Horizontal Flow Constructed Wetland for Greywater Treatment and Reuse: An Experimental Case

Tidal and vertical flow constructed wetland treatment for graywater modeling and reusing with biochar cadmium adsorption

This study addresses a persistent environmental concern related to graywater discharge from households, highlighting its potential to contribute to increased pollution in water bodies. To mitigate this issue, the research explores the use of subsurface flow-built wetlands, specifically focusing on the innovative application of constructed tidal and vertical flow wetlands (CTWFWs) as wastewater treatment systems. The study not only evaluates the efficacy of these CTWFW systems but also delves into the crucial aspects of their operation and their interactions with the biological, physical, and chemical characteristics of graywater. A key innovation of this research is the investigation of zeolite's effectiveness and the utilization of perlite-based plant species in both mixed and monoculture configurations to develop lab-scale hybrid constructed wetlands (HCWs). These HCWs are designed for the removal of organic matter and nutrients from graywater, offering a sustainable and cost-effective solution to this environmental challenge. The study also examines the dynamic processes involved in graywater treatment, emphasizing how the removal of parameters like biological oxygen demand (BOD), nutrients, total suspended solids (TSS), and disinfection efficiency can significantly impact the effectiveness of treatment systems. Furthermore, the research scrutinizes the intricate relationship between the treatment unit's dimensions and the specific criteria that need to be met for efficient graywater treatment. Intriguingly, the study tracks the changes in graywater composition and the treatment process over time. By conducting on-site measurements of various physicochemical characteristics such as temperature, dissolved oxygen (DO), electrical conductivity (EC), turbidity, total dissolved solids (TDS), and pH, the research offers a comprehensive understanding of the treatment system's performance and adaptability. The study dives into the microbial communities within the treatment systems, utilizing 16S rRNA amplicon sequencing to characterize the complex microbial ecosystem present in graywater. This approach sheds light on the interplay between microorganisms, physicochemical conditions, plant responses, substrate dynamics, and the production of microbial metabolites. It underscores the holistic nature of the research, encompassing various aspects of graywater treatment. Notably, the study explores the application of biochar in combination with the target heavy metal, cadmium (Cd), within constructed wetlands (CWs). This innovative approach aims to better understand the kinetics and isothermal adsorption of lead in the context of mouthwash residue, expanding the knowledge base in this critical area. The research findings are substantial, with remarkable removal efficiencies achieved for parameters like TSS, turbidity, chemical oxygen demand (COD), nitrate, and phosphate. These results underscore the practicality and effectiveness of the proposed treatment methods. This holistic and pioneering research significantly advances the understanding of sustainable graywater treatment, offering valuable insights and practical solutions to mitigate water pollution concerns. PRACTITIONER POINTS: This study addresses a persistent environmental concern related to greywater discharge from households, highlighting its potential to contribute to increased pollution in water bodies. The study not only evaluates the efficacy of these CTWFW systems but also delves into the crucial aspects of their operation and their interactions with the biological, physical, and chemical characteristics of greywater. A key innovation of this research is the investigation of zeolite's effectiveness and the utilization of perlite-based plant species in both mixed and monoculture configurations to develop lab-scale hybrid constructed wetlands (HCWs).

Greywater reuse as a key enabler for improving urban wastewater management

Sustainable water management is essential to guaranteeing access to safe water and addressing the challenges posed by climate change, urbanization, and population growth. In a typical household, greywater, which includes everything but toilet waste, constitutes 50-80% of daily wastewater generation and is characterized by low organic strength and high volume. This can be an issue for large urban wastewater treatment plants designed for high-strength operations. Segregation of greywater at the source for decentralized wastewater treatment is therefore necessary for its proper management using separate treatment strategies. Greywater reuse may thus lead to increased resilience and adaptability of local water systems, reduction in transport costs, and achievement of fit-for-purpose reuse. After covering greywater characteristics, we present an overview of existing and upcoming technologies for greywater treatment. Biological treatment technologies, such as nature-based technologies, biofilm technologies, and membrane bioreactors (MBR), conjugate with physicochemical treatment methods, such as membrane filtration, sorption and ion exchange technologies, and ultraviolet (UV) disinfection, may be able to produce treated water within the allowable parameters for reuse. We also provide a novel way to tackle challenges like the demographic variance of greywater quality, lack of a legal framework for greywater management, monitoring and control systems, and the consumer perspective on greywater reuse. Finally, benefits, such as the potential water and energy savings and sustainable future of greywater reuse in an urban context, are discussed.

