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Nano zero valent iron amended ceramic pot filters for enhanced virus and arsenic removal
No full textWorldwide 748 million people lacked access to improved sources of drinking water in 2014, of this group almost a quarter relies on untreated surface water (WHO & Unicef, 2014). According to the WHO, simple, socially accepted and low-cost household water treatment systems (HWTS), such as the Ceramic Pot Filter (CPF), can provide a solution for reliable drinking water on the short term. Although CPFs are used worldwide and are generally effective with regard to bacteria removal, they can in most cases not be indicated by the WHO as a “protective” HWTS, since the virus removal is insufficient. Another limitation of the CPF is the incapability of removing arsenic. Prolonged ingestion of water with elevated arsenic levels can lead to severe health issues including dermal lesions and various types of cancers (WHO, 2011b). The objective of this study was therefore to provide reliable experimental data to investigate whether it is feasible to extend the capabilities of CPFs with arsenic removal properties and enhanced virus inactivation by the incorporation of nano Zero Valent Iron (nZVI), which is a well-known arsenic adsorbent and has also potential capabilities for virus reduction. As a basis for the research approach, the following sub-objectives were formulated: (i) study the arsenic adsorption capacities nZVI amended CPFs, (ii) determine the microbiological inactivation efficiency by nZVI amended CPFs, (iii) evaluate the leaching of the incorporated nZVI and (iv) provide knowledge on the effect of incorporating nZVI into CPFs before firing. In this study Ceramic Disk Filters (CDFs) manufactured by combining clay soil with water and sawdust, pressing them in a disk shape and, firing them. Additionally, metals (nZVI, Composite Iron Matrix powder or silver nanoparticles (nAg)) were added to the clay mixture before firing, to obtain an iron content of 0.05%, 0.5% or 5% based on the weight of a dry disk. The manufactured CDFs were tested based on the following established requirements: (i) arsenic must be removed to below the provisional WHO guideline of 10 ?g/L, (ii) for bacteria a LRV of 2 or greater is required, (ii) for viruses a LRV of 3 or greater is required, (iv) the leached amount of metals must not exceed the WHO guidelines and (v) CDFs should have a flow rate of 0.08-0.24 L/h, which corresponds to 1-3 L/h for a full-size CPF. The removal of bacteria and viruses was quantified by loading the CDFs with test water with Escherichia coli and MS2 bacteriophages, as indicator organisms for bacteria and viruses, respectively. During this filter experiment also the metal leaching from the CDFs was evaluated, an arsenic breakthrough experiment was performed and the flow rates were measured. Furthermore, batch experiments were conducted with ground CDFs, both fired and unfired, to get more insight on the capabilities of the adsorption and inactivation of MS2 bacteriophages and the removal of arsenic, and to study the consequences of firing nZVI into the CDFs. Moreover, knowledge was obtained on the effect of firing nZVI into ceramic material by means of X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, optical microscopy and Scanning Electron Microscope – Energy Dispersive X-ray (SEM-EDX). The main findings, with regard to the requirements for a CPF, were: (i) although this study showed that ZVI on itself is an effective arsenic adsorbent an immediate total arsenic breakthrough of 200 ?g/L was observed for the CDFs with 5% nZVI; (ii) all CDFs, except the filter with 0.05% nZVI, were able to remove E. coli sufficiently to meet the requirements for bacteria removal (LRV 0.75-4.28); (iii) MS2 bacteriophages were poorly removed (LRV 0.11-0.24) (iv) there is no health-based guideline of the WHO for iron and the leached silver stayed far below the maximum WHO guideline of 0.1 mg/L; (v) the translated flow rates for CPFs were for all type filters higher than the requirement of 1-3 L/h (3.4 – 15.6 L/h), except for the filter with 0.05% nAg (1.5 L/h). Overall, it can thus be concluded that it is not recommended to incorporate nZVI in CPFs before firing with the purpose to enhance the removal of arsenic and viruses. Although, ZVI on itself is well capable of removing arsenic, especially at nano-scale, it was found that when it is incorporated into clay it looses effectiveness and when the clay is fired even more. In the batch experiments the unfired crushed CDF with 5% nZVI was able to remove approximately 90% of the initial 200 ?g/L As(III) in 30 minutes of contact time, while the fired crushed CDF only removed a few per cent As(III). Part of the faster As(III) removal of the