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Nanofiltration for Safe Drinking Water in Underdeveloped Regions – A Feasibility Study


Abstract and Figures

The fact from the United Nations that in 2015, about 663 million people worldwide did not have access to an improved drinking water source, does not resemble the reality wherein more than 1.8 billion people worldwide were consuming water which is unsafe for drinking. Nanofiltration, with the ability to reject several trace organic compounds, heavy metals and viruses at a lower energy demand than reverse osmosis, has found application for the production of high quality drinking water in developed nations. This study briefly reviewed the efficacy of nanofiltration for drinking water production considering various types of pollutants. Series of experiments were conducted using a pilot-scale nanofiltration unit, to assess the potential for drinking water production, from ground water, in a developing country like Ghana and to estimate the associated costs. The economic feasibility of a micro-enterprise (relying on nanofiltration) was evaluated for tackling the economic water scarcity in a rural area. The concept of micro-enterprise based on a pilot-scale nanofiltration system was found to be suitable for producing adequate quantity of safe drinking water (at a reasonable cost of less than €0.01 per litre) for a village in a developing country. Offering safe and economic drinking water with a possibility for small margins and employment opportunities aiming for poverty alleviation, its operation was found to be economical and sustainable.
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Nanofiltration for Safe Drinking Water in Underdeveloped
Regions A Feasibility Study
S. Ramaswami*, Z. N. Ahmad, M. Slesina, J. Behrendt and R. Otterpohl
Institute of Wastewater Management and Water Protection, Hamburg University of Technology, 21073 Hamburg,
The fact from the United Nations that in 2015, about 663 million people worldwide did not have
access to an improved drinking water source, does not resemble the reality wherein more than 1.8
billion people worldwide were consuming water which is unsafe for drinking. Nanofiltration, with
the ability to reject several trace organic compounds, heavy metals and viruses at a lower energy
demand than reverse osmosis, has found application for the production of high quality drinking
water in developed nations. This study briefly reviewed the efficacy of nanofiltration for drinking
water production considering various types of pollutants. Series of experiments were conducted
using a pilot-scale nanofiltration unit, to assess the potential for drinking water production, from
ground water, in a developing country like Ghana and to estimate the associated costs. The
economic feasibility of a micro-enterprise (relying on nanofiltration) was evaluated for tackling
the economic water scarcity in a rural area. The concept of micro-enterprise based on a pilot-scale
nanofiltration system was found to be suitable for producing adequate quantity of safe drinking
water (at a reasonable cost of less than 0.01 per litre) for a village in a developing country.
Offering safe and economic drinking water with a possibility for small margins and employment
opportunities aiming for poverty alleviation, its operation was found to be economical and
Developing country; high quality drinking water; micro-enterprise; nanofiltration; pilot-scale
To “Halve, by 2015, the proportion of the population without sustainable access to safe drinking
water and basic sanitation” was the among the targets of the United Nations (UN) Millennium
Development Goal (MDG) - ‘Ensure environmental sustainability’ (United Nations, 2015). The
MDG target was achieved in 2010, wherein 88% of the total global population had access to an
improved drinking water source compared to 76% in the year 1990 (UNICEF & WHO, 2015). The
World Health Organisation (WHO)/United Nations Children's Emergency Fund (UNICEF) Joint
Monitoring Programme for Water Supply and Sanitation (JMP) monitored the progress towards this
target. It had used the ‘use of an improved drinking water source’ as the indicator, due to the non-
availability of “nationally representative data on the safety of drinking water for the majority of
countries” (UNICEF & WHO, 2015). The emphasis of an improved drinking water source (like
public taps, boreholes, protected dug wells, piped water supply, etc.) relies on the likelihood that it
could be in general free from faecal contamination compared to an unimproved source, which
however is not universal (Bain et al., 2014b). Several other studies (Bain et al., 2012; Clasen, 2010;
Godfrey et al., 2011; Payen, 2011; WHO & UNICEF, 2012) also report that in many cases an
improved drinking water source (including piped water supply) suffers from faecal contamination,
especially in developing countries. According to UNICEF & WHO (2015) about 663 million people
were still using unimproved drinking water sources in 2015. This however is an underestimation
and more than 1.8 billion people worldwide use unsafe drinking water (Bain et al., 2014a; Onda,
LoBuglio, et al., 2012; Payen, 2011). And this number will increase further if chemical pollutants
are accounted (Godfrey et al., 2011) and becomes nearly 4 billion if the difficulty, risk and cost for
access to water are considered (Payen, 2011). Poor people in developing countries pay a large
portion of their meagre daily wages (see Figure 1) to gain access to an improved/safe water source
(like water tanker, street seller, etc.).
