PURIFYING WATER

"Lake water, the 'crib,' animation of operation of 'crib,' the pumping station. Removing sediment, settling tanks and animation showing operation, action of aluminum sulphate, sand and gravel filters, animation showing action, a filtration plant, cleaning sand, how water is contaminated, a safe well. Disinfecting water, chlorination plant, animation showing action of chlorine. Testing water, bacteriological laboratory, how tests are made." Ohio