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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: closed (15 January 2021) | Viewed by 48118

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Prof. Dr. James A. Smith

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Department of Engineering Systems and Environment, University of Virginia, Charlottesville, VA 22904-4742, USA
Interests: groundwater hydrology and contaminant transport; water, sanitation, and human health for the developing world; point-of-use water treatment, silver nanotechnology for water purification

Special Issue Information

Dear Colleagues,

In developed nations, high-quality drinking water is typically provided through centralized water treatment and distribution systems. In the developing world, these systems are often unreliable, unable to meet the demand for treated water, or simply do not exist. As a result, 2–3 billion people do not receive reliable, high-quality water delivered to their households. Instead, they must collect and store household water, often in open containers without any residual disinfectant. The consequences of these deficiencies include ingestion of unsafe water. This in turn contributes to high rates of morbidity and mortality from water-related diseases. The World Health Organization has indicated that one possible solution to this problem is to decentralize water treatment so that people treat their water right before they consume it in their homes. Designing sustainable “point-of-use” water treatment technologies is a challenging problem, as they must be low-cost, technologically effective, simple to use, and socially acceptable. Herein, we seek papers that present research on emerging technologies for household water treatment. We seek fundamental laboratory investigations of new materials and processes and field tests of new and existing technologies. Studies that consider social acceptance, economic sustainability, and human health benefits are also encouraged.

Dr. James A. Smith
Guest Editor

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Keywords

Point-of-Use water treatment
drinking water
centralized water treatment and distribution systems
household water treatment

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Published Papers (9 papers)

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Research

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15 pages, 2300 KiB

Open AccessArticle

A Hybrid Biological-Adsorption Approach for the Treatment of Contaminated Groundwater Using Immobilized Nanoclay-Algae Mixtures

by Sara Mollamohammada, Ashraf Aly Hassan, Mohamed Dahab and Sandeep Kumar

Water 2021, 13(5), 633; https://doi.org/10.3390/w13050633 - 27 Feb 2021

Cited by 7 | Viewed by 3087

Abstract

Mixing the Scenedesmus species with nanoclay and immobilizing in sodium alginate was evaluated as a sustainable treatment method for removing nitrate, atrazine, and metals from groundwater. Gel beads containing the hybrid mixture removed 100% of 10 mg/L N nitrate and 98% of 100 µg/L atrazine from synthetic groundwater in three days. The optimal amount of nanoclay was found to be 0.30 mg per bead. The experimental data fit well into a Freundlich adsorption isotherm and followed pseudo first-order kinetics. When tested in actual groundwater, 91% of nitrate and 100% of Cr, Se, and V were eliminated in three days without need for any nutrients or carbon source. Immobilizing algal beads embedded with nanoclay is a natural, low-cost alternative for groundwater treatment. The gel beads can be reused for at least two cycles without a compromise in performance. They are water-insoluble, easy to harvest, and offer high removal efficiency. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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18 pages, 2530 KiB

Open AccessFeature PaperArticle

Field Investigation and Economic Benefit of a Novel Method of Silver Application to Ceramic Water Filters for Point-Of-Use Water Treatment in Low-Income Settings

by Nkosinobubelo Ndebele, Joshua N. Edokpayi, John O. Odiyo and James A. Smith

Water 2021, 13(3), 285; https://doi.org/10.3390/w13030285 - 25 Jan 2021

Cited by 6 | Viewed by 4486

Abstract

In this study, we report on field testing of ceramic water filters (CWFs) fabricated using a new method of silver application (using silver nitrate as a raw material) compared to conventionally manufactured CWFs (fabricated with silver nanoparticles). Both types of filters were manufactured at the PureMadi ceramic filter production facility in Dertig, South Africa. Thirty households received filters fabricated with silver nitrate (AgNO₃), and ten of those households were given an extra filter fabricated with silver nanoparticles. Filter performance was quantified by measurement of total coliform and Escherichia coli (E. coli) removal and silver residual concentration in the effluent. Silver-nitrate CWFs had removal efficiencies for total coliforms and E. coli of 95% and 99%, respectively. A comparison of the performance of silver-nitrate and silver-nanoparticle filters showed that the different filters had similar levels of total coliform and E. coli removal, although the silver nitrate filters produced the highest average removal of 97% while silver nanoparticles filters recorded an average removal of 85%. Average effluent silver levels were below 10 ppb for the silver-nitrate and silver-nanoparticle filters, which was significantly below the Environmental Protection Agencies of the United States (EPA) and World Health Organization (WHO) secondary guidelines of 100 ppb. Silver-nitrate filters resulted in the lowest effluent silver concentrations, which could potentially increase the effective life span of the filter. A cost analysis shows that it is more economical to produce CWFs using silver nitrate due to a reduction in raw-material costs and reduced labor costs for production. Furthermore, the production of silver-nitrate filters reduces inhalation exposure of silver by workers. The results obtained from this study will be applied to improve the ceramic filtration technology as a point-of-use (POU) water treatment device and hence reduce health problems associated with microbial contamination of water stored at the household level. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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19 pages, 256 KiB

