Constructed wetlands for textile wastewater remediation: A review on concept, pollutant removal mechanisms, and integrated technologies for efficiency enhancement

Porous red mud ceramsite for aquatic phosphorus removal: Application in constructed wetlands

Red mud (RM) and spent oyster mushroom substrate (SOMS), by-products of industrial and agricultural production, can be recycled for polluted freshwater purification, bringing about a win-win situation. In this study, unacidified RM and RM acidified with oxalic acid (O-RM) and hydrochloric acid (H-RM), respectively, were mixed with SOMS to produce a porous ceramsite as a potential constructed wetlands (CWs) substrate. The results showed that the O-RM, H-RM, and RM ceramsites displayed fine compressive strengths of 7.75 ± 1.14, 8.40 ± 1.30, and 8.84 ± 0.69 MPa after calcining at 950 °C for 30 min, respectively. The phosphorus adsorption capacities of H-RM, O-RM, and RM ceramsite at a solid-liquid ratio of 25 g/L were 1.18 mg/g, 0.88 mg/g, and 1.06 mg/g, respectively. Toxicity release experiments showed that the ceramsites did not cause secondary environmental pollution, except for arsenic (ranging from 0.210 to 0.238 mg/L). The H-RM ceramsite was tested in a tidal flow-vertical flow CW (TF-VFCW) with Iris pseudacorus L. and Canna indica L plants. In the TF-VFCW, the average chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) removal rates were 81.01, 90.25, 66.90, and 77.32 %, respectively. Plant growth had less impact on COD and NH4-N removal but had greater limited TN and TP removal. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis confirmed that acid pretreatment and the incorporation of SOMS significantly increased the surface and interior porous structures of the ceramsite and enhanced phosphate adsorption by the polyhydroxyl aluminum-iron complex ions. Bacteroides and Campylobacter used the energy produced during polyhydroxyalkanoic acid (PHA) catabolism to absorb phosphorus. Therefore, the synergistic effect of the substrate, plants, and microorganisms achieved the removal of phosphorus from CWs and offered effective and environmentally friendly recycling of RM and SOMS.

Potential of nature-based solutions to reduce antibiotics, antimicrobial resistance, and pathogens in aquatic ecosystems. a critical review

This comprehensive scientific review evaluates the effectiveness of nature-based solutions (NBS) in reducing antibiotics (ABs), combating antimicrobial resistance (AMR), and controlling pathogens in various aquatic environments at different river catchment levels. It covers conventional and innovative treatment wetland configurations for wastewater treatment to reduce pollutant discharge into the aquatic ecosystems as well as exploring how river restoration and saltmarshes can enhance pollutant removal. Through the analysis of experimental studies and case examples, the review shows NBS's potential for providing sustainable and cost-effective solutions to improve the health of aquatic ecosystems. It also evaluates the use of diagnostic indicators to predict NBS effectiveness in removing specific pollutants such as ABs and AMR. The review concludes that NBS are feasible for addressing the new challenges stemming from human activities such as the presence of ABs, AMR and pathogens, contributing to a better understanding of NBS, highlighting success stories, addressing knowledge gaps, and providing recommendations for future research and implementation.

Enzymatic bioremediation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil: a study on the recombinant laccase TVL

Polycyclic aromatic hydrocarbons (PAHs) are pervasive and persistent pollutants in contaminated soil, posing a severe health and environmental threat. Enzymatic bioremediation presents a viable solution for the remediation of PAH-contaminated soil. In this study, a recombinant laccase with the encoding gene originating from Trametes villosa and recombinantly expressed in Aspergillus oryzae, designated as TVL, was discovered to possess strong PAH reduction capabilities. The specific enzyme activity of TVL was 73485 and 5102 LAMU/g enzyme protein at pH 5.0/7.0 and 37°C. Furthermore, it exhibited significant benzo[a]pyrene degradation, with 100% and 90.48% degradation at pH 5.0/7.0 after 24 h in the liquid phase. The degradation process of benzo[a]pyrene in soil was thoroughly investigated. Optimal conditions were identified as 15 mg/g NK-BSoil-3 and 1.35 mg/g HBT, resulting in a removal rate of 37.54% within 7 days when 0.01 U/g of TVL was applied. The potential mechanisms were investigated using molecular docking simulation. The binding energy between benzo[a]pyrene and TVL protein is notably robust, suggesting a higher propensity for enzyme binding. The TVL protein pocket contains nine amino acids that can interact most strongly with benzo[a]pyrene. Consequently, the recombinant laccase TVL holds considerable practical significance in bioremediation.

