<Li> Pre-chlorination for algae control and arresting biological growth </Li> <Li> Aeration along with pre-chlorination for removal of dissolved iron when present with small amounts relatively of manganese </Li> <Li> Coagulation for flocculation or slow - sand filtration </Li> <Li> Coagulant aids, also known as polyelectrolytes--to improve coagulation and for more robust floc formation </Li>

Which of the following processes is not used in a conventional method of water treatment