Open AccessArticle

Impact Evaluation of an SMS Campaign to Promote Household Chlorination in Rural Haiti

by Michael Ritter, Eveline Camille, Christophe Velcine, Rose-Kerline Guillaume, Jean Marcel Casimir and Daniele S. Lantagne

Water 2020, 12(11), 3095; https://doi.org/10.3390/w12113095 - 4 Nov 2020

Cited by 2 | Viewed by 4384

Abstract

Despite documented health benefits of household water treatment and storage (HWTS), achieving sustained use remains challenging. In prior evaluations of a long-term HWTS program in Haiti, multiple marketing interventions failed to increase use or had prohibitively high costs. Using mobile phones is a potentially cost-effective way to change HWTS behavior. We conducted a randomized experiment to evaluate the impact of sending short-message service (SMS) messages to promote household chlorination in this program in Haiti. Households (n = 1327) were randomly assigned to: One of four SMS frequencies; one of ten behavioral constructs; “cholera” or “disease” framing; and one or zero household visits from a sales agent. During the three-month campaign, there were no statistically significant relationships between the four outcomes related to chlorine purchases and any SMS frequency, any behavioral construct, or either “cholera” or “disease” framing. Receiving one visit increased the probability of purchasing a bottle of chlorine by 17.1 percentage points (p < 0.001) but did not affect subsequent purchase behavior. Costs of managing the SMS campaign were higher than expected. SMS campaigns may not be cost-effective behavior change interventions in certain contexts. If pursued, we recommend simple interventions, timed with the target behavior, and tailored to mobile phone usage patterns of the target population. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

17 pages, 5439 KiB

Open AccessArticle

Biosand Filter as a Point-of-Use Water Treatment Technology: Influence of Turbidity on Microorganism Removal Efficiency

by Daniela A. Duran Romero, Maria Cristina de Almeida Silva, Beni J. M. Chaúque and Antônio D. Benetti

Water 2020, 12(8), 2302; https://doi.org/10.3390/w12082302 - 17 Aug 2020

Cited by 11 | Viewed by 8936

Abstract

The number of people living without access to clean water can be reduced by the implementation of point-of-use (POU) water treatment. Among POU treatment systems, the domestic biosand filter (BSF) stands out as a viable technology. However, the performance of the BSF varies with the inflow water quality characteristics, especially turbidity. In some locations, people have no choice but to treat raw water that has turbidity above recommended levels for the technology. This study aimed to measure the efficiency with which the BSF removes microorganisms from well water and from fecal-contaminated water with turbidity levels of 3, 25, and 50 NTU. Turbidity was controlled by the addition of kaolin to water. Turbidity removal varied from 88% to 99%. Reductions in total coliform (TC) and Escherichia coli ranged from 0.54–2.01 and 1.2–2.2 log removal values (LRV), respectively. The BSF that received water with a higher level of turbidity showed the greatest reduction in the concentration of microorganisms. Additional testing with water contaminated with four bacterial pure cultures showed reductions between 2.7 and 3.6 LRV. A higher reduction in microorganisms was achieved after 30–35 days in operation. Despite the filter’s high efficiency, the filtrates still had some microorganisms, and a disinfection POU treatment could be added to increase water safety. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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13 pages, 2365 KiB

Open AccessArticle

Development of Ceramic Water Filter Clay Selection Criteria

by Zachary J. Shepard, Yichen Zhang, Nelson M. Anaya, Dawn Cardace and Vinka Oyanedel-Craver

