Grantee Research Project Results

2013 Progress Report: Use of Bone Char for the Removal of Arsenic and Uranium from Groundwater at the Pine Ridge Reservation

EPA Grant Number: SU835069
Title: Use of Bone Char for the Removal of Arsenic and Uranium from Groundwater at the Pine Ridge Reservation
Investigators: Werth, Charles J , Llewellyn, Alex , Parker, Kimberly M , Salvatore, Michelle , Becraft, Jacob , Genchanok, Yana , Dam, Emily Van , Freeck, Jason , Wang, Hanting , Nell, Marika , Feeney, Connor , Nguyen, Tien-Hung , Llewellyn, Brett , Marcinkevicius, Algimantas , Benson, Nora , Wisniewski, Alexander , Hou, Serena , DeMarco, Vanessa , Bollinger, Drew , Mosiman, Daniel , Knaizer, Brendon
Current Investigators: Werth, Charles J , Llewellyn, Alex , Parker, Kimberly M , Salvatore, Michelle , Becraft, Jacob , Genchanok, Yana , Dam, Emily Van , Freeck, Jason , Wang, Hanting , Nell, Marika , Feeney, Connor , Nguyen, Tien-Hung , Llewellyn, Brett , Marcinkevicius, Algimantas , Benson, Nora , Wisniewski, Alexander , Hou, Serena , DeMarco, Vanessa , Bollinger, Drew , Mosiman, Daniel , Knaizer, Brendon , Michelson, Kyle , Choe, Jong Kwon , Bergquist, Allison
Institution: University of Illinois Urbana-Champaign , Oglala Lakota College
EPA Project Officer: Page, Angela
Phase: II
Project Period: August 15, 2011 through August 14, 2013 (Extended to August 14, 2014)
Project Period Covered by this Report: August 15, 2012 through August 14,2013
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2011) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities

Objective:

In August of 2009, our undergraduate student team traveled to the Pine Ridge Reservation in

South Dakota, home of the Oglala Lakota Tribe. The purpose of the trip was to verify a U. S. Geological Survey (USGS) report from the 1990s which indicated that much of the groundwater on the reservation was contaminated with arsenic (As) and uranium (U) above the Environmental Protection Agency (EPA) maximum containment limits (MCLs). Samples of private wells, municipal sources, and spring sources were taken and it was confirmed that 35% of private wells contained As above the MCL and 6% contained U above the MCL. While some residents have access to contaminant-free municipal water sources, many prefer the taste of their non-chlorinated private well water.

Motivated by the results of that trip, the goal of the project is to develop a cost-effective filter that can remove both arsenic and uranium, focusing on people, prosperity, and planet. The Pine Ridge Reservation is home to 28,000 people, many of whom do not know the dangers of drinking contaminated water. Efforts are being taken to inform their community of the issues and develop an educational program in partnership with the Oglala Lakota College (OLC) to further an understanding of the need for clean drinking water on the reservation.

Phase I objectives were completed two years ago, and included: 1) evaluating As and U contamination in the Pine Ridge Reservation 2) characterizing bone char (BC), 3) assessing U and As removal capacity and kinetics using actual BC, and 4) developing a BC filtration device. 

The specific objectives of Phase II efforts are to 1) further test drinking water used by the residents of the Reservation, 2) to design and test a BC filter, 3) to help establish a small business for water treatment on the reservation, and 4) to educate students at Illinois and OLC. Additionally, an educational program is under development with OLC to further understanding in the tribe about the importance of safe drinking water. 

Phase II continues the work on arsenic and uranium removal capacity and removal kinetics using actual bone char. Although the mechanism of the removal process is not known, removal capacity and kinetics are being evaluated in order to optimize filter design. Water samples from the reservation have revealed the presence of arsenic (III), which, unlike arsenic (V), has proven difficult to remove with bone char. From the literature, our team identified zerovalent iron (ZVI) as a potential adsorbent for arsenic (III) removal, and subsequently tested this material in the laboratory with good success.  Our experimental efforts are now focused on finding the optimal mix of bone char and ZVI for plausible implementation.

Our team is testing bone char and ZVI removal capacity for uranium and arsenic using both batch studies, and flow-through columns with variable retention times.  As reported last year, we previously measured uptake of uranium and arsenic in batch studies using bone char.  This year, we measured uptake of uranium and arsenic (III) using different ratios of ZVI to bone char in order to identify optimal adsorbent loadings. The experimental results suggested that ZVI was much more effective at removing arsenic (III) than bone char. However, reservation waters contain varying amounts of arsenic (III), arsenic (V) and uranium, so the optimal ratio for removal of all three contaminants has yet to be determined.

Flow-through columns are 5 cm long and 0.5 to 1 cm diameter.  We completed bone char column tests for uranium removal using a 30-minute retention time.  Water contaminated with 50 ppb U was sent through the column and U was removed below the MCL for 53 days before breakthrough occurred. This suggests a breakthrough time of well over 1 year for a full-size model. Initial bone char column tests for uranium removal with a 15-minute retention time are complete, and indicate the breakthrough time is similar to the 30-minute retention time experiment. A replicate breakthrough experiment is currently underway to confirm these results. 