Centralised approach cannot solve this water crisis in developing countries and membrane
technologies are becoming preferred and plausible among the decentralised solutions (Arnal et al.,
2010; Cherunya et al., 2015; Huttinger et al., 2015; Peter-Varbanets et al., 2009; Peter-Varbanets, et
al., 2012; Sima and Elimelech, 2013). Ultrafiltration (UF) has been widely studied for the
production of bacteriologically safe drinking water in developing countries. However, it is also
known that viruses and some bacteria can permeate an UF membrane (Arkhangelsky and Gitis,
2008), for which reason some studies recommend a post-chlorination step (Arnal, et al., 2010;
Huttinger et al., 2015). Furthermore, ultrafiltration fails to reject dissolved organics (insecticides,
pesticides, humic substances, etc.) and heavy metals. On the other hand, several research works
(Afonso et al., 2004; Peter-Varbanets et al., 2009; Sima and Elimelech, 2013) have investigated the
reclamation of brackish water or sea water using reverse osmosis (RO) for the developing world
scenario. Nanofiltration (NF) is a fascinating technology, lying between the boundaries of UF and
RO, with better rejection capacities than UF and lower energy requirement than RO. Hardly any
study exists evaluating the suitability of nanofiltration for drinking water production in developing
regions, which is expected to become a promising technology (Hillie and Hlophe, 2007).
Figure 1. Typical low daily salary (in GBP) and the cost for 50L improved/safe water (in GBP) in
some countries [ adapted from WaterAid (2016a) ]
This study evaluates the feasibility of establishing micro-enterprises using nanofiltration as means
for producing safe and economic drinking water locally in developing regions. This paper will
review the efficacies of nanofiltration for drinking water production, present the results from
nanofiltration trials conducted at the Institute of Wastewater Management and Water Protection and
evaluate the micro-enterprise concept.
The demand for water is increasing worldwide with water resources becoming scarce, besides the
increasing global concern for micro-pollutants in the raw water sources for drinking water
production. Over the last two decades, nanofiltration has become popular and attractive for drinking
water production (see Table 1) in industrialised countries, since it can effectively remove these
pollutants present at very low concentrations in a single step and without the need for addition of
any secondary chemicals.
From the various studies reviewed in Table 1, it can be concluded that nanofiltration, compared to
conventional drinking water treatment (DWT) and ultrafiltration, is a promising technology for
producing high quality and safe drinking water free from heavy metals, micro-pollutants and
pathogens at lower capital and operational costs compared to reverse osmosis. Van der Bruggen et
al. (2001) and Costa and de Pinho (2006) estimated the cost of clean water produced using NF to be
about €0.2/m3 for a plant capacity of about 2000m3/d.
Table 1. Application of nanofiltration for the production of high quality drinking water a review
Pollutant / [Sources]
Bacter-, fung-, herb- and pesticides.
[Van der Bruggen et al., 2001; Košutić
et al., 2005; Ogutverici et al., 2016;
Pang et al., 2010; Saitúa et al., 2012;
Sanches et al., 2012]
Several NF membranes can remove many of these
compounds effectively. To pinpoint some, rejection
percentages up to 95, 94 and 92.5% have been reported
for triclosan, dichlorodiphenyltrichloroethane and
glyphosate by Ogutverici et al. (2016), Pang et al.
(2010) and Saitúa et al. (2012) respectively.
Emerging micro-pollutants (pharmace-
utical residues, hormones, endocrine
disruptors, etc.) and pathogens.
[Lopes et al., 2013; Radjenović, et al.,
2008; Sanches et al., 2012; García-
Vaquero et al., 2014; Yoon et al., 2007]
Studies (including full scale in DWT plants) confirm
that a wide spectrum of emerging pollutants can be
retained by NF, better than conventional treatment
powered with activated carbon adsorption. Depending
on the membrane properties and the chemical
characteristics of individual compounds, the rejection
capacities can range from about 30% to almost 100%.
Harmful monovalent anions (nitrate,
[Van der Bruggen et al., 2001; Garcia et
al., 2006; Shen and Schäfer, 2015]
Some NF membranes can effectively reject nitrate as
well as fluoride ions. The main criteria for membrane
selection would be the pore diameter, besides the
surface charge of the membrane.
Heavy metal ions (As, Ni, Pb, U, etc.).
[Harisha et al., 2010; Košutić et al.,
2005; Maher et al., 2014; Favre-
Réguillon et al., 2008]
Numerous studies (lab and pilot scale) report the ability
of NF to reject heavy metals from drinking water.
Harisha et al. (2010) and Košutić et al. (2005) report
rejection% of more than 85% for As using NF, which is
not much different from the rejection capacity of RO.
