Sustainable Clean Water Supply Research Articles

Filtration of Grey Water Using Herbs in a Columnar Evaluation

Filtration of Grey Water Using Herbs in a Columnar Evaluation

Development of a self-rating system for domestic water consumption in Malaysia

A positive growth in the global population would increase the need for clean water. Therefore, continuous, adequate, and sustainable clean water supply is a major concern in modern society. A highly effective approach to resolve this concern is to instil self-awareness in consumers. This study established a simple self-rating system for consumers to evaluate their domestic water usage. The rating classifications are ‘Poor’, ‘Fair’, ‘Average’, ‘Good’, and ‘Excellent’, based on a score established using statistical analysis. A high percentage of respondents received an Average (41.3%) or a Good (49.7%) rating. A lower percentage of respondents received a Fair (5.3%) or an Excellent (3.7%) rating. Minimising the frequency of indoor and outdoor activities, practising good water habits, including the use of water saving appliances such as dual-pump cisterns, buckets for showering and bathing, and rainwater harvesting systems are factors that contributed primarily to an Excellent rating. No respondent received a Poor rating, which suggests that there is intrinsic behaviour of good water usage and efforts to conserve water in the community. Consumers can become more aware of and motivated to use water saving practices when they can quantitatively rate their domestic water consumption thru the self-rating system developed in this study.

Plant-Based Tacca leontopetaloides Biopolymer Flocculant (TBPF) Produced High Removal of Turbidity, TSS, and Color for Leachate Treatment

Wastewater treatment is crucial to ensure a sustainable supply of clean water, especially for human use. Natural flocculants can overcome the disadvantages of chemical flocculants in wastewater treatment. This study proposes a new natural-based flocculant from the Tacca leontopetaloides plant for leachate treatment. The plant tuber was processed through gelatinization to produce Tacca leontopetaloides biopolymer flocculant (TBPF). The characterization of TBPF for flocculant properties was investigated, and the performance of TBPF on leachate treatment using a standard jar test procedure was examined at different pH values of leachate and TBPF dosages. The characteristics of TBPF in terms of amylose/amylopectin fraction, viscosity, and zeta potential were 26:74, 0.037–0.04 Pa·s, and −13.14 mV, respectively. The presence of –COOH and –OH structure in TBPF indicates the flocculant properties. TBPF reduced the turbidity, total suspended solids (TSS), and color from 218 NTU, 214 mg/L, 14201 PtCo to 45.8–54.5 NTU, 19.3–19.9 mg/L, and 852–994 PtCo, respectively, using 240 mg/L of TBPF at pH 3. These results show a high potential of the new plant-based TBPF for leachate treatment and water industry applications.

Water-stable MOFs-based core-shell nanostructures for advanced oxidation towards environmental remediation

Metal organic frameworks (MOFs) find many potential applications because of their versatile physicochemical properties. Advanced oxidation is an important way for wastewater remediation to realize sustainable supply of clean water. However, due to the lack of water-stable MOFs with sufficient catalytic activity, the application of MOFs in advanced oxidation processes (AOP) for wastewater treatment is greatly hindered. In this study, by taking advantage of the rich pores of water stable MOFs, we develop a MOFs-based core (water stable MOFs)-shell (NiP) structure as an efficient catalyst for peroxymonosulfate (PMS) activation in AOP. Here, water stable MIL-96 as the MOFs is synthesized by a hydrothermal method, and the core-shell structured MIL-96@NiP is facilely synthesized through electroless coating of the NiP layer. The as-prepared core-shell structure demonstrates superior performance in catalytic degradation of rhodamine B (RhB), over performing the individual MOFs and NiP parts, suggesting the appearance of synergistic effect between MOFs and NiP in the core-shell structure. Furthermore, the catalyst demonstrates four consecutive runs without losing significant catalytic activity. Temperature has a significant role in faster degradation of RhB. A plausible degradation mechanism is proposed through classical quenching tests study, and oxygen singlet is found to play imperative part in removal of RhB.

Solar Evaporator with Controlled Salt Precipitation for Zero Liquid Discharge Desalination.

