Grantee Research Project Results
Sustainable Water Treatment Facility for Communities with Arsenic Contaminated GroundwaterEPA Grant Number: SU835516
Title: Sustainable Water Treatment Facility for Communities with Arsenic Contaminated Groundwater
Investigators: Weber-Shirk, Monroe
Institution: Cornell University
EPA Project Officer: Levinson, Barbara
Project Period: August 15, 2013 through August 14, 2014
Project Amount: $14,999
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2013)
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Water
Poor water quality affects the health of more than 1 billion people and contributes to the death of at least 1.9 million people in developing countries every year (Lantagne & Gallo, 2008). Naturally occurring arsenic in groundwater that causes major health problems and has been estimated to impact 60 million people in South and East Asia.
Our objective is to develop a gravity-powered water treatment unit for small communities that will also remove arsenic to improve the health of those affected by unsafe drinking water. Coagulation with aluminum or iron salts, flocculation, and particle removal by sedimentation and/or filtration is a commonly used method of arsenic removal. Many of the arsenic contaminated wells serve small populations and thus provide very low flow rates. Treating these low flow rates is a significant technical challenge. Designs for low flow, gravity powered, high performing, flocculation-sedimentation-filtration facilities were not available prior to the creation of the AguaClara design tool (http://designserver.cee.cornell.edu/Designs/). As of 2012 the AguaClara team posted designed for facilities with treatment capacities between 6 and 70 L/s. Although these are low flow rates for municipal systems, even the lowest flow rate of 6 L/s would be enough for 2000 to 6000 people. An even lower flow rate treatment system would be useful for many of the arsenic contaminated wells.
Over the past year the AguaClara design team has created a new plant layout for flow rates between 0.8 and 3.2 L/s. With appropriate modification these new ultra low flow plant designs may be well suited for arsenic removal. The goal of this project is to identify the critical design parameters that need to be changed to optimize arsenic removal while also keeping cost low and simplifying operation.Approach:
A bench-scale low flow, gravity-powered water treatment plant will be designed and constructed to determine optimal parameters for efficient arsenic removal. Information gathered from testing this setup will contribute towards the design and eventual construction of water treatment facilities in India. The design, construction, and testing of the bench-scale facility will be completed by undergraduate and graduate students through design-based, sustainable water treatment course at Cornell University. Implementing this plant in the future will be coordinated with an implementation partner seeks to promote sustainable community managed water supplies.Expected Results:
Experiments will be conducted on a bench-scale plant to determine the most effective coagulant, coagulant dose, and alternative for pretreatment with oxidants. We anticipate that a lower coagulant dose can be used than has previously been described for arsenic removal by using a combination of high efficiency rapid mix, hydraulic flocculators, and floc blankets. Utilizing floc blankets with floc hopper sludge concentrators will reduce the amount of waste residuals produced. AguaClara built the first shallow sedimentation tanks that include both floc blankets and plate settlers at Atima, Honduras in 2012. Our online SMS based performance monitoring webpage (http://aguaclara.cornell.edu/projects/data) shows that the coagulant dosages used at Atima with the floc blanket are significantly lower than the coagulant dosages used at other facilities. If this benefit applies to arsenic removal, then the new AguaClara tank geometry that provides stable floc blanket operation in a shallow sedimentation tank could significantly reduce coagulant dosages and the volume of arsenic contaminated sludge. Research from the bench scale unit will be used to guide the pilot plant design that will be constructed by the NGO we will be partnering with. The final outcome for the one-year timeline is to have a bench-scale facility that can efficiently treat arsenic contaminated water to WHO standards of less than 10 μg/L.Supplemental Keywords:
arsenic, water treatment, gravity powered, flocculation, floc blanket;