate were observed in cases with limited alkalinity and carbon sources availability. Moreover, Mg(OH)2 dosing in upstream did not have any detrimental effects on anaerobic sludge digesters. Magnesium-phosphate precipitation led to a 31.7%±4.1% reduction in phosphate concertation in anaerobic digester sludge supernatant (56.1±10.4mgPL−1). The retention of magnesium in sludge increased settleability by 13.9%±1.6% and improved digested sludge dewaterability by 10.7%±5.3%. Consequently, the use of Mg(OH)2 dosing in sewers could potentially reduce downstream chemical demand and costs for carbon sources (e.g., acetate), pH adjustment and sludge dewatering.

Waste Activated Sludge-High Rate (WASHR) Treatment Process: A Novel, Economically Viable, and Environmentally Sustainable Method to Co-Treat High-Strength Wastewaters at Municipal Wastewater Treatment Plants.

High-strength wastewaters from a variety of sources, including the food industry, domestic septage, and landfill leachate, are often hauled to municipal wastewater treatment plants (WWTPs) for co-treatment. Due to their high organic loadings, these wastewaters can cause process upsets in both a WWTP's liquid and solids treatment trains and consume organic treatment capacity, leaving less capacity available to service customers in the catchment area. A novel pre-treatment method, the Waste Activated Sludge-High Rate (WASHR) process, is proposed to optimize the co-treatment of high-strength wastewaters. The WASHR process combines the contact stabilization and sequencing batch reactor processes. It utilizes waste activated sludge from a municipal WWTP as its biomass source, allowing for a rapid start-up. Bench-scale treatment trials of winery wastewater confirm the WASHR process can reduce loadings on the downstream WWTP's liquid and solids treatment trains. A case study approach is used to confirm the economic viability and environmental sustainability of the WASHR process compared to direct co-treatment, using life-cycle cost analyses and greenhouse gas emissions estimates.

Longitudinal monitoring reveals the emergence and spread of blaGES-5-harboring carbapenem-resistant Klebsiella quasipneumoniae in a Hong Kong hospital wastewater discharge line

Testing hospital wastewater (HWW) is potentially an effective, long-term approach for monitoring trends in antimicrobial resistance (AMR) patterns in health care institutions. Over a year, we collected wastewater samples from the clinical and non-clinical sites of a tertiary hospital and from a downstream wastewater treatment plant (WWTP). We focused on the extent of carbapenem resistance among Enterobacteriaceae isolates given their clinical importance. Escherichia coli and Klebsiella spp. were the most frequently isolated Enterobacteriaceae species at all sampling sites. Additionally, a small number of isolates belonging to ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species), except K. pneumoniae, were detected. Of the 232 Klebsiella spp. isolates, 100 (43.1 %) were multi-drug resistant (MDR), with 46 being carbapenem-resistant. Most of these carbapenem-resistant isolates were K. quasipneumoniae (CRKQ) (n = 44). All CRKQ isolates were isolated from the wastewater of a clinical site that includes intensive care units, which also yielded significantly more multi-drug resistant isolates compared to all other sampling sites. Among the CRKQ isolates, blaGES-5 genes (n = 42) were the primary genetic determinant of carbapenem resistance. Notably, three different CRKQ isolates, collected within the same month in HWW and the influent and effluent flow of the WWTP, shared >99 % sequence similarity between their blaGES-5 genes and between their flanking regions and upstream integron-integrase region. The influent isolate was phylogenetically close to K. quasipnuemoniae isolates from wastewater collected in Japan. Its blaGES-5 gene and surrounding sequences were > 99 % identical to blaGES-24 genes found in the Japanese isolates. Our results suggest that testing samples from sites located closer to hospitals could support antibiotic stewardship programs compared to samples collected further downstream. Moreover, testing samples collected regularly from WWTPs may reflect the local and global spread of pathogens and their resistances.

