Fate of contaminants of emerging concern in two wastewater treatment plants after retrofitting tertiary treatment for reduction of nitrogen discharge.

More and more previously designed wastewater treatment plants (WWTPs) are upgraded to tertiary treatment to meet the higher effluent discharge standards of conventional pollutants. Contaminants of emerging concern (CECs) can cause adverse effects on organisms and usually flow into WWTPs along with urban sewage. How the retrofitted WWTPs targeting conventional pollutants will influence the treatment efficiency of CECs is seldom discussed. This study investigates the removal of CECs in two full-scale newly retrofitted WWTPs (CD and JM WWTPs), containing high-efficiency sedimentation tank and denitrification deep bed filter for enhancing total nitrogen removal. The overall CEC removal efficiencies in the CD and JM WWTPs were 73.79 % and 93.63 %, respectively. Mass balance results indicated that CD WWTP and JM WWTP release a total of 36.89 and 88.58 g/d of CECs into the environment through effluent and excess sludge, respectively. Analysis of the concentration of CECs along the treatment process revealed most CECs were removed in the biological treatment units. The incorporation of newly constructed tertiary treatment proved beneficial for CEC removal and removed 2.93 % and 2.36 % CECs, corresponding to CEC removal of 2.92 and 27.49 g/d in the CD and JM WWTPs, respectively. The data of this study were further used to evaluate the suitability of the SimpleTreat model for simulating the fate of CECs in WWTPs. The predicted fraction of CECs discharged through the biological treatment effluent were generally within ten-fold difference from the measured results, highlighting its potential for estimating CEC removal in WWTPs.

Efficiency of pollutants removal in treated palm oil mill effluent (TPOME) using different concentrations of sodium alginate-immobilized Nannochloropsis sp. cells.

Palm oil mill effluent (POME) has high chemical oxygen demand (COD), thus requires effective treatments to environmentally benign levels before discharge. In this study, immobilized microalgae cells are used for removing pollutants in treated palm oil mill effluent (TPOME). Different ratios of microalgae beads to TPOME concentration were examined at 1:2.5, 1:5, and 1:10. The biomass concentration and COD removal were measured through a standard method. The color of the cultivated microalgae beads changed from light green to darker green after the POME treatment for 9 days, hence demonstrating that microalgae cells were successfully grown inside the beads with pH up to 9.84. The immobilized cells cultivated in the POME at 1:10 achieved a higher biomass concentration of 1.268 g/L and a COD removal percentage of 72% than other treatment ratios. The increment of the ratio of microalgae cells beads to POME concentration did not cause any improvement in COD removal efficiency. This was due to the inhibitory effect of self-shading resulting in the slow growth rate of microalgae cells which responsible for low COD removal. Therefore, this system could be a viable technology for simultaneous biomass production and POME treatment. This will contribute to research efforts toward the development of new and improved technologies in treating POME.

Pulp mill sludge-derived carbon activated with an alternative source of chemicals and its application in wastewater treatment - An approach for byproducts valorization.

The purpose of this study was to investigate pulp mill by-products valorization through activated carbon (AC) production and its application in wastewater treatment. Bio-sludge is a known promising precursor for AC production. The mill's chemical recovery stage generates an effluent (electrostatic precipitator ash leachate - EPAL) with high levels of potassium and sodium, which motivate studies regarding its viability as a chemical source for carbon activation. Bio-sludge and EPAL are problematic by-products and this research line would allow their return to the productive chain, as an adsorbent for the wastewater treatment. Two carbonization heating rates (3.5, 15 °C/min), three activation agents (NaOH, KOH, EPAL) and two activator:bio-sludge ratios (1:1, 2:1) were used for AC production. The best ACs in terms of surface area were those produced at 3.5 °C/min, with KOH or EPAL in 2:1 proportion. ACs produced under these conditions and commercial activated carbon (CAC) were used in adsorption tests with industrial wastewater. For color removal, KOH-activated carbon presented the greatest efficiency (80.45 %), followed by CAC (76.74 %) and EPAL-activated carbon (70.13 %). For COD removal, EPAL-activated carbon presented greater efficiency (53.49 %), followed by CAC (40.84 %) and KOH-activated carbon (36.86 %). Freundlich's model best described the experimental adsorption data. The KOH results were expected to be satisfactory, since KOH is proven to be effective for carbon activation. The EPAL-activated carbon results were remarkable, especially for COD removal, showing that EPAL can be used as an activator and that the by-products have potential for valorization according to the circular economy principles.