Natural organic matter.
[Costa and de Pinho, 2006; Ericsson et
al., 1997]
Almost all NF membranes can remove humic
substances effectively without compromising on
permeate flux unlike RO membranes.
In developing countries, rapid industrial growth with low environmental concern and lack of strict
regulation results in serious pollution of its water resources. Even the ground water in such
countries can be expected be more polluted than in the industrialised countries with strict
regulations. For these scenarios, nanofiltration could possibly be used to produce safe drinking
water at reasonable costs.
Ghana was chosen as a reference country for this study as: it is among the countries with economic
water scarcity (UNESCO, 2012), several organisations and NGOs have been working in its rural
areas (like Safe Water Network,, WaterAid) and the due to the availability of ample
scientific literature.
Materials & Methods
Since the surface waters in Ghana are mostly highly polluted (Abdul-Razak et al., 2009; Danquah et
al., 2011; Karikari and Ansa-Asare, 2006); for this study, ground water was chosen to be the raw
water source. Model ground water [ based on the average of values reported by Tay and Kortatsi
(2008) ], with a composition as in Table 2, was prepared using deionised water, inorganic salts and
sodium salt of humic acid (45-65% humic acid (HA) content, purchased from Carl Roth GmbH,
Germany). Membrane cleaning was carried out using solutions of sodium hydroxide and
hydrochloric acid. All chemicals used were of analytical grade.
Table 2. Composition of model ground water [ adapted from Tay and Kortatsi (2008) ]
* A high value was chosen by authors, as nominal values could not be obtained from literature
A schematic of the pilot scale nanofiltration unit is shown in Figure 2. Effluent treatment (ET)-
System [ more details of the system can be found elsewhere, ROCHEM (2008) ] comprising of disk
tube (DT) module packed with DOW NF270 membrane (active surface area of 1m2) was provided
by RTS Rochem Technical Services GmbH, Germany. The system has a rotary vane pump (coupled
to a 230 V, 750 W motor) capable of providing a flow rate of about 800 L/h over a range of
pressure from 3 to 9 bar (g). All experiments were performed at 14 ± 0.2oC.
Figure 2. Schematic of the nanofiltration setup used in the study
Two types of experiments were conducted to evaluate the water production capacity of the unit and
to study the fouling tendencies. In the first set of experiments (totalling 7 trials), feed water (initial
volume of 120 L) was concentrated up to 9 times at 7 bar pressure and the permeate was collected
in a container placed on a weighing scale. The weight of the permeate collected over time was
recorded and was used to calculate the temperature-corrected permeate flux. At the end of each
experiment, samples of concentrate and compounded permeate were collected and their pH,
conductivity and TOC content were measured. The collected permeate from permeate reservoir was
given back to the feed reservoir and mixed well before starting the new batch. After the 7 trials, the
membrane was subjected to chemical cleaning using NaOH (0.1%) and HCl (0.2%) solutions. In the
latter part of the study, filtration was carried out at 5 bar and both retentate & permeate were given
back into the reservoir. The setup was run continuously for 28 days and the volume flow rate of
permeate was measured regularly to determine the flux.
Conductivity and pH of the collected retentate and permeate samples were measured using GLF100
conductivity meter (Greisinger electronic GmbH, Germany) and Multi HQ40D device (Hach Lange
GmbH, Germany). Total organic carbon (TOC) and nitrate concentration in the samples were
determined using Multi N/C 3000 analyser (Analytik Jena AG, Germany) and V-550 UV/vis
spectrophotometer (JASCO Labor- und Datentechnik GmbH, Germany) respectively following the
German standard methods (GDCh & DIN, 2016).
Results & Discussion
The measured permeate flux from the seven consecutive batches (without membrane cleaning) can
be seen in Figures 3 and 4a. The initial rapid decline in flux during first batch (see Figure 4a) should
be attributed to compaction of the membrane (which was permitted before extracting permeate in
subsequent trials) and then some degree of fouling. There was hardly any difference in the initial
permeate flux or the trend during filtration in trials after first batch. This suggests that the fouling
Figure 3. Change of permeate flux during nanofiltration cycles (WCF≈0.88) – 7 operation cycles
without membrane cleaning
Figure 4. (a) Comparison of permeate flux from 1st, 2nd and 7th trials; (b) TOC content in retentate
(R) and permeate (P) during concentration of model ground water from trial 7
layer did not grow further and that the module could be used for longer durations without the need
for cleaning. A flux decline of about 25% was to be seen during each batch due to the increase in
osmotic pressure resulting from concentration of feed water.
