Fluoride EPA Proposal

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
sulfate concentration, causing aesthetic concerns.
The prior experience of using PACl and direct filtration to remove arsenic (Zhi, 2015) led to
the hypothesis that a similar approach might work with fluoride. The continuous flow design of
the improved method eliminates the previous constraints set by batch treatment, use of PACl
proves to be a more efficient coagulant that does not leave residual taste issues, and sand
filtration assists in the removal of small colloidal (floc) particles.
Assurance Research Misconduct has not Occurred During Reporting Period
The guiding philosophy of our research is to understand physical/chemical mechanisms so
that we can design better water treatment technologies and expand the coverage of safe drinking
water to communities. Given that our primary objective is improved technologies, we have no
motivation to engage in research misconduct because we know that misconduct would only
confound our effort to make the world a better place. Instead students are encouraged to learn
from mistakes even when that means abandoning multi-year research programs when it becomes
clear that a technology will not be viable without significant breakthroughs. No research
misconduct has occurred during the reporting period. All information in this report is true, has
been reviewed by the authors, and all outside sources are cited.

B. Proposal for Phase II
Challenge Definition and Relationship to Phase I
The challenge of Phase I was to evaluate the efficiency of PACl coupled with direct filtration
for the removal of fluoride from groundwater. Phase I results demonstrate that a simple reactor
system with a PACl dose of 50 mg/L Al reduced the fluoride concentration from 10 mg/L to
approximately 1 mg/L. This aluminum dose is 24 times less than that used for the Nalgonda
method and this large reduction in reagent makes this system economically viable as a treatment
method.
The shortcoming of the direct filtration method evaluated in Phase I was that a PACl dose of
50 mg/L resulted in a filter head loss of 1 m in about 10 minutes (Zhi, 2015). At these high
coagulant dosages the head loss in sand filters was found to be directly proportional to the mass
of coagulant introduced into the filter. Filter runtimes measured in minutes are not viable
because filter backwash results in a substantial wasting of water unless a recycle system with the
associated pumping is used. The need for a relatively high PACl dose for efficient fluoride
removal and the correlations between accumulated coagulant mass in a filter column, head loss,
short filter run times, and water waste during backwash made it clear that direct filtration was not
an optimal solution for fluoride removal. However, direct filtration may still be applicable as a
polishing step if high fluoride concentrations can be reduced using an alternative reactor
configuration that is not susceptible to the accumulation of head loss that occurs in a filter.
Over the past decade the AguaClara program has developed a high efficiency sedimentation
tank that combines the three processes of floc blanket, sludge consolidation, and plate settlers.
The AguaClara
sedimentation tank
(Figure 4) is self-cleaning,
has no mechanized parts,
and creates a highly
concentrated (and hence
low flow) waste stream.
When applied to turbid
surface water treatment
the AguaClara
sedimentation tank
develops a floc blanket
with a concentration
between 2 and 5 g/L and
sludge that is
approximately 100 g/L
(Garland, 2015). The
sedimentation sludge concentration is approximately 1000 times more concentrated than typical
backwash water from a rapid sand filter. A highly concentrated fluoride waste stream will
simplify and reduce the cost of waste management. In addition the AguaClara sedimentation tank
is a continuous flow separation process that unlike a rapid sand filter does not need to stop for
cleaning.
Given the superior solids handling capabilities of a well-designed sedimentation tank, Phase
II will focus on developing design parameters for a fluoride removal system that incorporates
flocculation, sedimentation, and possibly filtration as a polishing step.
Figure 4. Cross sectional view of an AguaClara sedimentation
tank showing the floc blanket, plate settlers, and sludge
consolidation zones.

The proposed multi-step treatment train will require testing of multiple parameters to obtain a
robust design. The design parameters values for surface water treatment provide a point of
departure for Phase II research, but those parameter values are not expected to be optimal for
fluoride removal from a low turbidity groundwater. The proposed fixed and variable design
parameters to be tested are given in Table 2.
Table 2. Proposed fixed and variable parameters for Phase II research. Primary parameters are
highlighted in green. Secondary parameters for optimization are highlighted in yellow.
Parameter Symbol AguaClara
design
Proposed research range
(default)
Fluoride concentration CF NA 4 - 20 mg/L (10 mg/L)
PACl dose CPACl variable 10-100 mg/L as Al (50 mg/L)
Clay concentration CClay variable 0 - 2400 mg/L
Hydrogen ion concentration pH variable 7 - 8 (8)
Flocculator velocity gradient G 100 s-1
100 s-1
Flocculator residence time θ 400 s 40 - 400 s (400 s)
Floc blanket upflow velocity VUp 1 mm/s 0.5 - 1 mm/s (1 mm/s)
Plate settler capture velocity VC 0.12 mm/s 0.05 - 0.12 mm/s (0.12 mm/s)
Countercurrent Floc blankets in
series
NFB 1 1-3 (1)
Filter approach velocity VFi 1.85 mm/s 1.85 mm/s
Filter bed depth HFiLayer 20 cm 20 cm