Horizontal subsurface flow constructed wetland for tertiary treatment of dairy wastewater: Removal efficiencies and plant uptake.

There are different physicochemical and biological methods to treat effluents. However, their efficiency is not enough to meet the effluents discharge limits. For this reason, it could be possible to employ a polished treatment. A suitable alternative for this goal could be constructed wetlands (CWs). The aim of the present research was to evaluate contaminants removal efficiency of a pilot scale horizontal subsurface flow constructed wetland (HSSFW) for tertiary treatment of dairy wastewater. A vegetation study was also conducted in order to determine the role of plants on nutrient removal. A pilot scale HSSFW planted with Typha domingensis was built in a dairy factory, after the biological treatment. The substrate used was river gravel. During a seven-month research period, thirty-two samples (influent and effluent) were taken and analyzed to determine physicochemical and microbiological parameters as well as removal efficiencies. Biomass, TP, TKN and organic matter content in plants was determined at the beginning and end of the monitoring period. Suspended solids showed significant differences between inlet and outlet, with a mean removal efficiency of 78.4%. For BOD and COD, mean removal efficiencies were respectively 57.9 and 68.7%. Removal percentages for TKN, Nitrates and TP were lower than other parameters (25.7%, 47.8% and 29.9%, respectively). Fecal Coliform bacteria decreased one order of magnitude in final effluent. In the case of Escherichia coli and Pseudomona aeruginosa results were variable. Total biomass increased 4.6 times at the end of the monitoring period. The study of plants indicated its important contribution in terms of contaminant uptake and retention. HSSFW would be an advisable alternative as a tertiary treatment of dairy wastewater.

Xenobiotics metabolization in Salix alba leaves uncovered by mass spectrometry imaging.

INTRODUCTION: Micropollutants are increasingly monitored as their presence in the environment is rising due to human activities, and they are potential threats to living organisms. OBJECTIVES: This study aimed at understanding the role of plants in xenobiotics removal from polluted environments by following xenobiotics metabolism in leaf tissues. METHODS: Different classes of micropollutants were investigated using liquid chromatography (LC) coupled to quadrupole-time of flight (Q-TOF) high resolution mass spectrometry (HRMS). The tissue localization of xenobiotics in the leaves of a spontaneous (not planted by humans) Salix alba growing near the water flux was further investigated using matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI). RESULTS: The LC-Q-TOF analysis revealed the distribution of micropollutants in three different compartments of a tertiary treatment wetland. When further investing the metabolic profile of S. alba leaves using MSI, different distribution patterns were observed in specific leaf tissues. Xenobiotic metabolites were predicted and could also be tentatively identified in S. alba leaves, shedding new light on the metabolic processes at play in leaves to manage xenobiotics uptake from a polluted environment. CONCLUSION: Using complementary metabolomics approaches, this study performed a large-scale exploration of micropollutants spreading in the environment at the exit of a tertiary treatment wetland. The use of MSI coupled with the prediction of xenobiotic metabolites yielded novel insights into plant metabolism during chronical exposure to low doses of a mixture of micropollutants.

Improving small-scale wastewater treatment plant performance by using a filtering tertiary treatment unit.

The demand for wastewater treatment plants purposed for a single household or groups of households continues to increase as the quality requirements for wastewater treatment become increasingly rigorous. Researchers are constantly searching for new methods to remove phosphorus compounds from wastewater that do not require the use of chemicals. This article describes a newly designed tertiary wastewater treatment unit that increases the effectiveness of the main small-scale (up to 1 m3/d) biological wastewater treatment unit. The tertiary treatment unit is filled with the sorbent material Filtralite P., after the main treatment wastewater flows through the filler without the use of electric power. A compact system consisting of a main (secondary) treatment unit and the newly designed tertiary wastewater treatment unit was tested in accordance with the harmonised European Standard EN 12566-3. During the testing period, no surplus sludge was discharged from the system, no reagents were dosed into it, the system only consumed 119 kW of electric power, and the treated wastewater contained <1 mg/L of phosphorus. The total wastewater treatment efficiency can be explained as follows: COD - 95.2%, BOD5 - 99.2%, SS - 99.4%, NH4-N - 99.6%, Nt - 82.2%, and Pt - 91.8%. The system is efficient, the operational cost is relatively low, it does not use chemical reagents, and it is environment friendly.