Water permeability with the feed model ground water (9-10 Lm-2h-1bar-1) was only slightly lower
than the measured clean water permeability of about 11 Lm-2h-1bar-1. Figures 4b and 5a show the
rejection efficacy of the membrane for organics and figure 5b shows the retention of total dissolved
solids (TDS) expressed in terms of conductivity. It is well known from various studies and from the
membrane datasheet from Dow Filmtec, that NF270 offers high water fluxes, high and low to high
rejections for organic and inorganic (depending on hydrated size and valency of the ion) solutes
respectively. At 88% water recovery, all permeate samples had less than 2 mg TOC/L and their
conductivity ranged from 140-170 µS/cm. pH value of all samples was measured to be within the
range of 7.2-8.2. NF270 does not have the ability to reject nitrate ions (also observed in this study,
data not shown). Should the raw water source contain high nitrate concentration (> 50 mg/L), an
appropriate membrane (for e.g. NF70 or NF90) must be selected.
Figure 5. Rejection of TOC and TDS during 7 consecutive trials (water recovery = 88%)
Figure 6. Decline in permeate flux during the fouling experiment at 5 bar
Figure 6 shows the decline in water flux (about 29% in 28 days) during the long-term fouling
experiment. A slight reduction in feed TOC was observed during this period (likely due to fouling),
however, the permeate TOC was about 1.5 mg/L during the entire period (data not shown). It could
be concluded that the module could provide a water permeability of about 8 Lm-2h-1bar-1 or more
(can be higher on-site, as ground waters usually have less than 15 mgTOC/L, assumed in this
study), with high quality (very low organic content and free from pathogens) for long operation
times or cycles.
As per the European Union, a company with “fewer than 10 employees and an annual turnover or
balance sheet below €2 million” is termed as a micro-enterprise. This study hypothesises that in
developing regions with economic water scarcity, a micro-enterprise can produce sustainable and
safe drinking water from locally available water resources using a pilot-scale nanofiltration unit and
deliver potable water at reasonable prices. A schematic of different operations in such a micro-
enterprise or drinking water company is shown in Figure 7.
1. Ground water
extraction from an
existing well or bore-
2. Pre-filtration using
cloth filter (if needed)
3. Nanofiltration using
4. Re-filling of clean 20L
container (disinfected)
5. Delivery of water and
return of empty
container door-to-
Figure 7. A sketch of operations in a micro-enterprise in a rural area [ from Ahmad (2015) ]
Based on the experimental results, it would be appropriate to consider an average water flux of 60
Lm-2h-1 at 8 bar (recommended optimum pressure in literature). Thus, with 20 hours operation per
day, the ET-System (with 1m2 membrane area) can produce 1200 L of high quality water per day,
sufficient to meet the needs for drinking and cooking of 120 five-member-households as per Ghana
Statistical Service (2014). Table 3 presents an estimate of the costs (fixed and variable) and the
revenue for a micro-enterprise. It has been assumed that the nanofiltration unit shall be chemically
cleaned (using solutions of NaOH and HCl) once in every two weeks, thus operating for 336 days a
year (6720 operating hours) producing 403.2m3 clean water per year. It is assumed that an existing
bore-hole or a well can be used as the raw water source. The ET-System has a life of 24,000-30,000
hours and an average of 27,000 hours (4 years) has been used in the calculations.
From Table 3, with just one employee, turnover in first 4 years amounts to about €3000 and to
about €6300 for every 4 years thereafter, which can be used for other costs not considered in this
evaluation. Requirements for land, electrical, mechanical and civil investments are minimal for the
establishment of such a micro-enterprise. Miscellaneous expenses (costs for storage tanks, other
maintenance works, pre-filtration, water quality analyses, etc.) and taxes (e.g. ground water
extraction, brine disposal) have not been included in the estimate. The electricity costs can be
reduced to a third, if obtained from energy providers based on renewable sources (GIZ, 2016).
There might be a scope for hiring another employee or reducing the water prices further.
Table 3. Fixed & variable costs and revenue for proposed drinking water company - an estimate
Fixed costs - for first 4 years
Variable costs
One-time investment
(in €)
For 4 yrs.
(in €)
ET-System (trade discount possible)
For electricity (€0.3 per kWh)
20 L water containers (250 nos.)
For chemicals (€2.6 per month)
Delivery vehicle (tricycle cart)
Personnel cost (per employee)
Initial investment for 4 yrs. (total)
Total variable costs
Fixed costs (for every 4 yrs.) after first 4 yrs.
Revenue for 4 yrs. (in €)
Motor plus pump (
Water cost (€0.01 per L)
Membrane (replacement, RTS)
Total fixed cost after first 4 yrs.
