| 摘要 |
<p>PURPOSE:To suppress nitrification of waste water contg. nitrogen compd. without decreasing the rate of BOD removal in an aeration tank by subjecting the waste water to an activated sludge treatment, and adding an acid to the return sludge to control the pH of the return sludge to 4.5-2. CONSTITUTION:Water A to be treated is pumped 6 through pipings 7, 8 to an aeration tank 2. The water A in the tank 2 is aerated under mixing with activated sludge by the air diffused from a perforated air diffusion pipe 10. The aerated water overflows from said tank and is introduced through a piping 11 into a settling tank 3. Supernatant liquid and concd. sludge are separated in said tank, and the separated activated sludge C is drawn out from the bottom part. Part thereof is discharged as excess sludge C' to the outside of the system and the greater part is pumped 12 through pipings 13, 14 into an acid adding tank 5. A pH controller 18 is provided in the tank 5 and the pH in the tank is maintained at 4.5-2 by controlling a pump 15.</p> |
