We newly developed an anoxic-aerobic high sludge concentration activated sludge process which possessed an effective nitrification and denitrification performance using organic carbon in the wastewater as the hydrogen donor. Comparing with other developed nitrogen removal processes, our process has a different flow of mixed liquor and a high sludge concentration in the process.
By analysing the nitrification and denitrification reactions in the anoxic tank and aerobic tank kinetically, we graphically determined the kinetic parameters which were needed for the designing of this process. We established the design formulae for this process based on the mass balance in the anoxic tank and the aerobic tank. Using a bench scale experimental apparatus designed and constructed from these design formulae, we were able to verify the usefullness and applicability of these design formulae.
Finally, we made a practical plant test for 3 years using the domestic wastewater from separated sewer system and revealed the influences of various factors which effect the nitrogen removal efficiency.

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Septic waste has been usually treated with night soil, but the condition of the night soil treatment goes bad by degrees when a large quantity of the septic waste is added to night soil. Therefore exclusive operating facilities for the septic waste have come into construction in recent years, however, facilities have been constructed, are not many up to now so far as we know.
There are some effectsof the studies on the treatment of septic waste we have carried out by use of recirculating aeration and contact aeration processes with Alum coagulation process.
As to the characteristics of effluents from the facility we have operated, BOD values ranged from 4.4 to 1.6 mg/l and suspended solids values ranged from 4.4 to 2.9 mg/l

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[in Japanese]

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