1 - personal communication, 2 -, 3 -, 4 - Ghana Statistical Service (2014)
About 663 million people worldwide lack access to ‘improved’ drinking water source; is often
misinterpreted. On the contrary, more than 1.8 billion people do not have access to safe drinking
water. Nanofiltration has been widely studied or implemented in industrialised countries for the
production of high quality drinking water. This study investigated the feasibility of establishing
micro-enterprises for producing potable water using a pilot-scale nanofiltration system in
developing countries. Ground water was considered as the raw water source for drinking water
production. It was found that a micro-enterprise using a pilot-scale nanofiltration unit can produce
adequate water of high quality, for less than €0.01 per litre, for meeting the potable water needs (for
drinking and cooking) of a village (with about 600 inhabitants) in a developing country. Micro-
enterprises employing nanofiltration can be a solution for the production of safe drinking water in
rural areas with economic water scarcity.
The authors acknowledge RTS Rochem Technical Services GmbH for providing the ET-System.
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and pharmaceuticals by nanofiltration and ultrafiltration membranes. Desalination, 202(1-3), 1623.
... The usage of filters means that no chemical additives are needed [12]. The filtrated water is purer and tasty because of the home filtrated system contains several filters that are gathered and work as same as the human kidney that clear the excess salts and lead to separate the metal ions, salts, impurities and purify the body from the toxic substances and eject them through urine which is the result of metabolism of food [13]. Micro filtration, Ultra filtration, Nano-filtration, and Reverse membrane (MF, UF, NF, and RO) respectively, are based on the osmotic pressure principle [14]. ...
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Secure drinkable water is decisive and fundamental in order to increase the welfare of current generations and beyond. A new design study represents, small, and portable system for production high-purified drinking water depends on several sources of electric power with nanotechnology principles by using nano-membranes. This system can purify the water from rivers, lakes and marshes wells, as well as any tap water, with the lowest level of water source, this system can work by depending on both AC, and DC power. Tests carried out on the filtered water samples showed that the well water hardness before filtering was 2783.2 mg/L and decreased to 431.2 mg/L, and the pH ratio increased slightly from 7.1-7.3 and this elevation was considered ineffective. TSS decreased from 15 to 11 mg / l, also TDS, Mg +2 , and Na +2 were all reduced as follows (4420-290), (414.03-21.46), (120-32) respectively, and for tap water TSS, Hardness, TDS, Mg +2 , Na +2 , and pH were all reduced as
... During the first year of the research project, NF permeate was produced at the institute (from the supplied RO retentate) using an Effluent Treatment System packed with DOW FILMTEC NF270 membrane provided by RTS Rochem Technical Services GmbH. More details about the nanofiltration setup can be found elsewhere [91,92]. Thereafter, NF permeate was provided from the pilot scale nanofiltration plant treating the RO retentate at the landfill site. ...
Landfill leachates containing high ammonia concentrations cannot be treated satisfactorily using reverse osmosis (RO) systems alone. In this work, leachate nitrification using aerated packed bed reactors was investigated to solve the problem of insufficient ammonia rejection faced by the multi-stage high pressure membrane system (comprising of RO and nanofiltration (NF) operations) treating the leachate at the Ihlenberg landfill site. Nitrification efficiencies greater than 97% were achieved with the NF permeate of RO retentate of raw leachate (having 16 g/L Cl-, 45 mS/cm) at loading rates of about 1100 g NH4+-N/(m3∙d) at 25°C. Based on the findings, a half-technical scale plant was conceptualised and commissioned at the Ihlenberg landfill site. -------------- FULL TEXT AVAILABLE AT:
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OBJECTIVE: To determine how data on water source quality affect assessments of progress towards the 2015 Millennium Development Goal (MDG) target on access to safe drinking-water. METHODS: Data from five countries on whether drinking-water sources complied with World Health Organization water quality guidelines on contamination with thermotolerant coliform bacteria, arsenic, fluoride and nitrates in 2004 and 2005 were obtained from the Rapid Assessment of Drinking-Water Quality project. These data were used to adjust estimates of the proportion of the population with access to safe drinking-water at the MDG baseline in 1990 and in 2008 made by the Joint Monitoring Programme for Water Supply and Sanitation, which classified all improved sources as safe. FINDINGS: Taking account of data on water source quality resulted in substantially lower estimates of the percentage of the population with access to safe drinking-water in 2008 in four of the five study countries: the absolute reduction was 11% in Ethiopia, 16% in Nicaragua, 15% in Nigeria and 7% in Tajikistan. There was only a slight reduction in Jordan. Microbial contamination was more common than chemical contamination. CONCLUSION: The criterion used by the MDG indicator to determine whether a water source is safe can lead to substantial overestimates of the population with access to safe drinking-water and, consequently, also overestimates the progress made towards the 2015 MDG target. Monitoring drinking-water supplies by recording both access to water sources and their safety would be a substantial improvement.
