A. Summary of Phase I Results 1. Background and Problem Definition The Cornell AguaClara project team designs sustainable drinking water treatment technologies. AguaClara’s commitment to sustainability encompasses environmental, social and economic feasibility. Fluoride removal is challenging especially in rural areas and on the village scale because treatment methods are limited. In Phase I we conducted preliminary research to evaluate the feasibility of improving the Nalgonda method of fluoride removal. This work builds on a previous EPA P3 project where we demonstrated efficient removal of arsenic with polyaluminum chloride (PACl). According to the World Bank, India is the leading user of groundwater in the world, with an estimated demand of 230 cubic kilometers per year (The World Bank, 2012). More than 80 percent of drinking water comes from groundwater sources (The World Bank, 2012). This dependency on groundwater becomes a critical problem when faced with the presence of fluoride contamination (Figure 1). Natural geological sources are the primary cause of the high fluoride levels. The World Health Organization (WHO) guideline for fluoride in drinking water is 1.5 mg/L (WHO, 2011). However in some places, such as areas within the Ajmer district of Rajasthan state, India, fluoride contamination can reach levels as high as 18 mg/L (Hua, 2008). Fluoride contaminations above 1.5 mg/L can cause detrimental health effects to users such as dental fluorosis. Fluoride is a difficult contaminant to remove because the ions are highly soluble in water. Current methods (see Singh et al., 2014) are based on the principle of adsorption (Raichur an Jyoti, 2001), ion-exchange (Singh, 1999), precipitation–coagulation (Saha, 1993 and Reardon and Wang, 2000), membrane separation process (Amor et al., 2001), electrolytic defluoridation (Mameri et al., 2001), and electrodialysis (Hichour, 1999). Of current available fluoride removal strategies, one of the methods that has significant potential to be implemented in small communities is the Nalgonda method. According to Singh et al., (2014), the problem with the Nalgonda method is that it is too expensive. The Nalgonda method requires a high dose of aluminum sulfate coagulant to aggregate with fluoride and precipitate. A study conducted by Dahi et al. (1996) suggests that 13 g/L alum (1.2 g/L as Al) is needed for the Nalgonda method to effectively treat fluoride levels between 9 and 13 mg/L. Despite the high concentrations of added coagulant, the fluoride residual in the test was still unable to meet the WHO fluoride guideline of 1.5 mg/L. The high dose of aluminum sulfate also leaves high sulfate residuals in the water, which causes taste and odor issues (Fawell, 2006). Figure 1. Global distribution of fluoride in groundwater (Amini et al., 2008).
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A. Summary of Phase I Results
1. Background and Problem Definition
The Cornell AguaClara project team designs sustainable drinking water treatment
technologies. AguaClara’s commitment to sustainability encompasses environmental, social and
economic feasibility. Fluoride removal is challenging especially in rural areas and on the village
scale because treatment methods are limited. In Phase I we conducted preliminary research to
evaluate the feasibility of improving the Nalgonda method of fluoride removal. This work builds
on a previous EPA P3 project where we demonstrated efficient removal of arsenic with
polyaluminum chloride (PACl).
According to the World Bank, India is the leading user of groundwater in the world, with an
estimated demand of 230 cubic kilometers per year (The World Bank, 2012). More than 80
percent of drinking water comes from groundwater sources (The World Bank, 2012). This
dependency on groundwater becomes a critical problem when faced with the presence of fluoride
contamination (Figure 1). Natural geological sources are the primary cause of the high fluoride
levels. The World Health
Organization (WHO)
guideline for fluoride in
drinking water is 1.5 mg/L
(WHO, 2011). However in
some places, such as areas
within the Ajmer district
of Rajasthan state, India,
fluoride contamination
can reach levels as high as
18 mg/L (Hua, 2008).
Fluoride contaminations
above 1.5 mg/L can cause
detrimental health effects
to users such as dental
fluorosis.
Fluoride is a difficult contaminant to remove because the ions are highly soluble in water.
