Sorption of micropollutants on selected constructed wetland support matrices

Full-scale studies are closer to reality than lab-scale ones: Tertiary treatment constructed wetlands maintain robust removal capability for pharmaceuticals and personal care products in cold weather conditions

In contrast to previous lab-scale studies, full-scale studies show that low temperatures do not significantly hinder pharmaceutical and personal care product (PPCP) removal in tertiary treatment constructed wetland (CW) systems. This study investigated PPCP removal pathways (substrate adsorption, plant uptake, microbial degradation) in two full-scale CWs, highlighting the differences between full-scale and lab-scale study outcomes. Results demonstrated that low temperatures did not adversely affect PPCP removal in full-scale CWs. Substrate adsorption was minimally impacted at a relevant concentration of 100 ng/L, unlike lab-scale studies with typically higher concentrations (1 mg/L). Plant uptake was not affected, as mature plants in CWs exhibited a lower PPCP uptake capacity compared to seedlings in lab-scale studies. Furthermore, low temperatures did not reduce microbial biodegradation performance. However, low temperatures increased dissolved oxygen concentrations in the influent, supporting aerobic microbial activity. These findings emphasize the value of full-scale CWs for stable PPCP removal under low-temperature conditions.

Investigating the application of novel filling materials in Vertical Subsurface Flow Constructed Wetlands for the treatment of anaerobic effluents originating from domestic wastewater

Vertical subsurface flow constructed wetlands (VSSF CWs) were employed to investigate the use of biochar that could be produced with local agricultural biomass through pyrolysis, recycled glass from local recycling companies and gel beads with decreased packing volume and shipping cost as substrate alternatives to sand. The materials were assessed in terms of granulometry, porosity, adsorption capacity and hydraulic conductivity and were used for the treatment of an upflow anaerobic sludge blanket (UASB) reactor, treating domestic wastewater, effluent. Granulometry was a major factor impacting TSS removal that ranged from 81% ± 10% to 97% ± 2%. The COD removal was affected by granulometry, porosity and the active biofilm formation, since biochar removal was slightly higher (up to 93% ± 3%) than that of sand and recycled glass (up to 86% ± 4% and 85% ± 5%, respectively) and significantly higher than that of gel beads (up to 68% ± 8%). The higher porosity of biochar affected NH4-N removal in which adsorption had a greater and longer effect. The overall NH4-N removal ranged between 84% ± 11% and 99% ± 1% for all materials. Sand, biochar and glass achieved an 80% average removal of selected contaminants of emerging concern (CECs), including ibuprofen (IBU), naproxen (NPX), triclosan (TCS), bisphenol A (BPA), diclofenac (DCF) and ketoprofen (KFN). The biochar and recycled glass are effective in treating UASB effluent and enable the treated wastewater reuse, since, high compliance rates with the EU Regulation 2020/741 - Class A were achieved (>98% for TSS, >88% for BOD5 and 100% for turbidity).

Biochar obtained from recovered cellulose and its mixture with conventional sources: Assessment of its potential for the removal of pollutants in water

Yearly thousands of tons of cellulose, in the form of toilet paper, end up in the wastewater treatment plants (WWTP) through the sewage. Cellulose was recovered with a 0.35 mm sieve and processed obtaining three different pellets: pure cellulose, straw mix (50 % cellulose-50 % straw) and wood mix (50 % cellulose-50 % wood). Those materials were carbonized at 750 °C for 210 min producing non-activated biochar. Then, a part of those biochars was biologically activated by fermentation adding minerals, nutrients and a mixture of bacteria. All biochar versions were characterized, assessing the surface, porosity and adsorption capacity for a dye (indigo carmine) and a selection of 5 micropollutants (MPs): benzotriazole, carbamazepine, clarithromycin, DEET, and diclofenac. However, results showed that conventional analysis for adsorbents was not adequate for biologically activated materials since biofilm can obstruct the pores of the supporting material hindering the pollutants' adsorption. Therefore, the biological degradation of the pollutants by the microorganisms was also tested. Finally, biologically activated WOW-Biochar straw mix was the selected material to be further applied in constructed wetlands (CW) due to its higher average MPs removal capacity. Validation test at mesocosm scale demonstrates the suitability of the material as an admixture in CW, reaching a MPs removal rate higher than the 90 % regarding the WWTP inlet.

