NCER ASSISTANCE AGREEMENT PROJECT REPORT EXECUTIVE SUMMARY Date of Project Report: March 28, 2016 EPA Agreement Number: SU836117 Project Title: Novel reactor design for enhanced removal of fluoride using a modified Nalgonda method. Faculty Advisor(s), Departments and Institutions: Monroe Weber-Shirk, School of Civil and Environmental Engineering, Cornell University Leonard Lion, School of Civil and Environmental Engineering, Cornell University Student Team Members, Departments and Institutions: Erika Axe, Environmental Science & Sustainability Major, Cornell University Katherine Dao, Chemical Engineering Major, Cornell University Pooja Desai, Human Biology, Health and Society Major, Cornell University Cindy Dou, Chemical Engineering Major, Cornell University Surya Kumar, Environmental Engineering Major, Cornell University Christine Leu, Chemical Engineering Major, Cornell University August Longo, Chemical and Biomolecular Engineering, Cornell University Disha Mendhekar, City and Regional Planning Major, Cornell University Amiel Middelmann, Environmental Engineering Major, Cornell University Rachelle Ng, School of Hotel Administration, Cornell University Amlan Sinha, Mechanical Engineering Major, Cornell University Lishan Zhu, Environmental Engineering Major, Cornell University
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NCER ASSISTANCE AGREEMENT PROJECT REPORT EXECUTIVE SUMMARY Date of Project Report: March 28, 2016 EPA Agreement Number: SU836117 Project Title: Novel reactor design for enhanced removal of fluoride using a modified Nalgonda method.
Faculty Advisor(s), Departments and Institutions:Monroe Weber-Shirk, School of Civil and Environmental Engineering, Cornell UniversityLeonard Lion, School of Civil and Environmental Engineering, Cornell University
Student Team Members, Departments and Institutions:Erika Axe, Environmental Science & Sustainability Major, Cornell UniversityKatherine Dao, Chemical Engineering Major, Cornell UniversityPooja Desai, Human Biology, Health and Society Major, Cornell UniversityCindy Dou, Chemical Engineering Major, Cornell UniversitySurya Kumar, Environmental Engineering Major, Cornell UniversityChristine Leu, Chemical Engineering Major, Cornell UniversityAugust Longo, Chemical and Biomolecular Engineering, Cornell UniversityDisha Mendhekar, City and Regional Planning Major, Cornell UniversityAmiel Middelmann, Environmental Engineering Major, Cornell UniversityRachelle Ng, School of Hotel Administration, Cornell UniversityAmlan Sinha, Mechanical Engineering Major, Cornell UniversityLishan Zhu, Environmental Engineering Major, Cornell University Project Period: 09/01/2016 – 08/31/2018
Description and Objective of Research: Groundwater is a feasible source of drinking water for many communities. In India, more
than 80 percent of water is obtained from groundwater sources (The World Bank, 2012). Dependence on groundwater becomes a health concern when the aquifer’s composition contains minerals that cause fluoride contamination. Fluoride ions are highly soluble in water, which makes treatment extremely difficult. In developing countries and rural villages, fluoride removal becomes an even greater challenge because technology and funding are limited. AguaClara seeks to overcome obstacles by creating innovative solutions focused on promoting environmental, social, and economic sustainability.
Few fluoride remediation methods are available, and most of them are expensive or are not effective at high fluoride concentrations (Singh, 1999). Fluoride removal by adsorption to
aluminum sulfate precipitate is known as the Nalgonda method (Venkobachar, 1997). In this method, aluminum sulfate is added to a batch of fluoridated water and the solution is mixed and allowed to settle. However, high aluminum sulfate concentrations are necessary and result in a large sludge volume and elevated sulfate concentration in the treated water (Fawell, 2006). The proposed research uses Polyaluminum chloride (PACl) and a continuous flow reactor to dramatically reduce the required chemical concentration. Previous research demonstrated that arsenic readily adsorbs to PACl (Zhi, 2015). Given that adsorption techniques are also an effective fluoride removal method, the proposed research tested PACl as the coagulant in the continuous flow reactor.
Key elements of the Phase I fluoride reactor design:● 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 sand 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 high energy rapid mixing to obtain a more uniform distribution of aluminum
hydroxide precipitate.Phase I demonstrated that fluoride, just like arsenic, can adsorb to PACl precipitate and be removed through sand filtration and that fluoride removal by a fluidized bed floc blanket is also possible.
Summary of Results (Outputs/Outcomes):
A direct filtration reactor system for the removal of fluoride was tested with an influent fluoride concentration of 10 mg/L (Figure 1). PACl was added at 20, 40, and 50 mg/L as Al. As expected, fluoride removal increased with PACl dose. Results showed that a PACl dose of 50 mg/L as aluminum (Al) effectively reduced fluoride concentrations from 10 mg/L (Dao et al., 2015) to meet the World Health Organization (WHO) fluoride standard of 1.5 mg/L (WHO, 2011). The 50 mg/L Al as PACl is much lower in contrast with the 1200 mg/L Al as aluminum
Figure 1. This was the apparatus used in Phase I research. PACl was directly added to fluoride contaminated water and sent through a hydraulic rapid mix and sand filter column.
sulfate required to treat similar fluoride concentrations (Dahi et al., 1996). These results suggest that a continuous flow PACl based fluoride reactor system provided effective removal and significant improvement in performance over the Nalgonda method.
Conclusions:Groundwater fluoride contamination poses a health threat to more than 66 million people in
India (Arlappa, 2013). According to the WHO, dental damage can occur at a fluoride concentration above 1.5 mg/L and crippling skeletal damage can arise at a concentration above 10 mg/L (WHO, n.d.). Therefore, access to safe drinking water is critical in maintaining the health and productivity of a community. In Phase I research, the student team demonstrated that fluoride contamination of 10 mg/L can be successfully treated to safe drinking standards using PACl in combination with sand filtration.