The experimental protocol will progress systematically to explore the parameter space to
refine the optimal range of testing for each parameter. The critical parameters that are already
known to have a dramatic impact on system performance are PACl dose, clay concentration, and
floc blanket upflow velocity. We hypothesize that clay will be required to produce a floc blanket
with settleable flocs and a concentrated waste stream. For surface water treatment it isn’t
necessary to add clay. The clay/coagulant mixture along with flocculator characteristics
determine the floc blanket concentration. For high mass ratios of coagulant/clay the resulting
flocs have low sedimentation velocities and produce low floc blanket concentrations. At
extremely high mass ratios the resulting flocs are so sticky that they produce gel like structures
that can fill a laboratory scale sedimentation tank and that
is carried upward by the flow of water.
In a close analogy to agile software development
(Beck, 2001), the AguaClara program seeks to test new
technologies in the field as soon as appropriate. The
number of variables that must be tested is large and it is
likely that sedimentation tank geometry may need to be
modified to handle larger and stickier flocs. Reactor
construction is facilitated by collaboration with the
School of Civil and Environmental Engineering’s
machine shop. The AguaClara laboratory has advanced
software capabilities for automation of experiments that
facilitate systematic variation of parameters to find
improved designs. The Process Control and Data
Acquisition (ProCoDA) software and hardware makes it
possible to systematically vary one or multiple
parameters while continuously monitoring performance.
ProCoDA will be used to accelerate exploration of the
parameter space to improve the cost effectiveness and
efficiency of the treatment process. The sludge
production rate will be measured with grab samples as
total suspended solids.
Preliminary Results
Preliminary experimentation with the floc blanket
reactor (Figure 5) yielded 61% fluoride removal using a
PACl concentration of 25 mg/L as Al and approximately
85% fluoride removal using a PACl concentration of 50
mg/L as Al (Figure 6). In Phase II, parameters and
reactor design will be varied to achieve a consistently
well performing system.
Proposal Quality
Innovation and Technical Merit
Phase I research has demonstrated the potential of a novel fluoride and arsenic removal
technology that uses a readily available and low cost coagulant. PACl is manufactured in India
and is widely available. The proposed Phase II research is designed to reduce labor costs,
Figure 5. Continuous flow floc
blanket reactor system proposed
for Phase II research. The
AguaClara sedimentation tank is
modeled by the vertical
sedimentation tube, 45 degree
upward branching tube settler and
45 degree downward angled floc
hopper shown on the right side.

minimize coagulant use, and minimize
the waste stream containing the
contaminants. Labor will be reduced by
using a floc blanket reactor to create a
continuous tiny flow of highly
concentrated waste. If a filter is
included in the treatment train the filter
run time will be long due to the very
low turbidity exiting the plate settlers of
the sedimentation tank. A
countercurrent reactor system with
multiple floc blankets will also be
tested to further reduce the amount of
coagulant required. The reactor design
will be published and shared on the
AguaClara design webpage (AguaClara
Design, 2016)
Expected Outputs and Results
The deliverables will be a working
laboratory scale fluoride removal
reactor, a published design and
fabrication method for a pilot scale
fluoride removal reactor, preliminary
pilot scale testing with our partners, and
research reports and papers submitted
on this new method of fluoride
removal.
Engagement with Local Communities
As part of the AguaClara RIDE
philosophy, we work with partner
organizations that have expertise in
implementing water treatment
technologies at the community scale. Our partners teach community members how to maintain
their own treatment plants and convey the importance of safe drinking water on tap. Over the
past decade AguaClara has developed a suite of new technologies that have been transferred to
Honduras and India. There are currently 12 operating AguaClara plants in Honduras and 4 pilot
projects in India. The long term sustainability of the AguaClara technologies in Honduras is a
direct result of an ongoing, trust-based relationship with the partner organization and the
community leaders. AguaClara LLC and the Tata Cornell Initiative will provide guidance on
when it is appropriate to begin a pilot system test in India in preparation for deployment in
villages.
Grant Fund Expenditure Plan
The AguaClara program uses a team organization that includes purchasing support from an
experienced graduate student, a student leadership team, and a group of student research advisors
who train new team members in the R&D methodologies that we have developed over the past
Figure 6. Effluent fluoride concentration using 25
mg/L PACl (top) and 50 mg/L PACl (bottom) and
the fluidized floc blanket reactor. The hydraulic
residence time of the system was 19 minutes and
the steady state performance was approximately
61% removal at 25 mg/L and 85% removal at 50
mg/L.

