Implementation of Floating Treatment Wetlands for Textile Wastewater Management: A Review

Industrial wastewater treatment using floating wetlands: a review

Industrial wastewater generated from various production processes is often associated with elevated pollutant concentrations and environmental hazards, necessitating efficient treatment. Floating wetlands (FWs) have emerged as a promising and eco-friendly solution for industrial wastewater treatment, with numerous successful field applications. This article comprehensively reviews the removal mechanisms and treatment performance in the use of FWs for the treatment of diverse industrial wastewaters. Our findings highlight that the performance of FWs relies on proper plant selection, design, aeration, season and temperature, plants harvesting and disposal, and maintenance. Well-designed FWs demonstrate remarkable effectiveness in removing organic matter (COD and BOD), suspended solids, nutrients, and heavy metals from industrial wastewater. This effectiveness is attributed to the intricate physical and metabolic interactions between plants and microbial communities within FWs. A significant portion of the reported applications of FWs revolve around the treatment of textile and oily wastewater. In particular, the application reports of FWs are mainly concentrated in temperate developing countries, where FWs can serve as a feasible and cost-effective industrial wastewater treatment technology, replacing high-cost traditional technologies. Furthermore, our analysis reveals that the treatment efficiency of FWs can be significantly enhanced through strategies like bacterial inoculation, aeration, and co-plantation of specific plant species. These techniques offer promising directions for further research. To advance the field, we recommend future research efforts focus on developing novel floating materials, optimizing the selection and combination of plants and microorganisms, exploring flexible disposal methods for harvested biomass, and designing multi-functional FW systems.

Incorporation of Cellulose-Based Aerogels into Textile Structures

Given their exceptional attributes, aerogels are viewed as a material with immense potential. Being a natural polymer, cellulose offers the advantage of being both replenishable and capable of breaking down naturally. Cellulose-derived aerogels encompass the replenish ability, biocompatible nature, and ability to degrade naturally inherent in cellulose, along with additional benefits like minimal weight, extensive porosity, and expansive specific surface area. Even with increasing appreciation and acceptance, the undiscovered possibilities of aerogels within the textiles sphere continue to be predominantly uninvestigated. In this context, we outline the latest advancements in the study of cellulose aerogels' formulation and their diverse impacts on textile formations. Drawing from the latest studies, we reviewed the materials used for the creation of various kinds of cellulose-focused aerogels and their properties, analytical techniques, and multiple functionalities in relation to textiles. This comprehensive analysis extensively covers the diverse strategies employed to enhance the multifunctionality of cellulose-based aerogels in the textiles industry. Additionally, we focused on the global market size of bio-derivative aerogels, companies in the industry producing goods, and prospects moving forward.

Pilot and full scale applications of floating treatment wetlands for treating diffuse pollution

Floating treatment wetlands (FTW) are nature-based solutions for the purification of open water systems such as rivers, ponds, and lakes polluted by diffuse sources as untreated or partially treated domestic wastewater and agricultural run-off. Compared with other physicochemical and biological technologies, FTW is a technology with low-cost, simple configuration, easy to operate; has a relatively high efficiency, and is energy-saving, and aesthetic. Water remediation in FTWs is supported by plant uptake and the growth of a biofilm on the water plant roots, so the selection of the macrophyte species is critical, not only to pollutant removal but also to the local ecosystem integrity, especially for full-scale implementation. The key factors such as buoyant frame/raft, plant growth support media, water depth, seasonal variation, and temperature have a considerable role in the design, operation, maintenance, and pollutant treatment performance of FTW. Harvesting is a necessary process to maintain efficient operation by limiting the re-pollution of plants in the decay phase. Furthermore, the harvested plant biomass can serve as a green source for the recovery of energy and value-added products.

