Abstract
The effect of on-off aeration control in term of ORP was studied for the nitrogen removal from sewage and night soil with the experiments conducted in bench and mini-plant scales.
The ORP was found to be as a function of ammonia concentration and to be a suitable barometer for the optimum on-off control of aeration in order to remove nitrogen. The nitrification and denitrification proceeded respectively when air .was applied and not, and the maximum removal of nitrogen was obtained at a certain ORP value which depended on the substrate concentration in the waste-water. The on-off aeration control in term of ORP was much more effective than in term of DO, because the rates of nitrification and denitrification is controlled more accurately by the former operation. The BOD/N substrate ratio was necessary to be 4 or more to remove 80% or more of nitrogen from the waste-water.
