Foam Filtration
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Numerous techniques of water filtration are in use today, most of which involve the use of sand as the porous media. A preliminary literature review revealed a dearth of information on foam filtration. Our team has decided to focus on investigating the actual filtering capacity of a polyurethane foam material as opposed to the traditional method of sand filtration. With proper implementation, a foam filter could reduce the amount of water that is wasted during the backwash cycle of a traditional sand filter. A foam filter requires less surface area, and could potentially be less expensive to build than a traditional sand filter. However, a foam filtration unit will also require a tight seal with all of the edges of the tank, in order to avoid preferential flow paths which will result in unfiltered water. In addition, a foam filter will likely require manual maintenance by the plant operator.
Foam filtration has been ruled out for an AguaClara plant because the foam would be too difficult for an operator to clean. However, previous research has proven that foam is an effective method of filtration, therefore this team decided to focus on designing a point of use foam filtration unit. However, due to chemical dosing and usability concerns, the point-of-use application was ruled out as a possibility for foam filtration. The team is now focusing on the design of an emergency filtration system that can be transported on the back of a pickup truck. Research will be done to optimize the design such that it is as efficient as possible and provides the desired standard of 1 NTU effluent water turbidity.
Note: Turbidity is defined as the cloudiness of a fluid caused by suspended particles. Higher turbidities correlate to more opaque fluids.
Current & Future Research
Our team is currently designing an emergency filtration unit to be built and tested. The design consists of a roughing filter that utilizes 30 ppi* foam and a finishing filter with 90 ppi foam. The filter unit will be built using PVC pipes, of which the diameter can be selected based on the volume of clean water needed. Additionally, the AguaClara chemical doser will be used. A prototype is being built and we will run a series of experiments testing the effectiveness of the unit itself.
Additionally, experiments with the foam column will continue. Fall 2011 experimental trials focused on testing 30 ppi foam as a roughing filter. Other research areas will be explored as well. This will include the effectiveness of an aluminum hydroxide wash to decrease the ripening time of the foam, the effects of natural organic matter on the foam material and the most efficient way to clean the foam material. Read more.