Current methods (see Singh et al., 2014) are based on the principle of adsorption (Raichur an
Jyoti, 2001), ion-exchange (Singh, 1999), precipitation–coagulation (Saha, 1993 and Reardon
and Wang, 2000), membrane separation process (Amor et al., 2001), electrolytic defluoridation
(Mameri et al., 2001), and electrodialysis (Hichour, 1999). Of current available fluoride removal
strategies, one of the methods that has significant potential to be implemented in small
communities is the Nalgonda method. According to Singh et al., (2014), the problem with the
Nalgonda method is that it is too expensive. The Nalgonda method requires a high dose of
aluminum sulfate coagulant to aggregate with fluoride and precipitate. A study conducted by
Dahi et al. (1996) suggests that 13 g/L alum (1.2 g/L as Al) is needed for the Nalgonda method
to effectively treat fluoride levels between 9 and 13 mg/L. Despite the high concentrations of
added coagulant, the fluoride residual in the test was still unable to meet the WHO fluoride
guideline of 1.5 mg/L. The high dose of aluminum sulfate also leaves high sulfate residuals in
the water, which causes taste and odor issues (Fawell, 2006).
Figure 1. Global distribution of fluoride in groundwater (Amini
et al., 2008).
In Phase I of this project, the AguaClara project team replaced aluminum sulfate with
polyaluminum chloride (PACl) as the coagulant in hopes of better efficiency and the absence of
sulfate residuals. After rapid mixing, the solution was sent through a sand filter column to
remove the fluoride and PACl precipitates. Results showed that fluoride concentrations could be
reduced from 10 mg/L to 0.6 mg/L to meet the WHO standard at a PACl dose of 50 mg/L as Al.
These results suggest that the combination of PACl and a continuous flow reactor that includes
direct filtration provided a significant improvement in performance over the Nalgonda method.
The proposed Phase II research would augment these initial experiments by investigating
alternative floc blanket reactor configurations to increase run times beyond those obtained using
direct filtration.
People
The AguaClara program empowers communities and community members with sustainable
technologies and the knowledge to operate and maintain their water supply infrastructure. A
commitment to open source and transparency fosters a continuous effort to improve the
technologies based on feedback from communities including real-time web-based performance
monitoring (http://monitor.wash4all.org/). High value research focused on developing high
performing, low cost, planet-friendly technologies and an agile development philosophy requires
trust based engagement with communities to accelerate the product development cycle. This idea
is evident in the Research, Invent, Design, Engage (RIDE) philosophy that AguaClara employs
to bring clean drinking water to communities. Involving communities fosters a sense of pride and
ownership and encourages sharing of observations and new ideas that accelerate innovation.
AguaClara values not only the scientific basis for treatment system design, but also a
growing network that includes government ministries, water sector professionals, non-
governmental organizations (NGOs), bilateral donors, communities, and their water authorities.
In Honduras the Cornell AguaClara program partners with Agua Para el Pueblo (APP), an NGO
that works with underserved towns to implement the AguaClara design for a municipal water
treatment system that then provides safe water on tap. The resulting water treatment plants are
owned and operated by the community water authority which hires plant operators, procures
necessary chemicals, and collects a water tariff from each household to sustainably cover
operating and maintenance costs. APP provides ongoing technical support for the community
water authorities which is a key reason why AguaClara treatment plants sustainably produce safe
drinking water in communities that were previously underserved.
Networks similar to those currently established in Honduras are also being developed in
India. A comparable method of collaboration will be incorporated into designing and
implementing the fluoride treatment technology.
Prosperity
Removal of excess fluoride from groundwater has the potential to benefit many people with
better health. Fluoride in high amounts can damage bones, deteriorate teeth and lead to growth
issues in children (WHO, 2004). The proposed fluoride removal method can also be applied to
other contaminants including arsenic. The Nalgonda method of fluoride removal requires large
aluminum sulfate dosages to be effective. Given an aluminum sulfate dose of 13 g/L, an
aluminum sulfate cost of approximately $1/kg, 20 L/person per day (WHO, n.d.), and a 6
member household yields a cost of almost $50 per household per month. This cost is too high for
many households in rural villages even if the amount treated is reduced to 2 L/person per day.
