GB2060422A

GB2060422A - Automatic circulation in waste water pumping stations

Info

Publication number: GB2060422A
Application number: GB8033082A
Authority: GB
Original assignee: Deutsche ITT Industries GmbH; ITT Industries Inc
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1979-10-23
Filing date: 1980-10-14
Publication date: 1981-05-07
Also published as: IT8025494A0; IT1193560B; DE3039216A1; DK446580A; JPS5666474A; NL8005675A; FR2467922A1; FI802414A; NO803100L; GB2060422B; AR226192A1; FR2467922B1; SE7908743L; AU6348080A; AU541992B2

Abstract

In the outlet (5) from a pump unit (4) a valve (7) is provided which opens a outlet (9) between the pump outlet (5) and the bottom of the pumping station (1). The valve (7) is controlled electrically or hydrostatically for a predetermined time at the commencement of each pumping operation to disturb and mix-up the sludge with the pumped liquid. <IMAGE>

Description

SPECIFICATION Automatic circulation in waste water pumping stations The invention relates to a waste-water pumping station, such as one which is a part of a municipal sewage system.

In a pumping station, which also serves as a storage chamber for waste water, banks of sludge will occur at the bottom as well as by the water surface. These banks occur more frequently when the water velocity is low and pumping intervals are long.

A microbiological breaking down of the sludge takes place the speed of which depends on the temperature. When the oxygen has been used, a fermentative process takes place producing H2S (hydrogen sulphide), CH4 (methane) etc. Acid is also produced which results in a lower pH value.

Hydrogen sulphide smells and is also poisonous.

Mortal accidents have occurred by service works in hydrogen sulphide filled pumping stations.

The hydrogen sulphide produces, together with oxygen, sulphuric acid having a pH value near 1.

This means heavy corrosion damage on details above the water surface such as electrical equipment and armature. In addition to this the pipe system corrodes when the water is pumped through. Pipes made of concrete may collapse because of corrosion and so block the connection.

The methane gas can easily be set on fire causing explosions. In order to prevent that it has been necessary to use expensive explosion proof installations.

In order to prevent sludge banks from occurring the pumping stations are flushed with clean water at regular intervals so that the sludge banks are broken down and mixed in the water.

This method to get rid of septic sludge is however very expensive as the sludge becomes septic after 4-6 hours in Northern Europe and within 1-3 in a tropic climate.

According to the present invention there is provided a method of operating a waste water pumping station containing one or more pump units, including the step of automatically opening a bypass means so that for at least one predetermined period of time during a pumping operation the pumped liquid recirculates in the pumping station to disturb and mix sludge lying at the bottom of the pumping station with the liquid being pumped, closing the bypass means at the end of said period, and continuing with the pumping operation.

The invention is described more closely below with reference to the enclosed drawings, in which: Fig. 1 shows a pumping station provided with a valve according to an embodiment of the invention, Fig. 2 shows a pumping station where the valve is arranged differently, according to another embodiment, Fig. 3 shows a suitable valve having a special kind of control device, and Fig. 4 shows a further embodiment of a valve suitable for use in the pumping station of Fig. 1 or Fig. 2.

In the Figures 1 stands for a pumping station having an inlet 2 and outlet 3; 4 stands for a submersible pump having an outlet 5 connected to a discharge unit 6 on the outlet pipe 3; 7 stands for a valve with a central device 8, outlet (spreader) 9 and outlet pipe or return pipe 10; 11 and 12 stand for water levels; 13 stands for a valve piston; 14 a rollmembrane; 1 5 a levelling tank; 1 6 a partition wall; 1 7 a return spring; 18 a valve needle; 19 a valve rod; 20 a pipe; 21 a connection pipe; 22 a valve plate and 23 a lever.

In Fig. 1 a conventionally equipped pumping station 1 is provided with a device according to the invention. According to the previous known method the pump 4 starts when the water level reached 1 The pump then works till the level 12 has been reached and restarts when the level 11 has been reached again. Valve 7 is connected to the outlet 5 of the pump 4. When the pump starts, the valve is open which means that the pumped medium flows back into the pumping station 1 and creates a strong current and mixing therein, thus homogenizing the pumped medium.