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Water quality and safe water sources are pivotal aspects of consideration for domestic water. Focusing on underserved households in Kenya, this study compared user perceptions and preferences on water-service provision options, particularly investigating the viability of decentralized models, such as the Safe Water Enterprise (SWE), as sustainable safe drinking water sources. Results showed that among a number of water-service provision options available, the majority of households regularly sourced their domestic water from more than one source (86% Ngoliba/Maguguni, 98% Kangemi Gichagi). A majority of households perceived their water sources to be unsafe to drink (84% Ngoliba/Maguguni, 73% Kangemi Gichagi). For this reason, drinking water was mainly chlorinated (48% Ngoliba/Maguguni, 33% Kangemi Gichagi) or boiled (42% Ngoliba/Maguguni, 67% Kangemi Gichagi). However, this study also found that households in Kenya did not apply these household water treatment methods consistently, thus indicating inconsistency in safe water consumption. The SWE concept, a community-scale decentralized safe drinking water source, was a preferred option among households who perceived it to save time and to be less cumbersome as compared to boiling and chlorination. Willingness to pay for SWE water was also a positive indicator for its preference by the underserved households. However, the long-term applicability of such decentralized water provision models needs to be further investigated within the larger water-service provision context.
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There is a critical need for safe water in healthcare facilities (HCF) in low-income countries. HCF rely on water supplies that may require additional on-site treatment, and need sustainable technologies that can deliver sufficient quantities of water. Water treatment systems (WTS) that utilize ultrafiltration membranes for water treatment can be a useful technology in low-income countries, but studies have not systematically examined the feasibility of this technology in low-income settings. We monitored 22 months of operation of 10 WTS, including pre-filtration, membrane ultrafiltration, and chlorine residual disinfection that were donated to and operated by rural HCF in Rwanda. The systems were fully operational for 74% of the observation period. The most frequent reasons for interruption were water shortage (8%) and failure of the chlorination mechanism (7%). When systems were operational, 98% of water samples collected from the HCF taps met World Health Organization (WHO) guidelines for microbiological water quality. Water quality deteriorated during treatment interruptions and when water was stored in containers. Sustained performance of the systems depended primarily on organizational factors: the ability of the HCF technician to perform routine servicing and repairs, and environmental factors: water and power availability and procurement of materials, including chlorine and replacement parts in Rwanda.
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This study examined the feasibility of nanofiltration (NF) and reverse osmosis (RO) in treating challenging natural tropical waters containing high fluoride and natural organic matter (NOM). A total of 166 water samples were collected from 120 sources within northern Tanzania over a period of 16months. Chemical analysis showed that 81% of the samples have fluoride levels exceeding the WHO drinking guideline of 1.5mg/L. The highest fluoride levels were detected in waters characterized by high ionic strength, high inorganic carbon and on some occasions high total organic carbon (TOC) concentrations. Bench-scale experiments with 22 representative waters (selected based on fluoride concentration, salinity, origin and in some instances organic matter) and 6 NF/RO membranes revealed that ionic strength and recovery affected fluoride retention and permeate flux. This is predominantly due to osmotic pressure and hence the variation of diffusion/convection contributes to fluoride transport. Different membranes had distinct fluoride removal capacities, showing different raw water concentration treatability limits regarding the WHO guideline compliance. BW30, BW30-LE and NF90 membranes had a feed concentration limit of 30-40mg/L at 50% recovery. NOM retention was independent of water matrices but is governed predominantly by size exclusion. NOM was observed to have a positive impact on fluoride removal. Several mechanisms could contribute but further studies are required before a conclusion could be drawn. In summary, NF/RO membranes were proved to remove both fluoride and NOM reliably even from the most challenging Tanzanian waters, increasing the available drinking water sources. Copyright © 2015 Elsevier B.V. All rights reserved.
