Grantee Research Project Results
Final Report: Application of Foam Filtration to Water Treatment for Rapid Emergency Response
EPA Grant Number: SU835715Title: Application of Foam Filtration to Water Treatment for Rapid Emergency Response
Investigators: Weber-Shirk, Monroe , Lion, Leonard William , Helbling, Damian E , Cashon, Andrea , Caglioni, Caroline , Chu, Kristin , Hinkley, Marlana , Hutchinston, Alena , Leeuwen, Lotta Van , Keller, Ethan , Peters, Alicia , Pietsch, Valerie , Yu., Tianchen
Institution: Cornell University
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2014 through August 14, 2015
Project Amount: $14,901
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2014) 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 goal of the foam filtration project is to develop water treatment technologies that will make clean water accessible to even smaller communities. Applications to disaster relief may also be possible because lightweight foam filtration units could be transported and deployed easily and rapidly. Providing access to clean drinking water to communities everywhere was identified by the National Academy of Engineers as one of fourteen Grand Challenges for Engineering (National Academy of Engineering, 2014). Provision of safe water on tap at the village scale is a significant engineering challenge because of the increasing cost per capita as the scale of the infrastructure decreases. Foam filtration has the potential to significantly reduce the capital cost of village scale drinking water treatment.
The foam filter design is based on the philosophy of Cornell University’s AguaClara program: simplicity, ease of operation, and long-term environmental, social, and economic sustainability. The foam filter consists of reticulated polyurethane foam of large and small pore sizes layered inside a 55 gallon drum or similarly sized receptacle, such as a 24 inch PVC pipe. The contaminated surface water is dosed with a coagulant that enables colloidal particles to aggregate and form larger particles, or flocs. As the water flows through the foam, the flocs are captured in its pores. The pores then fill with solids, and the resistance to flow (head loss) through the foam increases, eventually requiring that the filter be cleaned to restore its ability to remove solids. The high porosity of the reticulated foam (approximately 95%) permits a high filtration rate and the treatment of turbid waters that would otherwise quickly clog filters with lower porosities. Designing a system for cleaning the foam was a primary focus of Phase I research.
The foam filter system produces a minimal carbon footprint, as the system is entirely gravity- and human-powered, with no electricity required to operate or clean the filter. Foam filters process 150 times more water and can handle much higher influent turbidities than biosand filters of the same size. In addition, a foam filtration system for a village of several hundred individuals would be lighter than a biosand filter for only one household. The high output of the foam filtration system means that the carbon footprint of the source materials is small compared with household scale water treatment systems or compared with the plastic waste of bottled water.
Summary/Accomplishments (Outputs/Outcomes):
The objective of the Phase I foam filtration research was to design and fabricate a means for providing safe drinking water using a reticulated polyurethane foam filter. During Phase I research, the first task was to determine an effective method of cleaning the foam. Although a compression system (squeezing the foam) was originally thought to be the best cleaning option, a plunge wash system proved to provide higher cleaning efficiency (74% removal of retained solids compared to 54% with the compression system) with less applied force. The plunger system uses a lever to raise the foam filter pack and then plunge it rapidly through clean water that is in the bottom of the filter body. A pore velocity of up to 25 cm/s can be achieved by a single operator with the lever-arm design. During plunge cleaning, the water remains stationary and the foam is moved downward through the water. The high relative velocity between the water and the foam pushes the trapped solids out of the top of the foam to be discharged through a drain pipe on the side of the barrel (or pipe).
A pilot foam filter (Figure 1) was fabricated in El Carpintero, Honduras. The filter was designed jointly by the AguaClara teams at Cornell and Agua Para el Pueblo (APP) engineers in Honduras. The filter body is a 24 inch (60 cm) diameter PVC pipe (see Figure 1) and has a total foam depth of 43 cm, and a total height to allow 43 cm of head loss accumulation during filter operation. The design flow rate for the pilot filter is 1.5 L/s. The pilot system employs coagulant addition through a semi-automatic AguaClara Chemical Dose Controller (CDC) (Swetland, et al., 2013), similar to those used in AguaClara water treatment plants throughout Honduras. The CDC automatically adjusts the coagulant flow rates when the plant flow rate varies, and an operator can simply adjust a metal slide to vary the coagulant dose as the influent turbidity changes. The plant flow rate is communicated to the CDC by a float in conjunction with a Linear Flow Orifice Meter (LFOM) that linearly varies the height of the water in an entrance tank with volumetric flow (Swetland, et al., 2013). In the foam filtration system, the CDC was redesigned with (1) an altered constant head tank constructed from a Nalgene bottle, (2) a CDC float located within the LFOM, eliminating the need for a separate entrance tank, and (3) dose controller tubing in the CDC oriented vertically to achieve a more compact system. Chlorine disinfection can easily be added to the foam filtration system when it is ready to be used as a drinking water source. The pilot foam filter assembly is shown in Figure 1.
Figure 1. Foam Filter in Operation in El Carpntero, Honduras
The pilot foam filter in Honduras reduced the turbidity of water to below 5 NTU, the Honduran drinking water standard (Republic of Honduras Regulatory Authority of Drinking Water and Sanitation, 2005). The US EPA standard is 0.3 NTU (U.S. Environmental Protection Agency, 2014). The pilot system in Honduras has not performed as well as filters in the AguaClara laboratories at Cornell where turbidity is consistently reduced from 100 NTU to 1.5 NTU or less. The surface water at El Carpintero has a high concentration of dissolved organic matter (DOM), and it is hypothesized that this DOM may be responsible for the poorer performance of the foam filter. This insight will guide several of the research tasks for Phase II.
Conclusions:
Phase I research has yielded key improvements in the filter cleaning and chemical dosing systems. The pilot filter has demonstrated that the foam can be repeatedly cycled between filtration and cleaning modes. The compact design of the semi-automated CDC was successfully coupled with the foam filter to produce a complete water treatment system. The iterative feedback sequence of design - test - modify between the engineers in Honduras and the Cornell University students has facilitated rapid design improvements.
Successful deployment of the foam filtration unit will require additional improvements in performance to meet U.S. EPA drinking water standards. Performance gains from the addition of a flocculator, stratification of pore sizes, and multiple foam filters in series will be evaluated to assess which modifications to include in the pilot filter.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
drinking water, water treatment, water filtration, reticulated foam, filter, sustainable, community, HondurasRelevant Websites:
AguaClara Cornell Project Page 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.