Method for biological wastewater purification with phosphorous removal

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 an activated sludge tank (B tank) and then, in alternation, into one of a number of sedimentation and recirculation tanks (SU tanks) continuously connected hydraulically to the B tank and in which a number of operating cycles are carried out, including a sludge return phase, a mixing phase, a sedimentation phase and a draw-off phase (S phase, U phase, V phase, and A phase respectively), wherein the method further includes elimination of phosphor by using a tank for biological phosphor elimination (P tank), wherein the P tank is hydraulically connected with the B tank via one or more openings, wherein the wastewater is first introduced into the P tank and then subsequently transferred into the B tank, wherein in the S phase at least part of the thickened activated sludge is introduced from the SU tank into the P tank, and, wherein the volume of the P tank is mixed permanently or intermittently.

Claims

1. A method for carrying out biological purification of wastewater with the aid of activated sludge, the method comprising: providing an activated sludge tank that can be ventilated (the B tank); providing at least two sedimentation and recirculation tanks (the SU tanks), which are continuously connected hydraulically to the B tank and in which a number of operating cycles are 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); and providing a tank for biological phosphorus elimination (the P tank), wherein the P tank is hydraulically connected with the B tank via one or more openings, wherein the wastewater is first introduced into the P tank, in which the volume of the P tank is mixed permanently or intermittently with activated sludge and phosphorous is eliminated from the wastewater, and then the wastewater is subsequently transferred from the P tank into the B tank, and then from the B tank, in alternation, into the SU tanks, wherein consecutively, in the S phase at least part of a thickened activated sludge is introduced from the SU tank into the P tank, in the U phase the activated sludge is again mixed with the wastewater, in the V phase the activated sludge is sedimented, and in the A phase treated water is drawn off, wherein in the SU tanks the cycles are phase-shifted in relation to one another, the A phases are temporally adjacent to one another, a flow passes through the SU tanks only in the A phases, an approximately constant water level is provided, and therefore a wastewater treatment system discharge corresponding to the wastewater treatment system supply develops (continuous flow principle), wherein, when the SU tanks are arranged side by side on one side of the B tank, the P tank is arranged in one case on a side of the B tank opposite of the side where the SU tanks are arranged and in a second case between the SU tanks and the B tank, and, when the SU tanks are arranged on opposite sides of the B tank, the P tank is arranged in one case in the middle of the B tank and in a second case between the SU tanks and the B tank, and wherein the SU tanks are not in an aerobic condition.

2. The method according to claim 1, wherein excess sludge is received by the P tank.

3. The method according to claim 1, wherein the activated sludge flows from the SU tanks into the P tank by means of a pipe connecting the SU tanks with the P tank.

4. The method according to claim 1, wherein the width of the P tank is approximately L/6, with L being the width of the SU tanks.

5. The method according to claim 1, wherein the wastewater and the thickened activated sludge in the P tank are mixed by producing a flow in a longitudinal direction at the water level and a flow in an opposite direction at the bottom of the P tank.

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.) and wastewater treatment systems representing the S phase (FIGS. 2-6) are shown:

(2) FIG. 1 shows an operating cycle for the two SU tanks shown in the exemplary embodiments;

(3) FIG. 2 shows a schematic illustration of a wastewater treatment system, in which the SU tanks are arranged side by side on one side of the B tank and the P tank is arranged on a side of the B tank opposite of the side where the SU tanks are arranged.

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

(5) FIG. 4 shows a schematic view of a module of a large waste water treatment plant, in which the SU tanks are arranged on opposite sides of the B tank and the P tank is arranged in the middle of the B tank.

(6) FIG. 5 shows a schematic illustration of a wastewater treatment system, in which the SU tanks are arranged side by side on one side of the B tank and the P tank is arranged between the SU tanks and the B tank.

(7) FIG. 6 shows a schematic view of a module of a large waste water treatment plant, in which the SU tanks are arranged on opposite sides of the B tank and the P tank is arranged between the SU tanks and the B tank.

(8) FIG. 1 shows the operating cycle for the two SU tanks SU.sub.1 and SU.sub.2 shown in the exemplary embodiments, 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.

(9) FIG. 2 shows a schematic illustration of a wastewater treatment system, in which the two SU tanks SU.sub.1 and SU.sub.2 are arranged side by side on one side of the B tank and the P tank is arranged on a side of the B tank opposite of the side where the SU tanks SU.sub.1 and SU.sub.2 are arranged. FIG. 3 shows a vertical sectional view of the system of FIG. 2 (along a line which, in FIG. 2, extends horizontally through the system of FIG. 2). Q.sub.in signifies the flow of the wastewater introduced into the P tank, wherein Q.sub.out is the flow of the treated water flowing off the water treatment system. The thickened activated and aerated sludge 3 flows from the SU tanks SU.sub.1 and SU.sub.2 into the P tank via a pipe 1. In order to mix the waste water in the P tank efficiently with the thickened activated sludge 3, 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 tanks SU.sub.1 and SU.sub.2 via one or more openings 2 connecting the P tank with the B tank and the B tank with the SU tanks SU.sub.1 and SU.sub.2, respectively. 5 signifies the airlift operation unit for operation of the S phase. The width of the P tank is approximately L/6, with L being the width of the SU tanks SU.sub.1 and SU.sub.2.

(10) FIG. 4 shows a schematic view of a module 10 of a large waste water treatment plant, in which the SU tanks SU.sub.1 and SU.sub.2 are arranged on opposite sides of the B tank and the P tank is arranged in the middle of the B tank. Q.sub.in signifies the flow of the wastewater introduced into the P tank, wherein Q.sub.out is the flow of the treated water flowing off the water treatment system. The thickened activated and aerated sludge 13 flows from the SU tanks SU.sub.1 and SU.sub.2 into the P tank via pipes 11. In order to mix the waste water in the P tank efficiently with the thickened activated sludge 13, the volume of the P tank is mixed permanently or intermittently. The P tank is constructed in the form of a circulation tank ensuring efficient mixing of waste water and sludge. The mixture of waste water and sludge is then transferred into the B tank and further to the SU tanks SU.sub.1 and SU.sub.2 via one or more openings 12 connecting the P tank with the B tank and the B tank with the SU tanks SU.sub.1 and SU.sub.2, respectively.

(11) FIG. 5 and FIG. 6 show alternative arrangements of the arrangements of FIG. 2 and FIG. 4, wherein the P tank is situated between the SU tanks and the B tank.