unfired filter was a result of sorption by the clay, but the nZVI contributed considerably. Although, the LRVs for MS2 bacteriophages by fired filter material were higher in the batch experiment (LRV 0.42-1.52) than in the filter experiment – probably due more intensive contact - there was also no enhanced MS2 bacteriophage reduction noticed for the fired CDFs with nZVI compared to the fired blank CDF. There are probably several reactions that caused this loss of performance of ZVI. The results of the filter experiments indicated that there was insufficient surface contact with the nZVI particles; either due to unavailability of nZVI particles on the pore surface or due to too high flow rates. The addition of nZVI particles namely led to a considerable increase of flow rate, probably as a result of successive expansion and shrinking of the nZVI during firing. Furthermore, it is hypothesized that due to the vitrification process, in which the clay bonds together, the nZVI became enclosed in the clay structure. Furthermore, the 57Fe Mössbauer spectra evidenced that during firing all the added nZVI was oxidized into hematite, which probably affects the removal of arsenic. Different ZVI corrosion products have a different ability to adsorb arsenic: ZVI exhibits the greatest arsenic adsorption, secondly magnetite, then hematite and lastly goethite (Mamindy-Pajany et al. (2011)). This study showed that ZVI has potential for the removal of arsenic in HWTS, but with application in a different setting than by firing it in the CPF. Suggestions were made for potential alternatives: (i) CPFs with an iron coating; (ii) CPF with ZVI pre-treatment in the form of an hang-element or an extra bucket on top of the CPF, like the effective SONO filter for arsenic removal (Neumann et al., 2013); (iii) CPF with inside iron mixed ceramic pellets (Shafiquzzam et al.,2013). When designing a new type of CPF it is important to make sure that the iron (oxides) particles can be reached and that the flow rate is not too high, which ensures that the contact time with the iron (oxides) particles is long enough. Furthermore, additional research is needed on the enhancement of virus removal and inactivation. It is recommended to study the combination of nZVI and nAg in more detail and also to look at other combination of metals, such as Ag and copper. In order to better understand the adsorption of viruses onto different media it is advised to perform to determine the actual pHPZC of the used media. Lastly, it is advised that in a later stage of future research experiments should be performed with more challenging water and varying parameters such as the turbidity, the pH, competing ions, the ionic strength, influent arsenic concentration and different types of viruses.Sanitary EngineeringWater ManagementCivil Engineering and Geoscience
An Assessment of the Monsoon Water Situation in the Kathmandu Valley: Data collection and analysis of flow, water quality, land use and demand
No full textKathmandu, the capital of Nepal, is under increasing water stress. A rising water demand in the Kathmandu Valley is initiated by urbanisation with a rate of 4.7 % per year and amplified by a growing trend of per capita water consumption. At the same time, water availability seems to deteriorate. However, the severity of the problem is hardly known due to immense data gaps. This research aims to (1) estimate the urban water demand from literature research, (2) collect new field data about spring and stream flow, water quality, and ecological stream health, and (3) analyse remotely sensed data in order to characterise the linkages and inter-dependencies between land use, hydrology, and water quality in the Kathmandu Valley. The field data were collected in August and September 2016 and helped to get a decent picture of the water situation. The landuse classification performed using Landsat 8 images had an accuracy of 88 % and proved to be a meaningful source of data to link to the other research topics. Automated SEBAL was attempted to be used for computing evapotranspiration estimates but cannot successfully be used in mountainous areas yet. Penman-Monteith equation was used as alternative. A simplified water balance was performed for the months of August and September 2015. The outcome showed estimates to be 2, 2 x 106 m3/d for ET, 5.6 x 106 m3/d for precipitation, 2.0 x 106 m3/d for the Bagmati outflow and 1.4 x 106 m3/d for groundwater infiltration. To be able to comment on long term groundwater depletion, an annual water budget needs to be performed. The clearest influence on water quality parameters (pH, DO, EC and Rapid Stream Assessment class) was found to be the presence of developed area. With more than 20 % developed area within the considered sub-watershed, the water becomes of such poor quality that it cannot be used for any purpose without extensive treatment. In the headwater areas of the Valley, a significant amount of water with a higher quality (i.e. drinking water) is found in the streams. In September 2016 the total inflow of drinkable water to the Valley floor was estimated to be at least 1.0 x 106 m3/d. This value cannot be considered as fully available for anthropogenic purposes, as water needs to remain in the streams in order to not jeopardise ecosystem services and other functions.Civil Engineering and Geoscience
