Monday, October 17, 2011: 4:30 PM
L100 I (Minneapolis Convention Center)
Coagulant applications ranging from drinking water production to industrial waste treatment currently use inorganic chemicals and/or polymers. Costs and unwanted side effects from these chemicals have resulted in the study of naturally occurring, organic, inexpensive materials such as bacterial byproducts and plants. Indigenous knowledge and scientific studies suggests that the Opuntia genus of cactus may serve as a natural based coagulant for kaolin particles suspended in water. This project focuses on the use of the Opuntia ficus-indica as a potential coagulation tool for the separation of suspended bacteria (particularly Bacillus cereus, Bacillus anthracis, and Escherichia coli) and kaolin at high and low concentrations. Two distinct fractions of mucilage, a gelling (GE) and non-gelling (NE) were extracted from the cactus for studies. Through microscopy techniques, the surface characteristics of the extracted mucilage were studied and compared. Settling tests using kaolin and bacteria suspended in surrogate hard and soft waters demonstrated aggregation and increased settling times in the presence of mucilage. Ion concentration in the water was also observed to affect the settling and removal rates. Kaolin settling rate was observed to increase from 0.5 to 13.2 cm/min with mucilage treatments and flocculation of bacteria was observed in less than 10 minutes with high removal rates. Tests demonstrate that the two fractions of mucilage react differently under varying circumstances and suspension types. By testing both fractions of mucilage from the Opuntia ficus-indica the mechanism used in particle aggregation can be studied and the resulting knowledge can allow the mucilage to be applied according to its abilities. Mucilage is an ideal biomaterial for use as a coagulant because it is easy to grow, process, is biodegradable and avoids unwanted harmful side effects.