Minnetonka High School, Minnetonka, MN, USA
Since the middle ages people have had problems disposing of domestic waste water. Current systems breed bacteria to decompose the solids contained in the waste water. The most common form of bacteria used for this process is Fecal Coliform bacteria. Then a disinfection system is used to destroy the bacteria. Problems remain because many of the current systems leave chemicals which can become harmful to the environment. Justin Rainy and James Wilson attempted to resolve this problem by using ultrasound to destroy the bacteria. The EPA is currently studying the effectiveness of ultrasound but is neglecting to test the many variables. A major factor in the sonication [i.e., the use of ultrasound to disrupt cells] of bacteria is the amount of solids present. Current research indicates that solids present in the solution directly influence the effectiveness of the disruption of the bacteria. Therefore, Justin and James hypothesized that increasing the amount of suspended solids will increase the effectiveness of the sonication. Samples of waste water were allowed to settle for 30 min. Then the amount of solids was varied and the samples were sonicated for a constant amount of time and amplitude. Finally, Fecal Coliform membrane tests were performed ten times to determine the amount of bacteria destroyed. The data showed that the hypothesis was wrong and that the amount of suspended solids did not affect the effectiveness of sonication. Further research will be conducted to aid the development of the sonication processes.