Reduction of pathogens in greywater with biological and sustainable treatments selected through a multicriteria approach

Non-potable reuse of greywater (GW) can represent a valid alternative to freshwater consumption, satisfying the Sustainable Development Goals promoted by United Nations. The Multi-Criteria Analysis (MCA) was applied to select the most suitable processes for the reduction of microbiological contamination in GW. A pilot plant, including horizontal flow constructed wetland (CW) and anaerobic filtration (AF) in parallel, best treatment options according to MCA results, was built to treat GW collected from a Venezuelan family. (i) The removal efficiency of microbiological parameters, and (ii) the turbidity as possible microbiological contamination indicator and possible influence factor of disinfection treatment, were investigated. Except for Escherichia coli (4.1 ± 0.9 log reduction with AF), CW achieved the best reductions yields for total coliforms, faecal coliforms, and Salmonella, respectively equal to 3.1 ± 0.5 log, 4.3 ± 0.5 log, and 2.9 ± 0.4 log. In accordance with Venezuelan legislation and WHO guidelines, GW treated with CW was found to be suitable for irrigation reuse for non-edible crops. However, the reduction of pathogens by CW should be considered as a preliminary and not complete disinfection treatment. To reuse GW, especially in the irrigation of edible crops, stronger disinfection treatment should be considered as a complement to the preliminary disinfection performed by CW, to avoid any kind of risk. No significant correlation was found for turbidity either as a possible predictor of microbiological contamination or as an influence on biological disinfection.

Greywater characteristics, impacts, treatment, and reclamation using adsorption processes towards the circular economy

The gap between water demand and available water supply led to wastewater treatment, particularly greywater. Due to specific characteristics of grey wastewater, treatment and recycling of this type of wastewater capture global attention. This paper presents a literature review of the remediation of greywater by adsorption processes. Besides, the reclamation of the grey wastewater in the context of the circular economy is highlighted. In this regard, the characterization of various types of grey wastewater, the potential risks associated with greywater, and the properties of reclaimed water as per the regulation or guideline are summarized. These standards vary based on the application of reused water and from a country to another country. Furthermore, this review elucidates the adsorption process in terms of the type of adsorbents, modification of adsorbents and their regeneration process, adsorption isotherm, kinetics and thermodynamic of adsorption, and optimization of adsorption system. Finally, the removal of different pollutants from greywater by various adsorbents and techno-economic aspects are illustrated.

Attenuation mechanisms and key parameters to enhance treatment performance in vegetation filters: A review

In times when environmental concerns are on the rise and the search of ways to reduce waste generation and to create a circular economy is booming, Nature Based Solutions (NBSs) play a very important role. Vegetation Filters (VFs) are a type of Land Application System (LAS) in which wastewater is used to irrigate a forestry plantation to treat the water and produce biomass. VFs show multiple benefits that render this technology a suitable solution for wastewater treatment, especially for scattered populations or isolated buildings that lack of connection to sewer systems. This review aims to provide a comprehensive state of the art of VF implementation, highlighting the do's and don'ts for a successful performance focusing on those factors that are essential to water treatment. Results show that VFs have a great treatment capacity when all involving factors are considered, and their efficiency tends to increase with time, as the VF develops and "gets older". Indeed, the presence of fine-textured soils, the selection of a proper vegetation species, the use of pre-treated wastewater and a water balance-based irrigation schedule alternating wetting and -drying cycles are all factors that help to achieve the best performance. However, it is necessary to design and follow a simple but rigorous operation and maintenance schedule to avoid system failure, which could lead to NO₃-N leaching towards groundwater.

Feasibility of vertical ecosystem for sustainable water treatment and reuse in touristic resorts

To counteract increasing water scarcity in the Mediterranean region, this study provides data on the efficiency of a decentralized, nature-based solution for hotel greywater (GW) treatment and reuse. A pilot plant of a constructed wetland called Vertical Ecosystem (vertECO), installed in a large hotel with GW separation, was operated continuously for 12 months. vertECO achieved a removal efficiency higher than 84.0% for COD and TSS and higher than 95.4% for turbidity and BOD₅. The monitored physicochemical parameters in the effluent meet the requirements for many reuse purposes restricted in the water reuse legislation. Based on the pilot operation, an economic model was set to estimate its economic feasibility (CAPEX, OPEX and payback period of investment) at several treated volumes. The payback was calculated, at the water and energy prices of Spain and other countries, with a planned operation period of 20 years. The higher the water price, the lower was the payback period. Treated GW volumes of 10.5 and 20 m³/day correspond to payback periods for Spain of 10.1 years and 9.0 years, respectively. Finally, co-benefits of vertECO have been considered alongside economic terms, and compared with another intensive technology (i.e., membrane bioreactor).