Additionally, too much aluminum sulfate can cause high residual sulfate levels and potentially
health problems (Hua, 2008). The continuous flow, PACl-based method has the potential to
significantly reduce the cost for safe water in rural communities. The removal of excess fluoride
will reduce healthcare costs and improve economic productivity.
Planet
AguaClara designs water treatment technologies to be ultra-low energy (zero electricity) and
to minimize environmental impacts. This is evident in technologies such as the stacked rapid
sand filter tested in Phase I research as the final step of fluoride removal. Traditional filters use
electricity to power backwash pumps, while the AguaClara design relies on manipulation of a
siphon to switch between forward filtration and backwash and uses the same total flow for both
filtration and backwash modes of operation (Adelman et al., 2013).
The continuous flow PACl method of fluoride (and arsenic) removal that we are developing
uses less coagulant and thus simultaneously reduces cost and the impact on the environment for
resource extraction and waste management. Our first goal is to maximize the efficiency of the
fluoride removal as measured by the mass of fluoride removed per mass of coagulant utilized to
reduce the amount of sludge produced and lower the operating costs. Options for safe final
disposal of the sludge include binding with Portland cement (Ahmad, 2013).
Implementation of the P3 Project as an Educational Tool
The AguaClara program began in the fall of 2005. AguaClara is an innovation system that
engages Cornell students to research, invent, and design electricity-free novel water treatment
technologies that are needed in both developing and developed countries. The program initially
included undergraduates and M.Eng. students and then added Ph.D. students in 2007. To date
more than 525 undergraduates, 100 Master of Engineering, and 4 Ph.D. students have
participated in the program for academic credit. Each semester about 50 undergraduate and 10
Masters students participate in the program. Undergraduate and Masters students come from
across the university with the majority from engineering and currently over 70% are female.
Students engage through a novel curriculum that has 3 different project courses (CEE
2550/4550/5051-2) that co-meet, making it possible for students from first year to M. Eng. to
join the project teams and do research that leads to improved water technologies. The project
courses are offered every semester. In addition to the project courses, the curriculum includes a
theory course, CEE 4540, that provides the basis of the AguaClara water treatment technologies
and serves as a repository for the growing body of knowledge generated by the program. The
final two courses, CEE 4560 and CEE 4561, are the preparation and reflection courses that
bookend the two-week engineering-in-context trip to Honduras. The students do not build the
water treatment plants. That is the purview of APP in collaboration with a community. The
engineering-in-context trips provide an opportunity for an exchange of ideas, with Cornell
students demonstrating new technologies to APP and, in turn, learning about water treatment
successes and failures from the Hondurans. Those successes and failures are lessons learned that
are taken back to Cornell to guide the next innovation cycle.
The AguaClara project courses are part of a revolution in engineering education. Instead of
having to wait until junior or senior year to engage with real engineering, students from first year
to Master of Engineering join forces and combine their skills to develop new and improved water
and wastewater treatment technologies. Students learn from each other and are highly motivated,
knowing that what they discover will be used to provide safe drinking water for communities in
Honduras and India.
The proposed research will be conducted by students in Cornell University’s AguaClara
program as part of our RIDE innovation system. Student teams collaborate with partner
organizations to Research, Invent, and Design improved water treatment technologies and then
to Engage with implementation partners to build the facilities and assist communities with their
maintenance and operation. The AguaClara project presently consists of 70 students working on
18 different project teams. The teams are researching all of the unit processes in surface water
treatment plant, 3 different wastewater treatment processes, refining the design code for surface
water treatment plants, developing draft design code for upflow anaerobic sludge blanket
digesters, inventing fabrication methods for a village-scale water treatment plant, in addition to
the research into fluoride removal that is the subject of this proposal,
Multidisciplinary Teamwork
Sustained collaboration between faculty and students fostered the productive research that
was obtained in Phase I of this research. Environmental and chemical engineering students
optimized reactor performance using reactive characteristics of chemicals. Civil engineers
provided suggestions for the materials and design process of the filter system. Additionally,
students that study Human Biology, Health, and Society offered insight on the implications of
high fluoride concentrations on human health. These dedicated researchers form the foundational
relationships that will be brought into the proposed Phase II research.
