nitrogen

carbon dioxide

hydrogen sulphide

methane

parasitic

saprophytic

pathogenic

anaerobic

reducing the excessive flow in sewers

disposing of sludge

increasing the capacity of storage re-servoirs

increasing flow of sewage through imhoff tanks

oxidation

dehydration

reduction

alkalinization

starch iodide method

orthotolidine method

both starch iodide method and orthotolidine method

none of the above