Final Report: Evaluation of Chitosan Coagulation as a Sustainable Method for Point of Use Drinking Water Treatment in Developing CountriesEPA Grant Number: SU834295
Title: Evaluation of Chitosan Coagulation as a Sustainable Method for Point of Use Drinking Water Treatment in Developing Countries
Investigators: Sobsey, Mark D. , Ligon, Grant C. , Soros, Ampai , Armstrong, Andrew , Knee, Jackie , Casanova, Lisa
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Page, Angela
Project Period: August 15, 2009 through August 17, 2010
Project Amount: $9,990
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 - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
The purpose of this project is to evaluate the effectiveness of chitosan for improving the microbial quality of water. The goal of Phase 1 was to determine whether coagulation using chitosan, both alone and followed by filtration, can reduce the numbers of bacteria and viruses in drinking water. There were four project objectives:
- Determine the reduction of bacteria in drinking water using chitosan coagulation alone.
- Determine the reduction of viruses in drinking water using chitosan coagulation alone.
- Determine whether pretreatment with chitosan coagulation can increase the removal of bacteria achieved by a currently available POU technology, ceramic filtration.
- Determine whether pretreatment with chitosan coagulation can increase the virus removal achieved by ceramic filtration.
Chitosan A was found to remove up to 3.4 log10 E. coli, a reduction of 99.96%. The removal was dose dependent; up to a point, removal of E. coli increases with increasing dose. Removal of E. coli ranged from 0% removal by a dose of 1g/L to 99.96% (3.4 log10) removal by a dose of 20 g/L. One-way ANOVA showed that the amount of E. coli removed was significantly different between doses (p<0.0001). Chitosan B performed very poorly in comparison; it reduced E. coli by less than 0.5%. Chitosan C had the greatest removal of E. coli of all the chitosans tested. It also removed E. coli at lower doses than the other chitosans tested, with 99% (2 log10) reduction of E. coli at a dose of only 0.1 g/L. A dose of 10-15 g/L could reduce E. coli by 99.99996% (6.45 log10), meeting the USEPA efficacy standard for bacteria for a point of use (POU) drinking water treatment technology.
The removal of MS2 from water by Chitosan A was extremely poor; at a dose of 15 g/L, which removed 99.78% of E. coli, the reduction of MS2 was less than 0.5% (0.14 log10). Chitosan B was not tested because of its poor performance against E. coli. Chitosan C achieved the highest reduction of MS2. The highest dose tested, 15 g/L, removed 99.99993% of MS2 (6.15 log10). There was a dose effect above 5 g/L, with the removal increasing with increasing dose. The hypothesis that chitosan could remove 99% of MS2 from water was only accepted for chitosan C; this chitosan meets the USEPA POU technology standard for viruses (99.99% reduction) at a dose of 15 g/L.
Chitosan A was tested in combination with filtration by a ceramic filter to determine if it could increase the reductions of E. coli compared to filtration alone. Filtration alone was highly efficacious in removing E. coli; filtration removed an average of 99.99999% (7.0 log10) E. coli from water. Coagulant A and filtration, when used sequentially, removed 99.9999999% (10.0 log10) of E. coli, an increase of 99.9% (3 log10) over filtration alone. These results indicate that Chitosan A could meet the threshold for increasing the removal of E. coli by 99.99% over filtration alone. Based on the log reductions achieved in experiments with Chitosan C alone, it could increase the efficacy of filtration by >99.9999 (6 log10). Ceramic filtration alone was not effective in removing MS2; the reduction of MS2 by the ceramic filter was <0.5%. Ceramic filters appear to have insufficient pore sizes to trap and remove viruses; they pass through the filter into the effluent water. The combination of chitosan A and filtration produced no removal of viruses. Chitosan C could increase the efficacy of MS2 removal, but this was due solely to the coagulant action of the chitosan and not the filter.
Chitosan appears to be an efficacious coagulant for removing bacteria from water; efficacy against viruses can be obtained by using the lactate salt of chitosan. Phase 1 provided crucial proof-of-concept data that chitosans are potentially effective for improving the microbial quality of water. Phase 1 work clearly has shown that chitosans are highly effective for removing bacteria, but are deficient for removing viruses. Alternative water treatment methods are needed that can be used in tandem with chitosan to effectively control viruses.
Proposed Phase II Objectives and Strategies:
For Phase 2, we are incorporating an evaluation of the microbial quality of recycled stormwater from green buildings in North Carolina, and an evaluation of chitosan and chitosan nanoparticles for improving the quality of this water. In addition, we have added a team member who became interested in using chitosans for POU water treatment, and has been successful in securing a Fulbright scholarship to travel to Thailand to pursue this work. This has allowed us to add a project site in Thailand, as well as another partner, the Asian Institute for Technology. Therefore, the overall goal of Phase 2 is to optimize the use of chitosan in combination with metal ions to 1) improve the microbial quality of recycled rainwater captured from green building construction in the U.S., and 2) improve the microbial quality of recycled rainwater captured by rural households in Thailand for use as a primary source of drinking water.This work will be undertaken with the following specific aims:
- Specific aim 1: Measure the microbial quality of stormwater captured from green buildings in the U.S.
- Specific aim 2: Measure the microbial quality of rainwater collected by rural households in Thailand for use as drinking water
- Specific aim 3: Screen a collection of different chitosans and their nanoparticles for their ability to remove bacteria and viruses from rainwater collected by households in Thailand
- Specific aim 4: Screen a collection of different chitosans and their nanoparticles for their ability to remove metal ions from stormwater captured from green buildings in the U.S.
- Specific aim 5: Evaluate the user acceptability of chitosan and chitosan nanoparticles for treatment of collected rainwater in Thailand
- Specific aim 6: Measure the ability of metal ions, chitosans and chitosan nanoparticles in combination to improve microbial quality of stormwater from green buildings in the U.S.