decade. In addition, Cornell administration provides controls to ensure that grant funds are
expended appropriately and in an efficient manner using an online shopping portal. The PIs will
guide the project teams to ensure that the project addresses the most important research tasks, is
agile in responding to new information, and stays on schedule.
Ensuring Successful Achievement of Project Objectives
The AguaClara innovation system relies on mentoring, feedback, rapid prototyping and
testing, a collaborative team based laboratory where learning opportunities are maximized, and
robust systems exist for experimental design, data collection, and analysis. The team has
developed an excellent understanding of the physics of particle-particle-fluid-reactor geometry
interactions and the ability to design reactors for fluidized beds of fractal flocs that adsorb
fluoride.
The AguaClara laboratory includes state of the art process control and data acquisition. The
student research teams have workstations in a collaborative laboratory with a mix of experts and
novices. The team has extensive design and research experience with chemical dosing, rapid
mix, flocculation, floc blankets, sedimentation, and filtration. These platforms well be used as a
basis for additional innovations required for an efficient fluoride removal reactor.
Overall Sustainability
The low operating cost, simple operation, and ultra-low energy requirements of the proposed
fluoride removal reactor are expected to make it a competitive technology both in the US and
internationally. Ease of fabrication and operation allow the system to be built using locally
available materials and operated by trained community members. The proposed phase II research
would create an efficient fluoride removal treatment process that is well-suited for
implementation in rural communities.
Environmental Sustainability
The proposed fluoride removal method will reduce coagulant use by a factor of
approximately 24 for the removal of fluoride from water compared with the Nalgonda method.
The proposed method has a very high probability of also being applicable for the removal of
arsenic and thus could be helpful in reducing exposure to another environmental toxin. The
fluoride removal method does not require any electricity or mechanical mixing in the treatment
processes. Chemical addition will use the chemical dose controller that was invented in a
previous EPA P3 project. Rapid mix and flocculation will use approximately 40 cm of water
surface elevation decrease. The floc blanket and sedimentation tank require less than 10 cm of
water surface elevation decrease. The stacked rapid sand filter uses about 1 m of water surface
elevation drop to produce very high quality water. The overall treatment process will use
approximately 14 Joules of energy per liter of water produced. This does not include pumping
that will be required to lift water from a well to a village.
The addition of a high efficiency sedimentation tank will decrease the amount of wastewater
produced by the process. The dominant source of waste water from the fluoride removal process
will be filter backwash water if a filter is needed. It is possible to recycle backwash water and
thus only produce a highly concentrated sludge from the sedimentation tank. The addition of clay
will result in an increase in sludge production and our phase II research will focus on minimizing
the amount of clay required to produce a stable floc blanket.

Social Sustainability
AguaClara works with partners who in turn work with local communities to ensure long term
sustainability (Rivas et al., 2014). The 12 municipal water treatment plants designed by
AguaClara in Honduras demonstrate the power of the network and the commitment of
communities to responsibly manage their water supply systems. The AguaClara program
recognizes the power of engineering in collaboration with the communities.
Gaining community trust is a prerequisite for social sustainability. For this reason, AguaClara
takes the R&D stage of technology development very seriously and does not rush to implement
new technologies.
Economic Sustainability
The low cost and easy maintenance of current AguaClara treatment technology makes it an
economically sustainable option for communities in the developing world. Water treatment
plants are dependent on the tariffs that are collected from community members. In the United
States, we are usually fortunate to have access to high quality clean water at costs that are low
compared to the average income. Economic sustainability for communities with lower incomes
requires very low operating costs and that, in turn, requires more investment in R&D.
Education and Teamwork
The Cornell AguaClara program provides students the opportunity to invent new
technologies while learning fundamental engineering principles and engaging with partner
organizations including Agua Para el Pueblo in Honduras, AguaClara LLC and the Tata Cornell
Agriculture and Nutrition Initiative in India. Every year, students are given the opportunity to
visit Honduras and see first-hand the impact these water treatment systems are making in rural
towns. The proposed Phase II research will provide an opportunity for a team of students to
transfer the technologies they helped to develop to the partner organizations in India.
The AguaClara program provides a safe place for student teams to practice real engineering in an
environment where they have ready access to experts and mentors. Additionally, AguaClara also
draws awareness to the topic of clean drinking water by attending events such as the Social
Impact Conference and National Sustainable Design Expo. The achievements of AguaClara and
other sustainable design initiatives continue to impact those of the local Cornell community and
across the world.
Students come from environmental, chemical, civil, and mechanical engineering, city and
regional planning, and Cornell’s business college. Graduate students from City and Regional
Planning gain understanding of the resources required to construct a successful treatment system.
Students from the School of Hotel Administration contributed marketing strategies to help
AguaClara establish a global presence. With local implementation partners, AguaClara can
empower these villages with the knowledge and technology to be self-sustaining. The AguaClara
network includes Agua Para el Pueblo (a Honduran NGO), AguaClara LLC (fostering the spread
of AguaClara technologies to new regions), and Cornell Social Business Consulting. The
international presence and partnerships AguaClara has creates a learning environment for
students that encourages them to make future changes. After graduating, team members have the
opportunity to work in developing countries on implementing AguaClara technology. Teamwork
with the local community is an essential step to provide safe drinking water to any community.

