Low-cost Treatment Technology Research Articles

Overview of the low-cost technologies for household water treatment in developing countries

ABSTRACT This study explored various low-cost water treatment technologies that are used to minimize levels of pathogens and contaminants in raw water. The paper focused on techniques such as cloth filtration, boiling, chlorination, and solar water disinfection. In the communities, cloth filtration is applied as the initial step of treating raw water with the proper choice of cloth fabrics followed by either boiling, chlorination or solar water disinfection. In low-income communities with unclean burning fuel sources, boiling was found to be the preferred method. Chlorination was also a popular technique associated with the challenges of low or high levels of free chlorine at the point of use and disinfection by-products. Solar water disinfection required optimal residence time and detection sensors for microorganism inactivation. Overall, the paper provided valuable insights into the different low-cost water treatment techniques that are commonly used for household applications, particularly in developing countries.

Advancing rainwater treatment technologies for irrigation of urban agriculture: A pathway toward innovation

Urban agriculture (UA) has emerged for local food security since the 1960s. However, the access to sufficient and safe irrigation water remains a significant constraint. Municipal water supply, though commonly used in UA practices, proves unsustainable due to high costs, intensive energy consumption, and limited availability in many vacant urban spaces. In contrast, rainwater harvesting (RWH) exhibits a potential as a non-traditional water supply for urban farming. This article aims to provide insights into the advantages and challenges associated with RWH for UA irrigation, analyze existing low-cost RWH treatment technologies, and identify a visionary way toward innovative, new-generation RWH treatment processes in UA practices. Despite a promising water source, harvested rainwater is challenged for crop irrigation owing to the presence of various contaminants (e.g., waterborne pathogens, potentially toxic metals and metalloids, and synthetic organic chemicals). While established RWH treatment processes (e.g., first flush diversion, sedimentation, solar disinfection, chlorination, UV irradiation, granular filtration, and bio-sand filtration) can remove certain pollutants, they cannot offer viable treatment solutions for UA irrigation due to different technical, economic, and social restrictions. Particularly, their capacity to reliably remove contaminants of emerging concern in runoff remains limited or uncertain. Consequently, it is essential to develop next-generation RWH treatment technologies tailored specifically for UA irrigation. To this end, three fundamental principles are recommended. First, the focus should be on technically viable, low-cost, simple-operation, and easy-maintenance treatment technologies capable of simultaneously addressing traditional and emerging runoff contaminants, while minimizing the production of undesirable treatment byproducts. Second, advancing the understanding of the water, soil, and crop interactions enables the development of “right” RWH treatment processes for irrigation of “right” crops at a “right” place. Last, crop nutrients, if possible, are retained in rainwater to reduce the nutrient demand for crop production. The insights and perspectives have far-reaching implications for water conservation, stormwater management, and the integration of water, food, and energy systems within the urban environment.

Treatment of domestic effluents using sustainable biofilter methods

The discharge of effluents is a permanent environmental and sanitation concern. Efficient water management must include water treatment and reuse. It is therefore necessary to study treatment systems to improve their performance throughout the entire chain, from drinking water to wastewater or, more specifically, waste effluent. Currently, technologies using bio-filtration processes have proven to be an effective and low-cost method for treating industrial effluents and domestic sewage. In this study, a low-cost domestic sewage treatment system made up of biofilters and pipes was built on a bench model as a means of teaching practical classes, and its efficiency was also studied. The results showed that the equipment can be made from recyclable material and is low-cost, easy to detail technically and easy to handle and operate. The students involved can easily replicate the technology in their communities, thus spreading low-cost sanitation treatment technologies to low-income populations without access to conventional sanitation systems. The parameters pH, turbidity, chlorination, temperature, and electrical conductivity were all at acceptable levels for discharge into receiving bodies and domestic use.

