Performance Comparison of Different Constructed Wetlands Designs for the Removal of Personal Care Products

Free water surface constructed wetlands: review of pollutant removal performance and modeling approaches

Free water surface constructed wetlands (FWSCWs) for the treatment of various wastewater types have evolved significantly over the last few decades. With an increasing need and interest in FWSCWs applications worldwide due to their cost-effectiveness and other benefits, this paper reviews recent literature on FWSCWs' ability to remove different types of pollutants such as nutrients (i.e., TN, TP, NH4-N), heavy metals (i.e., Fe, Zn, and Ni), antibiotics (i.e., oxytetracycline, ciprofloxacin, doxycycline, sulfamethazine, and ofloxacin), and pesticides (i.e., Atrazine, S-Metolachlor, imidacloprid, lambda-cyhalothrin, diuron 3,4-dichloroanilin, Simazine, and Atrazine) that may co-exist in wetland inflow, and discusses approaches for simulating hydraulic and pollutant removal processes. A bibliometric analysis of recent literature reveals that China has the highest number of publications, followed by the USA. The collected data show that FWSCWs can remove an average of 61.6%, 67.8%, 54.7%, and 72.85% of inflowing nutrients, heavy metals, antibiotics, and pesticides, respectively. Optimizing each pollutant removal process requires specific design parameters. Removing heavy metal requires the lowest hydraulic retention time (HRT) (average of 4.78 days), removing pesticides requires the lowest water depth (average of 0.34 m), and nutrient removal requires the largest system size. Vegetation, especially Typha spp. and Phragmites spp., play an important role in FWSCWs' system performance, making significant contributions to the removal process. Various modeling approaches (i.e., black-box and process-based) were comprehensively reviewed, revealing the need for including the internal process mechanisms related to the biological processes along with plants spp., that supported by a further research with field study validations. This work presents a state-of-the-art, systematic, and comparative discussion on the efficiency of FWSCWs in removing different pollutants, main design factors, the vegetation, and well-described models for performance prediction.

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.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

Current research trends on emerging contaminants pharmaceutical and personal care products (PPCPs): A comprehensive review

Pharmaceutical and personnel care products (PPCPs) from wastewater are a potential hazard to the human health and wildlife, and their occurrence in wastewater has caught the concern of researchers recently. To deal with PPCPs, various treatment technologies have been evolved such as physical, biological, and chemical methods. Nevertheless, modern and efficient techniques such as advance oxidation processes (AOPs) demand expensive chemicals and energy, which ultimately leads to a high treatment cost. Therefore, integration of chemical techniques with biological processes has been recently suggested to decrease the expenses. Furthermore, combining ozonation with activated carbon (AC) can significantly enhance the removal efficiency. There are some other emerging technologies of lower operational cost like photo-Fenton method and solar radiation-based methods as well as constructed wetland, which are promising. However, feasibility and practicality in pilot-scale have not been estimated for most of these advanced treatment technologies. In this context, the present review work explores the treatment of emerging PPCPs in wastewater, via available conventional, non-conventional, and integrated technologies. Furthermore, this work focused on the state-of-art technologies via an extensive literature search, highlights the limitations and challenges of the prevailing commercial technologies. Finally, this work provides a brief discussion and offers future research directions on technologies needed for treatment of wastewater containing PPCPs, accompanied by techno-economic feasibility assessment.

Removal of pharmaceutical active compounds in wastewater by constructed wetlands: Performance and mechanisms

The occurrence of pharmaceutical active compounds (PhACs) in aquatic environments is a cause for concern due to potential adverse effects on human and ecosystem health. Constructed wetlands (CWs) are cost-efficient and sustainable wastewater treatment systems for the removal of these PhACs. The removal processes and mechanisms comprise a complex interplay of photodegradation, biodegradation, phytoremediation, and sorption. This review synthesized the current knowledge on CWs for the removal of 20 widely detected PhACs in wastewater. In addition, the major removal mechanisms and influencing factors are discussed, enabling comprehensive and critical understanding for optimizing the removal of PhACs in CWs. Consequently, potential strategies for intensifying CWs system performance for PhACs removal are discussed. Overall, the results of this review showed that CWs performance in the elimination of some pharmaceuticals was on a par with conventional wastewater treatment plants (WWTPs) and, for others, it was above par. Furthermore, the findings indicated that system design, operational, and environmental factors played important but highly variable roles in the removal of pharmaceuticals. Nonetheless, although CWs were proven to be a more cost-efficient and sustainable technology for pharmaceuticals removal than other engineered treatment systems, there were still several research gaps to be addressed, mainly including the fate of a broad range of emerging contaminants in CWs, identification of specific functional microorganisms, transformation pathways of specific pharmaceuticals, assessment of transformation products and the ecotoxicity evaluation of CWs effluents.