Feasibility study of vertical flow constructed wetland for tertiary treatment of nanosilver wastewater and temporal-spatial distribution of pollutants and microbial community.

Silver nanoparticles (AgNPs) have the potential to cause negative effects on nutrient removal in constructed wetlands (CWs), further leading to the deterioration of the water. The current work aimed to investigate the feasibility of vertical flow CW (VFCW) for tertiary treatment of AgNPs wastewater, temporal-spatial distribution of pollutants, and microbial community after 450-day exposure. Results reveal that the effluent of VFCW could still meet the discharge limits except the slightly excessive concentration of phosphorus (>0.5 mg/L) from day 390, with the average removal efficiencies of 83%, 61%, 42%, 70%, and 66% for the chemical oxygen demand, total nitrogen, ammonia nitrogen, total phosphorus, and soluble orthophosphate during 450 days, respectively. Results show that AgNPs removal was relatively stable over time, up to 96%. The temporal-spatial analysis reveals that all contaminants were mainly retained in the soil layer. The Ag concentrations in the upper soil layer and plant roots were higher than that in the lower soil layer and plant stems and leaves, respectively. Microbial sequencing analysis reveals the significant differences in the microbial community at different depths on day 450, with the dominant phyla of Proteobacteria, Acidobacteria, Chloroflexi and Bacteroidetes, and dominant genera of Halomonas and Pseudomonas. These results provide much needed knowledge for the implementation of ecological technologies for AgNPs and nutrient removal simultaneously.

DairyWater: striving for sustainability within the dairy processing industry in the Republic of Ireland.

This Review describes the objectives and methodology of the DairyWater project as it aims to aid the Irish dairy processing industry in achieving sustainability as it expands. With the abolition of European milk quotas in March 2015, the Republic of Ireland saw a surge in milk production. The DairyWater project was established in anticipation of this expansion of the Irish dairy sector in order to develop innovative solutions for the efficient management of water consumption, wastewater treatment and the resulting energy use within the country's dairy processing industry. Therefore, the project can be divided into three main thematic areas: dairy wastewater treatment technologies and microbial analysis, water re-use and rainwater harvesting and environmental assessment. In order to ensure the project remains as relevant as possible to the industry, a project advisory board containing key industry stakeholders has been established. To date, a number of large scale studies, using data obtained directly from the Irish dairy industry, have been performed. Additionally, pilot-scale wastewater treatment (intermittently aerated sequencing batch reactor) and tertiary treatment (flow-through pulsed ultraviolet system) technologies have been demonstrated within the project. Further details on selected aspects of the project are discussed in greater detail in the subsequent cluster of research communications.

Heterogeneous photocatalysis using TiO2 modified with hydrotalcite and iron oxide under UV-visible irradiation for color and toxicity reduction in secondary textile mill effluent.

The objective of this study was to evaluate ADMI color removal from a biologically treated textile mill effluent by heterogeneous photocatalysis with UV-visible irradiation (UV-vis) using a novel catalyst composed of TiO2 supported on hydrotalcite and doped with iron oxide (HT/Fe/TiO2). Simulated biological treatment of solutions of the dyes (50 mg/L) used in the greatest amounts at the mill where the textile effluent was collected resulted in no color removal in reactive dye solutions and about 50% color removal in vat dye solutions, after 96 h, indicating that the secondary effluent still contained a large proportion of anionic reactive dyes. Photocatalytic treatments were carried out with TiO2 and HT/Fe/TiO2 of Fe:Ti molar ratios of 0.25, 0.5, 0.75 and 1, with varying catalyst doses (0-3 mg/L), initial pH values (4-10) and UV-vis times (0-6 h). The highest ADMI color removal with unmodified TiO2 was found at a dose of 2 g/L and pH 4, an impractical pH value for industrial application. The most efficient composite was HT/Fe/TiO2 1 at pH 10, also at a dose of 2 g/L, which provided more complete ADMI color removal, from 303 to 9 ADMI color units (96%), than unmodified TiO2, from 303 to 37 ADMI color units (88%), under the same conditions. Hydroxyl radicals were responsible for the color reduction, since when 2-propanol, an OH scavenger, was added color removal was very low. For this reason, the HT/Fe/TiO2 1 composite performed better at pH 10, because the higher concentration of hydroxide ions present at higher pH favored hydroxyl radical formation. COD reductions were relatively low and similar, approximately 20% for both catalysts after 6 h under UV-vis, because of the low initial COD (78 mg/L). Secondary effluent toxicity to Daphnia similis (EC50 = 70.7%) was reduced by photocatalysis with TiO2 (EC50 = 95.0%) and the HT/Fe/TiO2 1 composite (EC50 = 78.6%). HT/Fe/TiO2 1 was reused five times and still lowered secondary effluent ADMI color below local discharge limits. Benefits of the HT/Fe/TiO2 1 catalyst compared to TiO2 include its lower bandgap energy (2.34 eV vs 3.25 eV), higher ADMI color removal and its magnetic nature that facilitated its recovery and would reduce treatment costs.