Water 2020, 12(6), 1657; https://doi.org/10.3390/w12061657 - 10 Jun 2020

Cited by 7 | Viewed by 5215

Abstract

Ceramic water filters (CWFs) are point-of-use drinking water treatment systems that are manufactured and used in under-served communities around the world. The clayey material (CM) used to manufacture CWFs is a locally sourced mixture of clay, sand, slit and amorphous material (usually dug near the CWF factory). CM varies in composition and purity depending on the geographical location and geological setting. In this study, a set of 13 CM samples collected from around the world were analyzed using grain size analysis, as well as liquid and plastic limit tests. Mineralogical composition was determined using X-ray diffraction. A selection of three CM samples (Guatemala, Canada, and Guinea Bissau) with a range of compositions were used to study biofilm growth on CM before and after firing. Biofilm coverage was studied on CM (before firing) and CWF material (after firing) using Pseudomonas fluorescens Migula. The average biofilm coverages for Guatemala, Canada, and Guinea Bissau CM were 20.03 ± 2.80%, 19.28 ± 0.91%, and 9.88 ± 4.02%, respectively. The average biofilm formation coverages for Guatemala, Canada, and Guinea Bissau CWF were 13.08 ± 1.74%, 10.36 ± 3.41%, and 8.66 ± 0.13%, respectively. The results presented here suggest that CM can be manipulated to manufacture better performing CWFs by engineering the soil characteristics, such as grain size, liquid and plastic limits, and mineralogy. This could improve the durability and biofilm resistance of CWFs. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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12 pages, 1818 KiB

Open AccessArticle

Effect of Chloride Ions on the Point-of-Use Drinking Water Disinfection Performance of Porous Ceramic Media Embedded with Metallic Silver and Copper

by Rekha Singh, Woohang Kim and James A. Smith

Water 2020, 12(6), 1625; https://doi.org/10.3390/w12061625 - 6 Jun 2020

Cited by 4 | Viewed by 3232

Abstract

This study quantifies the effects of chloride ions on silver and copper release from porous ceramic cubes embedded with silver and copper and its effect on E. coli disinfection in drinking water. Log-reduction of E. coli by silver ions decreased after 4 h of contact time as the chloride ion concentration increased from 0 to 250 mg/L but, it was not changed by copper ions under the same conditions. For silver addition by silver-ceramic cubes, log reductions of E. coli decreased sharply from 7.2 to 1.6 after 12 h as the chloride concentration increased from 0 to 250 mg/L. For the silver-ceramic cube experiments, chloride ion also reduced the total silver concentration in solution. After 24 h, total silver concentrations in solution decreased from 61 µg/L to 20 µg/L for corresponding chloride ion concentrations. According to the MINTEQ equilibrium model analysis, the decrease in disinfection ability with silver embedded ceramic cubes could be the result of precipitation of silver ions as silver chloride. This suggests that AgCl was precipitating within the pore space of the ceramic. These results indicate that, although ionic silver is a highly effective disinfectant for E. coli, the presence of chloride ions can significantly reduce disinfection efficacy. For copper-ceramic cubes, log reductions of E. coli by copper embedded cubes increased from 1.2 to 1.5 when chloride ion concentration increased from 0 to 250 mg/L. Total copper concentrations in solution increased from 4 µg/L to 14 µg/L for corresponding chloride ion concentrations. These results point towards the synergistic effect of chloride ions on copper oxidation as an increased concentration of chloride enhances copper release. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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16 pages, 3171 KiB