Water research for the world
No full textLet’s start with the United Nations Millennium Development Goals Report 2012. Remember the target? Halve, by 2015, the proportion of the population without sustainable access to safe drinking water and basic sanitation. Thanks to China and India the world has met the drinking water target in 2010, but the work is not done yet. The poorest lag behind, especially in Sub-Saharan Africa (Figure 1). Over 40 per cent of all people without improved drinking water live in sub-Saharan Africa. The gap between urban and rural areas still remains wide, with the number of people in rural areas without an improved water source five times greater than in urban areas. Ruralurban disparities in access to sanitation are even more pronounced than for access to drinking water. The number of people forced to resort to open defecation remains a widespread health hazard and a global scandal. Nearly 60 per cent of those practicing open defecation live in India. In sub-Saharan Africa, 75 per cent of the households have to collect water from some distance. The time and energy devoted to this manner of water collection is considerable. For 25 sub-Saharan countries combined, it is estimated that 26 million hours are spend per day, which equals the working hours of the lifetimes of 300 people. An important note: water quality is not accounted for in United Nations report – so results may well be overestimated. But isn’t that what it’s all about? Providing improved water sources, not just any source.Water ManagementCivil Engineering and Geoscience
Subsurface iron and arsenic removal for drinking water treatment in Bangladesh
No full textArsenic contamination of shallow tube well drinking water is an urgent health problem in Bangladesh. Current arsenic mitigation solutions, including (household) arsenic removal options, do not always provide a sustainable alternative for safe drinking water. A novel technology, Subsurface Arsenic Removal, relies on the existing technology of Subsurface Iron Removal. The principle of this technology is that aerated water is periodically injected into an anoxic or anaerobic aquifer through a tube well. The injection water partially displaces the original iron and arsenic containing groundwater. The oxygen-rich injection water oxidized adsorbed iron on the soil grains around the tube well. Once the flow direction is reversed, the oxidized iron (precipitated as iron (oxy)hydroxides) provides adsorption sites for soluble iron and arsenic. Subsequently groundwater with reduced iron and arsenic concentrations can be abstracted. This technology has the potential to be an affordable, robust and chemical-free arsenic removal solution for decentralized application. In this PhD study a combination field and laboratory research, in Bangladesh and the Netherlands, has resulted in better understanding of the subsurface processes determining the sustainable operation in diverse geochemical settings.Water MangamentCivil Engineering and Geoscience
Arsenic removal in rapid sand filters
No full textArsenic (As) mobility in water is worldwide studied since its toxicity was proven in 1888. Intake of As can lead to skin disease, cancer, kidney and heart failure, diabetes and paralysis. In the Netherlands, groundwater used for drinking water production contains As in the range from 0 – 70 μg/L. Currently, all groundwater treatment plants reduce As in drinking water below the WHO standard of 10 μg/L. However, to ensure no adverse health effects occur by the intake of drinking water, Dutch drinking water companies investigate implications of distributing water with As concentrations below 1 μg/L. The new target value causes 58% of the treatment plants with measurable As in the raw water (19% of all total groundwater treatment plants) to need some sort of adjustment to their treatment scheme to comply with the new As target value...Sanitary Engineerin
Managed aquifer recharge as a barrier for ozone-based advanced oxidation by-products: BrO3- and H2O2