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Groundwater samples from 68 communities within the Densu basin were sampled and analysed over a period of 1 year for various physico-chemical water quality parameters using appropriate certified and acceptable international procedures, in order to assess the water types as well as the suitability of groundwater within the basin for drinking and other domestic uses. The study showed that most of the physico-chemical parameters were within the World Health Organization limits recommended for drinking water. However, a few of the boreholes were slightly acidic. Some boreholes showed high level of mineralization. Borehole (GaD 6) at Pokuasi recorded the highest conductivity value of 7780.0 µS/cm. High levels of nitrates were also recorded in certain communities within the basin. These include Aponsahene (105.8 mg/l), Damang (66.0 mg/l), Adzen Kotoku (61.5 mg/l), Afabeng (50.8 mg/l), New Mangoase (48.3 mg/l), Asuoatwene (41.3 mg/l), Potrase (33.6 mg/l) and Maase (33.3 mg/l). Correlations between major ions showed expected process-based relationship between Ca 2+ and Cl-(r = 0.86); Mg 2+ and Cl-(r = 0.84); Na + and SO 4 2-(r = 0.77); Na + and Cl-(r = 0.75); Mg 2+ and SO 4 2-(r = 0.74); Mg 2+ and Ca 2+ (r = 0.71); Ca 2+ and SO 4 2-(r = 0.58); and K + and SO 4 2-(r = 0.51), derived mainly from the geochemical and biochemical processes within the aquifer. Two major hydrochemical water types constituting 41% of groundwater sources within the basin have been delineated. These are Ca-Mg-HCO 3 water (19%) and Na –Cl or Na –Cl –HCO 3-Cl water (22%) types. Fifty-nine per cent of groundwater sources are mixed waters with no particular cation predominating, and having either HCO 3-or SO 4 2-ions as the main anion.
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Water quality assessment conducted in the Densu basin of Ghana between July 2003 and March 2004 identified human, animal and agricultural activities as the main sources of pollution. The pH of the water was neutral (pH range 7.20–7.48) and was unaffected by seasonal variation. The river waters were moderately soft to slightly hard (range of hardness 91.2–111 mg/l CaCO 3) with high turbidity due to poor farming practices, which result in large quantities of topsoil ending up in the river after rains. High nutrient loads observed in the basin were due to domestic, agricultural and industrial activities. The waters exhibited a general ionic dominance pattern of Na > Ca > Mg > K and HCO 3 > Cl > SO 4 , a pattern which is an intermediate between fresh and sea water systems. The dominance of chloride over sulphate could probably be due to domestic activities resulting from household effluents, fertilizer use and other anthropogenic point sources. Trace metal levels were low suggesting low metal contamination of the river. However, the microbial quality of the river water was poor due to direct contamination by animal and human excreta and other activities such as swimming, washing of clothes, etc. The river water cannot be used for domestic purposes without any form of treatment.
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This study assessed the quality of the Aboabo River and examined the anthropogenic factors that lead to river pollution. Physico-chemical and bacteriological assessment of water samples showed that water from the Aboabo river was polluted and therefore not suitable for domestic consumption. Observation, in-depth interviews, informal conversation and a cross-sectional survey of 396 households in the river basin were employed to elicit qualitative and quantitative data. Direct anthropogenic factors identified were indiscriminate dumping of refuse, channelling of raw sewage, open defecation and indiscriminate dumping of industrial waste into the Aboabo River. Remote factors identified were population growth and institutional challenges. Recommendations made include enforcement of by-laws, provision of adequate sanitation facilities and the encouragement of opinion leaders to play an active role in promoting the inculcation of environmentally friendly practices amongst residents.
Objectives: To estimate exposure to faecal contamination through drinking water as indicated by levels of Escherichia coli (E. coli) or thermotolerant coliform (TTC) in water sources. Methods: We estimated coverage of different types of drinking water source based on household surveys and censuses using multilevel modelling. Coverage data were combined with water quality studies that assessed E. coli or TTC including those identified by a systematic review (n = 345). Predictive models for the presence and level of contamination of drinking water sources were developed using random effects logistic regression and selected covariates. We assessed sensitivity of estimated exposure to study quality, indicator bacteria and separately considered nationally randomised surveys. Results: We estimate that 1.8 billion people globally use a source of drinking water which suffers from faecal contamination, of these 1.1 billion drink water that is of at least ‘moderate’ risk (>10 E. coli or TTC per 100 ml). Data from nationally randomised studies suggest that 10% of improved sources may be ‘high’ risk, containing at least 100 E. coli or TTC per 100 ml. Drinking water is found to be more often contaminated in rural areas (41%, CI: 31%–51%) than in urban areas (12%, CI: 8–18%), and contamination is most prevalent in Africa (53%, CI: 42%–63%) and South-East Asia (35%, CI: 