Exploring research on ecotechnology through artificial intelligence and bibliometric maps

Ecotechnology, quintessential for crafting sustainable socio-environmental strategies, remains tantalizingly uncharted. Our analysis, steered by the nuances of machine learning and augmented by bibliometric insights, delineates the expansive terrain of this domain, elucidates pivotal research themes and conundrums, and discerns the vanguard nations in this field. Furthermore, we deftly connect our discoveries to the United Nations' 2030 Sustainable Development Goals, thereby accentuating the profound societal ramifications of ecotechnology.

A comprehensive review on the treatment of pesticide-contaminated wastewater with special emphasis on organophosphate pesticides using constructed wetlands

Pesticides pose a significant threat to aquatic ecosystems due to their persistent nature and adverse effects on biota. The increased detection of pesticides in various water bodies has prompted research into their toxicological impacts and potential remediation strategies. However, addressing this issue requires the establishment of robust regulatory frameworks to determine safe thresholds for pesticide concentrations in water and the development of effective treatment methods. This assessment underscores the complex ecological risks associated with organophosphate pesticides (OPPs) and emphasizes the urgent need for strategic management and regulatory measures. This study presents a detailed examination of the global prevalence of OPPs and their potential adverse effects on aquatic and human life. A comprehensive risk assessment identifies azinphos-methyl, chlorpyrifos, and profenfos as posing considerable ecological hazard to fathead minnow, daphnia magna, and T. pyriformis. Additionally, this review explores the potential efficacy of constructed wetlands (CWs) as a sustainable approach for mitigating wastewater contamination by diverse pesticide compounds. Furthermore, the review assess the effectiveness of CWs for treating wastewater contaminated with pesticides by critically analyzing the removal mechanism and key factors. The study suggests that the optimal pH range for CWs is 6-8, with higher temperatures promoting microbial breakdown and lower temperatures enhancing pollutant removal through adsorption and sedimentation. The importance of wetland vegetation in promoting sorption, absorption, and degradation processes is emphasized. The study emphasizes the importance of hydraulic retention time (HRT) in designing, operating, and maintaining CWs for pesticide-contaminated water treatment. The removal efficiency of CWs ranges from 38% to 100%, depending on factors like pesticide type, substrate materials, reactor setup, and operating conditions.

Recent advances in swine wastewater treatment technologies for resource recovery: A comprehensive review

Swine wastewater (SW), characterized by highly complex organic and nutrient substances, poses serious impacts on aquatic environment and public health. Furthermore, SW harbors valuable resources that possess substantial economic potential. As such, SW treatment technologies place increased emphasis on resource recycling, while progressively advancing towards energy saving, sustainability, and circular economy principles. This review comprehensively encapsulates the state-of-the-art knowledge for treating SW, including conventional (i.e., constructed wetlands, air stripping and aerobic system) and resource-utilization-based (i.e., anaerobic digestion, membrane separation, anaerobic ammonium oxidation, microbial fuel cells, and microalgal-based system) technologies. Furthermore, this research also elaborates the key factors influencing the SW treatment performance, such as pH, temperature, dissolved oxygen, hydraulic retention time and organic loading rate. The potentials for reutilizing energy, biomass and digestate produced during the SW treatment processes are also summarized. Moreover, the obstacles associated with full-scale implementation, long-term treatment, energy-efficient design, and nutrient recovery of various resource-utilization-based SW treatment technologies are emphasized. In addition, future research prospective, such as prioritization of process optimization, in-depth exploration of microbial mechanisms, enhancement of energy conversion efficiency, and integration of diverse technologies, are highlighted to expand engineering applications and establish a sustainable SW treatment system.