Ferrous ions reused as catalysts in Fenton-like reactions for remediation of agro-food industrial wastewater.

Cassava is the most important tuberous root in tropical and subtropical regions of the world, being the third largest source of carbohydrates. The root processing is related to the production of starch, an important industrial input, which releases a highly toxic liquid wastewater due to its complex composition, which inhibits high performances of conventional effluent treatments. This study aims to evaluate Fenton-like and photo-Fenton-like reactions for treatment of cassava wastewater, reusing ferrous ions from the preliminary coagulation stage. Pre-treated cassava wastewater was submitted to oxidation in three variations of hydrogen peroxide concentrations, with more relevant analytical responses verified in color, turbidity, COD (Chemical Oxygen Demand), and acute toxicity in Artemia salina, besides the action of radicals during Fenton-like reactions. At higher peroxide concentrations, a decrease of 68% in turbidity and 70% in COD on the photo-Fenton-like system was observed, even at slow reaction rates (fastest rate constant k = 2 × 10-4 min-1). Inclusion of UV increases the viability of the Fenton-like reactions by supplementing the reaction medium with hydroxyl radicals, verified by the tert-butanol tests. The oxidation process leads to high EC50 values in 24 h of incubation in Fenton-like reactions and 48 h in photo-Fenton-like reactions. Final COD and turbidity suggests that the reuse of iron, which remains in the preliminary treatment step shows a great potential as a catalyst for Fenton-like advanced oxidation processes. Tertiary treatment can be less expensive and harmful to the environment, reducing production of residual sludge and metal content in the final effluent, which reduces polluting potential of the effluent regarding solid waste.

Application of heterogeneous catalytic ozonation as a tertiary treatment of effluent of biologically treated tannery wastewater.

The present study employed a Mn-Cu/Al2O3 heterogeneous catalytic ozonation process for tertiary treatment of actual tannery wastewater, focusing on its feasibility in that application. The primary factors affecting the removal efficiency of organic pollutants were investigated, including catalyst dosage, ozone dosage, and initial pH value. The experimental results showed that the addition of a Mn-Cu/Al2O3 catalyst improved the removal efficiency of chemical oxygen demand (COD) during ozonation, which initiated a 29.3% increase for COD removal, compared to ozonation alone after 60 min. The optimum pH, catalyst dosage, and ozone dosage were determined to be 7.0, 2.0 g/L, and 0.3 g/h, respectively. Under these conditions, following 60 min of reaction, the COD removal efficiency and the concentration in effluent were 88%, and 17 mg/L, respectively. In addition, the presence of tert-butanol (a well known hydroxyl radical scavenger) strongly inhibited COD removal via Mn-Cu/Al2O3 catalytic ozonation, indicating that the Mn-Cu/Al2O3 catalytic ozonation process follows a hydroxyl radical (OH·) reaction mechanism. The Mn-Cu/Al2O3 catalyst exhibited good stability and reusability. Finally, the kinetic analysis revealed that the apparent reaction rate constant of COD removal with the Mn-Cu/Al2O3 catalytic ozonation system (0.0328 min(-1)) was 2.3 times that of an ozonation system alone (0.0141 min(-1)). These results demonstrated that the catalytic ozonation using Mn-Cu/Al2O3 is an effective and promising process for tertiary treatment of tannery effluent in biological systems.

Conventional methods and emerging wastewater polishing technologies for palm oil mill effluent treatment: a review.