Optimization of Ceramic Filter for Greywater Treatment by using Horizontal Flow Constructed Wetland

Wetland technology is an effective and sustainable treatment process that relies on a combination of components. Media components, which vary based on the material used, play an important role in this technology. Ceramic-based filters are a natural and versatile water filtration method that can be used in combination with wetland systems to create a simple, low-cost, and efficient wastewater treatment technology. The aim of this study was to assess the performance and efficiency of two experimental scale horizontal flow constructed wetlands (HFCW) as a secondary stage for the treatment of household greywater. This was achieved by examining the untreated and treated greywater characteristics; evaluating the effectiveness of planted wetlands with ceramic addition in removing chemical oxygen demand (COD), biological oxygen demand (BOD5), nutrients, total suspended solids (TSS), and coliforms from the greywater; and monitoring the adaptation and growth of Bacopa monnieri L. in the treatment systems. The results showed that both treatment systems significantly improved all the greywater characteristics. The use of ceramic, gravel, and plants in wetlands enhanced the removal efficiency of Mg+2, TDS, and total hardness (TH). A higher treatment efficiency was observed in the ceramic-gravel bed than in the gravel bed.

Effects of particle size on the pyrolysis of waste tires during molten salt thermal treatment

Recently, waste tires gain a growing recognition of the potential as value-added fuel via pyrolysis. In the present study, molten salt was proposed to be used for the waste tires pyrolysis, aims to enhance heat transfer efficiency, and then reduce energy input for the mechanical shredding of waste tires into small particles before pyrolysis. In detail, the conversion and products formation behavior of two waste tires (of different particle sizes) were compared by a constructed molten salt thermal treatment system. Results show that H2 and CH4 contents of the pyrolysis gas increased substantially, and smaller tire particles produced more H2 and CH4 (up to 500%), while CO2 content dropped to zero. Also, the contents of benzene increased remarkably with molten salt added (growth rate is between 1100% and 1800%) for electro-mobile tires, while caprolactam was disappeared. Specifically, benzene yield increases and then decreases with increasing particle size. In addition, molten salts were also effective in removing sulfur and ash from pyrolytic char, with more than 60% of the sulfur fraction being removed. These findings could provide theoretical support for the development of low-cost thermal treatment technology for waste tires.

Applicability of hybrid treatment to reduce the footprint of domestic and industrial wastewater of developing countries

Wastewater pollution is a serious concern, especially in developing countries such as Pakistan. The untreated domestic and industrial wastewater is typically discharged into sewers, natural drains, or water bodies. There is a dire need to evaluate the applicability of low-cost treatment technologies. Hybrid wastewater treatment (HWWT), comprising of chemically enhanced primary treatment (CEPT) and intermittent sand filter (ISF), was adopted to treat domestic, process and manufacturing, and food industry wastewaters. The wastewater pollution and contamination were assessed in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS). The removal efficiency (RE) performance of HWWT was compared with the CEPT system only. Considering the CEPT only, the RE of BOD was ≈70 % for domestic, >80 % for process and manufacturing, and ≈50 % for the food industry. For COD, the RE was high in process & manufacturing (RE ≈ 81 %), followed by food (RE ≈ 55 %) and domestic wastewater (RE ≈ 17 %). Furthermore, the CEPT provided >95 % TSS removal in all wastewater types. The HWWT increased TSS removal by ≈2 %, BOD removal by ≈13 %, and COD removal by ≈27 % compared to the CEPT system. Therefore, HWWT proved more efficient in treating both domestic and industrial wastewater. The HWWT reduced the greywater footprint (GWF) by 50–60 % when compared to the CEPT system. This study provided knowledge of the characteristics of domestic and industrial wastewater. Furthermore, provides a basis to assess the applicability and performance of various wastewater treatment systems under given settings.