Project Schedule
Spring 2016 This semester, the research team is focusing on designing a reactor system that is
adapted from the current AguaClara floc blanket sedimentation tank design. They will evaluate
the effects of using a floc blanket in precipitating fluoride and enhancing flocculation. Results
will be evaluated over different combinations of PACl dose and influent fluoride concentrations.
Fall 2016 Test the clay concentration required to achieve a continuous flow sedimentation tank
with a floc blanket. ProCoDA will use a Proportional, Derivative, Integral (PID) feedback
algorithm to control the influent turbidity by varying the flow of a clay stock. The floc blanket
upflow velocity may be varied to accommodate lower clay concentrations. Explore floc blanket
upflow velocity and reactor geometry to reduce the amount of clay required.
Spring 2017 Test 2 or 3 counter current floc blanket reactors in series to optimize efficiency of
coagulant use. In this reactor design the coagulant would be added to the final floc blanket in a
series of reactors and then the floc hopper discharge would be returned to the upstream floc
blanket. This process would be repeated for each floc blanket reactors in the series. This reactor
design would have the advantages of being able to achieve efficiencies comparable to plug flow
systems even though the flocs in a floc blankets are close to completely mixed over the time
scale of the residence floc residence time. Assess the value of the efficiency gains vs the more
complex reactor geometry. Evaluate methods to simplify the countercurrent reactor geometry
Fall 2017 Optimize PACl dose as a function of fluoride concentration using the reactor
configuration selected in the spring of 2017. Assess the need for a filter given that municipal
scale AguaClara sedimentation tanks routinely achieve settled water turbidity well below 2 NTU
(OpenSourceWater, 2016). ProCoDA will be used to measure settled water turbidity using an
HFScientific inline turbidimeter. Begin designing a pilot scale fluoride removal facility. Evaluate
sites for pilot scale testing in collaboration with TCi and AguaClara LLC. Maintain a
conversation with AguaClara LLC engineers in India and the Tata-Cornell Agriculture and
Nutrition Initiative (TCi) to evaluate the status of our research and to assess the minimum
requirements to begin testing the technologies at pilot scale in India.
Spring 2018 Continue testing and iterating on reactor design, coagulant feed, and clay feed.
Fabricate 0.1 L/s pilot scale facility at Cornell and document all fabrication steps.
Summer 2018 Fabricate and set up pilot scale facility in India in collaboration with TCi and
AguaClara LLC. Test performance, propose design changes prior to piloting in a community and
explore funding opportunities for deployment of the first village scale treatment system.

Quality Assurance Statement
The PIs have over 40 years of drinking water treatment research experience and have been
guiding student research/invent/design/engage teams since founding the AguaClara program in
2005. The ProCoDA (Process Control and Data Acquisition) software that is used by the student
teams to automate the control of experimental apparatus and to collect real time data from
sensors and meters was authored by one of the PIs. The primary parameters required to evaluate
fluoride removal system performance are filter head loss (pressure sensor), turbidity (HF
Scientific online turbidimeter), and fluoride ion selective electrode. These data sources will be
captured by the ProCoDA software and logged to a shared drive with backup protection.
Peristaltic pumps are used to meter flows and the flows are verified using an electronic balance
and stopwatch.
The data sources required for this research are routinely used in the AguaClara project
laboratory and thus method development is routine. Turbidimeter calibrations are performed
based on the manufacturer's’ requirements. Pressure sensor accuracy is checked using measured
depths of water. The fluoride probe is calibrated daily using calibration standards. Analysis and
organization of data is required for the bi-weekly reports that each team submits. Additionally,
project data is organized in a shared computer drive that can be easily accessed by Cornell
students. Reports are posted on the AguaClara wiki at
https://confluence.cornell.edu/display/AGUACLARA/Home. Students regularly schedule online
meetings with engineers in Honduras and India and in-person meetings with project team
advisors to assure they are on track to meeting project goals and that the data is correctly
analyzed and interpreted.
Partnerships
The AguaClara program at Cornell has ongoing collaborative partnerships with Agua Para el
Pueblo in Honduras (since 2005) and AguaClara LLC (since 2012) and Tata Cornell initiative
(since 2013) in India. These partners are committed to deploying new AguaClara technologies as
they are developed, designed, and demonstrated at lab scale.

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