Constructed wetlands for the removal of pharmaceuticals and personal care products (PPCPs) from wastewater: origin, impacts, treatment methods, and SWOT analysis

The continuous exposure to pharmaceuticals and personal care products can lead to a series of individual antagonistic and synergistic effects and long-lasting toxicity to humans and aquatic lives. This may also lead to developing antibiotic resistance, teratogenic, carcinogenic, and endocrine-disrupting effects. However, several PPCPs are also considered biologically active for non-target aquatic organisms, such as mosquito fish, goldfish, and the algae Pseudokirchneriella subcapitata. Various physicochemical methods such as ozonation, photolysis, and membrane separation are recognized for the effective removal of PPCPs. However, the high operation and maintenance costs and associated ecological impacts have limited their further use. Constructed wetlands are considered eco-friendly and sustainable for the removal of pharmaceuticals and personal care products together with antibiotic resistance genes. Several mechanisms such as sorption, biodegradation, oxidation, photodegradation, volatilization, and hydrolysis are occurring during the phytoremediation of PPCPs. During these processes, more than 50% of PPCPs can be eliminated through constructed wetlands. They also offer several additional benefits as obtained macrophytic biomass may be used as raw material in pulp and paper industries and a source for second-generation biofuel production. In this study, we have discussed the origin and impacts of PPCPs together with their treatment methods. We have also investigated the strengths, weaknesses, opportunities, and threats associated with constructed wetlands during the treatment of wastewater laden with pharmaceutical and personal care products.

Cosmetic wastewater treatment technologies: a review

Over the past three decades, environmental concerns about the water pollution have been raised on societal and industrial levels. The presence of pollutants stemming from cosmetic products has been documented in wastewater streams outflowing from industrial as well as wastewater treatment plants. To this end, a series of consistent measures should be taken to prevent emerging contaminants of water resources. This need has driven the development of technologies, in an attempt to mitigate their impact on the environment. This work offers a thorough review of existing knowledge on cosmetic wastewater treatment approaches, including, coagulation, dissolved air flotation, adsorption, activated sludge, biodegradation, constructed wetlands, and advanced oxidation processes. Various studies have already documented the appearance of cosmetics in samples retrieved from wastewater treatment plants (WWTPs), which have definitely promoted our comprehension of the path of cosmetics within the treatment cycle; however, there are still multiple blanks to our knowledge. All treatments have, without exception, their own limitations, not only cost-wise, but also in terms of being feasible, effective, practical, reliable, and environmentally friendly.

Sustainable Treatment Techniques for Emerging Pollutants—The Case of Personal Hygiene Products

Personal care products (PCPs) enter wastewater primarily through greywater. Treatment plants have not been able to remove this type of contaminant, although PCP abatement techniques have been developed in recent years. The objective of the current study has been to encounter the sustainable technique that keeps the optimal balance between the criteria considered in the comparison. Therefore, a bibliographic review was conducted in scientific databases of the last eight years, demonstrating that co-composting, anaerobic–aerobic sequencing bioreactors and contaminant absorption through the use of carbon nanotubes are the ones with the least environmental impact. Subsequently, the Saaty and Modified Saaty methods were applied, with a comparative criteria of construction costs, maintenance costs, efficiency and the stage of development. The results indicated that the co-composting technique is the best sustainable technique of those studied, with a score of 0.86/1, which means that the criteria analyzed maintain very close values between them. The co-composting technique yields a low environmental impact in eliminating personal care products. This research work constitutes a practical and easy-to-use tool for decision makers, since it allows finding an optimal elimination treatment for PCPs.

Performance Efficiency of Conventional Treatment Plants and Constructed Wetlands towards Reduction of Antibiotic Resistance

Domestic and industrial wastewater discharges harbor rich bacterial communities, including both pathogenic and commensal organisms that are antibiotic-resistant (AR). AR pathogens pose a potential threat to human and animal health. In wastewater treatment plants (WWTP), bacteria encounter environments suitable for horizontal gene transfer, providing an opportunity for bacterial cells to acquire new antibiotic-resistant genes. With many entry points to environmental components, especially water and soil, WWTPs are considered a critical control point for antibiotic resistance. The primary and secondary units of conventional WWTPs are not designed for the reduction of resistant microbes. Constructed wetlands (CWs) are viable wastewater treatment options with the potential for mitigating AR bacteria, their genes, pathogens, and general pollutants. Encouraging performance for the removal of AR (2-4 logs) has highlighted the applicability of CW on fields. Their low cost of construction, operation and maintenance makes them well suited for applications across the globe, especially in developing and low-income countries. The present review highlights a better understanding of the performance efficiency of conventional treatment plants and CWs for the elimination/reduction of AR from wastewater. They are viable alternatives that can be used for secondary/tertiary treatment or effluent polishing in combination with WWTP or in a decentralized manner.