Research on the Progress of Agricultural Non-Point Source Pollution Management in China: A Review

In the 1980s, China began to recognize the gravity of the problem of non-point agricultural source pollution and conduct research on it. Agricultural non-point source pollution in China, on the other hand, differs from foreign agricultural non-point source pollution and industrial point source pollution. Because the features of agricultural non-point source pollution are complicated, it is critical to investigate a whole-chain management policy system appropriate for China’s agricultural pattern. Based on the current situation of agricultural non-point source pollution in China, this study summarizes the four stages of agricultural non-point source pollution prevention and control policies, namely the discovery stage with macro policies as the main focus, the exploration stage with single research indicators, the initial systematic strengthening stage, and the focused stage with targeted characteristics. Simultaneously, it examined the technological approaches that are suitable for China’s national circumstances and have been investigated by relying on international experience in present-day Chinese management. However, there are still some problems and challenges in agricultural non-point source pollution management policies, such as a lack of non-point source information support, a lack of coordination between different departments, a lack of support in measurement and retroactive calculation and treatment, a lack of an in-depth concept of zoning and classification, a lack of policy, an institutional system, and insufficient capital investment. Based on these problems and combining them with Green Agriculture, Beautiful China, and other goals, this paper puts forward suggestions to strengthen the policy data support of the agricultural non-point source pollution management system, enhance the research and development of the law of pollutant migration and transformation, encourage the innovation of low-cost and high-benefit treatment technology, improve the construction of the management system, strengthen the collaboration of departments, increase the investment of funds, and make other suggestions so as to promote the treatment of agricultural non-point source pollution with high quality and efficiency.

Titanium dioxide-based nanoparticles and their applications in water remediation

Water is an essential component of life. Only 2.5% of the total percentage of water available on earth is fresh. As the world’s population is increasing, water pollution is becoming more complex and difficult to remove. Due to change in climatic conditions globally, many regions of the world are facing multiple challenges in sustainable supply of water, and their magnitude is rapidly increasing. Therefore, reuse of waste water is becoming a common necessity. However, due to the presence of water contaminants, such as heavy metals, organic pollutants and many other complex compounds, treatment of contaminated waste water is essential for a healthy life. Nanotechnology offers opportunities to provide efficient, cost-effective and environmentally sustainable solutions for supplying potable water for human use and clean water for agricultural and industrial uses. Photocatalytic processes have shown great potential as a low-cost, environmentally friendly and sustainable treatment technology for water purification. Photocatalytic degradation has been used efficiently for the degradation and removal of toxic and harmful chemicals to improve water quality. Titanium-based semiconductors have been employed as photocatalysts in degradation of organic molecules. In this review, titanium dioxide-based nanoparticles and their applications in water remediation are discussed.

Sustained anaerobic degradation of 4-chloro-2-methylphenoxyacetic acid by acclimated sludge in a continuous-flow reactor

4-Chloro-2-methylphenoxyacetic acid (MCPA) is a widely used herbicide across the world. MCPA is persistent and easily transports into anoxic environment, such as groundwater, sediments and deep soils. However, little research on anaerobic microbial degradation of MCPA was carried out. The functional microorganisms as well as the catabolic pathway are still unknown. In this research, an anaerobic MCPA-degrading bacterial consortium was enriched from the river sediment near a pesticide-manufacturing plant. After about 6 months’ acclimation, the MCPA transformation rate of the consortium reached 4.32 μmol g−1 day−1, 25 times faster than that of the original sludge. 96% of added MCPA (2.5 mM) was degraded within 9 d of incubation. Three metabolites including 4-chloro-2-methylphenol (MCP), 2-methylphenol (2-MP) and phenol were identified during the anaerobic degradation of MCPA. An anaerobic catabolic pathway was firstly proposed: firstly, MCPA was transformed to MCP via the cleavage of the aryl ether, then MCP was reductively dechlorinated to 2-MP which was further demethylated to phenol. The 16S rRNA gene amplicon sequencing revealed a substantial shift in the bacterial community composition after the acclimation. SBR1031, Acidaminococcaceae, Aminicenantales, Syntrophorhabdus, Acidaminobacter, Bacteroidetes_vadinHA17, Methanosaeta, Bathyarchaeia, KD4-96, Anaeromyxobacter, and Dehalobacter were significantly increased in the enriched consortium after acclimation, and positively correlated with the anaerobic degradation of MCPA as suggested by heat map correlation analysis. This study provides a basis for further elucidation of the anaerobic catabolism of MCPA, and contributes to developing efficient and low-cost anaerobic treatment technologies for MCPA pollution.