Green synthesis of zinc oxide nanoparticles using Brassica oleracea var. botrytis leaf extract: Photocatalytic, antimicrobial and larvicidal activity

Green synthesis of nanomaterials has emerged as an ecofriendly sustainable technology for the removal of dyes in the last few decades. Especially, plant leaf extracts have been considered as inexpensive and effective materials for the synthesis of nanoparticles. In this study, zinc oxide nanoparticles (ZnO NPs) were prepared using leaves extract of Brassica oleracea var. botrytis (BO) by co-precipitation and applied for photocatalytic/antibacterial activity. The synthesized BO-ZnO NPs was characterized by different instrumental techniques. The UV-vis Spectrum of the synthesized material showed maximum absorbance at a wavelength of 311 nm, which confirmed the formation of BO-ZnO NPs. The XRD pattern of BO-ZnO NPs represents a hexagonal wurtzite structure and the average size of particles was about 52 nm. FT-IR spectrum analysis confirms the presence of hydroxyl, carbonyl, carboxylic, and phenol groups. SEM images exhibited a flower like morphology and EDX spectrum confirming the presence of the elements Zn and O. Photo-catalytic activity of BO-ZnO NPs was tested against thiazine dye (methylene blue-MB) degradation under direct sunlight irradiation. Around 80% of the MB dye got degraded at pH 8 under 75 min of sunlight irradiation. Further, the study examined that the antimicrobial and larvicidal activity of BO-ZnO NPs obtained through green synthesis. The antimicrobial study results showed that the BO-ZnO NPs formed zones against bacterial pathogens. The results showed the formation of an inhibition zone against B. subtills (16 mm), S.aureus (13 mm), K. pneumonia (13 mm), and E. coli (9 mm) respectively at a concentration of 100 μg/mL of BO-ZnO NPs. The larvicidal activity of the BO-ZnO NPs was tested against the fourth instar of Culex quinquefasciatus mosquito larvae The LC₅₀ and LC₉₀ values estimated through the larvicidal activity of BO-ZnO NPs were 76.03, 190.03 ppm respectively. Hence the above findings propose the synthesized BO-ZnO NPs by the ecofriendly method can be used for various environmental and antipathogenic applications.

Investigation of functional performance of treatment systems for textile wastewater in selected textile industries in Tanzania

Textile industrialization is an integral part of the economic growth in Tanzania. However, the corresponding wastewater from textile treatment processes consists of dyes and auxiliaries associated with acute toxicological impacts. This necessitates an investigation of the functional performance of the industrial treatment systems used before effluent discharge. The study primarily accesses the catalog of industrial dyes and the functionality of the treatment system at Arusha, Morogoro and Dar es Salaam vis-à-vis the effluent physicochemical properties. The analytical study reveals disperse (42%), vat (34%) and reactive (26%) as the most used industrial dyes. The physicochemical properties of the quantified wastewater reveal a significant amount of and phosphorus which was consequent to the high turbidity, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) apart from the color at the different sampling points. Although the treatability of the wastewater was 90% efficient using an activated carbon system (237.33 ± 0.67 mg/L). Similarly, the use of aerated constructed wetlands shows efficiency in the remediation of the recalcitrant having a value of 12.13 ± 0.89^b mg/L (90%) and 13.22 ± 0.15^a mg/L (94%). Thereafter, needful recommendations were suggested based on the physicochemical properties of the textile wastewater and to improve the functionality of the treatment systems in the respective industries.

Understanding the Phytoremediation Mechanisms of Potentially Toxic Elements: A Proteomic Overview of Recent Advances

Potentially toxic elements (PTEs) such as cadmium (Cd), lead (Pb), chromium (Cr), and arsenic (As), polluting the environment, pose a significant risk and cause a wide array of adverse changes in plant physiology. Above threshold accumulation of PTEs is alarming which makes them prone to ascend along the food chain, making their environmental prevention a critical intervention. On a global scale, current initiatives to remove the PTEs are costly and might lead to more pollution. An emerging technology that may help in the removal of PTEs is phytoremediation. Compared to traditional methods, phytoremediation is eco-friendly and less expensive. While many studies have reported several plants with high PTEs tolerance, uptake, and then storage capacity in their roots, stem, and leaves. However, the wide application of such a promising strategy still needs to be achieved, partly due to a poor understanding of the molecular mechanism at the proteome level controlling the phytoremediation process to optimize the plant's performance. The present study aims to discuss the detailed mechanism and proteomic response, which play pivotal roles in the uptake of PTEs from the environment into the plant's body, then scavenge/detoxify, and finally bioaccumulate the PTEs in different plant organs. In this review, the following aspects are highlighted as: (i) PTE's stress and phytoremediation strategies adopted by plants and (ii) PTEs induced expressional changes in the plant proteome more specifically with arsenic, cadmium, copper, chromium, mercury, and lead with models describing the metal uptake and plant proteome response. Recently, interest in the comparative proteomics study of plants exposed to PTEs toxicity results in appreciable progress in this area. This article overviews the proteomics approach to elucidate the mechanisms underlying plant's PTEs tolerance and bioaccumulation for optimized phytoremediation of polluted environments.