Greywater as a sustainable source for development of green roofs: Characteristics, treatment technologies, reuse, case studies and future developments

Municipal activities are one of the most important water users worldwide; thus, the treatment and reuse of greywater for non-potable purposes helps to reduce a remarkable amount of consumed water within urban communities. To achieve greywater reuse standards, and remove surfactants, micropollutants, organic matters, microorganisms and other pollutants various methods including physical, chemical and biological processes have been used. Treated greywater can be used on site for different purposes: carwash, toilet flushing, fire protection, green roofs, green walls, non-food irrigation etc. Among them, the use of greywater is very important in the expansion of the green roofs. Green roofs offer many benefits to urban areas such as decreasing air pollution, reducing building cooling needs, promoting mental health of habitants, noise reduction and aesthetics improvement. Therefore, this article provides an overview mainly from two aspects, the possibilities of greywater reuse by studying the characteristics and available options for greywater treatment and its benefits toward the developing green roofs.

Modeling and Economic Analysis of Greywater Treatment in Rural Areas in Jordan Using a Novel Vertical-Flow Constructed Wetland

Water scarcity in Jordan is becoming more severe with time, which resulted in an indispensable need for economic innovative approaches to maximize the utilization of nonconventional water resources through reuse options. Within the framework of the current study, a novel vertical flow constructed wetland system was implemented for greywater treatment in four different rural areas in Jordan. In this paper, the primary objective was to develop a regression-based nonlinear model to predict BOD effluent concentration from the proposed system. The model obeyed the first-order kinetics and found to provide an efficient tool in predicting the effluent BOD value as exemplified by an R² of 0.78. Moreover, a cost analysis was carried out to verify the feasibility of the proposed system. The economic results revealed a NPV range of 295-1209 JOD (420-1730$), IRR range of 6-10.7%, and a payback period range of 8.8-15.5 years. The average calculated costs of greywater treatment using the VFCWs were found to be 0.391 (USD/m³ treated) and 0.672 (USD/kg BOD removed). Finally, the energy saving from using the proposed system was quantified and an estimate of 70 JOD (100$)/year household was obtained.

Disinfection of Wastewater by UV-Based Treatment for Reuse in a Circular Economy Perspective. Where Are We at?

Among the critical issues that prevent the reuse of wastewater treatment plants (WWTPs) effluents in a circular economy perspective, the microbiological component plays a key role causing infections and diseases. To date, the use of conventional chemical oxidants (e.g., chlorine) represent the main applied process for wastewater (WW) disinfection following a series of operational advantages. However, toxicity linked to the production of highly dangerous disinfection by-products (DBPs) has been widely demonstrated. Therefore, in recent years, there is an increasing attention to implement sustainable processes, which can simultaneously guarantee the microbiological quality of the WWs treated and the protection of both humans and the environment. This review focuses on treatments based on ultraviolet radiation (UV) alone or in combination with other processes (sonophotolysis, photocatalysis and photoelectrocatalysis with both natural and artificial light) without the dosage of chemical oxidants. The strengths of these technologies and the most significant critical issues are reported. To date, the use of synthetic waters in laboratory tests despite real waters, the capital and operative costs and the limited, or absent, experience of full-scale plant management (especially for UV-based combined processes) represent the main limits to their application on a larger scale. Although further in-depth studies are required to ensure full applicability of UV-based combined processes in WWTPs for reuse of their purified effluents, excellent prospects are presented thanks to an absent environmental impact in terms of DBPs formation and excellent disinfection yields of microorganisms (in most cases higher than 3-log reduction).

Adsorption of Fluorides in Drinking Water by Palm Residues

Fluorides represent a significant problem in low- and middle-income countries (LMICs). In fact, this ion is essential for human health but, if taken in excess, it can cause dental and skeletal fluorosis. In LMICs, the pollution of groundwater from fluorides is of natural origin. Therefore, if providing alternative sources for drinking water (DW) supply is not possible, the use of specific processes for the removal of fluorides becomes essential. The adsorption on alternative materials, such as agro-food residues, can be a valid treatment for the removal of fluorides in the LMIC considering: (i) their optimal removal yields, (ii) the high availability, and (iii) the low cost. In recent years, the interest on the use of palm residues (PRs) becomes significant. Optimal pH, temperature, adsorbent dosage, and possible combination with metals to increase adsorption performances were deeply investigated. The activated PRs also present two other advantages: (i) very high surface area, and (ii) very low reduction in uptake capacity when regenerated. However, all tests were conducted with synthetic waters in laboratory-scale reactors while application on real-scale are absent. This makes other studies on this type of alternative adsorbent material still necessary.