Although the highly soluble fluoride ions are difficult to remove from water, results from Phase I demonstrated the potential for efficient removal using PACl and direct filtration. Experimentation proved that PACl and continuous flow direct filtration removed enough fluoride to reach WHO standards of 1.5 mg/L (WHO, 2011). Compared to previously documented values (Dahi et al., 1996), the apparatus used in Phase I required 24 times less mass of aluminum per mass of fluoride removed.
AguaClara’s improved fluoride removal technique incorporates the elements of People, Prosperity, and the Planet into a sustainable water treatment system (Rivas, 2014). The technologies are designed to use non-proprietary materials available in the national supply chain, and leverage community engagement and municipal resource management. Advanced technologies that deliver operational simplicity can decrease failure modes and improve economic efficiency. The long-term goal of AguaClara is to create and implement reliable and intuitive designs so communities can independently maintain their own water treatment system. The improved PACl fluoride treatment system embodies the idea of optimization by accomplishing fluoride removal with 24 times less mass as aluminum than the Nalgonda method. As a result, less residual sludge is generated. Since less coagulant and physical labor is necessary, the improved fluoride treatment technique has the potential to improve access to safe drinking water in villages with contaminated groundwater.
Proposed Phase II Objectives and Strategies:A disadvantage of sand filtration evaluated in Phase I is that head loss accumulation is
directly proportional to the mass of coagulant introduced into the filter. When PACl concentrations as high as 50 mg/L as Al are added, filter head loss accumulates 1 m in about 10 minutes (Zhi, 2015). Short filter run times are not sustainable in a water treatment system because large volumes of water are required for cleaning. In the past decade, the AguaClara program has developed a high efficiency settling (sedimentation) tank with a fluidized suspension of conglomerated particles (or floc blanket), sludge consolidation, and plate settlers. This sedimentation tank has the potential to efficiently remove arsenic and fluoride as well as particles and pathogens.
One main advantage of the sedimentation tank is that it can operate continuously and produce a very small amount of concentrated waste. The AguaClara sedimentation tank produces a much lower volume of waste than rapid sand filters. The AguaClara sedimentation tank will be added to the treatment train in Phase II to reduce the solids loading on the rapid sand filter to extend the filter runtime and reduce the volume of waste. The new reactor features a floc blanket system to create a small continuous flow of highly concentrated sludge.
Over the course of Phase II research, a series of parameters will be varied to develop an efficient reactor design. Critical parameters already known to affect system performance are PACl dose, clay concentration, velocity at which water flows through the floc blanket (upflow velocity), and reactor configuration. Optimization strategies will focus around modifying the PACl and clay concentrations, since both significantly affect floc structure and floc blanket density. AguaClara researchers hypothesize that adequate clay concentrations are required to produce settleable flocs and concentrated residual sludge. Since groundwater has a relatively low clay concentration compared to surface water, more clay may need to be added to enhance floc blanket formation. Reactor configuration will be varied and will include a test with multiple floc blankets in series with countercurrent floc flow to reduce the required coagulant dose.
Publications/Presentations: None to report at this time.
Arlappa, N., Aatif Quresh, I., & Srinivas, R. (102AD). Fluorosis in India: an overview. Retrieved from http://www.feingold.org/Research/PDFstudies/Arlappa2013.pdf
Dahi, E., Mtalo, F., Njau, B., & Bregnhj, H. (1996). Defluoridation using the Nalgonda Technique in Tanzania. Reaching The Unreached: Challeneges for the 21st Century, 266–268. Retrieved from http://wedc.lboro.ac.uk/resources/conference/22/Dahi.pdf
Dao, K., Desai, P., & Longo, A. (2015). Fluoride, Fall 2015. Cornell University.
Fawell, J. K., Bailey, K., & Organization, W. H. (2006). Fluoride in Drinking-water. World Health Organization. Retrieved from http://www.who.int/water_sanitation_health/publications/fluoride_drinking_water_full.pdf
Rivas, M. G., Beers, K., Warner, M. E., & Weber-Shirk, M. (2014). Analyzing the potential of community water systems: the case of AguaClara. Water Policy,16(3), 557–577. http://doi.org/10.2166/wp.2014.127
Singh, G., Kumar, B., Sen, P. K., & Majumdar, J. (1999). Removal of Fluoride from Spent Pot Liner Leachate Using Ion Exchange. Water Environment Research, 71(1), 36–42. http://doi.org/10.2175/106143099X121571
The World Bank. (2012). India Groundwater: a Valuable but Diminishing Resource. Retrieved March 22, 2016, from http://www.worldbank.org/en/news/feature/2012/03/06/india-groundwater-critical-diminishing
Venkobachar, C., Iyengar, L., & Mudgal, A. K. (1997). Household Defluoridation Of Drinking Water Using Activated Alumina (In Proceedings of the 2nd International Workshop on Fluorosis Prevention and Defluoridation of Water) (pp. 138–145). Nazareth, Ethiopia. Retrieved from http://www.de-fluoride.net/2ndproceedings/138-145.pdf
WHO | Naturally occurring hazards. (n.d.). Retrieved March 22, 2016, from http://www.who.int/water_sanitation_health/naturalhazards/en/index2.html
WHO. (2011). WHO | Guidelines for drinking-water quality, fourth edition 2011. Retrieved March 20, 2016, from http://www.who.int/water_sanitation_health/publications/2011/dwq_chapters/en/
Zhi, Hui (2015) Arsenic(V) removal from drinking water by concurrent introduction of As contaminated water and Polyaluminum chloride in a sand filter medium. Thesis. Cornell University