Adsorptive Removal of Methylene Blue Dye Using Biowaste Materials: Barley Bran and Enset Midrib Leaf

In this study, several biowaste materials are screened for adsorptive removal of methylene blue (MB) from synthetic water. Among the tested adsorbents, barley (Hordeum vulgare) bran (BB) and enset (Ensete ventricosum midrib leaf, EVML) were selected for further evaluation of MB (a model cationic dye) adsorption. Batch MB adsorption performance of BB and EVML adsorbents was significantly high in a wide pH range (4-9). The well fitting of experimental data with pseudosecond-order kinetic model suggests a monolayer adsorption of MB. The MB adsorption onto both adsorbents was fit well with the Langmuir isotherm model with maximum MB adsorption capacities of 63.2 mg/g (BB) and 35.5 mg/g (EVML). The biowaste materials exhibit considerable adsorption capacity for cationic dye (MB), perform well under acidic and basic conditions, and are reusable. Therefore, the use of these materials as adsorbents may have an environmental benefit in terms of the conversion of wastes into valuable materials. Further studies are suggested to investigate the performance of these adsorbents in a continuous mode using real wastewater.

Review of hydraulics of Floating Treatment Islands retrofitted in waterbodies receiving stormwater

Stormwater pollution causes an excessive influx of nutrients and metals to the receiving waterbodies (stormwater ponds, lakes, and rivers), which can cause eutrophication and metal toxicity. One of the most cost-effective and eco-friendly solutions to stormwater pollution is constructing Floating Treatment Islands (FTIs) within the waterbodies receiving stormwater runoff. Treatment efficiency of FTIs depends on many factors including plant species, temperature, detention time, and pollutant loading rate. Another important factor is FTI hydraulics, which determines the amount of inflow to the root zone and residence time, greatly impacting the treatment. However, only a few studies refer to the hydraulics of waterbodies retrofitted with FTIs. This paper reviews available literature on field-scale, laboratory-scale and numerical studies on the hydraulics of FTI retrofitted waterbodies. Because of limited knowledge on the factors affecting hydraulics of waterbodies retrofitted with FTIs, current practices cannot ensure maximum hydraulic performance of this system. This review paper identifies different factors affecting the FTI hydraulics, investigates knowledge gaps, and provides future research direction for hydraulically efficient design of FTIs to treat stormwater. It was found that there is a need to investigate the impact of new design parameters such as FTI shape, FTI coverage, inlet-outlet configurations, and shape of waterbody on the hydraulic performance of FTI retrofitted waterbodies. A lack of dimensional analysis on FTI retrofitted waterbodies in existing literature revealed that field-scale values were not properly scaled down in laboratory experiments. Although a few short-circuiting prevention mechanisms (SPMs) were used in different field-scale studies, those mechanisms may be vulnerable to short-circuiting in the vertical dimension. It was revealed that studying the role of eddy diffusion and gap layer for vertical short-circuiting can help designing better SPMs. This review also identified that further investigation is required to incorporate root flexibility in the current modeling approach of FTI retrofitted waterbodies.

Investigating degradation metabolites and underlying pathway of azo dye "Reactive Black 5" in bioaugmented floating treatment wetlands

The direct discharge of azo dyes and/or their metabolites into the environment may exert toxic, mutagenic, and carcinogenic effects on exposed fauna and flora. In this study, we analyzed the metabolites produced during the degradation of an azo dye namely Reactive Black 5 (RB5) in the bacterial-augmented floating treatment wetlands (FTWs), followed by the investigation of their underlying toxicity. To this end, a FTWs system was developed by using a common wetland plant Phragmites australis in the presence of three dye-degrading bacteria (Acinetobacter junii strain NT-15, Pseudomonas indoloxydans strain NT-38, and Rhodococcus sp. strain NT-39). We found that the FTW system effectively degraded RB5 into at least 20 different metabolites with the successful removal of color (95.5%) from the water. The fish toxicity assay revealed the nontoxic characteristics of the metabolites produced after dye degradation. Our study suggests that bacterially aided FTWs could be a suitable option for the successful degradation of azo dyes, and the results presented in this study may help improve the overall textile effluent cleanup processes.