A sustainable supply of clean water is essential for the development of modern society, which has become increasingly dependent on desalination technology since 96.5% of the water on Earth is salt water. Thousands of desalination plants are producing massive waste brine as byproduct, and the direct discharge of brine raises serious concerns about its ecological impact. The concept of zero liquid discharge (ZLD) desalination is regarded as the solution, but the current ZLD technologies are hampered by their intensive use of energy and high cost. In this work, a 3D cup shaped solar evaporator was fabricated to achieve ZLD desalination with high energy efficiency via solar distillation. It produces solid salt as the only byproduct and uses sunlight as the only energy source. By rationally separating the light absorbing surface from the salt precipitation surface, the light absorption of the 3D solar evaporator is no longer affected by the salt crust layer as in conventional 2D solar evaporators. Therefore, it can be operated at an extremely high salt concentration of 25 wt % without noticeable water evaporation rate decay in at least 120 h. This new solar evaporator design concept offers a promising technology especially for high salinity brine treatment in desalination plants to achieve greener ZLD desalination as well as for hypersaline industrial wastewater treatment.

Financing Watershed Services in the Foothills of the Himalayas

Watershed management is critical for the sustainable supply of clean water to urban centers, particularly in areas of developing countries where large-scale infrastructure projects are costly to implement. In this paper, we discuss the potential for financing improvements in watershed services in the foothills of the Himalayas through Payments for Ecosystem Services. Through the use of a choice experiment to disentangle household preferences, we show that downstream water users are interested in improvements in water quality through source water protection. Households in Dharan municipality are willing to finance watershed management to the extent of USD 118,000 per year. These payments can be used to incentivize upstream households to decrease domestic livestock grazing, change agricultural practices and reduce open defecation to improve the drinking water quality and quantity in downstream areas. The estimated cost of these activities is less than $50,000 per year. Through discussions with local stakeholders, we propose a tri-partite institutional structure to facilitate transactions between downstream and upstream communities and to improve watershed services.

Forward osmosis: an emerging technology for sustainable supply of clean water

Nowadays, inadequate access to clean water has become one of the most pervasive problems due to the rapidly expanding global population and thus the exponentially growing demand in water and food supply, industry and social life (Shannon et al. 2008). Problems with water have called out for a large number of researchers to pay more attention to water sustainability and put forth effort to explore more robust technologies for wastewater treatment and desalination in addition to improving the efficiency of the current water production and distribution systems (Sikdar 2011). Among many potential solutions, membrane processes such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF) have found their overwhelming applications in water industry. However, these technologies are either chemically or energetically intensive, thus are castigated for high cost due to substantial chemical and energy consumptions as well as high fouling propensity which requires frequent backwash or cleaning. Forward osmosis (FO), utilizing the natural phenomenon of osmosis, is an emerging membrane process driven by the osmotic pressure gradient created across a semipermeable membrane by two flowing streams of varying concentration (i.e., the draw solution and the feed). Hence, the energy required to transport water across the membrane is almost negligible. Far from being so, FO creates much less problem of fouling and cleaning (Mi and Elimelech 2010). By virtue of these unique features, FO distinguishes itself from other membrane processes for sustainable supply of clean water. An example of the FO unit for wastewater treatment is shown in Fig. 1. In the FO process as illustrated, the draw solution (an aqueous solution of magnetic nanoparticles covered with thermosensitive polymer) (Ling et al. 2011) and the feed (wastewater) partitioned by the membrane flow co-currently through corresponding channels. The draw solution, having a higher osmotic pressure than the feed, draws water from the feed and flows back to the reservoir. As it continuously takes clean water from the feed, the draw solution in the reservoir becomes diluted. A regeneration process is connected to the reservoir to re-concentrate the draw solution as well as to produce clean water. A portion of the diluted draw solution is pre-heated with the aid of solar panel or waste heat and traverses a magnetic field. Upon heating, the magnetic nanoparticles covered with thermosensitive polymers change their surface property from hydrophilic to hydrophobic and are easily seized by the magnetic field or other filtration processes. As a result, clean water freely passes through and is collected as the product. The trapped magnetic nanoparticles are then sent back to the reservoir to replenish the draw solution. The 1st key component of the FO unit is the membrane material which should be semipermeable, i.e., allowing water to permeate through while blocking all the solutes in the draw and feed solutions. A tremendous amount of research has been conducted on the molecular design of new membrane materials with superior FO performance and great progress has been achieved in the past 5 years. To date, several types of FO membranes have been reported such as (1) flat sheet membranes made of cellulose esters (Wang et al. 2010a; Zhang et al. 2010); (2) J. Su M. M. Ling T.-S. Chung (&) Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore e-mail: chencts@nus.edu.sg