Final Report: Undergraduate Project on Virus Removal in Slow Sand Filters for Rural Mayan Communities

EPA Grant Number: SU834296
Title: Undergraduate Project on Virus Removal in Slow Sand Filters for Rural Mayan Communities
Investigators: Nguyen, Thanh (Helen) H.
Institution: University of Illinois at Urbana-Champaign
EPA Project Officer: Nolt-Helms, Cynthia
Phase: I
Project Period: August 15, 2009 through August 14, 2010
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2009) RFA Text |  Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Materials & Chemicals , P3 Challenge Area - Pollution Prevention , P3 Challenge Area - Water , P3 Awards , Sustainability


Engineers Without Borders (EWB) at the University of Illinois at Urbana-Champaign (UIUC) was contacted by Wuqu' Kawoq, a non-profit medical nongovernmental organization (NGO) that works with the indigenous people of Guatemala. Wuqu' Kawoq identified the Mayan village of Socorro as suffering from medical conditions that can easily be alleviated by clean drinking water. With 450 people, Socorro is plagued with water- and soil-borne pathogens that cause problems such as scabies, diarrhea, dysentery, hepatitis A, giardiasis, shigellosis, amoebiasis, and soil-transmitted helminthes infections. EWB-UIUC assessed multiple water purification and distribution alternatives in order to identify the most effective remediation option. Ultimately, it was concluded that point-of-use biosand filters installed in individual family homes would be the most effective.

A travel team for EWB-UIUC, which consisted of five students in Environmental Engineering and Spanish Studies and a professional engineer specializing in concrete, arrived in Socorro on December 29, 2009. Prior to EWB-UIUC’s arrival, four albañiles (professional concrete workers) received training in the construction and maintenance of concrete biosand filters from a partner NGO, Servants 4 Him. Having built several filters on campus, the EWB team shared its own construction techniques to augment the knowledge of the concrete workers and those from Servants 4 Him. All materials needed in the construction of the filters are available locally.

EWB-UIUC trained two social workers on sanitary and hygienic practices including the disposal of waste, hand washing techniques, procedure to boil water, biosand filter maintenance and use, and proper storage of clean water. With the aid of the social workers, a specialized educational program was developed for the community that utilizes educational images developed by the Center for Affordable Water and Sanitation Technologies (CAWST). The social workers discuss hygiene and filter use with every new family that receives a filter. Additionally, seven grade school teachers and the principal were given information on proper sanitation, hygiene, and the biosand filter and they are teaching these topics to their students.

At the University of Illinois, research efforts are being made to improve the overall efficiency and design of the biosand filter. Considering the criteria of water quantity produced, water quality, ease of use, and ease of access, biosand filters have been identified as the point-of-use technology having the most potential to deliver sustainable potable water treatment to the developing world. However, as our experimental results show, they are not effective in removing viruses, as sand and viruses are both negatively charged in neutral water. A novel technology being investigated is the use of iron oxides to enhance virus removal. Negatively charged viruses are expected to adsorb to positively charged iron oxide surfaces at neutral pH.

Studies conducted by the team investigated the removal of virus by zerovalent iron. Small-scale studies using glass columns simulated the average use of a biosand filter (one gravity-fed pore volume [PV] charge) and tested different orientations of iron placement. Large-scale studies then were performed with both plastic and concrete filters, comparing virus removal between commonly found mild steel nails and commercially available zerovalent iron particles. Lastly, studies were performed to determine whether locally available iron materials would sufficiently remove viruses from source water. The research objective is to design a modification that can be applied to the filters being built in Socorro and, potentially, elsewhere.

Summary/Accomplishments (Outputs/Outcomes):

Long-Term Removal in Columns

To simulate the normal operation of a biosand filter, 4 glass columns (Figure 1) packed with different iron orientations were charged daily with 1 PV of aquifer water containing ~108 pfu/mL of MS-2 bacteriophage, a commonly used surrogate for enteric virus, and 2.5% pasteurized primary effluent (PE). While the sand column averaged only 1-log10 (90%) removal, all three iron columns had greater than 5-log10 (99.999%) removal for the duration of the experiment.