Impact of short-term irrigation of diverse distillery wastewater types on plant attributes and antioxidative enzymes of pea (Pisum sativum L. var. Rachna)

The study was focused on evaluating the short-term irrigation effect of three different types of distillery wastewater, i.e., untreated, primary treated, and secondary treated, on the germination, growth, photosynthetic pigments, and antioxidant enzymes of pea (Pisum sativum L. var. Rachna). The findings indicated that exposure to 50% secondary treated distillery wastewater (ST50) resulted in the maximum values for positive germination parameters of pea, including germination percentage, germination value, germination index, peak value, vigor index, speed of germination, and tolerance index. The minimum values were observed at 100% concentration of untreated wastewater (UT100). In contrast, the maximum values for various negative germination parameters, i.e., percent inhibition, seedling mortality, and germination period, were observed at UT100 and minimum at ST50. All the growth parameters studied, i.e., length of shoot, length of root and length of seedlings, fresh weight of shoot, fresh weight of root, dry weight of shoot, and dry weight of root, showed maximum values at ST50 and minimum at UT100. Photosynthetic pigment analysis also followed a similar trend. The antioxidative enzyme characterization of Pisum sativum L. var. Rachna revealed the minimum values of catalase, ascorbic peroxidase, glutathione reductase, and superoxide dismutase at ST25 (25% concentration of secondary treated distillery wastewater) and maximum values were observed at UT100.

Removal of pharmaceutical contaminants from hospital wastewater using constructed wetlands: a review

AbstractPharmaceutical compounds are a significant source of environmental pollution, particularly in hospital wastewater, which contains high concentrations of such compounds. Constructed wetlands have emerged as a promising approach to removing pharmaceutical compounds from wastewater. This paper aims to review the current state of knowledge on the removal of pharmaceutical compounds from hospital wastewater using constructed wetlands, including the mechanism of removal, removal efficiency, and future prospects. Pharmaceutical contaminants have been considered to be one of the most emerging pollutants in recent years. In this review article, various studies on constructed wetlands are incorporated in order to remove the pharmaceutical contaminants. The nature of constructed wetland can be explained by understanding the types of constructed wetland, characteristics of hospital wastewater, removal mechanism, and removal efficiency. The results of the review indicate that constructed wetlands are effective in removing pharmaceutical compounds from hospital wastewater. The removal mechanism of these compounds involves a combination of physical, chemical, and biological processes, including adsorption, degradation, and uptake by wetland plants. The removal efficiency of constructed wetlands varies depending on several factors, including the type and concentration of pharmaceutical compounds, the design of the wetland system, and the environmental conditions. Further research is necessary to optimize the performance of these systems, particularly in the removal of emerging contaminants, to ensure their effectiveness and long-term sustainability.

Insights into current bio-processes and future perspectives of carbon-neutral treatment of industrial organic wastewater: A critical review

With the rise of the concept of carbon neutrality, the current wastewater treatment process of industrial organic wastewater is moving towards the goal of energy conservation and carbon emission reduction. The advantages of anaerobic digestion (AD) processes in industrial organic wastewater treatment for bio-energy recovery, which is in line with the concept of carbon neutrality. This study summarized the significance and advantages of the state-of-the-art AD processes were reviewed in detail. The application of expanded granular sludge bed (EGSB) reactors and anaerobic membrane bioreactor (AnMBR) were particularly introduced for the effective treatment of industrial organic wastewater treatment due to its remarkable prospect of engineering application for the high-strength wastewater. This study also looks forward to the optimization of the AD processes through the enhancement strategies of micro-aeration pretreatment, acidic-alkaline pretreatment, co-digestion, and biochar addition to improve the stability of the AD system and energy recovery from of industrial organic wastewater. The integration of anaerobic ammonia oxidation (Anammox) with the AD processes for the post-treatment of nitrogenous pollutants for the industrial organic wastewater is also introduced as a feasible carbon-neutral process. The combination of AnMBR and Anammox is highly recommended as a promising carbon-neutral process for the removal of both organic and inorganic pollutants from the industrial organic wastewater for future perspective. It is also suggested that the AD processes combined with biological hydrogen production, microalgae culture, bioelectrochemical technology and other bio-processes are suitable for the low-carbon treatment of industrial organic wastewater with the concept of carbon neutrality in future.