UV-Visible-Near-Infrared-Driven Photoelectrocatalytic Urea Oxidation and Photocatalytic Urea Fuel Cells Based on Ruddlensden–Popper-Type Perovskite Oxide La2NiO4

Photocatalysis and photoelectrocatalysis, as green and low-cost pollutant treatment technologies, have been widely used to simultaneously degrade pollutants and produce clean energy to solve the problems of environmental pollution and energy crisis. However, the disadvantages of photocatalysts in a narrow absorption range and low utilization rate of solar energy still hinder the practical application. Here we fabricate two-dimensional porous Ruddlensden–Popper type nickel-based perovskite oxide La2NiO4 as a noble metal-free photoanode for photoelectrocatalytic urea oxidation under full spectrum sunlight irradiation. The transient photocurrent density under near infrared (NIR) light (λ > 800 nm) can reach 50 μA cm−2. Urea wastewater was used as the fuel to obtain low-energy hydrogen production, and round-the-clock hydrogen production was achieved with the optimal yield of 22.76 μmol cm−2 h−1. Moreover, a photocatalytic urea fuel cell (PUFC) was constructed with La2NiO4 as the photoanode. The power density under UV-vis-NIR was 0.575 μW cm−2. Surprisingly, the filling factor (FF) under NIR light was 0.477, which was much higher than those under UV-vis-NIR and visible light. The results demonstrated that PUFCs constructed from low-cost nickel-based perovskite oxides have potential applications for low-energy hydrogen production and efficient utilization of sunlight.

Carbon-based materials for water disinfection and heavy metals removal

ABSTRACT The presence of heavy metals and/or harmful bacteria in drinking water represents significant risks to human health. This study aimed to develop a low-cost water treatment technology using synthesized nanocomposites with metal nanoparticles supported on activated carbon (AC) for bacteria and heavy metal removal. In addition, the performance of the developed nanomaterials was compared with that of commercial materials – carbon fibers of three different typologies. The chemical and textural properties of all tested materials were characterized. To simulate a technology to be applied in a water outlet point, removal tests were carried out in a continuous system using suspensions of Escherichia coli and/or Staphylococcus aureus, wherein the contact time with the two phases was minimal (1 min). The obtained results revealed that iron and copper oxides supported on AC with a calcination treatment (CuFeO/AC-C) was the nanocomposite with the best performance, achieving a 6 log reduction for both bacteria in the same suspension up to 9 h operation. A mix of bacteria and heavy metals, simulating a real water, was treated with CuFeO/AC-C obtaining a 6 log reduction of bacteria, a Pb2+ removal >99.9% and Cd2+ removal between 97 and 98% over 180 passage times.

Reversible controlled switching of photocatalysis for microorganism protection in the coupling of photocatalysis and biodegradation

The coupling of photocatalysis and biodegradation (CPB) has shown great potential as a low-cost, environmental friendly and sustainable wastewater treatment technology. However, the photo-generated reactive oxidative species (ROS) could attack microorganisms in the CPB. Here, a photo-controlled reversible photocatalytic system was developed for protecting microorganisms from ROS attack in CPB. Thermal-responsive polymer (TRP) was coated on the surface of yolk-shell CdS@SiO2, and then CdS@SiO2 @TRP was attached to the surface of graphene (photo-thermal converter) to form the photo controlled reversible photocatalytic system (RPS). Without light irradiation, the soluble contaminants could be absorbed into the void space of CdS@SiO2 @TRP. And under light irradiation, the photo-generated ROS would be locked inside the silica shell to degrade the absorbed organic molecules, avoiding harming microorganisms in CPB. Batch results showed that this CPB system could simultaneously remove 97.24 % of phenol (model contaminant) and 91.12 % of TOC under intermittent light irradiation, which was superior to other control groups. This work provides a new strategy to protect microorganisms in CPB for effective wastewater treatment.