Distinctive hospital and community resistomes in Scottish urban wastewater: Metagenomics of a paired wastewater sampling design

The wastewater microbiome contains a multitude of resistant bacteria of human origin, presenting an opportunity for surveillance of resistance in the general population. However, wastewater microbial communities are also influenced by clinical sources, such as hospitals. Identifying signatures of the community and hospital resistome in wastewater is needed for interpretation and risk analysis. In this study, we compare the resistome and microbiome of hospital, community, and mixed municipal wastewater to investigate how and why the composition of these different sites differ. We conducted shotgun metagenomic analysis on wastewater samples from eight wastewater treatment plants (WWTPs), four hospitals, and four community sites in Scotland, using a paired sampling design. Cluster analysis and source attribution random forest models demonstrated that the hospital resistome was distinct from community and WWTP resistomes. Hospital wastewater had a higher abundance and diversity of resistance genes, in keeping with evidence that hospitals act as a reservoir and enricher of resistance. However, this distinctive ‘hospital’ signature appeared to be weak in the resistome of downstream WWTPs, likely due to dilution. We conclude that hospital and community wastewater resistomes differ, with the hospital wastewater representing a reservoir of patient- and hospital environment-associated bacteria. However, this ‘hospital’ signature is transient and does not overwhelm the community signature in the resistome of the downstream WWTP influent.

Intersex manifestation in the rainbow darter (Etheostoma caeruleum): Are adult male fish susceptible to developing and recovering from intersex after exposure to endocrine active compounds?

For over a decade, intersex has been observed in rainbow darter (RD) (Etheostoma caeruleum) populations living downstream wastewater treatment plants (WWTPs) in the Grand River, Ontario, Canada. To further our understanding of intersex development in adult male fish, the current study addressed three objectives: i) can intersex be induced in adult male fish, ii) is there a specific window of exposure when adult male fish are more susceptible to developing intersex, and iii) can pre-exposed adult male fish recover from intersex? To assess intersex induction in adult male fish, wild male RD were exposed in the laboratory for 22 weeks (during periods of spawning, gonadal regression, and gonadal recrudescence) to environmentally relevant concentrations of 17α-ethinylestradiol (EE2) including nominal 0, 1, and 10 ng/L. Intersex rates and severity at 10 ng/L EE2 were similar to those observed historically in adult male populations living downstream WWTPs in the Grand River and confirmed previous predictions that 1–10 ng/L EE2 would cause these adverse effects. To assess a window of sensitivity in developing intersex, male RD were exposed to nominal 0, 1 or 10 ng/L EE2 for 4 weeks during three different periods of gonadal development, including (i) spawning, (ii) early recrudescence and (iii) late recrudescence. These short-term exposures revealed that intersex incidence and severity were greater when RD were exposed while gonads were fully developed (during spawning) compared to periods of recrudescence. To assess if RD recover from intersex, wild fish were collected downstream WWTPs in the Grand River and assessed for intersex both before and after a 22-week recovery period in clean water that included gonadal regression and recrudescence. Results showed that fish did not recover from intersex, with intersex rates and severity similar to those both before and after the transition to clean water. This study further advances our knowledge on intersex manifestation in adult male fish including their sensitivity to endocrine active compounds during different periods of their annual reproductive cycle and their limited ability to recover from intersex after onset of the condition.

Assessment of the Impact of a New Industrial Discharge on an Urban Wastewater Treatment Plant: Proposal for an Experimental Protocol

Assessing the compatibility of industrial discharges with the biological process of a municipal wastewater treatment plant (WWTP) may represent a critical task. Indeed, either focusing only on chemical characterization or ecotoxicity tests designed to assess the impact on surface waters may lead to questionable or misleading conclusions. The feasibility of an industrial connection to the sewer should better take into account the features of the downstream WWTP, in particular by studying the potential effects on the biomass of that specific plant. With this aim, a multi-step experimental protocol applicable by water utilities has been proposed: (step 1) calculation of the flow rate/load ratio between industrial discharge (ID) and urban wastewater (WW); (step 2) analysis of the modified operating conditions of the biological stage; (step 3) experimental assessment of the impact of the ID on the WWTP biomass by means of respirometric tests. An application of this protocol is presented in this work as a case study, namely a new ID (average flowrate 200 m3 d−1) coming from an aqueous waste treatment plant (AWTP) to be connected to the public sewer. The integrated evaluation of results showed that no negative impacts could be expected on the downstream urban activated sludge WWTP (treating a flow rate of around 45,000 m3 d−1).