The Malaysian palm oil industry is a major revenue earner and the country is ranked as one of the largest producers in the world. However, growth of the industry is synonymous with a massive production of agro-industrial wastewater. As an environmental protection and public health concern, the highly polluting palm oil mill effluent (POME) has become a major attention-grabber. Hence, the industry is targeting for POME pollution abatement in order to promote a greener image of palm oil and to achieve sustainability. At present, most palm oil mills have adopted the ponding system for treatment. Due to the successful POME pollution abatement experiences, Malaysia is currently planning to revise the effluent quality standards towards a more stringent discharge limits. Hence, the current trend of POME research focuses on developing tertiary treatment or polishing systems for better effluent management. Biotechnologically-advanced POME tertiary (polishing) technologies as well as other physicochemical methods are gaining much attention as these processes are the key players to push the industry towards the goal of environmental sustainability. There are still ongoing treatment technologies being researched and the outcomes maybe available in a while. However, the research completed so far are compiled herein and reported for the first time to acquire a better perspective and insight on the subject with a view of meeting the new standards. To this end, the most feasible technology could be the combination of advanced biological processes (bioreactor systems) with extended aeration, followed by solids separation prior to discharge. Chemical dosing is favoured only if effluent of higher quality is anticipated.

Removal of phosphorus from trickling filter effluent by electrocoagulation.

As regulatory requirements for contaminants in wastewater discharged to the environment get stricter, alternative or additional treatment processes to those already being used are necessary. One contaminant of particular concern associated with discharging treated municipal wastewater to a receiving water body is phosphorus (P). A continuous scale electrocoagulation (EC) system was investigated as an alternative to conventional chemical addition for P removal from municipal wastewater. The EC process was optimized for iron dose delivery by changing the electrical current, electrode spacing and the reactor contact time, and a comparison was made with conventional ferric dosing through jar testing. Results showed that EC could achieve P removal to meet a P consent of 1 mg L⁻¹ at a dose of 154 mg L⁻¹ Fe. The process was shown to provide a supplementary benefit for chemical and biological oxygen demand removal of 86% and 82%, respectively, but gave no significant removal of other sanitary pollutants. When compared directly with conventional iron dosing, EC required approximately twice the iron dose. When electrical costs were also factored into the comparison, EC was shown to be approximately double the cost of conventional dosing and at present is not a feasible alternative to conventional coagulation using ferric chloride.

Efficient treatment of secondary treated refinery wastewater using sand biofiltration: Removal of hazardous organic pollutants.

This study explored the potential of sand biofiltration for tertiary treatment of real refinery wastewater. The biofilter (2 cm (I.D.) x 15 cm (L)) operated on secondary treated refinery wastewater at flow rate of 1 mL/min had empty bed contact time (EBCT) of 47.12 min for one circulation. Maximum reduction in COD after 4, 8 and 12 times recirculation was 25 %, 52 % and 56 %; while the TOC reduction was 33 %, 43 % and 51 %, respectively, after biofilm development over 30 days. Quantification using two dimensional gas chromatography - time of flight mass spectrometry (GCxGC-TOF MS) revealed that several of the identified target compounds could not be detected in the wastewater after 12 recirculations. After 8 times recirculation, most of the compounds showed very high removal efficiency. For biofiltration over the flow rate range 2-10 mL/min, the reduction in COD and NH4+-N ranged from 62-73 % and 78-86 %, respectively, after 8 times recirculation. The nitrite concentration first increased and subsequently decreased, while the nitrate concentration continuously increased with increase in the number of recirculations. Solid phase micro-extraction (SPME) analysis of the aqueous phase using GCxGC-TOF MS and a semi-quantitative approach indicated that the removal of predominant classes of compounds was greater than 95 % after 8 times recirculation, with maximum reduction occurring in the first pass through the biofilter. Assimilable organic carbon (AOC) reduction was 98 % after 8 times recirculation. Metagenomic analysis revealed that Proteobacteria was the most dominant phylum in the biofilter. Many known polynuclear aromatic hydrocarbon (PAH) degraders, such as Sphingomonadales, Burkholderiales, Rhodobacterales and Rhodospirillales, were found in the biofilter leading to high removal efficiency of hazardous organic pollutants.

An evaluation of conventional and nature-based technologies for controlling antibiotic-resistant bacteria and antibiotic-resistant genes in wastewater treatment plants.