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor.

The presence of excessive concentrations of nitrate in industrial wastewaters, agricultural runoff, and some groundwaters constitutes a serious issue for both environmental and human health. As a result, there is considerable interest in the possibility of converting nitrate to the valuable product ammonia by electrochemical means. In this work, we demonstrate the efficacy of a novel flow cathode system coupled with ammonia stripping for effective nitrate removal and ammonia generation and recovery. A copper-loaded activated carbon slurry (Cu@AC), made by a simple, low-cost wet impregnation method, is used as the flow cathode in this novel electrochemical reactor. Use of a 3 wt % Cu@AC suspension at an applied current density of 20 mA cm-2 resulted in almost complete nitrate removal, with 97% of the nitrate reduced to ammonia and 70% of the ammonia recovered in the acid-receiving chamber. A mathematical kinetic model was developed that satisfactorily describes the kinetics and mechanism of the overall nitrate electroreduction process. Minimal loss of Cu to solution and maintenance of nitrate removal performance over extended use of Cu@AC flow electrode augers well for long-term use of this technology. Overall, this study sheds light on an efficient, low-cost water treatment technology for simultaneous nitrate removal and ammonia generation and recovery.

Constructed Wetland for Sustainable and Low-Cost Wastewater Treatment: Review Article

There is a growing need for more sustainable wastewater treatment technologies to provide non-conventional water sources. Constructed Wetland systems (CW) are viewed as a low-cost treatment technology with proven treatment efficiency. CWS can treat a variety of contaminants using low energy and natural systems by altering various design parameters. There are two configuration types of constructed wetlands: vertical (VF) and horizontal flow CW (HF). Both configurations have been widely adopted in both large and pilot scale studies with proven records of reasonable wastewater treatment efficiency. The current article reviews the recent development of CW technology and highlights the main achievements and successful applications for wastewater treatment at various locations. The review has indicated that a considerable removal efficiency is attained while using engineered CW systems with variable treatment rates for various pollutants. The treatment efficiency is a function of various parameters including wastewater type, scale dimensions, applied plant and the retention time. The review compared the treatment efficiency for both VF and HF and has revealed that various removal rates of BOD, COD, TSS, TN, TP and NH₄ was attained using both configurations. Yet, the removal efficiency in the case of VF was slightly higher compared with the HF with an average treatment level of 77% and 68% was achieved in both systems, respectively. The review revealed that the CW is an effective and sustainable technology for wastewater treatment with the initial influent level, microbial biofilm, detention time, plant species and configuration among the most dominating parameters that are directly controlling the removal rates.

Synthesis, characterizations, and RSM analysis of Citrus macroptera peel derived biochar for textile dye treatment

Textile wastewater discharging to the surface water body is a great concern because it contains different pollutants such as dyes, organics, surfactants, inorganic salt and heavy metals. An effective low-cost treatment technology has not been developed yet. The objective of this study was to develop a low-cost biochar adsorbent from was from a novel Citrus macroptera peels (CMPs) using a conventional slow pyrolysis process and applied it for the treatment of methylene blue dye in an aqueous solution. The chemical functionalities, surface textures, and crystallinity of the synthesized biochar were characterized by Fourier Transform-Infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscope (FESEM) analysis, and X-ray powder Diffraction (XRD), respectively. Different functional groups such as -COOH, OH, and R-OH, randomized porous structures with tunnel-like cracks were confirmed from the FTIR and FESEM, respectively. Typical non-linear disordered 3D carbon structure was predicted from the XRD. Response surface methodology (RSM) was performed with the central composite design (CCD) technique, and analytical tuning of the process variables, e.g., pH, contact time, and methylene blue concentration, was also carried out to validate the RSM optimization. The adsorption isotherms and kinetics were investigated, where isotherm and kinetics followed Langmuir and pseudo 2nd order models. RSM results at pH 8 showed 85% of dye removal within 75 min of contact time. According to the Langmuir isotherm model, the maximum adsorption capacity, qm was 139.7 mg/g, which aligned with the experimental value. The present work shows that the low-cost CMPs-derived biochar has the potential for dye removal from industrial effluents.

