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Gholami M, O'Sullivan AD, Mackey HR. Nutrient treatment of greywater in green wall systems: A critical review of removal mechanisms, performance efficiencies and system design parameters. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 345:118917. [PMID: 37688961 DOI: 10.1016/j.jenvman.2023.118917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 08/28/2023] [Accepted: 08/29/2023] [Indexed: 09/11/2023]
Abstract
Greywater has lower pathogen and nutrient levels than other mixed wastewaters, making it easier to treat and to reuse in nature-based wastewater treatment systems. Green walls (GWs) are one type of nature-based solutions (NBS) that are evolving in design to support on-site and low-cost greywater treatment. Greywater treatment in GWs involves interacting and complex physical, chemical, and biological processes. Design and operational considerations of such green technologies must facilitate these pivotal processes to achieve effective greywater treatment. This critical review comprehensively analyses the scientific literature on nutrient removal from greywater in GWs. It discusses nutrient removal efficiency in different GW types. Total nitrogen removal ranges from 7 to 91% in indirect green facades (IGF), 48-93% for modular living walls (MLW), and 8-26% for continuous living walls (CLW). Total phosphorus removal ranges from 7 to 67% for IGF and 2-53% for MLW. The review also discusses the specific nutrient removal mechanisms orchestrated by vegetation, substrates, and biofilms to understand their role in nitrogen and phosphorus removal within GWs. The effects of key GW design parameters on nutrient removal, including substrate characteristics, vegetation species, biodegradation, temperature, and operating parameters such as irrigation cycle and hydraulic loading rate, are assessed. Results show that greater substrate depth enhances nutrient removal efficiency in GWs by facilitating efficient filtration, straining, adsorption, and various biological processes at varying depths. Particle size and pore size are critical substrate characteristics in GWs. They can significantly impact the effectiveness of physicochemical and biological removal processes by providing sufficient pollutant contact time, active surface area, and by influencing saturation and redox conditions. Hydraulic loading rate (HLR) also impacts the contact time and redox conditions. An HLR between 50 and 60 mm/d during the vegetation growing season provides optimal nutrient removal. Furthermore, nutrient removal was higher when watering cycles were customized to specific vegetation types and their drought tolerances.
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Affiliation(s)
- Moeen Gholami
- Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
| | - Aisling D O'Sullivan
- Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand; Centre for Ecological Technical Solutions (CELTS.org.nz), University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand.
| | - Hamish R Mackey
- Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand.
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Hassan N, Lezy J, Parmentier D, Van Hulle SWH. Electrocoagulation flotation as a municipal wastewater (pre-)treatment technology: Effect of weather conditions and current density. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 345:118906. [PMID: 37660424 DOI: 10.1016/j.jenvman.2023.118906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 08/11/2023] [Accepted: 08/27/2023] [Indexed: 09/05/2023]
Abstract
Electrocoagulation (EC) is a promising compact alternative technology, despite its viability in municipal wastewater treatment (MWWT) is currently challenged by its energy-intensive and batch-mode operation. This study introduces an innovative continuous electrocoagulation flotation (ECF) design for MWWT. ECF shows promising pollutant removal efficiencies, with identical results using both iron (Fe) and aluminum (Al) anodes. At a current density (CD) of 120 A/m2, it achieved significant removals: 90% tCOD, 98% TP, 94% TSS, 60% BOD5, and 40% TN. Designed ECF is proposed as a pre-treatment step due to limited TN removal. The study investigated optimal ECF performance under varying weather conditions using CD ranges of 40, 80, and 120 A/m2. Both Fe and Al ECF outperformed in treating rainy weather (RW) and dry weather (DW) municipal wastewater (MWW). However, Al anode's super-faradaic behavior resulted in higher residual concentrations in effluent, (i.e., an average of 6.53-33.7 mg/L), and operational costs compared to Fe ECF. Optimized Fe ECF setting needs to be changed depending in the weather variation. Fe ECF achieved high removal rates for tCOD (94%) and TP (95%) in RW MWW at a low CD of 40 A/m2. Comparative to this, the optimum CD for treated DW MWW was between 40 and 80 A/m2, removing tCOD (71-73%) and TP (85-95%). Specifically, at these conditions, the operational expenses were respectively 0.47 ± 0.03 €/m3 (RW MWW), and 0.37 ± 0.02 €/m3 to 0.81 ± 0.04 €/m3 (DW MWW). Moreover, ECF enables resource recovery and a circular economy through anaerobic sludge digestion, with Fe ECF generating more biogas than Al.
