Method and apparatus for biological wastewater purification
A biological wastewater is mixed in an activated sludge tank with activated sludge that is concentrated in the activated sludge tank to a predetermined value. The mixture of wastewater and activated sludge running off in a drain of the activated sludge tank is then sieved to effect an incomplete solid/liquid separation that leaves a separated solid phase in the activated sludge tank. The liquid phase including a remnant of solids is then removed from the tank.
1. A method of biological wastewater purification comprising the steps of:
mixing wastewater in an activated sludge tank with activated sludge,
concentrating the activated sludge in the activated sludge tank to a predetermined value,
sieving the mixture of wastewater and activated sludge running off through a sieve belt at a drain of the activated sludge tank to effect an incomplete solid/liquid separation,
leaving a separated solid phase in the activated sludge tank, and
removing a liquid phase including a remnant of solids.
2. The method according to claim 1 wherein the solid/liquid separation takes place by filtration conducted in such a manner that a part of the undissolved substances is removed with the liquid phase.
3. The method according to claim 1 , further comprising the step of:
establishing a dry substance content of 4 to 8 g/l in the activated sludge tank.
4. The method according to claim 1 , further comprising the step of
conducting the liquid phase into a secondary clarification tank.
5. The method according to claim 1 wherein it is a membrane-activated sludge method.
6. The method according to claim 5 wherein a dry substance content of 8 to 20 g/l is established in the activated sludge tank.
7. An apparatus for biological wastewater purification, the apparatus comprising:
an activated sludge tank comprising an inlet and an outlet, and
an endless sieve belt for incomplete solid/liquid separation at the outlet.
8. The apparatus according to claim 7 wherein the apparatus for the solid/liquid separation comprises a fabric.
9. The apparatus according to claim 7 , further comprising
a secondary clarification tank downstream of the activated sludge tank.
10. The apparatus according to claim 7 wherein the activated sludge tank is a membrane-activated sludge reactor.