Identifying influential priority of factors governing the acute biological toxicity of two kinds of industrial wastewaters

Abstract Identifying the key parameters or components mainly contributing to the acute toxicity of wastewater would be helpful to quickly and conveniently reflect their biological toxicity. In this study, the components/parameters and biological toxicity of 64 effluent samples collected from two factories producing konjac and glass were analyzed. It was found that the two types of wastewaters were not effectively dealt with. Moreover, the acute biological toxicity evaluated by the bioluminescence inhibition to Vibrio fischeri revealed that ∼90% of the effluents were marked as toxic with bioluminescence inhibition higher than 50%. By applying a grey relational analysis (GRA) method to investigate the influential priorities of the effluent characteristics on biological toxicity, the results demonstrated that the top four influential factors on the bioluminescence inhibition were as follows: TN ≈ SO42− > Cl− > As ≈ Hg (for konjac-manufacturing effluents) and Zn > SO42− ≈ TN > As > Cl− (for glass-producing effluents). These results would be useful for fast recognizing the biological toxicity features of industrial effluents via evaluating the most influential parameters, and helpful for reducing the biological acute toxicity to protect the downstream wastewater treatment plant from abrupt collapse.

Large spatiotemporal variability in metabolic regimes for an urban stream draining four wastewater treatment plants with implications for dissolved oxygen monitoring

Urbanization and subsequent expansion of wastewater treatment plant (WWTP) capacity has the potential to alter stream metabolic regimes, but the magnitude of this change remains unknown. Indeed, our understanding of downstream WWTP effects on stream metabolism is spatially and temporally limited, and monitoring designs with upstream-downstream comparison sites are rare. Despite this, and despite observed spatiotemporal variability in stream metabolic regimes, regulators typically use snapshot monitoring to assess ecosystem function in receiving streams, potentially leading to biased conclusions about stream health. To address these important practical issues, we assessed the spatiotemporal variability in stream metabolism at nine sites upstream and downstream of four WWTPs in a suburban stream. We used one year (2017–2018) of high-frequency dissolved oxygen (DO) data to model daily gross primary productivity (GPP) and ecosystem respiration (ER). We found that GPP was 1.7–4.0 times higher and ER was 1.2–7.2 times higher downstream of the WWTPs, especially in spring when light was not limited by canopy shading. Critically, we observed that these effects were spatially limited to the kilometer or so just downstream of the plant. These effects were also temporally limited, and metabolic rates upstream of WWTPs were not different from sites downstream of the plant after leaf-out at some sites. Across sites, regardless of their relation to WWTPs, GPP was positively correlated with potential incident light suggesting that light is the dominant control on GPP in this system. Temporal windowing of DO to proposed regulatory monitoring lengths revealed that the violation frequency of water quality criteria depended on both the monitoring interval and start date. We conclude that spatiotemporal variability in metabolism and DO are crucial considerations when developing monitoring programs to assess ecosystem function, and that evidence of WWTP effects may only arise during high light conditions and at limited scales.

Recovery of in-sewer dosed iron from digested sludge at downstream treatment plants and its reuse potential

Iron-based coagulants are dosed in enormous amounts and play an essential role in various segments of our urban water infrastructure. In order for the water industry to become circular, a closed-loop management strategy for iron needs to be developed. In this study, we have demonstrated for the first time that in-sewer dosed iron, either in the form of FeCl3 or ferric-based drinking water sludge (Fe-DWS) as a means to combat sewer corrosion and odour, can be recovered in the form of vivianite in digested sludge in down-stream wastewater treatment plants. Importantly, about 92 ± 2% of the in-sewer dosed Fe was estimated to be bound in vivianite in digested sludge. A simple insertion of Neodymium magnet allowed to recover 11 ± 0.2% and 15.3 ± 0.08% of the vivianite formed in the digested sludge of the in-sewer dosed iron in the form of FeCl3 and Fe-DWS, respectively. The purity of recovered vivianite ranged between 70 ± 5% and 49 ± 3% for in-sewer dosed FeCl3 and Fe-DWS, respectively. Almost complete (i.e. 98 ± 0.3%) separation of Fe in the form of ferrihydrite was achieved from vivianite after alkaline washing. Subsequent batch experiments demonstrated that the recovered ferrihydrite can be directly reused for efficient sulfide control in sewers. At a ferrihydrite-Fe:S molar ratio of 1.2:1, sewage dissolved sulfide concentrations was reduced from 15 mgS/L to below 0.5 mgS/L within 1 h of reaction. Overall, the results obtained in our study flag a first step for utilities towards a closed-loop iron-based coagulant management approach.