2. Purpose, Objectives, Scope
AguaClara research teams have already demonstrated efficient removal of arsenic using
PACl followed by direct filtration. This treatment scheme has the potential to significantly
reduce the costs of arsenic and possibly fluoride treatment to make safe drinking water more
affordable where contaminated groundwater is the best source of drinking water. Given that
aluminum sulfate is an effective coagulant in treating fluoride contaminated groundwater, Phase
I research applied similar chemical theory to a novel fluoride removal design. Other coagulants
such as PACl have exemplified superior performance compared to aluminum sulfate, and
previous research concluded that arsenic readily adsorbs to PACl (Zhi, 2015). Phase I would
confirm or disprove that fluoride similarly adsorbs to PACl precipitates. The experimental setup
used tap water contaminated with sodium fluoride (NaF) to simulate fluoride contaminated
groundwater. Current AguaClara groundwater treatment systems in India utilize a stacked rapid
sand filter (SRSF) as the finishing step to removing particles. A SRSF was incorporated into the
experimental design as a lab-scale filter column to simulate similar conditions. Based on the
Phase I results, this system has the potential to improve drinking water quality where there is
excessive fluoride contamination. The research addresses the global issue of groundwater
fluoride and arsenic contamination, with the goal of creating a sustainable and cost effective
treatment option.
3. Data, Findings, Outputs/Outcomes
Below are the modifications incorporated into the reactor system (Figure 2) as previously
outlined in the Phase I proposal:
● Substitute polyaluminum chloride (PACl) in place of aluminum sulfate. PACl may be
more efficient at fluoride removal than alum and will not add sulfate to the water.
● Use direct
filtration to obtain
better removal of
fluoride at a lower
coagulant dose and
thus lower
operating cost.
● Replace batch
processes with
continuous flow
processes.
● Use a hydraulic
rapid mix with a
high energy
dissipation rate to
obtain a more uniform distribution of aluminum hydroxide precipitate.
In the apparatus design, PACl and fluoridated ―raw water‖ solutions were sent through a
hydraulic rapid mix, then filtered by a laboratory-scale sand filter. A fluoride ion selective
electrode (ISE) probe was placed in the exit container to evaluate the effluent fluoride
concentration.
The reactor system was tested at a fluoride concentration of 10 mg/L to represent a relatively
high level of contamination. PACl
was added at 20, 40, and 50 mg/L
as Al. As expected, fluoride
removal efficiency increased with
PACl dose. A PACl concentration
of 50 mg/L brought the fluoride
concentration from 10 mg/L to
below the WHO standard of 1.5
mg/L, achieving around 86-94%
removal (Dao et al., 2015).
Fluoride concentrations in filtered
water over time in an experiment
at the 50 mg/L PACl dose are
shown in Figure 3. Fluoride
removal efficiencies at other PACl
doses are summarized in Table 1.
The 50 mg/L Al required using
PACl is much more efficient at
fluoride removal than the 1200
mg/L Al required when using
aluminum sulfate (Dahi et al., 1996).
Overall Evaluation of Success
Phase I research results exceeded our expectations. The high solubility of the fluoride ion had
led us to be somewhat skeptical of the feasibility of inventing an economically viable method for
Figure 2. Schematic of apparatus used in Phase I research using
direct filtration (Dao et al., 2015).