24%–45%). Estimates were not sensitive to the exclusion of low quality studies or restriction to studies reporting E. coli. Conclusions: Microbial contamination is widespread and affects all water source types, including piped supplies. Global burden of disease estimates may have substantially understated the disease burden associated with inadequate water services. Objectifs: Estimer l'exposition à la contamination fécale par l'eau potable, telle qu'indiquée par les quantités d’Escherichia coli (E. coli) ou de coliformes thermo-tolérants (CTT) dans les sources d'eau. Méthodes: Nous avons estimé l’étendue de la couverture en différents types de sources d'eau potable à partir d'enquêtes sur les ménages et des recensements à l'aide de la modélisation à multi-niveaux. Les données de couverture ont été combinées avec des études de qualité de l'eau évaluant E. coli ou les CTT y compris celles identifiées par une revue systématique (n = 345). Les modèles prédictifs pour la présence et le niveau de contamination des sources d'eau potable ont été développés en utilisant la logistique de régression à effets aléatoires et une sélection de covariables. Nous avons évalué la sensibilité de l'exposition estimée pour étudier la qualité, les bactéries indicatrices et avons séparément considéré des études nationales randomisées. Résultats: Nous estimons que 1,8 milliard de personnes dans le monde utilisent une source d'eau potable porteuse de contamination fécale. Parmi celles-ci 1,1 milliard boivent de l'eau avec un risque assez «modéré» (>10 E. coli ou CTT par 100 ml). Les données des études nationales randomisées indiquent que 10% des sources améliorées pourraient être à risque «élevé», i.e. contenant au moins 100 E. coli ou CTT par 100 ml. L'eau potable se trouve être plus souvent contaminée dans les zones rurales (41%, IC: 31–51) qu'en milieu urbain (12%, IC: 8–18) et la contamination est la plus répandue en Afrique (53%, CI: 42–63) et en Asie du sud-est (35%, IC: 24–45). Les estimations n’étaient pas affectées par l'exclusion des études de faible qualité ou par la restriction aux études rapportant sur E. coli. Conclusions: La contamination microbienne est très répandue et affecte tous les types de sources d'eau, y compris les fournitures par tuyauterie. Les estimations de la charge mondiale des maladies pourraient avoir sensiblement sous-estimé la charge de morbidité associée à des services d'eau inadéquats. Objetivos: Calcular la exposición a la contaminación fecal a través del agua para consumo, según los niveles de Escherichia coli (E. coli) o coliformes termotolerantes (CTT) en las fuentes de agua. Métodos: Utilizando modelos multinivel, hemos calculado la cobertura de diferentes tipos de fuentes de agua para consumo basándonos en encuestas a hogares y censos. Los datos de cobertura se combinaron con estudios de calidad del agua que evaluaron niveles de E. coli o CTT, incluyendo aquellos identificados mediante una revisión sistemática (n = 345). Los modelos predictivos para la presencia y nivel de contaminación de las fuentes de agua para consumo se desarrollaron utilizando una regresión logística de efectos aleatorios y covariables seleccionadas. Evaluamos la sensibilidad de la exposición calculada según la calidad del estudio, la bacteria utilizada como indicador y tuvimos en cuenta de forma separada los ensayos nacionales aleatorizados. Resultados: Hemos calculado que 1.8 billones de personas a nivel global utilizan una fuente de agua para beber que sufre de contaminación fecal; de estas 1.1 billones consumen agua que es al menos de riesgo “moderado” (>10 E. coli o CTT por 100 mL). Datos de estudios nacionales aleatorizados sugieren que un 10% de las fuentes de agua mejoradas pueden ser de‘alto’ riesgo, al contener al menos 100 E. coli o CTT por 100 mL. El agua para consumo se encuentra más a menudo contaminada en áreas rurales (41%, IC: 31–51%) que en áreas urbanas (12%, IC: 8–18%) y la contaminación es más prevalente en África (53%, IC: 42–63%) y el Sudeste Asiático (35%, CI: 24–45%). Los cálculos no eran sensibles a la exclusión de estudios de mala calidad o a la restricción de estudios en los que se reporta E. coli. Conclusiones: La contaminación microbiana está ampliamente extendida y afecta todos los tipos de agua, incluyendo la distribuida a través de tuberías. Los cálculos de la carga global de enfermedad podrían haber subestimado sustancialmente la carga de enfermedad por servicios de agua inadecuados.
Nanofiltration (NF) is known as a very effective technology in the removal of micropollutants from surface water for drinking water purposes. In this study, NF of triclosan (TCS) which is a commonly used biocide in many different domestic and industrial applications was investigated in relation to its interaction with natural organic matter (NOM). A laboratory scale cross-flow device was operated in total recycle mode using a thin-film composite membrane with a real surface water. The effect of NOM content on TCS removal was elucidated through addition of humic acid (HA) into raw water. The performance of the membrane was evaluated by TCS retention, as well as flux behavior. The results showed that NOM had a positive effect on TCS removal due to TCS-HA complex formation that limits TCS permeation through the membrane. On the other hand, NOM was found to increase Molecular weight cut off (MWCO), but not resulting in a decrease in TCS rejection due to HA-TCS complex formation. NOM lead to an increase in TCS removal mainly by sorption into the membrane.