Opportunities for reducing coagulants usage in urban water management: The Oxley Creek Sewage Collection and Treatment System as an example

Iron and aluminium based coagulants are used in enormous amounts and play an essential role in urban water management globally. They are dosed at drinking water production facilities for the removal of natural organic matter. Iron salts are also dosed to sewers for corrosion and odour control, and at wastewater treatment plants (WWTPs) for phosphate removal from wastewater and hydrogen sulfide removal from biogas. A recent laboratory study revealed that iron dosed to sewers is available for phosphate and hydrogen sulfide removal in the downstream WWTP. This study demonstrates for the first time under real-life conditions the practical feasibility and effectiveness of the strategy through a year-long full-scale investigation. Over a period of 5 months, alum dosing at ∼190 kg Al/day to the bioreactor in a full-scale WWTP was stopped, while FeCl2 dosing at ∼160 kg Fe/day in the upstream network was commenced. Extensive sampling campaigns were conducted over the baseline, trial and recovery periods to investigate sulfide control in sewers and its flow-on effects on phosphate in WWTP effluent, H2S in biogas, as well as on the WWTP effluent hypochlorite disinfection process. A plant-wide mass balance analysis showed that the Fe2+ dosed upstream was effectively used for P removal in the activated sludge tanks, with an effluent phosphate concentration comparable to that in the baseline period (i.e. with alum dosing to the bioreactor). Simultaneously, hydrogen sulfide concentration in biogas decreased ∼43%, from 495 ± 10 to 283 ± 4 ppm. No effects on biological nitrogen removal and disinfection processes were observed. Both effluent phosphate and H2S in biogas increased in the recovery period, when in-sewer dosing of FeCl2 was stopped. X-ray diffraction failed to reveal the presence of vivianite in the digested sludge, providing strong evidence that thermal hydrolysis prevented the formation of vivianite during anaerobic digestion. The latter limits the potential for selective recovery of Fe and P through magnetic separation. Overall, our study clearly demonstrates the multiple beneficial reuse of iron in a real urban wastewater system and urges water utilities to adopt an integrated approach to coagulant use in urban water management.

Flow cytometry analysis of low/high DNA content (LNA/HNA) bacteria as bioindicator of water quality evaluation

Anthropogenic activities such as agriculture, industry and climate change have been creating an enormous pressure on freshwater ecosystems leading to its degradation. Because the Water Framework Directive (WFD; main EU instrument for ecological water quality assessment) is costly and time-consuming, the main goal of this study was to use the scoring by flow cytometry (FCM) of bacterial communities with high DNA content (HNA) and low DNA content (LNA), a fast and easy methodology, as bioindicators. To portray this study, 3 sampling sites of Caima river with different levels of environmental impact (site 1 – no anthropogenic impacted site; site 2 – downstream wastewater treatment plant and site 3 – downstream a deactivated mine) were analysed along the 4 seasons of the year 2017 (winter, spring, summer and autumn). The ecological status of the sampling sites was accessed following the methodology described by WFD and biotic index results obtained for macroinvertebrate and periphyton communities, as well as the BOD5, were compared with the bacterial community scored as HNA and LNA.Bacteria community analysis showed high bacteria density at site 2 corresponding to high amounts of organic input by the wastewater treatment plant. Also, HNA bacteria were found to be in higher quantities at site 2, related to an increase of nutrients, while LNA bacteria were more prominent in river headwater, corresponding to an oligotrophic environment. Correlations between biological indices and bacteria community composition were very strong, showing that bacteria communities may serve as indicators of water quality assessment. Although this FCM technique provide good responses, further investigations are needed to confirm the feasibility of this method.