Wastewater treatment plant performance assessment using time-function-based effluent quality index and multiple regression models: the case of Bahir Dar textile factory

Extensive water and chemicals are used in the textile industry processes. Therefore, treatment of textile wastewater is vital to protect the environment, maintain the public health, and recover resources. However, due to poor operation and plant performance the partially treated textile wastewater was directly discharged to a nearby river. Thus, the aim of this study was to characterize the wastewater physicochemical properties and evaluate the performance of the textile factory-activated sludge process wastewater treatment plant (WWTP) in Bahir Dar, Ethiopia. In inlet and outlet of the WWTP, samples were collected for 6 months and analyzed on-site and in a laboratory for parameters including, dissolved oxygen, pH, temperature, total Kjeldhal nitrogen (TKN), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total suspended solids (TSS), total nitrogen (TN), total phosphorous (TP), nitrite, nitrate, and metallic compounds. The TSS, BOD5, COD, TP, nitrite, ammonia, and total chromium result were above the discharge limit with 73.2 mg/L, 48.45 mg/L, 144.08 mg/L, 7.9 mg/L, 1.36 mg/L, 1.96 mg/L, and 0.16 mg/L, respectively. Multiple regression models were developed for each overall, net moving average, and instantaneous effluent quality index (EQI). The predictor parameters BOD5, TN, COD, TSS, and TP (R2 = 0.995 to 1.000) estimated the net pollution loads of all predictors as 492.55 kg/day and 655.44 kg/day. Except TN, TKN, and NO3, the remaining six performance parameters were violating the permissible limit daily. Furthermore, the overall plant efficiency was predicted as 38 % and 42 % for the moving average and instantaneous EQI, respectively. Our study concluded that the integrated regression models and EQI can easily estimate the plant efficiency and daily possible pollution load.

Sustainable and Green Synthesis of Iron Nanoparticles Supported on Natural Clays via Palm Waste Extract for Catalytic Oxidation of Crocein Orange G Mono Azoic Dye

In this study, the removal of Crocein Orange G dye (COG) from aqueous solution was investigated using an innovative green catalyst to overcome problems with chemical techniques. Clay bentonite El Hamma (HB)-supported nanoscale zero-valent iron (NZVI) was used as a heterogeneous Fenton-like catalyst for the oxidation of harmful COG. Palm waste extract was herein used as a reducing and capping agent to synthesize NZVI, and HB clay was employed, which was obtained from the El Hamma bentonite deposit in the Gabes province of Tunisia. HB and HB-NZVI were characterized by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer, Emmett, and Teller (BET), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), X-ray diffraction (XRD), and zeta potential. Under optimal conditions, total degradation of COG was attained within 180 min. Kinetic studies showed that the dye degradation rate followed well the pseudo-second-order model. The apparent activation energy was 33.11 kJ/mol, which is typical of a physically controlled reaction. The degradation pathways and mineralization study revealed that the adsorption-Fenton-like reaction was the principal mechanism that demonstrated 100% degradation efficiency of COG even after three successive runs. Obtained results suggest that HB-NZVI is an affective heterogeneous catalyst for the degradation of COG by H2O2 and may constitute a sustainable green catalyst for azoic dye removal from industrial wastewaters.

Kinetics and Thermodynamics Study of Methylene Blue Adsorption to Sucrose- and Urea-Derived Nitrogen-Enriched, Hierarchically Porous Carbon Activated by KOH and H3PO4