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Affiliation(s)
- Nazia Hassan
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens-Latemlaan 2B/5, 8500, Kortrijk, Belgium; Environmental Science Discipline, Khulna University, Khulna, 9208, Bangladesh.
| | - Jente Lezy
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens-Latemlaan 2B/5, 8500, Kortrijk, Belgium; Hello water, Kastanjeboomstraat 13, 8550, Zwevegem, Belgium
| | - Dries Parmentier
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens-Latemlaan 2B/5, 8500, Kortrijk, Belgium; Noah Water Solutions bvba, Burchtweg 7, B-9890, Gavere, Belgium
| | - Stijn Wim Henk Van Hulle
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens-Latemlaan 2B/5, 8500, Kortrijk, Belgium
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Mosquera-Romero S, Ntagia E, Rousseau DP, Esteve-Núñez A, Prévoteau A. Water treatment and reclamation by implementing electrochemical systems with constructed wetlands. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2023; 16:100265. [PMID: 37101565 PMCID: PMC10123341 DOI: 10.1016/j.ese.2023.100265] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 03/09/2023] [Accepted: 03/13/2023] [Indexed: 06/19/2023]
Abstract
Seasonal or permanent water scarcity in off-grid communities can be alleviated by recycling water in decentralized wastewater treatment systems. Nature-based solutions, such as constructed wetlands (CWs), have become popular solutions for sanitation in remote locations. Although typical CWs can efficiently remove solids and organics to meet water reuse standards, polishing remains necessary for other parameters, such as pathogens, nutrients, and recalcitrant pollutants. Different CW designs and CWs coupled with electrochemical technologies have been proposed to improve treatment efficiency. Electrochemical systems (ECs) have been either implemented within the CW bed (ECin-CW) or as a stage in a sequential treatment (CW + EC). A large body of literature has focused on ECin-CW, and multiple scaled-up systems have recently been successfully implemented, primarily to remove recalcitrant organics. Conversely, only a few reports have explored the opportunity to polish CW effluents in a downstream electrochemical module for the electro-oxidation of micropollutants or electro-disinfection of pathogens to meet more stringent water reuse standards. This paper aims to critically review the opportunities, challenges, and future research directions of the different couplings of CW with EC as a decentralized technology for water treatment and recovery.
