Method for biological wastewater purification

Abstract

The invention relates to a method for carrying out biological purification of wastewater with the aid of activated sludge, in which the wastewater is introduced into a tank for phosphor elimination (P tank), then into an activated sludge tank (B tank) and then into at least one sedimentation and recirculation tank (SU tank), in which a number of operating cycles are carried out, including a sludge return phase, a recirculation phase, a pre-sedimentation phase and a draw-off phase (S phase, U phase, V phase, and A phase respectively), wherein the method further includes the elimination of settleable solids of the inflow, the storage of the produced primary and excess sludge and the reduction of the rising of the water level in the wastewater purification system by using an additional tank (S tank), wherein the S tank is hydraulically connected with the P tank, the P tank with the B tank, and the B tank with the at least one SU tank, wherein the wastewater is first introduced into the S tank, then into the P tank, then into the B tank and subsequently into the at least one SU tank, wherein in the S phase the thickened activated sludge is introduced from the at least one SU tank into the P tank, in the U phase the volume of the at least one SU tank is mixed, in the V phase the activated sludge is settled, and in the A phase the treated wastewater is flowing out of the system and wherein the settled sludge of the S tank is transported from time to time to another special treatment plant.

Claims

1. A method for carrying out biological purification of wastewater with the aid of activated sludge in a wastewater treatment system, the method comprising: introducing the wastewater first into a tank for elimination of settlable solids of the inflowing wastewater, the storage of produced primary and excess sludge, and the reduction of a rising of the water level in the wastewater purification system (the S tank); and then introducing the wastewater into a tank for biological phosphor elimination (the P tank), wherein the volume of the P tank is mixed permanently or intermittently; and then introducing the wastewater into an activated sludge tank that is ventilated (the B tank) and then into a sedimentation and recirculation tank (the SU tank), in which at least one operating cycle is carried out over the course of a day, the operating cycles including a sludge return phase (the S phase), a recirculation phase (the U phase), a pre-sedimentation phase (the V phase), and a draw-off phase (the A phase), wherein the P tank is hydraulically connected with the B tank, and, wherein the B tank is hydraulically connected with the SU tank, wherein the S tank is hydraulically connected with the P tank via one or more openings; wherein consecutively, in the S phase a thickened activated sludge is introduced from the at least one SU tank into the P tank, in the U phase the volume of the SU tank is mixed, in the V phase the activated sludge is settled, and in the A phase treated water is drawn off, a flow of treated wastewater passes through the at least one SU tank only in the A phase, a rising water level in the phases S, U and V is provided and, therefore, a wastewater treatment system discharge corresponding to the wastewater treatment system supply develops (filling up-principle), and, wherein the at least one SU tank is not in an aerobic condition, wherein excess sludge present in the P tank is transferred from the P tank to the S tank.

2. The method according to claim 1, wherein the activated sludge is pumped from the at least one SU tank into the P tank via a pipe connecting the at least one SU tank with the P tank.

3. The method according to claim 1, wherein the volume of the P tank is approximately V/3, with V being the volume of the SU tank.

4. The method according to claim 1, wherein the dimension of the tanks is selected based on the quantity and quality of the wastewater and on the evacuation of the stored sludge.

5. The method according to claim 1, wherein the excess sludge is taken out of the P tank by means of an airlift at a position being approximately at one third of the height of the wastewater relative to the bottom of the P tank.

6. The method according to claim 1, wherein the thickened activated sludge is pumped from the at least one SU tank into the P tank by means of an airlift.

7. The method according to claim 1, wherein the S, P, B, and SU tanks do not form a connected round or angled unity, but different hydraulically connected single tanks.

8. The method according to claim 1, wherein the mixing of the P tank and the at least one SU tank is performed with coarse air bubbles.

9. The method according to claim 1, wherein a sludge stored in the S tank is taken out therefrom and transported by means of a vacuum-operated tank car.

10. The method according to claim 1, wherein computer-controlled magnet vents are used to vent the B tank in the operation of the wastewater treatment system.

11. The method according to claim 1, wherein in the A phase an outlet for treated wastewater of the wastewater treatment system is closed in order to prevent the sludge from leaving the system.

12. The method according to claim 11, wherein the outlet does not comprise an electric closure, but comprises a closure with compressed air.

13. The method according to claim 1, wherein more than one SU tank is used, and the cycles carried out in the SU tanks are phase-shifted in relation to one another.

Description

(1) Further details of the present invention will emerge from the following drawings, which illustrate exemplary, non-limiting embodiments of the invention. In the drawings, an operating cycle (FIG. 1) and a wastewater treatment system (FIGS. 2-3) are shown:

(2) FIG. 1 shows an operating cycle for the SU tank and the associated water level in the SU tank. H.sub.0 is the water level in the SU tank at the start of the overflow. FIG. 1 also shows a possible operating of the P tank.

(3) FIG. 2 shows a schematic illustration of a wastewater treatment system (ground plan).

(4) FIG. 3 shows a vertical sectional view of the wastewater treatment system of FIG. 2.

(5) FIG. 1 shows the operating cycle for the SU tank and the associated water level in the SU tank, wherein time extends in horizontal direction from left to right. The course and function of the individual phases, i.e. S phase, U phase, V phase and A phase, have already been discussed above in greater detail. FIG. 1 also shows a possible operation of the P tank comprising three steps: mixing of the volume 11, sedimentation of the settleable solids 12 and drawing-off of the excess sludge 13.

(6) FIG. 2 shows a schematic ground plan of a wastewater treatment system, in which the following features are designated with the following reference signs:

(7) 1 flow from the S tank to the P tank

(8) 2 flow of the excess sludge from the P tank to the S tank

(9) 3 flow of thickened activated sludge from the SU tank into the P tank,

(10) 4 flow of the P tank volume to the B tank

(11) 5 flow of the B tank volume to the SU tank

(12) 6 outlet with an overflow and a closure with compressed air

(13) 7 airlift for the excess sludge

(14) 8 airlift for the thickened activated sludge

(15) FIG. 3 shows a vertical sectional view of the system of FIG. 2 (along a line which, in FIG. 2, extends between A-A). Q.sub.in signifies the flow of the wastewater introduced into the S tank, wherein Q.sub.out is the flow of the treated water flowing off the water treatment system. The thickened activated and aerated sludge flows from the SU tank into the P tank (flow 3) via an airlift 8. In order to mix the waste water in the P tank efficiently with the thickened activated sludge 9, the volume of the P tank is mixed permanently or intermittently. The mixture of waste water and sludge is then transferred into the B tank and further to the SU tank via one or more openings connecting the P tank with the B tank (flow 4) and the B tank with the SU tanks (flow 5), respectively. 8 signifies the airlift operation unit for operation of the S phase.

(16) The volume of the P tank is approximately V/3, with V being the volume of the SU tank. The SU tank is mixed in the U phase with coarse air bubbles 10.