Foam Filtration

Currently, the effluent water from an AguaClara plant can produce effluent water after sedimentation with a turbidity of about 5 NTU. Our goal is to reduce the effluent turbidity to less than 1 NTU. One potential method of accomplishing this is adding a filtration unit to the AguaClara plants.

Numerous techniques of water filtration are in use today, most of which involve the use of sand as the porous media. After preliminary research revealed the a lack 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 could also potentially require less area, and be less expensive to build than a traditional sand filter.

With these advantages in mind, we have considered a number of different designs which could provide the desired standard of 1 NTU effluent water turbidity.

(Include your disadvantages here too or include a separate section in your wiki to compare and contrast sand filter and filter foam including cleaning)

Foam Filtration Current Research

Flat Foam Sheet Experiments

Prior to considering the actual design of a proposed filtration unit, it is necessary to test the know the actual filtering capacity of the foam material we would like to use. Therefore, a number of experimental trials on foam with varying pore sizes and flow rates were conducted. (How are pore sizes measured?) Briefly, it was found that the flat foam sheets alone do not provide enough colloid removal, under the conditions tested, to be an implementable method of filtration for the AguaClara plants. However, under more realistic conditions, rather than the worst case lab conditions as tested, foam filtration may in fact be feasible. (What do you mean by more realistic conditions? More foam?) Please see the results and discussion of each experiment for further explanation.

Foam Filtration Future Research

Later this semester, we would like to further investigate a few different methods of achieving our goal of 1 NTU effluent turbidity, as outlined below.

Flat Foam Sheet Experiments with flocculated particles

(The above should be changed to coagulated particles since very little flocculation will occur in the system as you currently have it designed)

Currently, we are testing the filtering capacity of foam under the worst case lab conditions, which consists of filtering water containing unflocculated clay particles. This is not a realistic condition (Why? This is a condition that could occur if the operator did not add alum which is a practice that some AguaClara plants do for water under 6 NTU), and we would like to test the filtering capacity of the foam under conditions that are more reflective of conditions in an AguaClara plant. This involves adding alum and tube flocculation to our system, in order to produce larger particles, which will then lead to, hopefully, higher levels of colloid removal. (I think we should be more clear that we are testing both the effect of coagulation and potentially comparing this to the presence of flocculation. In effect, this may allow us to distinguish different removal mechanisms that are occuring in filter foam.)

Foam Media Upflow Design

An alternative to using the foam simply as a flat sheet which water is filtered through is to design a hybrid upflow filter, which uses small pieces of the foam as the filtering material, as opposed to the traditional upflow sand filter. This idea is based on the technique outlined in this article:http://www.wioa.org.au/conference_papers/06_vic/documents/StewartShipard.pdf

(This is an interesting idea that does warrant further investigation, but maybe for another semester. Do you have pictures of what your proposed idea would look like?)