No full textManaged Aquifer Recharge (MAR) is a technology that relies on soil passage - after pond infiltration - for water treatment. MAR is a proven technology for the removal of pathogenic micro-organisms, turbidity and a selection of specific organic micro-pollutions (OMPs). Nevertheless, removal of the wide variety of OMPs found in surface waters requires additional treatment. The application of O3-based advanced oxidation processes (AOPs) before MAR has been proposed as a smart solution, because previous studies have documented complementary and synergetic benefits for the removal of OMPs. However, the effect of the installation of O3-based AOP as a chemical process on the subsequent MAR as a biological process is not known yet. Especially the behaviour and fate of O3-based AOP by-products and residuals on MAR raise many questions. This thesis focused on the behaviour and fate of BrO3 - as an O3-based AOP by-product andH2O2 as an AOP residual during MAR.Sanitary Engineerin
Ceramic silver impregnated pot filters for household drinking water treatment in developing countries
No full textCivil Engineering and Geoscience
Riverbank filtration in highly turbid rivers
No full textRiverbank filtration (RBF) is a surface water filtration method for drinking water through the banks and bed of a river, using extraction wells located near the water body in order to ensure direct aquifer recharge. As the surface water travels through the sediments, contaminants, such as suspended and colloidal solids and pathogenic microorganisms, are removed. Apart from water quality improvement, RBF has the advantage of reducing peak concentrations which commonly pass through a river. RBF has been widely used in Europe, USA and, nowadays, in some Asian countries (e.g., South Korea, India, China). Latin-American and specifically Colombian river basins, have been suffering a continuous deterioration, leading to high suspended sediment loads being transported by the rivers. The RBF technology has not been proven yet in highly turbid waters, in which the excessive transport of suspended sediments threatens sustainable operation. Clogging of both the riverbed and deeper aquifer may increase flow resistance, reducing water revenues over the course of time. To assess the feasibility of RBF for highly turbid river waters in Colombia, a combination of field and laboratory research was conducted – both in the Netherlands and Colombia. In Colombia, the studies were done at the Cinara institute's Research and Technology Transfer (R&TT) Station for drinking water and at the Fluid Mechanics lab. The station is located at the Northeast of Cali, Colombia, and was built at the premises of the main water treatment plant of Cali, Puerto Mallarino. In the Netherlands, the laboratory work was done at the Delft University of Technology, running infiltration column experiments at the Sanitary Engineering lab and the flume experiments at the Fluid Mechanics lab...Sanitary Engineerin
Municipal effluent disinfection by Iron Electrocoagulation
No full textIn a global context of ever increasing population, climate change, and freshwater quality deterioration, water reclamation presents itself as a valid and valuable supplier of the resource. However, sewage and treated effluents remain important sources for waterborne pathogens, including Antibiotic Resistant Bacteria (ARB), a global emerging threat with potential to cripple our health systems and make us vulnerable once again to simple infections. Effluent disinfection thus becomes paramount to ensure suitable microbiological water quality and reuse applicability, although other water quality parameters critical for reuse applications (i.e. solid content, nutrients and organic matter) should also be addressed. Technologies developed for drinking water disinfection, such as chlorination, UV-irradiation, or ozone, usually fail to satisfy reclamation standards across all microbial groups, are not designed for nutrient or solid removal, and are known sources of hazardous disinfection by-products (DBPs). This research looks into a rather unknown water treatment technology, Iron Electrocoagulation (Fe-EC), as a suitable candidate for municipal effluent reclamation, based on its inactivation efficacy of a wide range of microorganisms, nutrient and solid removal, and absence of DBPs. The disinfection of ARB by Fe-EC and other processes is also described in detail, especially due to the shortage of literature regarding their inactivation, their general absence in water quality standards, and the health risk they pose to users. Significant efforts were made as to understand if indeed ARB are more resistant than other faecal indicator bacteria (FIB) when it comes to wastewater treatment, and if disinfection of both groups can be correlated...Sanitary Engineerin
Arsenic Removal for Drinking Water Production in Rural Nicaraguan Communities
No full textSanitary Engineerin
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