Prediction of the removal efficiency of emerging organic contaminants in constructed wetlands based on their physicochemical properties

This study investigates the prediction of the removal efficiency of emerging organic contaminants (EOCs) (pharmaceuticals-PhCs, personal care products-PCPs, and steroidal hormones-SHs) in constructed wetlands based on their physicochemical properties (e.g., molecular weight-MW, octanol-water partition coefficient-Log Kow, soil organic carbon sorption coefficient-Log Koc, octanol-water distribution coefficient-Log Dow, and dissociation constant-pKa). The predictive models are formed based on statistical analysis underpinned by principle component, correlation, and regression analyses of a global data set compiled from peer-reviewed publications. The results show that the physicochemical properties of EOCs emerged as good predictors of their removal efficiency. Log Koc, Log Dow, and Log Kow are the most significant predictors, and combination with MW and/or pKa often improved the reliability of the predictions. The best performing model for PhCs was composed of MW, Log Dow, and Log Koc (coefficient of determination-R²: 0.601; probability value-p < 0.05; root mean square error-RMSE: training set: 11%; test set: 27%). Log Kow and Log Koc for PCPs (R²: 0.644; p < 0.1; RMSE: training set: 14%; test set: 14%), and a combination of MW, Log Kow, and pKa for SHs (R²: 0.941; p < 0.1; RMSE: training set: 3%; test set: 15%) formed the plausible models for predicting the removal efficiency. Similarly, reasonably good combined models could be formed in the case of PhCs and SHs or PCPs and SHs, although their individual models were comparatively better. A novel decision support tool, named as REOCW-PCP, was developed to readily estimate the removal efficiency of EOCs, and facilitate the decision-making process.

The anaerobic biodegradation of emerging organic contaminants by horizontal subsurface flow constructed wetlands

The horizontal subsurface flow constructed wetland (HFCW) is widely studied for the treatment of wastewater containing emerging organic contaminants (EOCs): pharmaceuticals, personal care products, and steroidal hormones. This study evaluates the performance of HFCW for the removal of these types of EOCs based on the data collected from peer-reviewed journal publications. In HFCW, anaerobic biodegradation is an important removal mechanism of EOCs besides their removal by the filter media (through sedimentation, adsorption, and precipitation) and plant uptake. The average removal efficiency of 18 selected EOCs ranged from 39% to 98%. The moderate to higher removal efficiency of 12 out of 18 selected EOCs in HFCW indicates the suitability of this type of constructed wetland (CW) for the treatment of wastewater containing these EOCs. The reasonably good removal (>50% in most of the cases) of these EOCs in HFCW might be due to the occurrence of anaerobic biodegradation as one of their major removal mechanisms in CWs. Although the effluent concentration of EOCs was substantially decreased after the treatment, the environmental risk posed by them was not fully reduced in most of the cases. For instance, estimated risk quotient of 11 out of 18 examined EOCs was extremely high for the effluent of HFCW.

A decision tree framework to support design, operation, and performance assessment of constructed wetlands for the removal of emerging organic contaminants

There is an increasing focus on research related to the removal of emerging organic contaminants (EOCs) from wastewater by using constructed wetlands (CWs). However, research is lacking on translating the available scientific evidence into decision support tools. In this paper, a novel decision tree framework is developed and demonstrated. The proposed framework consists of five steps: (1) generate a list of EOCs by the analysis of the wastewater; (2) select the best type of CW for each of the selected EOCs; (3) select a final type of CW for the removal of the selected EOCs; (4) identify detailed design and operational features of the proposed CW such as, depth, area, plants, support matrix, hydraulic loading rate, organic loading rate, and hydraulic retention time; and (5) assess the expected removal efficiency of EOCs in the selected CW. A novel decision support tool, named as DTFT-CW, was developed to generate data and information for the application of the proposed decision tree framework. DTFT-CW (given as a supplementary material) was developed using Microsoft Excel 2016 to support decisions on the design, operation, and performance of CWs for the removal of 59 EOCs (33 pharmaceuticals-PhCs, 15 personal care products-PCPs, and 11 steroidal hormones-SHs). The paper demonstrates the usefulness of the developed decision-making tools by considering 19 EOCs (13 PhCs, one PCPs, and five SHs) as an example, which pose high environmental risk and are on the European Union watch list (six of the 19 EOCs). An integrated design of HCW (combining vertical flow CW, horizontal flow CW-HFCW, and free water surface CW) is recommended for the treatment of multiple EOCs instead of a single type of CW such as HFCW that is most widely used in practice. The proposed tools could be useful for decision makers such as policy makers, design engineers, and researchers.

The Influence of Design and Operational Factors on the Removal of Personal Care Products by Constructed Wetlands

This research presents the correlation analysis of selected design and operational factors (depth, area, hydraulic and organic loading rate, and hydraulic retention time), and physicochemical parameters (pH, temperature, and dissolved oxygen) of constructed wetlands (CWs) with the removal efficiency of personal care products (PCPs). The results demonstrated that the removal efficiencies of the studied PCPs exhibit a significant correlation with two or more of these factors. The role of plants in the removal of PCPs is demonstrated by the higher performance of planted compared with unplanted CWs due to direct uptake of PCPs and their aerobic biodegradation. The enhanced removal of PCPs was achieved with the use of substrate material of high adsorption capacity and with high surface area in CWs. The removal efficiency of almost all of the studied PCPs revealed seasonal differences, but significant difference was established in the case of galaxolide and methyl dihydrojasmonate. Most of the examined PCPs demonstrated adsorption and/or sorption as their most dominant removal mechanism followed by biodegradation and plant uptake. Therefore, the efficient removal of PCPs demands the integrated design ensuring suitable environment for the occurrence of these processes along with the optimal values of design and operational factors, and physicochemical parameters.