Figure 3. Effluent fluoride concentration using 50 mg/L
PACl and direct filtration. The hydraulic residence time
of the system was 12.3 minutes and the steady state
performance was approximately 85% removal (Dao et
al., 2015).
removal of fluoride using a
coagulant. To treat 20 L of
water per person for a 6
member household, it would
cost almost $50 per
household per month
(WHO, n.d.) using
aluminum sulfate. The
switch to a better coagulant
and to a continuous flow
system resulted in a
dramatic 24 fold
improvement in the
efficiency as measured by
the mass of aluminum
required per mass of
fluoride removed. Phase I
results indicate that this
technology has the potential
to serve the many
communities that suffer from dangerously high fluoride concentrations in their drinking water.
Progress Towards Sustainability
AguaClara water treatment systems are sustainable (Rivas, 2014) because they rely on a
locally available non-proprietary materials, community management, and local ownership.
Sourcing all necessary materials locally decreases costs and complexities of obtaining
replacement parts. Technologies that minimize failure modes directly translate into cost
efficiency and operational simplicity, so any community can independently maintain their water
treatment system. The AguaClara technologies developed for surface water treatment now
provide a technology platform that can readily be adapted to additional contaminants. The
gravity powered chemical dosing system, hydraulic flocculation, sedimentation, and stacked
rapid sand filtration are all potentially useful in the development of a high efficiency fluoride and
arsenic removal system.
4. Discussion, Conclusions, Recommendations
Elements of People, Prosperity, and the Planet
The challenge of sustainability for People, Prosperity, and the Planet was met in Phase I by
reducing the mass of aluminum required to treat fluoridated groundwater by a factor of 24. These
improvements pave a path for Phase II research to further reduce waste and simplify operation in
preparation for pilot testing. With a commitment to open-source engineering the team will
continue to foster self-sufficient, sustainable designs for communities that currently lack safe
drinking water.
The main health benefit of drinking water with safe levels of fluoride is a decrease in risk for
dental and skeletal fluorosis, especially in youth that are in the process of developing bone
Table 1: Fluoride removal as a function of PACl dose using direct
filtration (Dao et al., 2015).
Trial
Number
Coagulant
Dosage
(mg/L as
Al)
Influent
fluoride
concentration
(mg/L)
Effluent
fluoride
concentration
(mg/L)
Percent
Removal
1 20 8.9 3.7 58%
2 20 10.3 5.7 56%
3 40 10.8 1.75 84%
4 40 10.7 2 81%
5 50 10.3 1.40 86%
6 50 10.4 0.64 94%
structure. A healthy community of people improves overall welfare and increases productively in
each individual’s life. The improved method of fluoride removal can provide all these benefits to
communities in developing countries while keeping the environmental footprint small.
Since the improved fluoride treatment technique uses significantly less coagulant and
physical labor, this system is a cost-effective option for use both in the United States and
globally. It produces safe drinking water and protects people from harmful skeletal diseases in
areas where there is high fluoride contamination.
Quantifiable Benefit of the Project
India is home to more than 1.2 billion people, and more than 66 million people are at risk for
skeletal fluorosis due to fluoride contamination (Arlappa, 2013). AguaClara demonstrated that
fluoride contamination of 10 mg/L can be successfully treated using PACl in combination with
hydraulic rapid mixing and sand filtration. After treatment, the effluent fluoride concentration is
below the 1.5 mg/L WHO standard. This is all accomplished using a PACl coagulant dose that is
24 times less than the amount of aluminum sulfate required to treat the same concentration of
fluoride.
Adaptation of Existing Knowledge
The Nalgonda method was invented by the National Environmental Engineering Research
Institute in India in 1975 to combat fluorosis issues (Venkobachar, 1997). This technique was
intended to be carried out in batch processes and mixed by hand to simulate flocculation.
Aluminum sulfate is first added to the added to the water as a coagulant, and later lime is added
to enhance settling and raise the mixture back to a neutral pH. While the Nalgonda method is
effective at low fluoride contamination levels, problems arise when higher concentrations of
fluoride need to be removed. In order to precipitate the highly soluble fluoride ion, it is necessary
to use a concentration of aluminum sulfate as high as 1000 times the concentration of fluoride
present. After the treatment process is over, high dosages of aluminum sulfate leave an excessive