We are also currently running a bone char (70% by mass) plus ZVI (30% by mass) column experiment for uranium removal only.  The influent uranium concentration is 40 ppb, and the retention time is 15 minutes.  The goal of the experiment is to demonstrate that the presence of ZVI does not diminish the capacity of bone char to remove uranium. Once this test is complete, we will test the bone char plus ZVI mixture for arsenic (III) removal. 

The design and testing of a BC filter, as well as establishment of a small business for water treatment on the reservation, must wait on the results of the column testing. However, the last objective of Phase II is currently underway. A video is being produced to increase awareness of the contamination of water, its effects, and our efforts to create a solution for the problem. The video will showcase individual members of the team discussing their project involvement.  Furthermore, our team is working with students in Engineers Without Borders, hoping to increase involvement and awareness as the project progresses. 

Aside from the research progress being made, our team has been working with Dave Johnson from the Bureau of Drinking Water and Groundwater for Oconto County, Wisconsin.  The groundwater in this area is contaminated with arsenic, and samples from this area will be used to test the BC filter.  We are also exploring the possibility of getting groundwater samples from a Navajo reservation in Arizona, which is possibly contaminated with uranium.  Our goal is to expand the number and quality of groundwater sources that the filter design is tested with. 

Our team members are also working on developing an educational program for elementary students in the Oglala Lakota tribe.  The program focuses on water purification ideas and techniques, and will serve as a bridge for implementing our design.  It also increases awareness in a nonintrusive manner.  In order to ensure that the plans are appropriate for elementary students, the program materials are being reviewed by students in education-focused majors and by practicing elementary school teachers.     Since receipt of Phase II, much progress has been made on the social and scientific fronts of this project.  In August 2011, our team again visited the Pine Ridge Reservation to collect water samples and survey the contamination.  At the Reservation, samples were collected from 13 additional locations across the reservation.  Samples were collected from a variety of sources including indoor faucets, outdoor wells, and an outdoor pipe that was continuously flowing.  All of these locations were frequently used by residents of the Pine Ridge Reservation, and covered a wide geographical area on the reservation.     While collecting samples, our team also spoke with the residents and local Oglala Lakota College leaders on the reservation to discuss a prototype of the filter design and to see whether or not the filter would actually be of use in their homes.  The team collected valuable design feedback.  We also discussed technical feasibility of BC production on the Reservation with science leaders at the college. Currently, one of our team members is continuing to engage the residents of the Pine Ridge Reservation. Serena Hou is both a member of KOLA, a group of masters of business administration students dedicated to economic development on the reservation, and a member of the Oglala Lakota Water Project. She and other members of KOLA visited the reservation in December of 2013, and she found tribe members who may be interested in working with us on a business plan for the water filter, and on implementation of our educational program.

Progress Summary:

Figure 1 shows the results of a bench-scale column experiment.  The column used in this experiment was 5 cm in length and 1 cm in diameter.  The column contained approximately 2.16 g of bone char that ranged between 300 um and 2 mm in diameter.    

While the full duration of the experiment was 69 days (an estimate for breakthrough was ~60 days), there were gaps in the continuous flow-through experiment due to normal student conflicts with breaks, excess testing during a certain week, etc.  Because our research group recorded all of the missed times, we were able to accurately calculate the full run time of the column, a cumulative time of 52.6 days.  Using an estimate of bone char porosity of ρ = 0.5, a column volume of V = 3.93 cm³, and a flow rate of Q = 4.00 ml/h, the number of pore volumes that flowed through the column over the length of the experiment was calculated to be V_P = 2527.  Throughout the length of the experiment, effluent samples were analyzed using Ion Coupled Plasma - Mass Spectrometry(ICP-MS).  The results are plotted below.

                            Normalized Effluent Concentration Over Time, Exp.A

Figure 1—Normalized Breakthrough Curve for the Removal of U (30 minute Retention Time)

The breakthrough curve plotted above shows that after 52.6 days of run time, breakthrough in the column started but did not reach completion.  The highest concentration was less than 6% of the influent concentration, and the average concentration was less than 1% for nearly 40 days.  In the last 12 days, however, the concentration rose sharply, signaling the beginning of breakthrough.  

A new column was then started with a retention time of 15 minutes. Due to scheduling conflicts, this column was stopped after 30 days, but breakthrough had not occurred during this period.  The results suggest that breakthrough for a 15-minute retention time exceeds 30 days, and breakthrough for a 30minute retention time exceeds 50 days.  This is excellent news, and suggests that a full-scale column can be in operation for one year or longer.

Figure 2 shows batch results for arsenic removal with varying amounts of bone char and ZVI and 100 mL of water containing 24 ppb arsenic (III).  The results indicate the effectiveness of ZVI in removing arsenic (III).  In all batch systems where ZVI was added, arsenic (III) was removed to below the MCL.  Also, having a higher proportion of ZVI to bone char led to much greater and faster removal of arsenic (III). 