After a certain time the valve is closed and the medium is pumped through the outlet 3 in the usual way till the level 12 has been reached. The valve is then reopened and remain in this position till the next pump start.

In Fig. 2 another connection of the valve according to the invention is shown. When the valve 7 is open, the pumped medium flows back into the pumping station through the pipe 10 which ends near the bottom, where the sludge banks occur. In every other respect this device works in the same way as the device according to Fig. 1.

The valves described above are controlled electrically. In Fig. 3 a hydrostatically controlled valve is shown which works in the following way: When the pump starts the valve is open leaving an open connection between the pump outlet and the pumping station so that a return flow, described above, is obtained. The piston 13 is then in its upper position influenced by the spring 1 7.

The roll membrane 14 is pressed downwards by the pressure in the pipe 20 which is connected to the pump outlet. The speed of the downward movement, the closing time, is determined by a needle valve device where a leakage hole in a partition wall and the needle 1 8 cooperate. The closing speed may be varied by a waist on the needle. When the piston 1 3 has reached its lower position the connection pipe 21 is closed and remains so as long as the pump works. When the pump stops, the pressure in the pipe 21 decreases and the spring 1 7 presses the rollmembrane 14 and the piston 1 3 back to their original positions for a new mixing-pumping cycle.

In the embodiment shown in Fig. 4 the valve is formed like a two-way turnable valve arranged in the outlet 3. When the pump starts, the outlet is closed by the means 22, while the port to the return pipe 10 is open. The fluid is then flowed through the rotatable spreader pipe 9. The driving unit 8, which is controlled by a time relay, will, after a certain time, turn the means 22 so that the port to the return pipe is closed, while the port to the outlet is open.

Claims

1. A method of operating a waste water pumping station containing one or more pump units, including the step of automatically opening a bypass means so that for at least one predetermined period of time during a pumping operation the pumped liquid recirculates in the pumping station to disturb and mix sludge lying at the bottom of the pumping station with the liquid being pumped, closing the bypass means at the end of said period, and continuing with the pumping operation.

2. A method according to claim 1 wherein the bypass means is always open at the commencement of each pumping operation.

3. An automatic liquid recirculation arrangement for a waste water pumping station comprising one or more pump units and bypass means connected to the pump outlet whereby, when the bypass means is opened, pumped liquid is recirculated in the pumping station to disturb and mix sludge lying at the bottom of the pumping station with the liquid being pumped, and means for opening the bypass means for at least one predetermined period of time during each pumping operation.

4. An arrangement according to claim 3 wherein said bypass means is arranged to be open at the commencement of each pumping cycle.

5. An arrangement according to claim 3 or 4 wherein the bypass means comprises an electrically controlled valve arranged in the outlet of the pump.

6. An arrangement according to claim 3 or 4 wherein the bypass means comprises a hydrostatically controlled valve arranged in the outlet of the pump.

7. An arrangement according to claim 6 wherein the valve includes a cylinder having a flexible membrane influenced by a spring connected to the valve to maintain the valve in an open condition against a reduced pump outlet pressure and pressure control means arranged to allow pressure build-up against the membrane to overcome the spring after a time interval to cause the valve to close.

8. An arrangement according to claim 5, 6 or 7, wherein the valve is positioned in the outlet pipe from the pump.

9. An arrangement according to any one of claims 3-8, wherein the bypass means is located above the maximum water level and is provided with a return outlet pipe ending adjacent the bottom of the pumping station.

10. An arrangement according to any one of claims 3-9 wherein the bypass means outlet is movable to direct the recirculated liquid in different directions.

11. An arrangement according to claim 5, 6 or 7, wherein the valve is a turnable two-way valve.

12. An automatic liquid recirculation arrangement for a waste water pumping station substantially as described with reference to the accompanying drawings.

13. A waste water pumping station having a recirculation arrangement substantially as described with reference to the accompanying drawings.