Selection of performance reference compound (PRC) for passive sampling of pharmaceutical residues in an effluent dominated river

A passive sampling device, a polar organic chemical integrative sampler (POCIS), was used to monitor 13 pharmaceuticals and 8 transformation products in upstream and downstream wastewater treatment plant effluent. A POCIS laboratory calibration study was performed to determine uptake behavior and the effect of water flow on the sampling rate. Most compounds showed a linear accumulation, and the sampling rate values ranged from 0.031 to 0.559 L/day. The developed POCIS samplers were used in field experiments in a wastewater-impacted river. Using the calculated sampling rates, the time-weighted average concentration values were measured by three different approaches: (1) laboratory calibration sampling rates (2) performance reference compound (PRC) correction sampling rates and (3) field calibration sampling rates. Nine deuterated compounds (acetaminophen-d3, antipyrine-d3, sulfamethoxazole-d4, carbamazepine-d10, diclofenac acid-d4, clofibric acid-d4, bezafibrate-d6, ibuprofen-d3 and naproxen-d3) were studied as PRCs. Antipyrine-d3 was successfully tested as a PRC for sulfamethoxazole, ibuprofen, 2-hydroxy ibuprofen, diclofenac acid, 4-hydroxydiclofenac acid, carbamazepin, carbamazepin 10,11-epoxide, sulfadiazine, 1-naphthol, antipyrine, naproxen and 4-chlorobenzoic acid. Finally, the POCIS was used to monitor target compounds in river water and measure their attenuation. For most compounds, the POCIS attenuation results were not significantly different from those of the spot samples, which demonstrated that a POCIS with a PRC correction can determine the attenuation of organic micropollutants in rivers.

Simultaneous phosphorous and nitrogen recovery from source-separated urine: A novel application for fertiliser drawn forward osmosis

Re-thinking our approach to dealing with waste is one of the major challenges in achieving a more sustainable society. However, it could also generate numerous opportunities. Specifically, in the context of wastewater, nutrients, energy and water could be mined from it. Because of its exceptionally high nitrogen (N) and phosphorous (P) concentration, human urine is particularly suitable to be processed for fertiliser production. In the present study, forward osmosis (FO) was employed to mine the P and N from human urine. Two Mg2+-fertilisers, i.e. MgSO4 and Mg(NO3)2 were selected as draw solution (DS) to dewater synthetic non-hydrolysed urine. In this process, the Mg2+ reverse salt flux (RSF) were used to recover P as struvite. Simultaneously, the urea was recovered in the DS as it is poorly rejected by the FO membrane. The results showed that, after concentrating the urine by 60%, about 40% of the P and 50% of the N were recovered. XRD and SEM – EDX analysis confirmed that P was precipitated as mineral struvite. If successfully tested on real urine, this process could be applied to treat the urine collected in urban areas e.g., high-rise building. After the filtration, the solid struvite could be sold for inland applications whereas the diluted fertiliser used for direct fertigation of green walls, parks or for urban farming. Finally, reduction in the load of N, P to the downstream wastewater treatment plant would also ensure a more sustainable urban water cycle.

Model-based Management and Control of the Bioreactions in a Collection System

A fast, convenient and user-friendly modelling tool was used to model biochemical and physico-chemical processes in the collection system. With this new tool two case studies were investigated with different scopes and purposes: one with a focus on the integrated modelling of sewer and wastewater treatment plants (WWTP) and the other aiming at a large-scale sewer network. Scenario analysis was carried out under different chemical dosing strategies. The work proves that processes in sewers can cause a significant impact on a downstream WWTP, and the wastewater treatment process can be better managed and optimized with the help of sewer-WWTP integrated modelling. The tool can also identify hotspots of key indicators like total dissolved sulfide in a large-scale collection system. It is suggested that investigating the network from a wider perspective can help target key issues and regions.