Figure 2— The Dependence of As(III) Adsorption on the Ratio of Bone Char (BC) to ZVI 

For the control case when only bone char is used, there was still significant removal of As(III) (~47.5%).  We previously found that there was no removal of arsenic from natural water using bone char. We had previously assumed that this was because the arsenic was present as arsenic (III), and this did not adsorb to bone char.  These new results (Figure 2) suggest that something else in the natural water negatively affected the adsorption of arsenic on bone char.

For the case when only ZVI was used, the fastest and most removal (99.2%) of arsenic (III) was realized.  In fact, after 5 minutes only 0.88 ppb arsenic (III) remained.  We originally thought that ZVI would oxidize arsenic (III) to arsenic (V), and then bone char would be needed to adsorb arsenic (V).  It appears that ZVI alone can remove arsenic (III) effectively. Other research studies have also shown the effectiveness of ZVI in removing arsenic (III).  It is not clear if arsenic (III) is being adsorbed directly, if it is first oxidized to arsenic (V) and then adsorbing, or if it is some combination of these two mechanisms.  Prior research suggests that HCO₃^-, H₄SiO₄, and H₂PO₄^2- can all possibly interfere with arsenic adsorption.  Therefore, it is not clear if ZVI will be as effective in natural waters due to the likely presence of these interfering ions. So further testing is needed utilizing natural groundwater from Pine Ridge reservation.

It should also be noted that one side effect of using the ZVI is an orange color of the solution due to rusting of the ZVI. This was observed in the batch studies but not the column studies. In the batch studies, the color was filtered out when sampling, but this colloidal iron could potentially affect an in-line column filter. This effect will be explored in the next stage of our work.

Future Activities:

Our team needs to perform more batch studies in order to identify the optimal combination of ZVI and bone char for other water sources.  Thus far we have tested synthetic groundwater with arsenic (III).  We need to continue tests with synthetic groundwater with uranium only and begin tests with synthetic groundwater with arsenic and uranium and natural water from the Pine Ridge Reservation that contains both uranium and arsenic. These tests will determine if uranium adsorption is hindered or helped by the addition of ZVI, as well as whether natural water constituents interfere with uranium and/or arsenic removal. 

Our team needs to run more columns with shorter retention times and more water sources in order to determine if the filter design can be smaller and cheaper than our current Phase II prototype.  A shorter retention time will allow us to more accurately determine if uptake kinetics is limiting adsorption in the columns.  This work will require ordering additional reciprocating syringe pumps, and several more months of testing so that breakthrough can be measured.  Columns for analyzing the breakthrough time of uranium (in the form of uranyl chloride) will contain bone char only, or bone char and ZVI. Columns for analyzing the breakthrough time of arsenic will contain varying ratios of ZVI and bone char. Ultimately, our final design will contain both bone char for uranium and ZVI for arsenic, and natural water from the reservation will be tested with columns containing both of these adsorbents. Results from batch studies will help us select the best ratios of ZVI to bone char in the column studies.  We plan to complete our efforts by August of 2014.  Results from the column studies will be used to design the full-scale filter system that will safely clean arsenic and uranium contaminated water for a known period of time.  

Once we have a reliable filter design, we will discuss full-scale filter designs with the Oglala Lakota College (OLC), in addition to implementation plans.  We have already discussed the feasibility of implementing the filter with the communities at the Pine Ridge Reservation.  This occurred during a site assessment and data collection trip in Summer 2011.  The OLC seemed very positive regarding filter implementation, so we look forward to continue the dialogue to advance our legitimacy with the community and move towards implementation.

Our future plans are highlighted in the bullet points below.

Spring 2014:

• Continue column experiments to determine a full breakthrough curve for U removal with bone char media and a full breakthrough curve for arsenic (III) removal in ZVI/bone char column
• Conduct batch studies using natural groundwater and varying ratios of ZVI to bone char 
• Conduct column experiments with varying ratios of ZVI to bone char in order to determine the optimum ratio in a column setting for removal of arsenic
• Continue collaboration with KOLA, a philanthropic business student organization that we formerly partnered with to create a business plan for the manufacture of bone char filtration units on and for the Pine Ridge Reservation

Summer/Fall 2014:

• Conduct column experiments that test both As and U removal using varying ratios of ZVI to bone char
• Complete design of in-home bone char filtration unit and construct a prototype
• Take an assessment trip to talk with communities at PRR, and take household pipe measurements
• Implement a community water education program

 

Journal Articles:

No journal articles submitted with this report: View all 4 publications for this project

Supplemental Keywords:

Bone char, hydroxylapatite, hydroxyapatite, arsenic, uranium, human health, Oglala Lakota, Pine Ridge Reservation

Progress and Final Reports:

Original Abstract

2012 Progress Report

Final Report

P3 Phase I:

Use of Bone Char for the Removal of Arsenic and Uranium from Groundwater at the Pine Ridge Reservation  | Final Report