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Affiliation(s)
- Suanny Mosquera-Romero
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, B-9000, Ghent, Belgium
- ESPOL Polytechnic University, Escuela Superior Politécnica del Litoral, ESPOL, Facultad de Ciencias Naturales y Matemáticas, BOX9050, Ecuador
- Department of Green Chemistry and Technology, Ghent University, Sint-Martens-Latemlaan 2B, B-8500, Kortrijk, Belgium
- Centre for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9000, Ghent, Belgium
| | - Eleftheria Ntagia
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, B-9000, Ghent, Belgium
- Université Paris-Saclay, INRAE, PROSE, 92160, Antony, France
| | - Diederik P.L. Rousseau
- Department of Green Chemistry and Technology, Ghent University, Sint-Martens-Latemlaan 2B, B-8500, Kortrijk, Belgium
| | - Abraham Esteve-Núñez
- Universidad de Alcalá, Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Alcalá de Henares, Spain
| | - Antonin Prévoteau
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, B-9000, Ghent, Belgium
- Centre for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9000, Ghent, Belgium
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Lakho FH, Qureshi A, Novelli LDD, Depuydt V, Depreeuw T, Van Hulle SWH, Rousseau DPL. Performance of a green wall (Total Value Wall™) at high greywater loading rates and Life Cycle Impact Assessment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 821:153470. [PMID: 35093344 DOI: 10.1016/j.scitotenv.2022.153470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/20/2022] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Nature-based greywater (GW) treatment and reuse in urban areas has become an up-and-coming option. A 14.4 m2 green wall system called Total Value Wall (TVW) was installed at a terraced house in Gent (Belgium) for treating GW and reusing the effluent for toilet flushing. In a previous study, the TVW was loaded at 7 L.m-2.d-1 and efficiently removed TSS (67%), COD (43%), BOD5 (83%) and total coliforms (log 2), but a number of issues were reported related to nutrient leaching from the substrate, and the excessive retention time in the storage tanks. In this study results are reported from a follow-up study during which an adapted TVW was subjected to both higher hydraulic and pollutant loading rates in order to investigate the treatment capability of TVW. The design of the system, i.e. substrate contained in geotextile bags, did not sustain the higher hydraulic loading rates as excessive leakage occurred. Despite this, the higher pollutant loading rates still resulted in an acceptable effluent quality with 15 mg.L-1 TSS (90%), 85 mg.L-1 COD (82%), and 15 mg.L-1 BOD5 (95%). Ammonium, E. coli and total coliforms were removed with removal rates of 98%, 63% (0.4 log units), and 36% (0.2 log units), respectively. Finally, a life cycle assessment (LCA) was performed for the TVW with and without treating GW to analyze the environmental burden. The LCA impacts showed that replacing tap water and chemical fertilizer by GW, and the reuse of effluent, have a positive impact. However, the energy use for pumping has a major impact and should be minimized by using an efficient pump and distribution system to reduce the overall footprint.
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Affiliation(s)
- Fida Hussain Lakho
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500 Kortrijk, Belgium.
| | - Asif Qureshi
- Université du Québec en Abitibi-Témiscamingue (UQAT), 445 Boulevard de l'Université, Rouyn-Noranda, QC J9X 5E4, Canada
| | - Laura De Donno Novelli
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500 Kortrijk, Belgium
| | - Veerle Depuydt
- Flanders Knowledge Center Water (Vlakwa), Leiestraat 22, B-8500 Kortrijk, Belgium
| | - Teun Depreeuw
- Muurtuin, Vandenpeereboomstraat 16, 2140 Borgerhout, Belgium
| | - Stijn W H Van Hulle
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500 Kortrijk, Belgium
| | - Diederik P L Rousseau
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500 Kortrijk, Belgium
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Alalam S, Marciniak A, Lessard MH, Bérubé A, Chamberland J, Pouliot Y, Labrie S, Doyen A. Evolution of bacterial communities during the concentration and recirculation of dairy white wastewater by reverse osmosis. Int Dairy J 2022. [DOI: 10.1016/j.idairyj.2021.105283] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Zhang R, Wang L, Hussain Lakho F, Yang X, Depuydt V, Igodt W, Quan Le H, Rousseau DP, Van Hulle S. Iron oxide coated sand (IOS): Scale-up analysis and full-scale application for phosphorus removal from goat farm wastewater. Sep Purif Technol 2022. [DOI: 10.1016/j.seppur.2021.120213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Lakho FH, Vergote J, Ihsan-Ul-Haq Khan H, Depuydt V, Depreeuw T, Van Hulle SWH, Rousseau DPL. Total value wall: Full scale demonstration of a green wall for grey water treatment and recycling. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 298:113489. [PMID: 34426216 DOI: 10.1016/j.jenvman.2021.113489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/13/2021] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