M2-2 Removal by BSFs

Plastic biosand filters were used to study virus removal by BSFs amended with iron nails. The nail filter started with a 6.5-log10 removal (99.99997%) but retention of virus particles quickly declined as flow paths short-circuited the iron. These independent flow paths were caused by the difference in size and shape between the nails and sand media. To avoid this problem, two concrete biosand filters were constructed using a steel mold built to specifications provided by CAWST. The filters were packed and charged daily with commercially available iron particles. The sand filter achieved an average of only about 2-log10 (90%) removal (Figure 2), while the iron particle filter maintained an average of 6-log10 (99.9999%) reduction of viriron particles. The iron particles had dimensions similar to the sand and, thus, promoted near plug-flow conditions that allowed for sufficient contact time between each filter charge.

Testing for Locally Available Iron Materials

It is highly desirable to pack the filters with iron that is readily obtained in rural Guatemala. Four plastic bottles, shown in Figure 3, packed with different iron sources were charged with 1 PV aquifer water and ~108 pfu/ml MS-2. The bottles were run for a period of 2 weeks. Nails achieved an average of only 3-log10 removal, which continued to decline over the course of the experiment. Zerovalent iron particles obtained an average removal of approximately 7-log10 and steel wool an average removal of 5.5-log10 (Figure 3). The large surface area of zerovalent iron particles and steel wool facilitated higher removal.


For Phase I of the P3 grant, our goals were four-fold: implementation, research, student advancement, and education outreach. In terms of these goals, Phase I of our project has been a success.

Implementation of the biosand filters is underway and will be completed by May 2010. The four albañiles have become experts on the building, operation, and maintenance of the filters. The community’s respect for these men and trust in the social workers has been pivotal in the project’s operation within the particular ethnic, linguistic, and social characteristics of the community. This strong collaboration has led to widespread acceptance of the filters. It also has established knowledgeable, local leaders that will sustain the project in the future, independent of foreign assistance.

The extensive laboratory studies performed by the team focused on the removal of viruses using biosand filters amended with inexpensive, locally available iron materials. Concrete filters utilizing sand media amended with commercially available iron shavings displayed an average of ~6-log10 removal of MS-2 phage. The national (US-EPA) standard for removal is 4-log10.

Students have been actively promoting awareness about Socorro and water-related projects, in general. Frequent presentations are given to elementary and high school students, and a multidisciplinary group of students has been formed to aid research in the lab. Three teams of five students also have been organized into research teams to help collect data. In addition to learning to build and run the filters, the teams learn the theory and application of pertinent lab techniques and are presenting their work to both the academic and scientific community through conferences, presentations, and open houses. These productions often are the first time students have had the opportunity to actively present to the academic and scientific community, allowing them to practice their public speaking and presentation skills.

Proposed Phase II Objectives and Strategies:

Continued Technical Innovation

Our Phase I findings show that amending the BSF’s sand media with iron particles of similar size results in effective MS-2 bacteriophage removal. Before applying this technology to Socorro’s biosand filters, the research team proposes testing the filters onsite using the community’s typical practices. This requires establishing an onsite laboratory in the community for the analysis of microbial reductions by biosand filters charged daily with the community’s tap water seeded with pathogen surrogates. The tap water is distributed from a contaminated river, so the proposed studies will give insight into surface water quality fluctuations and the biosand filter’s buffering capacity. Also, the different sand and iron media used in Socorro may affect microbial removal. It is imperative that final design of an iron-amended filter includes rigorous testing of actual scenarios. This research will be the first to evaluate the removal capabilities of a biosand filter packed with a mixture of sand and low-cost iron oxide materials in the developing world. The filter construction materials and source iron are available locally. Lab specimens, supplies, and equipment will be purchased in the United States and brought to the community.

In extension of the existing research, EWB-UIUC proposes to expand into studying the removal of MS-2 bacteriophage under additional water quality and filter usage conditions. The goal is to more concretely define the capabilities of the biosand filter, highlight best operation practices, and test the removal efficacy of human enteric pathogens. This research will be valuable to NGOs and international communities where people can adopt practices to enhance the biosand filter’s water treatment without requiring additional treatment that can be burdensome or costly.

