Grantee Research Project Results
Final Report: Pathogen and NOM Removal in Riverbank Filtration for the Village of La Barranca Honduras
EPA Grant Number: SU834716Title: Pathogen and NOM Removal in Riverbank Filtration for the Village of La Barranca Honduras
Investigators: Heydinger, Andrew , Chua, Huan Han , Orozco, Andrea , Hessler, Christopher , Nichols, Erin , Rehman, Ghias , Sendamangalam, Varun , Seo, Youngwoo , Wang, Zhikang
Institution: University of Toledo
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The Village of La Barranca is located within the Municipality of Orocuina, in the Department of Choluteca, Honduras and is approximately 2 miles south of Orocuina Centro. A fully functioning water system existed there until it was destroyed by Hurricane Mitch in 1998. Since then, the village has unsuccessfully petitioned local government agencies to restore the water supply. Currently, villagers obtain water from a local farmer who gives priority to cattle, as well as from the nearby Rio Choluteca. The water obtained from the farmer has contained large maggots and Rio Choluteca, known for its pollution, is also used for bathing and washing.
EWB-UToledo has proposed a riverbank filtration and pump system as an inexpensive and sustainable water treatment solution. Riverbank filtration is already widely used in Europe and interest in North America has begun to grow as a result of its ability to remove water born pathogens and low maintenance requirements. However, the role of biological activity in RBF systems, such as indigenous biofilm formation, is still not well understood. Biofilm formation in natural environments is ubiquitous and it changes hydrodynamics and conductivity in riverbank filtration systems significantly. Originally, the proposed project sought to answer two specific questions regarding biological activities in riverbank filtration. First, E.Coli and fecal coliforms were found in initial water tests of Rio Choluteca, and this presence implies that this water could pose chronic health hazards to villagers. Therefore, an objective of this project is monitoring how biofilm formation in riverbank filtration affects the filtration rate, pathogen removal efficiency, and filtered water quality. Second, the filtered water must be disinfected in order to ensure that pathogens not removed by the riverbank filtration do not contaminate the filtered drinking water. For this purpose, chlorine was chosen for its effectiveness and its ease of use, but this disinfectant is also highly reactive with surface water and can produce unwanted disinfection by-products (DBPs). To curb the influence of these DBPs, natural organic matter (NOM, precursors of DBPs) must be removed. The effect of biofilm formation on removal of these NOMs was studied using simulated column tests
Summary/Accomplishments (Outputs/Outcomes):
In pathogen removal tests, a significant difference was not evident between a biologically active column with indigenous biofilm activity versus a control column. Due to encountered problems with unknown bacteria contamination which can utilize lactose, experiments were repeated several times without any conclusive data. Long term E.Coli removal tests are currently in progress. Based on obtained data, it generally appears that injected E.Coli began to appear in effluent samples from both columns after 10 hours and reached breakthrough approximately 5 days after initial injection. Considering total filtration length (over 100 ft length) and flow rate (around 3.3 ft/day) in field scale river bank filtration systems, E.Coli breakthrough in the real system was expected after over 100 days continuous operation. However, lab results did not fully reflect the complexity of a field scale riverbank filtration systems.
In NOM removal experiments, initial operation of a biologically active column showed much higher (around 10 times) total organic carbon concentration than influent organic carbon concentration due to detachment of bacterial inoculums and biofilm activity. Effluent TOC concentration from the biologically active column began to stabilize and decreased after three days, suggesting a slight NOM removal.
Overall, even though the system was tested with simulated ground water flow rate (1 m/day), the short column length (0.30 m, 0.98 ft) cannot effectively simulate both NOM and pathogen removal in river bank filtration (36 m, 120 ft). However, significant removal and reduction of NOM and E.Coli are expected in a field scale system, considering the conditions in field scale systems Based on our experimental data, significant biological activities in any riverbank filtration systems will cause treated water quality to decline, increasing total organic carbon concentration.
In addition to monitoring removal of E.Coli and DBP precursors in simulated river bank filtration systems, additional experiments for the removal of heavy metals (lead and cadmium) in the river bank filtration systems were also conducted based on updated water quality analysis data. In a field assessment of water quality conducted by a team from University of Toledo chapter of Engineers Without Borders (EWB-UTOLEDO), high concentrations of both lead and cadmium were discovered in the RBF system and Rio Choluteca. These concentrations were in excess of the US EPA’s maximum contamination levels. Accordingly, the RBF as originally designed would not be suitable for prolonged heavy metal removal. Thus, an extensive literature review was conducted discovering sustainable and easily accessible absorbents (wood chips and phosphate rich apatite) for cadmium and lead removal. Metal isotherm tests were first conducted with two tested absorbents. The tested hardwood chips exhibited a capacity to remove lead but did not effectively remove cadmium. The phosphate rich apatite showed very high sorption capacity for lead and adequate capacity for cadmium. Then, using crushed apatite, continuous flow tests were conducted to monitor total heavy metal removal. Over one month, column reactor tests were conducted examining the addition of apatite to the simulated RBF system. Using an influent concentration five times greater than indicated by water quality reports, the tested column reactor completely removed both lead and cadmium during the course of the experiment. Long term evaluation tests are in progress now and breakthrough curve will be obtained from the ongoing tests.
Conclusions:
Based on lab scale column experiment results for river bank filtration simulation, it was difficult to simulate the complexity of real river bank filtration systems which typically use over 100 ft long filtration length. However, lab scale experiments revealed that increased indigenous biological activities (biofilm formation) did not significantly enhance pathogen removal. Additionally, NOM removal was not significant in the biologically active column and contributed to increased effluent TOC level. However, simple calculations based on the obtained experimental data from lab scale experiments suggest that NOM and pathogen removal can be achieved in field scale riverbank filtration systems.
Furthermore, we also found that phosphate-rich apatite could be employed as an effective adsorbent for heavy metal contaminants. It may be a sustainable option to remove toxic heavy metals from source water. In terms of application, it would be possible to incorporate this adsorbent into the La Barranca, Honduras riverbank filtration system by embedding apatite into an engineered trench to achieve long-term removal of lead and cadmium
Supplemental Keywords:
Biofilm, Riverbank filtration, Heavy Metals, Apatite, NOMRelevant Websites:
Engineers without Borders at the University of Toledo Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.