Static Mixers for Coagulation and Disinfection

Book excerpt: Static mixers are an attractive alternative for the mixing of chemicals in water treatment plants. The attraction comes from the fact that static mixers do not require an external input of energy and do not have moving parts. Static mixers consist of mixing elements fixed on the inside of a pipe of channel. The elements do not move. Chemicals, added just upstream of the mixers, mix with the bulk fluid because of the complex, three-dimensional fluid motion generated by the elements. The goal of this project is to explore the use of static mixers in two of the key processes in drinking water treatment: for the mixing of coagulants for destabilization and the mixing of disinfectants for the inactivation of Cryptosporidium parvum oocysts in disinfection. The role of mixing in both of these processes is not well understood. But for each process experimental and theoretical evidence suggests that, at least in some circumstances, the mixing environment provided when chemicals are introduced into the flow will affect the resulting destabilization or inactivation.