The NGO CAWST has recently developed a newer version of the biosand filter, Version 10.0, and has started to promote its use in international projects. Previous publications analyzed removal efficacy of an earlier filter design, and no current publications focus on the Version 10.0 design. We would like to investigate the removal of surrogate organisms MS-2 and Escherichia coli by the Version 10.0 biosand filter.

While testing the Version 10.0 filter, the team also will investigate the removal of MS-2 and E. coli with variations in the pause period, ranging from 1 hour to 48 hours, and pore volumes that range from 5 L to 40 L. It is widely believed that user habits can alter bacterial removal, and preliminary studies performed by EWB-UIUC indicate that removal efficacy increases as the pause period increases.

In a biosand filter, viruses and bacteria are removed through a combination of physical, chemical, and metabolic processes in the biofilm and the sand media; however, the exact mechanisms or removal due to each type of mechanism is still unknown. To determine the effect that each mechanism has on bacteria and virus removal, we propose establishing two separate types of columns: a shallow sand column that would consist entirely of the biologically active layer and sand columns of varying depth without a biofilm. Each column would be run with water seeded with MS-2 and E. coli and removal rates analyzed.

Future work includes determining the removal efficacy of the human pathogens Cryptosporidium oocysts and rotavirus. Laboratory experiments will follow the methods established in Phase I. Long-term study also will be conducted to determine the longevity of biosand filters.

Continued Social Innovation

The current implementation of the biosand filters will lead to the establishment of a local enterprise for four current biosand filter construction workers in Socorro. The EWB team will present final research recommendations to the workers and collaborate in the utilization of these recommendations in their business. The EWB team also will collaborate with the community of Socorro, our NGO partners in the area such as Wuqu’ Kawoq and Servants 4 Him, and international NGOs such as CAWST, to develop a successful and sustainable business plan and educational series that builds upon past biosand filter endeavors. Beyond the direct benefits for Socorro, which include a revenue stream for the small community and improved community health through enhanced water treatment, the business will examine the feasibility of expanding the amended biosand filters beyond Socorro.

Continued Educational Innovation

Education and personal advancement are vital components of the project. In Urbana-Champaign, approximately 15 undergraduate engineering students were introduced to the Environmental Engineering Laboratories during Phase I of the project and began learning about biosand filtration functionality, laboratory techniques, and advanced problem solving. Past research has shown that combining a formal classroom education with a lab or undergraduate research experience augments the student’s education. Phase II will build upon the learning objective achieved in Phase I and will incorporate additional undergraduate students and activities. In addition, the EWB group will collaborate with a UIUC research group led by Dr. Litchfield and funded by the National Science Foundation to investigate student learning in international service projects.

The final objective of Phase I was to educate students and teachers about international water projects and basic drinking water treatment practices. Presentations at grade and high schools have been successful, and the team plans to work with our partners at The Center for the Advance Materials for the Purification of Water with Systems (WaterCAMPWS) and the EWB-UIUC outreach committee to establish a regular education program. The values of this project will be reflected in a lesson plan in which young students learn about foreign cultures, teamwork, and water treatment.

With a focus on community-based implementation, laboratory research, student advancement, and education outreach, Phase II of the project will continue to build upon the progress of Phase I to benefit Socorro, the student team, and the general public. The People affected by the project will have an improved level of Prosperity. When Socorro’s population receives water, their subsequently improved health will allow them to live more comfortable and productive lives. The student team gains experience and life lessons by working on this project, and the public that they reach out to becomes more aware of water issues. This project reduces the release of harmful human waste without the production of toxic byproducts, pollution caused by long-distance transportation of materials, or a large input of energy, and thereby promotes the wellbeing of the Planet.

Journal Articles:

No journal articles submitted with this report: View all 9 publications for this project

Supplemental Keywords:

Water treatment, virus removal, pathogen disinfection, human health, electrostatic adsorption, zero-valent iron, biosand filtration, slow sand filtration,

Relevant Websites:


Progress and Final Reports:

Original Abstract
2010 Progress Report

P3 Phase II:

Virus Removal in Biosand Filters for Rural Mayan Communities  | 2011 Progress Report