Amended biochar in constructed wetlands: Roles, challenges, and future directions removing pharmaceuticals and personal care products

Pharmaceuticals and personal care products (PPCPs) in wastewater pose significant threats to both human health and aquatic ecosystems. Wastewater discharge from various sources is the primary cause of these contaminants, and proper treatment is essential for protecting the environment. Traditional treatment technologies are often too expensive and ineffective in removing PPCPs. Constructed wetlands (CWs) offer a sustainable, cost-efficient alternative for wastewater treatment, though their capability to eliminate PPCPs can vary based on multiple aspects. Recent studies highlight biochar-a carbon-rich material resultant from biomass pyrolysis-as a promising amendment to improve CW performance. However, there is a deficiency of proper literature reviews on using biochar in CWs specifically for PPCP removal. This review focuses on biochar's role in CWs and its effectiveness in removing PPCPs and enhancing microbial activity and nutrient cycling. A bibliometric analysis using Vosviewer software was used to assess the current research trends in the biochar-amended CWs to attenuate PPCPs. While biochar shows potential in eliminating PPCPs, challenges, such as optimizing its application and addressing long-term operational concerns for treating emerging pollutants like PPCPs. Future research should enhance biochar production and low-cost techniques for diverse groups of PPCPs and perform field trials to validate laboratory results under actual conditions exploring microbial-biochar and plant-biochar interactions. Addressing these challenges is crucial to advancing biochar-amended CWs and enhancing wastewater treatment on a global scale.

Hydroponic materials improve organic micropollutant removal in vertical flow constructed wetlands treating wastewater

Unconventional substrata like activated carbon or clay beads can enhance micropollutant removal in constructed wetlands. However, hydroponic materials widely used in horticulture have not yet been investigated for their potential to remove micropollutants. In addition, potential effect of plant species other than reeds on micropollutant removal has not been sufficiently investigated. Therefore, a nature-based, post-treatment technology called improved vertical flow constructed wetlands (CW) with hydroponic (H) materials (CWH) was designed by employing cocopeat and mineral with ornamental plant species syngonium and periwinkle. A mesocosm CWH system was tested in a climate-controlled greenhouse for 550 days for its potential to remove frequently found micropollutants in wastewater, namely sulfamethoxazole, trimethoprim, diclofenac, erythromycin, carbamazepine, pyrimethanil, tebuconazole, pymetrozine, atrazine and DEET from wastewater effluent. The main focus was to understand the contribution of sorption, microbial degradation and phytoremediation on the removal of those micropollutants. It was found that cocopeat showed a capacity for sorbing micropollutants, ranging between 80 and 99% of the compounds added while less than 10% sorption was observed for mineral wool. Additionally moderate to high biological removal (25-60 μg of compound/kg dry weight of substratum/day) for most of the studied compounds was observed in all the cocopeat biotic groups. Furthermore, it could be stated that plants appear not to be an important factor for micropollutant removal. The observed differences in removal between the cocopeat and mineral wool systems could be explained by the difference in physico-chemical properties of the substrata, where cocopeat has a higher water holding capacity, moisture content, nutrient and organic matter content, and a higher intraparticle porosity and surface area. This study revealed notable removal of persistent and mobile micropollutants in cocopeat CWH, namely carbamazepine (80-86%) and diclofenac (97-100%). These results demonstrate the potential beneficial use of hydroponic materials as substratum in more advanced constructed wetlands designed to remove micropollutants.

Next-generation hybrid technologies for the treatment of pharmaceutical industry effluents

