Introduction and Theory

In multiple AguaClara plants in Honduras, it is has been noted that there is a film formation at the point of rapid mix. However to date it is unknown how or why the film is formed. During the summer of 2009, our team will run experiments in order to replicate the film formed in these plants while also identifying the cause of the film formation.

We will first vary the alum dosage because research supports that surface foam can be attributed to the overdosing of aluminum sulfate. Additionally, the presence of natural organic matter (NOM) has been proven to lower surface tension in water, thus creating a surface film. The location of the alum addition is also thought to effect the film formation. This is because in small quantities, alum precipitates air is entrained and the alum becomes less dense than water.

List of Parameters

In our rapid mix experiment we plan to vary the following independent variables:

• Alum Dosage
• Turbidity
• The Location of the alum addition

Experimental Design

• We are first testing the alum dosage to determine whether it is the cause of the film formation. We will use the following dosages of alum (35 mg/L, 45 mg/L, 55 mg/L, 65 mg/L).

• We hypothesize that as the alum dosage increases there will be an increase in the formation of the surface film.

• We also are testing to the effect of natural organic matter (NOM) on film formation. We hypothesize that as the turbidity of the water increases so will the film formation.

• The film formation may not be due to the alum dosage or the turbidity, it may in fact be due to the location that the alum is added to the system; above water surface vs below water surface. We hypothesize that the film formation will be greater when the alum is applied to the surface of the water.

• For all of the experiments conducted we will take pictures at 10 minute intervals of the surface of the water to determine if there is film formation.