AguaClara Stacked Rapid Sand Filtration – A Robust Filtration Process For Sustainable Drinking Water InfrastructureEPA Grant Number: SU835307
Title: AguaClara Stacked Rapid Sand Filtration – A Robust Filtration Process For Sustainable Drinking Water Infrastructure
Investigators: Weber-Shirk, Monroe , Morris, Julia E. , Lion, Leonard William , Will, Jeffrey , Adelman, Michael
Current Investigators: Weber-Shirk, Monroe , Lion, Leonard William , Rausch, Heidi , LaPan, Kristopher
Institution: Cornell University
EPA Project Officer: Hahn, Intaek
Project Period: August 15, 2012 through August 14, 2013
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2012) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Water , P3 Challenge Area - Green Infrastructure , P3 Awards , Sustainability
The AguaClara stacked rapid sand filter (AC-SRSF) is an efficient, inexpensive, and fully hydraulic unit process for municipal-scale water treatment. It is expected to be a sustainable alternative, especially for communities in the developing world where conventional water treatment technology has often failed. The costs associated with backwashing are an important limitation to the widespread application of rapid sand filters in municipalities in the developing world. A novel geometry of the sand bed with inlets and outlets throughout the bed creates multiple layers in the AC-SRSF, and allows it to use the same flow rate for filtration and backwash. As a result, no pumps, elevated tanks, or redundant filter units are required to achieve the necessary backwash velocity. This project will encompass the ongoing development of the AC-SRSF at the laboratory and field scale.
The technology employed in this research is a form of rapid-sand filtration, but depends on some key innovations that differentiate it from conventional technology. In an AC-SRSF, there are four inlets spaced throughout the sand with three outlets in between to create six layers. During a filtration cycle, flow is divided among these six layers; during the backwash cycle, the entire flow enters through the bottom inlet and exits above the sand bed into a backwash system. This creates a velocity six times higher for the backwash cycle with the same incoming flow rate, thus eliminating the need for pumps or other expensive infrastructure to create high backwash flows. The novel arrangements of inlets and outlets required several key innovations in the hydraulic design of the AC-SRSF, including slotted pipe manifolds in the sand bed and a siphon / air trap / air valve system for fluidic control of the mode of operation.
A laboratory AC-SRSF has been developed to test this novel filtration process. The results to date suggest that stacked filtration is a viable technology, and that continued investigation is warranted. Laboratory investigation will use both bench-scale and pilot-scale equipment to develop design parameters and investigate fundamental questions. The first full-scale AC-SRSF has been built in the field at a water treatment plant in Támara, Francisco Morazán, Honduras, and several full-scale experiments will be carried out in an attempt to improve its performance and inform future designs. The results of this data collection are expected to better characterize the operation of the AC-SRSF in the field, and lead to insights into its efficient operation.