Hierarchically porous nitrogen-enriched carbon materials synthesized by polymerization of sucrose and urea (SU) were activated by KOH and H₃PO₄ (SU-KOH and SU-H₃PO₄, respectively). Characterization was undertaken and the synthesized materials were tested for their ability to adsorb methylene blue (MB). Scanning electron microscopic images along with the Brunauer-Emmett-Teller (BET) surface area analysis revealed the presence of a hierarchically porous system. X-ray photoelectron spectroscopy (XPS) confirms the surface oxidation of SU upon activation with KOH and H₃PO₄. The best conditions for removing dyes utilizing both activated adsorbents were determined by varying the pH, contact time, adsorbent dosage, and dye concentration. Adsorption kinetics were evaluated, and the adsorption of MB followed second-order kinetics, suggesting the chemisorption of MB to both SU-KOH and SU-H₃PO₄. Times taken to reach the equilibrium by SU-KOH and SU-H₃PO₄ were 180 and 30 min, respectively. The adsorption isotherm data were fitted to the Langmuir, Freundlich, Temkin, and Dubinin models. Data were best described by the Temkin isotherm model for SU-KOH and the Freundlich isotherm model for SU-H₃PO₄. Thermodynamics of the adsorption of MB to the adsorbent was determined by varying the temperature in the range of 25-55 °C. Adsorption of MB increased with increasing temperature, suggesting that the adsorption process is endothermic. The highest adsorption capacities of SU-KOH and SU-H₃PO₄ (1268 and 897 mg g^-1, respectively) were obtained at 55 °C. Synthesized adsorbents were effective in removing MB for five cycles with some loss in activity. The results of this study show that SU activated by KOH and H₃PO₄ are environmentally benign, favorable, and effective adsorbents for MB adsorption.

Textile wastewater phytoremediation using Spirodela polyrhiza (L.) Schleid. assisted by novel bacterial consortium in a two-step remediation system

The study aims at developing a phyto-microremediation system for textile wastewater treatment using Spirodela polyrhiza (L.) Schleid. and a consortium of bacterial strains isolated from textile wastewater-contaminated matrices and rhizosphere of S. polyrhiza. The sequential phyto-microremediation of textile wastewater was carried out utilizing two-stage phyto-microremediation systems I [phytoremediation system (Stage 1) preceded microremediation system (Stage 2)] and II [microremediation system (Stage 1) preceded phytoremediation system (Stage 2)]. Pseudomonas stutzeri, Janibacter anophelis, Bacillus safensis, Bacillus pumilus, Bacillus thuringiensis, and Bacillus cereus constituted the bacterial consortium that was involved in the microremediation of textile wastewater. Biochemical characterization of Spirodela on exposure to untreated textile wastewater showed cadmium and nickel uptake as 26.03 and 22.99 mg g^-1 dw^-1. S. polyrhiza exhibited anatomical changes like distortion in the structure of the xylem, phloem, lower epidermis, and increased aerenchyma formation when remediating textile wastewater. The textile wastewater bioremediation in phyto-microremediation system I gives final reduction of COD 77.36%, color 91.70%, calcium 61.65%, iron 69.41%, nickel 89.30%, cadmium 88.37%, nitrate 70.83%, phosphate 73.11%, and sulfate 75.49%. Further, LC-MS analysis of treated wastewater from phyto-microremediation system I have shown biotransformation of metabolites into simpler compounds like 2-{Bis [4-(2-cyanophenoxy)phenyl]methyl}benzoic acid (C₃₄H₂₂N₂O₄). The FTIR spectrum of bacterial biomass exposed to textile wastewater exhibits substantial shifts of various bands in the IR region for functional groups such as alcohol, alkene, esters, azide, and amine as compared to non-exposed biomass.

Effects of Ag nanoparticles on plant growth, Ag bioaccumulation, and antioxidant enzyme activities in Phragmites australis as influenced by an arbuscular mycorrhizal fungus

