Use of constructed wetlands to prevent overloading of wastewater treatment plants

Recent progress, challenges, and future prospects in constructed wetlands employing biochar as a substrate: a comprehensive review

Constructed wetlands (CWs) are a cost-effective, efficient, and long-term wastewater treatment solution in various countries. The efficacy and performance of constructed wetlands are greatly influenced by the substrate. Recently, biochar as a substrate, along with sand and gravel in constructed wetlands, has gained importance due to its various physical, chemical, and biological properties. This review presents a detailed study of biochar as a substrate in CWs and the mechanism involved in efficiency enhancement in pollutant removal. Different methods for producing biochar using various types of biomasses are also addressed. The effect of biochar in removing pollutants like biological oxygen demand (BOD), chemical oxygen demand (COD), nitrogen, heavy metals, and non-conventional pollutants (microcystin, phenanthrene, antibiotics, etc.) are also discussed. Furthermore, post-harvest utilization of constructed wetland macrophytic biomass via bioenergy production, biochar formation, and biosorbent formation is explained. Various challenges and future prospects in biochar-amended constructed wetlands are also discussed. Biochar proved to be an effective substrate in the removal of pollutants and proved to be a promising technique for wastewater treatment, especially for developing countries where the cost of treatment is a constraint. Biochar is an effective substrate; further modification in biochar with the right plant combination for different wastewater needs to be explored in the future. Future researchers in the field of constructed wetlands will benefit from this review during the utilization of biochar in constructed wetlands and optimization of biochar characteristics, viz., quantity, size, preparation method, and other biochar modifications.

Upgrade constructed wetlands wastewater quality by solar-driven photochemical quaternary treatments in raceway pond reactor at pilot plant scale

This study explores the potential application of solar photochemical processes (SPPs) for simultaneous disinfection and decontamination of urban wastewater (UWW) when combined with constructed wetlands (CWs). Two SPPs based on the addition of low concentrations of hydrogen peroxide and peroxymonosulfate (PMS) were evaluated. SPPs were carried out at pilot plant scale using low-cost solar open photoreactors (Raceway Pond Reactor (RPR)) under natural sunlight. The performance of the SPPs was analyzed by monitoring naturally occurring bacteria (Escherichia coli, Enterococcus spp. and Salmonella spp.) and Contaminants of Emerging Concern (CECs), such as pharmaceutical products, pesticides, antibiotics and their metabolites, simultaneously. SPP best operating conditions were determined by testing a wide range of oxidant concentrations (0-5.9 mM, 0-3.0 mM) and liquid depths (5, 10 and 15 cm) in the RPR. SPP treatment efficacy was tested on the actual inlet and outlet of the CW system, showing the high influence of their different physicochemical characteristics on the oxidants' performance. H2O2/solar SPP in the actual inlet of the CWs showed slightly higher inactivation kinetics when increasing H2O2 concentration at both water depths (5 and 10 cm), while no significant CECs degradation rates were obtained. However, much higher efficacy was obtained with PMS/solar process attaining high bacteria inactivation under dark conditions and 79 % CEC degradation at 3.0 mM after only 10 min of reaction time. SPPs assessment on the outlet of the CWs also showed better efficacy of the PMS as oxidant compared to the H2O2 for the simultaneous CECs removal (95 % at 1.0 mM of PMS, after only 5 min of treatment) and bacteria inactivation (confirming the no-regrown after 24 h). SPPs have demonstrated to be a low-cost and eco-sustainable polishing alternative to regenerate CW effluents complying with the actual European regulation on the minimum water quality requirements for reusing treated UWW in agriculture.

Performance of vertical flow constructed wetland for the treatment of effluent from a brassware industry in city of Fez, Morocco: a laboratory scale study

Brassware industry constitutes the second most polluting industrial sector in Fez city, Morocco, owing to its high heavy metal load. The aim of this study is to examine and evaluate the performance of vertical flow constructed wetlands in treating brassware effluents using various plant species. Ten treatment systems were planted with four types of plants: Chrysopogon zizanioides, Typha latifolia, Phragmites australis, and Vitex agnus-castus, while another system remained unplanted. These systems underwent evaluation by measuring various parameters, including pH, electrical conductivity, suspended solids, chemical oxygen demand, biological oxygen demand, sulfates, orthophosphates, total Kjeldhal nitrogen, ammonium, nitrates, nitrites, and heavy metals such as silver, copper, and nickel, using standard methods over of ten weeks. The results obtained demonstrate effectiveness of these systems. When planted with Ch. zizanioides, the systems achieved elimination rates of 83.64%, 98.55%, 91.48%, 86.82%, 80.31%, 96.54%, 98%, and 98.82% for suspended solids, ammonium, nitrites, BOD5, sulfates, orthophosphates, silver, and nickel, respectively. System with V. agnus-castus showed significant reductions in nitrate and copper, with rates of 84.48% and 99.10%, respectively. Considerable decrease in pH and electrical conductivity values was observed in all systems, with a notable difference between planted and control systems regarding effectiveness of treatment for other parameters.