Antibiotic resistance is a globally recognized health concern which leads to longer hospital stays, increased morbidity, increased mortality, and higher medical costs. Understanding how antibiotic resistance persists and exchanges in environmental systems like soil, water, and wastewater are critically important for understanding the emergence of pathogens with new resistance profiles and the subsequent exposure of people who indirectly/directly come in contact with these pathogens. There are concerns about the widespread application of prophylactic antibiotics in the clinical and agriculture sectors, as well as chemicals/detergents used in food and manufacturing industries, especially the quaternary ammonium compounds which have been found responsible for the generation of resistant genes in water and soil. The rates of horizontal gene transfer increase where there is a lack of proper water/wastewater infrastructure, high antibiotic manufacturing industries, or endpoint users - such as hospitals and intensive agriculture. Conventional wastewater treatment technologies are often inefficient in the reduction of ARB/ARGs and provide the perfect combination of conditions for the development of antibiotic resistance. The wastewater discharged from municipal facilities may therefore be enriched with bacterial communities/pathogens and provide a suitable environment (due to the presence of nutrients and other pollutants) to enhance the transfer of antibiotic resistance. However, facilities with tertiary treatment (either traditional/emerging technologies) provide higher rates of reduction. This review provides a synthesis of the current understanding of wastewater treatment and antibiotic resistance, examining the drivers that may accelerate their possible transmission to a different environment, and highlighting the need for tertiary technologies used in treatment plants for the reduction of resistant bacteria/genes.

Second life of water and wastewater in the context of circular economy - Do the membrane bioreactor technology and storage reservoirs make the recycled water safe for further use?

In recent years water demand drastically increased which is particularly evident in tourism-burdened mountain regions. In these areas, climate neutral circular economy strategies to minimize human impact on the environment can be successfully applied. Among these strategies, treated wastewater reuse and retaining water in storage reservoirs deserve particular attention. This study aimed to determine if recycled water produced with two circular economy systems, namely membrane bioreactor treatment plant (MBR) with UV-light effluent disinfection and a storage reservoir, is safe enough for further use in green areas irrigation in summer and artificial snow production in winter. The assessment was based on the presence and concentration of antimicrobial agents, antibiotic resistant bacteria, antibiotic resistance genes, bacterial community composition and diversity. The treated water and wastewater was compared with natural water in their vicinity. Both systems fulfill the criteria set by the European Union in terms of reclaimed water suitable for reuse. Although the MBR/UV light wastewater treatment substantially reduced the numbers of E. coli and E. faecalis (from e.g. 32,000 CFU/100 ml to 20 CFU/100 ml and 15,000 CFU/100 ml to nearly 0 CFU/ml), bacteria resistant to ampicillin, aztreonam, cefepime, ceftazidime, ertapenem and tigecycline, as well as ESBL-positive and multidrug resistant E. coli were highly prevalent in MBR-treated wastewater (88.9 %, 55.6 %, 33.3 %, 22.2 % and 11.1 % and 44.4 and 55.6 %, respectively). Applying additional tertiary treatment technology is recommended. Retaining water in storage reservoirs nearly eliminated bacterial contaminants (e.g. E. coli dropped from 350 CFU/100 ml to 10 CFU/100 ml), antibiotic resistant bacteria, resistance genes (none detected in the storage reservoir) and antibiotics (only enrofloxacin detected once in the concentration of 3.20 ng/l). Findings of this study point to the limitations of solely culture-based assessment of reclaimed water and wastewater while they may prove useful in risk management and prevention in wastewater reuse.

Tertiary treatment of municipal wastewater in an IBFR dominated by PD/A with unique niche.

To explore the feasibility of biofilter reactor to treat municipal secondary effluent deeply without extra carbon source, this paper proposed an integrated biofilter reactor (IBFR) coupling partial denitrification (PD) with anammox (A) to treat the secondary effluent and raw sewage with the flow ratio of 3:1 together. The results show that the effluent concentration of TN and COD in IBFR could be reduced to 10 mg/L and 15 mg/L, respectively, under hydraulic retention time of 1.5 h and nitrogen loading rate of 0.55 kg/(m3·d). The highest specific anammox activity (19.2 mg N/(g TVS·d)) and the maximum extracellular polymeric substance (EPS) content (107.21 mg/g TVS) occurred at the 25-50 cm section of IBFR, where Thauera, Candidatus Anammoximicrobium and Candidatus Brocadia were the dominant denitrifiers and anammox bacteria. Furthermore, the cyclic self-stratification occurred along the reactor height, where the utilization, decomposition, transformation and cross-feeding of EPS enhanced the performance stability of nitrogen and carbon removal, strengthened the niche structure and promoted the synergistic symbiosis. In conclusion, IBFR coupling PD and A demonstrated the possibility to treat secondary effluent without additional carbon sources, which is expected as an alternative approach for tertiary treatment of municipal wastewater.