Water and industries are intangible units of the globe that are always set to meet the population's demand. The global population depends on one-third of freshwater increasing the demand. The increase in population along with urbanization has polluted the fresh water resources. The pharmaceutical industry is marked as an emerging contaminant of water pollution. The most common type of pharmaceutical drugs that are detected in the environment includes antibiotics, analgesics, NSAIDs, and pain-relieving drugs. These drugs alter the food chain of the organisms causing chaos mainly in the marine ecosystem. Pharmaceutical drugs are found only in shallow amounts (ng/mg) they have a huge impact on the living system. The consumption of water contaminated with pharmaceutical ingredients can disrupt reproduction, hormonal imbalance, cancer, and respiratory problems. Various methods are used to remove these chemicals from the environment. In this review, we mainly focused on the emerging hybrid technologies and their significance in the effective treatment of pharmaceutical wastewater. This review paper primarily elaborates on the merits and demerits of existing conventional technologies helpful in developing integrated technologies for the modern era of pharmaceutical effluent treatment. This review paper further in detail discusses the various strategies of eco-friendly bioremediation techniques namely biostimulation, bioaugmentation, bacterial degradation, mycoremediation, phytoremediation, and others for the ultimate removal of pharmaceutical contaminants in wastewater. The review makes clear that targeted and hybrid solutions are what the world will require in the future to get rid of these pharmacological prints.

Study on the performance of vertical flow constructed wetland microcosm with Canna sps. for treatment of high chromium-containing wastewater

Chromium (Cr (VI)) pollution has plagued the environment due to chromite mining and various industrial actions. Constructed wetlands (CW) have emerged as a potential wastewater management technique that utilizes physical, chemical, and biological processes. The present study investigates the use of vertical flow-constructed wetlands (CW) using manure-rich garden soil and sand as substrates in planted CW (CW-P) and unplanted CW (CW-UP) to remove Cr (VI) from simulated wastewater. The experiment was performed in two phases, i.e., Phase I and II, in the same system. In Phase I, initial Cr (VI) concentrations were varied between 5 and 200 mg/l at a fixed hydraulic retention time (HRT) of 48 h, while in Phase II, the effect of HRT (24 h, 48 h, and 96 h) was studied at a fixed Cr (VI) concentration of 200 mg/L in the influent. At 24 h, HRT removal efficiencies were 90.20% for CW-P and 86.41% for CW-UP. However, at 96 h of HRT, the system showed nearly the same removal efficiency. Scanning electron microscopy with energy dispersion X-Ray spectroscopy analysis suggested the conversion of Cr (VI) to Cr (III) in soil precipitate and the translocation of Cr (VI) in plant tissues (Canna sps.). Moreover, microbial diversity profiling indicated that microbial diversity involved in pollutant removal differed in both systems. The phytotoxicity test clearly showed the decrease in toxicity level in the treated effluent, concluding the reusability of treated water. This exploratory study suggested that the CW can potentially remove a higher concentration of hexavalent chromium at longer HRT.

The removal of micropollutants from treated effluent by batch-operated pilot-scale constructed wetlands

Micropollutants (MPs), such as pharmaceuticals and antibiotics, are present in the environment at low concentrations (ng/L-μg/L). A constructed wetland (CW) is a nature-based wastewater treatment technology, which can be used to remove MPs from wastewater treatment plant effluent. This study aimed to improve MP removal of CWs by optimizing the design of batch-operated CW. Three pilot-scale CWs were built to study the effect of two design-features: the use of a support matrix (a mixture of bark and biochar) and continuous aeration. The use of bark-biochar as support matrix increased the removal of 11 of 12 studied MPs compared to the CW filled with conventional material sand. The highest improved removal by the addition of bark-biochar was more than 40% (median) for irbesartan, carbamazepine, hydrochlorothiazide and benzotriazole. Aerating the bed of the bark-biochar CW did not change MP removal. Besides, the presence of bark-biochar also enhanced the removal of total nitrogen during 10 months of operation, but no improvement was observed on the total organic carbon and total phosphorus removal. Considering the application in a batch-operated CW, MP removal can be greatly enhanced by replacing sand with bark-biochar that will act as MP adsorbing matrix.