Experimental study on discharging current to reduce voltage stress during underwater shock wave generation

In food processing using underwater shock waves, the intensity of shock waves is determined by a discharging current from an output capacitor. In past studies, to realize efficient food processing, the underwater shock wave has been generated by charging a high voltage to the output capacitor with high withstand voltage characteristics. For this reason, the conventional method suffers from high manufacturing costs. Furthermore, the conventional method is dangerous due to high voltage requirements such as 3.5 kV. In this work, a low-cost and safe non-heat treatment technology using underwater shock waves is presented for food processing. Unlike the conventional methods, the proposed method generates underwater shock waves by using multiple large output capacitors with low withstand voltage characteristics. Therefore, the proposed method can achieve safe and low-cost non-thermal food processing, because the output capacitors do not need to be charged at high voltage. In the proposed method, the output voltage is about one-fourth that of the conventional methods. The effectiveness and reliability of the proposed technique are confirmed by several experiments using a laboratory experimental system. The experiment revealed that the proposed technique can process a target food at 865 V output, where the rise time of the high voltage generator is 126 s and the output capacitor is 3300 μF.

Plant-based amyloids from food waste for removal of heavy metals from contaminated water

Water pollution is one of the major global threats brought about by industrial, agricultural, and any other anthropogenic activity. Heavy metals represent a large group of water pollutants that can accumulate in the human body, causing cancer and mutagenic diseases. Technologies currently used to treat polluted wastewaters of heavy metals employ chemical, ion-exchange, and membrane purification methods. However, these techniques are energy-intensive due to high pressure and power requirements for membrane-based technologies, or highly selective, as in ion-exchange resins, making drinking water less affordable in developing countries. In this study, plant amyloid-carbon membranes consisting of sunflower and peanut amyloid fibrils were fabricated through a green and sustainable process and were used to remove toxic heavy metal pollutants to drinkable standards with negligible energy consumption. Protein-rich sunflower and peanut meals serve as low-cost raw materials, from which proteins were extracted, isolated, and self-assembled into functional amyloid fibrils for heavy metal removal. These amyloid fibrils were incorporated into hybrid carbon/amyloid membranes and used to filer Pt-, Cr-, and Pb-containing water to produce water of drinkable standards containing < 10 ppb heavy metals. This process can easily be upscaled due to its simplicity and minimal use of chemical reagents, pointing towards the future of low-cost yet efficient water treatment technologies.

Constructing a novel NaLa(WO4)2/g-C3N4 Z-scheme heterojunction with efficient carrier separation for excellent photocatalytic purification of NO

In this paper, a novel NaLa(WO4)2/g-C3N4 photocatalyst with Z-scheme heterojunction was synthesized for the first time, and the photocatalytic purification of NOx was used as an evaluation method of its activity. The structure was analyzed in depth by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and other characterization methods. NaLa(WO4)2 and g-C3N4 have obvious interfaces and successfully constructed a Z-scheme heterojunction structure. The combination of photogenerated electrons on the conduction band (CB) of NaLa(WO4)2 with holes on the valence band (VB) of g-C3N4 leads to the accumulation of the remaining holes and electrons on the VB of NaLa(WO4)2 and CB of g-C3N4, and finally realizes the effective separation of photogenerated carriers and maintains the high redox ability of the catalyst. The NaLa(WO4)2/g-C3N4 composite catalyst has a highest NO purification rate of 47.18%, which is 16.51% higher than pure g-C3N4. Moreover, the In-situ DRIFTS monitors the reaction intermediates and final products of NO on the NaLa(WO4)2/g-C3N4 heterojunction surface under visible light irradiation, and provides the corresponding reaction equations. This work provides a new type of photocatalyst that is easy to prepare and highly active, as well as a low-cost photocatalytic treatment technology to remove NO in the environment.