Greywater treatment and reuse for non-potable purposes in urban areas has become a widely researched topic to reduce the burden on fresh water resources. This study reports on the use of a green wall for treating grey water and reusing the effluent for toilet flushing, called Total Value Wall (TVW). Initially, the effectiveness of (mixtures of) different substrates, i.e. lava, lightweight expanded clay aggregates, organic soil and biochar was investigated by means of column tests. All substrates were first examined for hydraulic characteristics and later on the columns were fed with synthetic grey wastewater and followed up in terms of removal efficiency of COD and detergents. The mixture consisting of lava (50%), organic soil (25%) and biochar (25%) proved to be optimal both in terms of percolation rates and removal efficiencies, and was thus selected for the full-scale system. The full-scale TVW of 14.4 m2 was installed at a terraced house in Ghent (Belgium), and was loaded with grey water at 100 L per day. Influent and effluent quality were routinely monitored by grab sampling, water savings were monitored by means of flow meters, and electricity consumption was also accounted for. The TVW was further equipped with sensors that measure temperature, Particulate Matter (PM10) and CO2 in the air. The full-scale system obtained effluent concentrations of 13 mg.L-1 TSS, 91 mg.L-1 COD and 5 mg.L-1 BOD5. Ammonium and total coliforms were removed with removal rates of 97% and 99% (2 log units) respectively. However, an increase in effluent concentration of nitrate and phosphate was observed due to leaching from the selected substrate. Available data from the temperature sensors have clearly demonstrated the additional benefit of the TVW as an insulating layer, keeping the heat outside on warmer days, and keeping the heat inside on colder days. Overall, this study demonstrated that the TVW is a sustainable system for greywater treatment and reuse.
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Affiliation(s)
- Fida Hussain Lakho
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500, Kortrijk, Belgium.
| | - Jarne Vergote
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500, Kortrijk, Belgium
| | - Hafiz Ihsan-Ul-Haq Khan
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500, Kortrijk, Belgium
| | - Veerle Depuydt
- Flanders Knowledge Center Water (Vlakwa), Leiestraat 22, B-8500, Kortrijk, Belgium
| | - Teun Depreeuw
- Muurtuin, Vandenpeereboomstraat 16, 2140, Borgerhout, Belgium
| | - Stijn W H Van Hulle
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500, Kortrijk, Belgium
| | - Diederik P L Rousseau
- Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University Campus Kortrijk, Sint-Martens Latemlaan 2B, B-8500, Kortrijk, Belgium
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Politaeva N, Badenko V. Magnetic and electric field accelerate Phytoextraction of copper Lemna minor duckweed. PLoS One 2021; 16:e0255512. [PMID: 34347844 PMCID: PMC8336833 DOI: 10.1371/journal.pone.0255512] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 07/18/2021] [Indexed: 11/19/2022] Open
Abstract
In accordance with the opinion of the World Health Organization and the World Water Council the development of effective technologies for the treatment of wastewater from heavy metals for their discharge into water bodies or reuse is an urgent task nowadays. Phytoremediation biotechnologies is the most environmentally friendly and cheapest way of the treatment of wastewater, suitable for sustainable development principals. The main disadvantage of the phytoremediation is the slow speed of the process. A method for accelerating the process of phytoremediation by the combined effect of magnetic and weak electric fields is proposed. The purpose of this study is to determine the values of the parameters of the magnetic and weak electric fields that are most suitable for extracting cuprum ions from wastewater using the higher aqua plants (Lemna minor). A corresponding technological process based on the results of the study is proposed. The results have shown that the removal of copper cations from sulfate solutions effectively occurs in the initial period of time (1–5 hours) under the influence of a magnetic field with an intensity of H = 2 kA/m. Under the combined influence of an electrical current with density j = 240 μA/cm2 and a magnetic field (H = 2 kA/m) the highest rate of copper extraction by duckweed leaves is achieved. Under these conditions, the greatest growth and development of plant leaves occurs. The paper presents the results of determining of the parameters of the electrochemical release from the eluate of the spent phytomass of duckweed. It has been determined that the release of metal occurs at E = 0.32 V. An original scheme for wastewater treatment from copper with subsequent separation of copper from the spent phytomass of duckweed is proposed. In general, the presented results are a scientific justification of wastewater treatment technologies and a contribution to resolving the crisis in the field of fresh water supply. An important contribution in the circular economy is a technology recommendation proposed for recovering copper from duckweed after wastewater treatment.