Roles of substrates in removing antibiotics and antibiotic resistance genes in constructed wetlands: A review

Antibiotics and corresponding antibiotic resistance genes (ARGs) are emerging pollutants in wastewater that pose a significant threat to the environment and human health. Constructed wetlands (CWs) are a cost-effective technology for eliminating these pollutants through substrates, plants, and microorganisms. Detailed reviews of the roles of CW substrates on antibiotic and ARG removal and recent progress in the field are lacking. This paper reviews the mechanisms influencing antibiotic and ARG (intracellular and extracellular) removal in CWs, and natural, biomass, chemical, modified, industrial, novel, and combined substrates on their removal efficiencies. Generally, substrates remove antibiotics and ARGs mainly through adsorption, biodegradation, chemical oxidation, and filtration. Other mechanisms, such as photolysis, may also contribute to removal. Natural substrates (e.g., gravel, zeolite) are more frequently employed than other types of substrates. The removal performance of antibiotics and intracellular ARGs by zeolite was better than that of gravel through enhanced substrate adsorption, filtration, and biodegradation processes. Moreover, Mn ore showed promising high capability to remove high concentration of antibiotics through various removal pathways. In addition, combined substrates of soil/sand/gravel and other substrates further facilitate antibiotic removal. Future research is suggested to explore the mechanisms of competitive adsorption and redox-controlled biodegradation, investigate the effect of Fe/Mn oxides on the removal of antibiotics and ARGs via chemical oxidation, evaluate the removal of extracellular ARGs by CWs with different substrates, and investigate the effect of substrates on removal of antibiotics and ARGs in full-scale CWs.

Removal performance, biotransformation pathways and products of sulfamethoxazole in vertical subsurface flow constructed wetlands with different substrates

For decades, sulfamethoxazole (SMX) has been frequently detected in the aquatic environments due to its high usage and refractory to degradation. Constructed wetland (CW) is regarded as an efficient advanced wastewater technology to eliminate organic pollutants including SMX. In CW system, substrate adsorption and further biodegradation are extremely important in SMX removal; however, the removal performance of SMX by CWs with different substrates varies greatly, and the biotransformation pathways, products, and mechanisms of SMX remain unclear. To address this, we constructed a CW with conventional substrate (CS, gravel) as control (C-CW) and three CWs with emerging substrates (ES, biochar, zeolite and pyrite for B-CW, Z-CW and P-CW, respectively), and explored the performance and mechanisms of SMX removal in CWs. Results illustrated that the removal performance of SMX in CWs with ES reached 94.89-99.35%, and significantly higher than that with CS of 89.50% (p < 0.05). Biodegradation contributed >90% SMX removal in all CWs. The microbial compositions and functions differed among CWs at the middle layer (mixed layer), which shaped diverse resistance pattern and metabolism pathways of microbiomes under SMX stress: P-CW and B-CW cope with SMX stress by enhancing material and energy metabolism, whereas Z-CW does that by enhancing metabolism and exocytosis of xenobiotics. Additionally, nine transformation pathways with 15 transformation products were detected in this study. A reversible process of desamino-SMX being reconverted to SMX might exist in P-CW, which caused a lower SMX removal efficiency in P-CW. This study provided a comprehensive insight into the processes and mechanisms of SMX removal in CWs with different substrates, which would be a useful guidance for substrate selection in CWs in terms of enhanced micropollutants removal.

Mesocosm constructed wetlands to remove micropollutants from wastewater treatment plant effluent: Effect of matrices and pre-treatments

The contamination of the aquatic environment by micropollutants (MPs) brings risks for the ecosystem and human health. Constructed wetlands (CWs) were an eco-friendly technology to remove MPs from wastewater treatment plant effluent. In this study, the removal of MPs was evaluated in seven vertical flow mesocosm CWs with different configurations, including different support matrices (sand and a combination of bark-biochar), light pre-treatments (UVC and sunlight) or bioaugmentation in support matrices (activated sludge). The CWs with bark-biochar as support matrix significantly enhanced the removal of irbesartan and carbamazepine (>40 %), compared to the CW filled with the conventional support matrix sand. UVC irradiation as pre-treatment was more efficient in removing MPs than sunlight irradiation. After UVC pre-treatment, less MPs accumulated in the plants in the subsequent CW unit compared to the CW unit without any pre-treatment. Moreover, in the UVC combined CW system, less sulfamethoxazole, furosemide, mecoprop and diclofenac were accumulated in the plants (<0.5 μg) than other MPs (>3 μg). The addition of 0.5 % activated sludge combined with the aeration of influent did not improve MP removal in the CW. Considering the application, a bark-biochar based CW combined with UVC pre-treatment will result in more MP removal than a conventional sand CW.