Assessment of the properties of aging biochar used as a substrate in constructed wetlands.

Biochar has gained global recognition as an effective tool for environmental remediation, and is increasingly being used as an alternative substrate in constructed wetlands (CWs). While, most studies have focused on the positive effects of biochar for the pollutant removal in CWs, less is known about aging and longevity of the embedded biochar. This study investigated the aging and stability of biochar embedded in CWs post-treating the effluent of a municipal and an industrial wastewater treatment plant. Litter bags containing biochar were inserted into two aerated horizontal subsurface flow CWs (350 m2 each), and retrieved on several dates (8-775 days after burial) for assessment of weight loss/gain and changes in biochar characteristics. Additionally, a 525-day laboratory incubation test was conducted to analyze biochar mineralization. The results showed that there was no significant biochar weight loss over time, but a slight increase in weight (2.3-3.0%) was observed at the end, likely due to mineral sorption. Biochar pH remained stable except for a sudden drop at the beginning (8.6-8.1), while the electrical conductivity continued to increase (96-256 µS cm-1) throughout the experiment. The sorption capacity of the aged biochar for methylene blue significantly increased (1.0-1.7 mg g-1), and a change in the biochar's elemental composition was also noted, with O-content increasing by 13-61% and C content decreasing by 4-7%. Despite these changes, the biochar remained stable according to the criteria of the European Biochar Foundation and International Biochar Initiative. The incubation test also showed negligible biochar mass loss (<0.02%), further validating the stability of the biochar. This study provides important insights into the evolution of biochar characteristics in CWs.

Continuous solar photo-Fenton for wastewater reclamation in operational environment at demonstration scale.

For the first time, a continuous flow solar photo-Fenton demonstration plant has been assessed for wastewater reclamation according to the EU 2020/741 regulation. The treated water qualities achieved under two operating strategies (acidic and neutral pH) in a 100-m2 raceway pond reactor were explored in terms of liquid depth, iron source, reagent concentrations, and hydraulic residence time over three consecutive days of operation. The results obtained at acidic pH showed removal percentages of contaminants of emerging concern (CECs) > 75% and water quality classes B, C and D according to EU regulation at both assessed operating conditions, with treatment capacities up to 1.92 m3 m-2 d-1. At neutral pH with ferric nitrilotriacetate (Fe3+-NTA), 50% of CEC removal and only water quality class D were achieved with the most oxidizing condition assessed, giving a treatment capacity of 0.80 m3 m-2 d-1. The treatment capacities obtained in this work, which have never been achieved with solar water treatments, demonstrate the potential of this technology for commercial-scale application.

The efficiency of full-scale subsurface constructed wetlands with high hydraulic loading rates in removing pharmaceutical and personal care products from secondary effluent.

Constructed wetlands (CWs) are usually operated at low hydraulic load rates (HLRs) of < 0.5 m3/m2/d, and can efficiently remove pharmaceuticals and personal care products (PPCPs) from wastewaters. They however often occupy a large area of land, especially when treating the secondary effluent from wastewater treatment plants (WWTPs) in megacities. High-load CWs (HCWs) with an HLR ≥ 1 m3/m2/d, requiring smaller land areas, are a good option for urban areas. However, their performance for PPCP removal is not clear. In this study, we evaluated the performance of three full-scale HCWs (HLR: 1.0-1.3 m3/m2/d) to remove 60 PPCPs, and found they had a stable removal performance and a higher areal removal capacity than the previously reported CWs operated at low HLRs. We verified the advantages of HCWs by testing the efficiency of two identical CWs at a low HLR (0.15 m3/m2/d) and a high HLR (1.3 m3/m2/d) fed with the same secondary effluent. The areal removal capacity during the high-HLR operation was 6-9 times higher than that during the low-HLR operation. A high dissolved oxygen content, and low COD and NH4-N concentrations in the secondary effluent were critical for the robust PPCP removal by tertiary treatment HCWs.