Accelerated degradation of sulfadiazine by nitrogen-doped magnetic biochar-activated persulfate: Role of oxygen vacancy

Modification using biochar as a carrier is a promising method to improve the activation of peroxymonosulfate (PMS) by magnetic nanoparticles. In this study, we provided an effective strategy to control the generation of oxygen vacancy to prepare N-doped magnetic biochar (NMB) by optimizing the heat treatment process of gas foaming. The NMB exhibited superior catalytic performance and stable recycling use in the activation of PMS to degrade sulfadiazine (SDZ). Through multiple characterization techniques and density functional theory (DFT) calculations, the mechanism of the reaction process about oxygen vacancy was explored for the first time in magnetic biochar. In addition, the degradation kinetics, recycling experiment, and removal of total organic carbon were carried out to evaluate the degradation performance of NMB/PMS system. After 15 min of reaction, the removal rate of SDZ reached 95.2%. After the fifth cycle of use, the removal rate of SDZ remained at 79.6%. In addition to SDZ, the NMB/PMS system could also efficiently remove ofloxacin, reactive brilliant red, and bisphenol A, suggesting excellent degradation reactivity for different types of pollutants. The oxygen vacancy was found to play an important role in the catalytic process probably through changing the electronic structure of the NMB catalyst and thereby activating the charge transfer to participate in the degradation. The results from this study might deepen the understanding of the activation mechanism driven by magnetic biochar and provide insights into the development of low-cost wastewater treatment technologies.

Effects of Constructed Wetlands Plants on Phosphorus Removal from Domestic Wastewater in Gaborone, Botswana

The United Nations, Sustainable Development Goal (SDG) Target 6.3. aims at “halving the proportion of untreated waste water and substantially increasing recycling and safe reuse globally” by 2030. To achieve this target, sustainable and context-specific wastewater treatment systems are urgently needed. Constructed wetlands (CW) is one of the wastewater treatment technological options available. CW have been widely accepted and acknowledged as simple, low cost, alternative and appropriate domestic wastewater treatment technology. CW were piloted by the Department of Water Affairs, Gaborone, Botswana to assess their treatment performance. Specifically, the study investigated the effects of CW plants on Phosphorus (P) removal from domestic wastewater. The first CW cell (CA) was a control which was filled with sand only, the second cell (CB) was planted with Typha Latifolia, the third (CC) with Cyperus Papyrus and the fourth (CD) with Phragmites Mauritianus. Each cell had a surface area of 100m2 and received a wastewater discharge of 4m3 /day. River sand with porosity of 0.44 and particle size diameter ranging from 2-7mm was used as plants growing media. Wastewater samples were analysed in accordance with Standard Methods for Examination of Water and Wastewater. The results showed that the P treatment performance efficiencies for CA, CB, CC, and CD were 93.6%, 97.4%, 98.1% and 98.4% respectively. Despite that there was CW plants contribution towards P removal from domestic wastewater, there was however no statistically significant performance difference (p&gt;0.05) in P removal between the CW cells planted with different plant species. The mean effluent P concentrations from the different CW cells were; CA 0.62mg/l, CB 0.28mg/l, CC 0.19mg/l and CD 0.16mg/l. Thus, the mean P concentration from the effluent of C1 was above the Botswana Bureau of Standards Limits of 0.5mg/l. Hence the effluent was non-compliant with Botswana standards for the discharge of effluent into the environment.