State-of-the-Art Review on the Application of Membrane Bioreactors for Molecular Micro-Contaminant Removal from Aquatic Environment

In recent years, the emergence of disparate micro-contaminants in aquatic environments such as water/wastewater sources has eventuated in serious concerns about humans’ health all over the world. Membrane bioreactor (MBR) is considered a noteworthy membrane-based technology, and has been recently of great interest for the removal micro-contaminants. The prominent objective of this review paper is to provide a state-of-the-art review on the potential utilization of MBRs in the field of wastewater treatment and micro-contaminant removal from aquatic/non-aquatic environments. Moreover, the operational advantages of MBRs compared to other traditional technologies in removing disparate sorts of micro-contaminants are discussed to study the ways to increase the sustainability of a clean water supplement. Additionally, common types of micro-contaminants in water/wastewater sources are introduced and their potential detriments on humans’ well-being are presented to inform expert readers about the necessity of micro-contaminant removal. Eventually, operational challenges towards the industrial application of MBRs are presented and the authors discuss feasible future perspectives and suitable solutions to overcome these challenges.

Phytoremediation of micropollutants by Phragmites australis, Typha angustifolia, and Juncus effuses

Micropollutants (MPs) include organic chemicals, for example, pharmaceuticals and personal care products. MPs have been detected in the aquatic environment at low concentrations (ng/L-µg/L), which may lead to negative impacts on the ecosystem and humans. Phytoremediation is a green clean-up technology, which utilizes plants and their associated rhizosphere microorganisms to remove pollutants. The selection of plant species is important for the effectiveness of the phytoremediation of MPs. The plant species Phragmites australis, Typha angustifolia, and Juncus effuses are often used for MP removal. In this study, batch experiments were conducted to select plant species with an optimal ability to remove MPs, study the effect of temperature on MP removal in plants and the phytotoxicity of MPs. This study also explored the degradation of a persistent MP propranolol in plants in more detail. Data show that all three investigated plant species removed most MPs efficiently (close to 100 %) at both 10 and 21.5 °C. The tested plant species showed a different ability to translocate and accumulate propranolol in plant tissues. Typha angustifolia and Juncus effuses had a higher tolerance to the tested MPs than Phragmites australis. Typha angustifolia and Juncus effuses are recommended to be applied for phytoremediation of MPs.Novelty statement The novelty of this study is the selection of Typha angustifolia and Juncus effuses as proper plant species for phytoremediation of micropollutants (MPs). These two plant species were selected due to their good ability to remove MPs, tolerate low temperature, and resist the toxicity of MPs. The outcomes from this study can also be applied for constructed wetlands in removing MPs from wastewater. This study demonstrates the uptake and degradation processes of persistent MP propranolol in plants in more detail. Understanding the degradation mechanisms of a MP in plants is significant not only for the application of phytoremediation on MP removal but also for the development of constructed wetland studies.

Bioremediation of 27 Micropollutants by Symbiotic Microorganisms of Wetland Macrophytes

Background: Micropollutants in bodies of water represent many challenges. We addressed these challenges by the application of constructed wetlands, which represent advanced treatment technology for the removal of micropollutants from water. However, which mechanisms specifically contribute to the removal efficiency often remains unclear. Methods: Here, we focus on the removal of 27 micropollutants by bioremediation. For this, macrophytes Phragmites australis, Iris pseudacorus and Lythrum salicaria were taken from established wetlands, and a special experimental set-up was designed. In order to better understand the impact of the rhizosphere microbiome, we determined the microbial composition using 16S rRNA gene sequencing and investigated the role of identified genera in the micropollutant removal of micropollutants. Moreover, we studied the colonization of macrophyte roots by arbuscular mycorrhizal fungi, which are known for their symbiotic relationship with plants. This symbiosis could result in increased removal of present micropollutants. Results: We found Iris pseudacorus to be the most successful bioremediative system, as it removed 22 compounds, including persistent ones, with more than 80% efficiency. The most abundant genera that contributed to the removal of micropollutants were Pseudomonas, Flavobacterium, Variovorax, Methylotenera, Reyranella, Amaricoccus and Hydrogenophaga. Iris pseudacorus exhibited the highest colonization rate (56%). Conclusions: Our experiments demonstrate the positive impact of rhizosphere microorganisms on the removal of micropollutants.