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Affiliation(s)
- Natalia Politaeva
- Civil Engineering Institute, Peter the Great Saint Petersburg Polytechnic University, Saint Petersburg, Russian Federation
| | - Vladimir Badenko
- Civil Engineering Institute, Peter the Great Saint Petersburg Polytechnic University, Saint Petersburg, Russian Federation
- * E-mail:
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Hube S, Wu B. Mitigation of emerging pollutants and pathogens in decentralized wastewater treatment processes: A review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 779:146545. [PMID: 33752021 DOI: 10.1016/j.scitotenv.2021.146545] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 06/12/2023]
Abstract
Emerging pollutants (such as micropollutants, microplastics) and pathogens present in wastewater are of rising concern because their release can affect the natural environment and drinking water resources. In this decade, with increasing numbers of small-scale decentralized wastewater systems globally, the status of emerging pollutant and pathogen mitigation in the decentralized wastewater treatment processes has received more attention. This state-of-the-art review aims to discuss the mitigation efficiencies and mechanisms of micropollutants, microplastics, and pathogens in single-stage and hybrid decentralized wastewater treatment processes. The reviewed results revealed that hybrid wastewater treatment facilities could display better performance compared to stand-alone facilities. This is because the multiple treatment steps could offer various microenvironments, allowing incorporating several mitigation mechanisms (such as sorption, degradation, filtration, etc.) to remove complicated emerging pollutants and pathogens. The factors (such as system operation conditions, environmental conditions, wastewater matrix) influencing the removals of emerging pollutants from wastewater in these systems have been further identified. Nevertheless, it was found that very limited research work focused on synergised or conflicted effects of operation conditions on various emerging pollutants naturally present in the wastewater. Meanwhile, effective, reliable, and rapid analysis of the emerging pollutants and pathogens in the complicated wastewater matrix is still a major challenge.
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Affiliation(s)
- Selina Hube
- Faculty of Civil and Environmental Engineering, University of Iceland, Hjardarhagi 2-6, IS-107 Reykjavik, Iceland
| | - Bing Wu
- Faculty of Civil and Environmental Engineering, University of Iceland, Hjardarhagi 2-6, IS-107 Reykjavik, Iceland.
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Application of constructed wetlands in treating rural sewage from source separation with high-influent nitrogen load: a review. World J Microbiol Biotechnol 2021; 37:138. [PMID: 34278536 DOI: 10.1007/s11274-021-03105-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 07/05/2021] [Indexed: 10/20/2022]
Abstract
Constructed wetlands (CWs) are characterized by low construction cost, convenient maintenance and management, and environmentally friendly features. They have emerged as promising technologies for decentralized sewage treatment across rural areas. Source separation of black water and gray water can facilitate sewage recycling and reuse of reclaimed water, reduce the size of treatment facilities, and lower infrastructure investment and operating cost. This is consistent with the concept of sustainable development. However, black water contains high concentrations of ammonia nitrogen, and the denitrification capacity of CWs is not excellent due to insufficient carbon source. Therefore, application of CWs for black water treatment faces challenges. This article provides a review on the progress in CWs for treatment of the sewage with high-influent nitrogen load, with emphasis on the commonly used strengthening means and the role of plants in nitrogen removal via CWs. The current issues of rural sewage treatment with high-influent nitrogen load by CWs are also assessed. Finally, the challenges and perspectives are discussed for the optimization of CWs-enhanced denitrification strategies.
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