Open AccessArticle

Towards a Predictive Model for Initial Chlorine Dose in Humanitarian Emergencies

by Hongjian Wu and Caetano C. Dorea

Water 2020, 12(5), 1506; https://doi.org/10.3390/w12051506 - 25 May 2020

Cited by 8 | Viewed by 4394

Abstract

Free chlorination is a widely employed disinfection method in humanitarian water provision due to its many advantages. However, its effective application is hindered by the challenge in determining adequate initial doses to achieve free chlorine residuals that satisfy both health and aesthetic requirements. Current guidelines show varying recommended dosing strategies, and many do not adequately consider chlorine decay mechanisms that occur during water storage. Even though turbidity is commonly used as a criterion for deciding chlorine dose, it may not be an adequate proxy for the water quality in many cases. This paper addresses the fundamental relationships between chlorine decay kinetics and selected key water parameters (i.e., natural organic matter, water temperature, chlorine demand) by conducting chlorine decay tests in controlled conditions and in jerrycans (i.e., simulating humanitarian water treatment conditions). Chlorine decay constant from the Feben and Taras’s empirical model and first order model formed linear and exponential relationships with two water parameters (UVA₂₅₄ and 30-min chlorine demand). With these relationships, the two chlorine decay models can be calibrated quickly and frequently in the field, allowing effective determination of initial chlorine dose. These two models calibrated based on the suggested water parameters from the study could predict chlorine decay in water having a main chlorine demand-inducing constituents as natural organic matter. However, they underpredicted chlorine decay in surface water with additional chlorine reactants. Further research on additional chlorine decay mechanisms is needed to expand the applicability of the models. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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24 pages, 5113 KiB

Open AccessArticle

Modeling Improved Performance of Reduced-Height Biosand Water Filter Designs

by James A. Phillips and Samuel J. Smidt

Water 2020, 12(5), 1337; https://doi.org/10.3390/w12051337 - 8 May 2020

Cited by 2 | Viewed by 4726

Abstract

Point-of-use biosand water filters are widely distributed in undeveloped or developing regions due to their water treatment success and low-cost design, but two gaps remain in the basic technology: (1) the filter body is oversized relative to its contaminant removal performance, and (2) the heavy design largely excludes difficult to reach locations in need of clean water solutions. Here, we model design modifications to the v.10 Centre for Affordable Water and Sanitation Technology biosand filter using a reduced filter height, increased biolayer area, and conserved reservoir volume. We compare the hydraulic characteristics (dynamic velocity and head pressure) and percent contaminant removal of bacteria Escherichia coli and virus MS2 of the modified designs to the traditional control design using a finite element approximation of Darcy’s law with discrete time steps and a slow-sand filtration model. We demonstrate that a reduced-height design has a greater impact on contaminant removal compared to the traditional design (largely due to the increased residence time from the decreased flow rate inside the filter). For example, our 70% reduced-height filter design removed 99.5% and 73.93% of E. coli and MS2, respectively, where the traditional filter design removed 62.81% and 27.6%, respectively. Reduced-height designs should be pursued as a viable solution to improve filter performance while allowing for alternative construction techniques with greater end-user accessibility compared to the traditional design. Full article

(This article belongs to the Special Issue Point-of-Use Water Treatment)

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85 pages, 708 KiB

Open AccessFeature PaperReview

Methods, Protocols, Guidance and Standards for Performance Evaluation for Point-of-Use Water Treatment Technologies: History, Current Status, Future Needs and Directions

by Emily S. Bailey, Nikki Beetsch, Douglas A. Wait, Hemali H. Oza, Nirmala Ronnie and Mark D. Sobsey

Water 2021, 13(8), 1094; https://doi.org/10.3390/w13081094 - 15 Apr 2021

Cited by 17 | Viewed by 8048

Abstract

It is estimated that 780 million people do not have access to improved drinking water sources and approximately 2 billion people use fecally contaminated drinking water. Effective point-of-use water treatment systems (POU) can provide water with sufficiently reduced concentrations of pathogenic enteric microorganisms to not pose significant health risks to consumers. Household water treatment (HWT) systems utilize various technologies that physically remove and/or inactivate pathogens. A limited number of governmental and other institutional entities have developed testing protocols to evaluate the performance of POU water treatment systems. Such testing protocols are essential to documenting effective performance because inferior and ineffective POU treatment technologies are thought to be in widespread use. This critical review examines specific practices, procedures and specification of widely available POU system evaluation protocols. Testing protocols should provide standardized and detailed instructions yet be sufficiently flexible to deal with different treatment technologies, test microbe priorities and choices, testing facility capabilities and public health needs. Appropriate infectivity or culture assays should be used to quantify test enteric bacteria, viruses and protozoan parasites, or other appropriate surrogates or substitutes for them, although processes based on physical removal can be tested by methods that detect microbes as particles. Recommendations include further research of stock microbe production and handling methods to consistently yield test microbes in a realistic state of aggregation and, in the case of bacteria, appropriately physiologically stressed. Bacterial quantification methods should address the phenomenon of bacterial injury and repair in order to maximally recover those that are culturable and potentially infectious. It is only with harmonized national and international testing protocols and performance targets that independent and unbiased testing can be done to assure consumers that POU treatment technologies are able to produce water of high microbial quality and low health risk. Full article

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