Ag nanoparticles (AgNPs) are considered an emerging contaminant in recent years, and their harmful effects on plants pose new concerns, especially in coexistence with soil microorganisms. Arbuscular mycorrhizal fungi (AMF), as mutualistic fungi with most terrestrial plants, may contribute to alleviating nanotoxicity in plants. Herein, AgNP toxicity of different concentrations (1, 5, 10, 50, 100 mg/kg) on reed (Phragmites australis (Cav.) Trin. ex Steudel) as influenced by mycorrhizal inoculation with Funneliformis mosseae was investigated. The results revealed that concentration is the main factor influencing the AgNP phytotoxicity; AgNP dose had biphasic effects on AMF colonization, plant biomass, and antioxidant enzyme activities. Thereinto, different antioxidant enzymes had different tolerances to AgNP stress, and the turning point of their activities was respectively the following: POD-5 mg/kg < SOD-10 mg/kg < CAT-50 mg/kg. The growth configuration (root:shoot ratio) of Phragmites australis increased firstly and then decreased to cope with the increasing AgNP concentration. Additionally, the Ag accumulation and translocation of AgNP-exposed plants were relatively lower than that of equivalent Ag⁺-exposed plants. However, AMF inoculation improved plant antioxidant capability and biomass growth in response to AgNP-induced toxicity. Meanwhile, AMF effectively regulated the root:shoot ratio to accommodate AgNP stress. The linear model fittings and heat maps showed that the mycorrhizal plants exhibited a higher Ag accumulative rate and root partitioning (Ag organ distribution: root > stem > leaf) than the non-inoculated plants. Overall, our results demonstrated that AMF could diminish the negative effects induced by AgNPs and promote Ag immobilization in plant roots so as to alleviate AgNP-posed environmental risks.

Performance and mechanism of azo dyes degradation and greenhouse gases reduction in single-chamber electroactive constructed wetland system

A single-chamber microbial fuel cell-microbial electrolytic cell with a novel constructed wetland system was proposed for synergistic degradation of congo red and reduction in emissions of greenhouse gases. The closed-circuit system showed higher chemical oxygen demand and congo red removal efficiencies by 98 % and 96 % on average, respectively, than traditional constructed wetland. It could also significantly reduce the emissions of CH₄ and N₂O (about 52 % CO₂-equivalents) by increasing the electron transfer. Microbial community analysis demonstrated that the progressive enrichment of dye-degrading microorganisms (Comamonas), electroactive bacteria (Tolumonas, Trichococcus) and denitrifying microorganisms (Dechloromonas) promoted pollutant removal and electron transfer. Based on gene abundance of xenobiotics biodegradation, the congo red biodegradation pathway was described as congo red → naphthalene and alcohols → CO₂ and H₂O. In summary, the single-chamber closed-circuit system could significantly improve the degradation of congo red and reduce the emissions of greenhouse gases by influencing electron transfer and microbial activity.

Experience of Application of Natural Treatment Systems for Wastewater (NTSW) in Livestock Farms in Canary Islands

A real-scale application experience Natural Treatment Systems for Wastewater (NTSW) operating in continues with livestock farms for one year. These systems are based on digesters, subsurface vertical flow constructed wetlands (SVFCW) and facultative ponds. Chemical Oxygen Demand removal efficiency (CODRE) has obtained between 70 and 90%. Likewise, it have been possible to compare the operation of cascade flow digesters (CFD) (<76% CODRE) versus complete mixing digesters (CMD) (<50% CODRE). Facultative ponds (FP) when combined with (SSFCW), removed a higher percentage of CODRE compared with ponds (92%). Correlations of interest have been found between the variables evaluated in each plant. Finally, different elements are alternated in the same system, this system is capable of supporting variations in changes in flow rate and organic load coming from the farm, maintaining an adequate elimination of COD and other parameters of interest.

Exploring the Removal of Organic Matter in Constructed Wetlands Using First Order Kinetic Models

Mathematical models have become an excellent tool to evaluate the characteristics and performance of Constructed Wetlands (CWs). They help to characterize the dynamics of pollutant removal in these systems. The aim of this research was to evaluate the kinetics of organic matter removal in CWs using two models: (i) the conventional first order model and (ii) the sigmoidal or k-n model. For this purpose, data from 41 CWs where domestic sewage is treated were used. The cluster analysis was performed to identify similar groups of CWs based on the estimation of model coefficients. According to the results obtained, the model that provides a better fit for the removal of organic matter in CWs is the sigmoidal-type. However, its “n” coefficient, which would represent an increase in resistance to degradation, remains a not totally explained variable. The sigmoidal or k-n model is promising, presenting good adjustment indices.