GB1589275A

GB1589275A - Method of pumping sewage

Info

Publication number: GB1589275A
Application number: GB44056/76A
Authority: GB
Original assignee: CHITTENDEN J
Current assignee: CHITTENDEN J
Priority date: 1977-10-21
Filing date: 1977-10-21
Publication date: 1981-05-07

Description

(54) A METHOD OF PUMPING SEWAGE (71) 1, JEREMY BARROW CHITTENDEN, a British Subject, of Lytes Cary Manor, Lytes Cary, Somerton, Somerset, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the handling of sewage (including sewage sludge) by means of air lift pumps. Such pumps can be used to raise sewage through a small head, and one application of this is in the discharge of settled sludge from a settling tank under automatic control.

According to this invention there is provided a method of pumping sewage comprising: (i) providing pumping apparatus having an air lift pipe with an entry for sewage or sludge at a low point in the pipe, an air delivery pipe for delivering air to a low point in the air lift pipe, and a blocking member at the outlet to the air delivery pipe, the blocking member being biassed into a position obstructing air outflow from the delivery pipe and being displaceable by the pressure of air in the delivery pipe to reduce obstruction of outflow and thereby break up the air outflow from the delivery pipe, (ii) allowing sewage to flow into the air lift pipe through the said entry, and (iii) delivering air down the said delivery pipe so that it flows out through the said outlet into the sewage or sludge in the air lift pipe, thereby raising the sewage or sludge up the air lift pipe so that it overflows from the top thereof. Such a blocking member causes the air to be delivered into the sewage as a plurality of small bubbles, which in turn inhibits "coring" of sewage sludge, when this is the form of sewage being pumped, i.e.

without effecting any lifting of the sludge.

The blocking member may be biassed against the outlet end of the delivery pipe by a spring.

The apparatus may include timing means controlling the supply of air to the delivery pipe to provide periods of air outflow through the delivery pipe alternately with periods of at least reduced air outflow, and preferably complete interruption of the flow, both periods being predetermined or adjustable within at least part of the range from to 60 minutes. They may be in the range i- to 15 minutes. A minimum of 1 minute may be preferable, and the periods may both be within the narrow range of 2 to 10 minutes.

When sludge is being removed from a settling tank with walls which slope to a sludge outlet at the bottom of the tank, the periods of reduced or interrupted flow can inhibit coring within the sludge in the settling tank and allow sludge settled within the tank to level off at the base of the tank.

The timing means may include at least one timer which runs in a cycle during the course of which it determines a said period, and is then reset to its condition at the beginning of the period. Preferably this timer runs in a cycle during the course of which it determines a period of air delivery and a period of reduction or interruption thereof, the length of each period being adjustable independently of the other.

The method of the invention can be employed for removing sludge from a sewage settling tank having a sludge outlet at a low point in the tank connected to a said entry at a low point in said air lift pipe which rises to an upper outlet above the top water level of the settling tank, the method comprising allowing sludge to flow into the air lift pipe from the tank, and delivering air down the said delivery pipe, thereby raising sludge up the air lift pipe so that it overflows over the said upper outlet of the air lift pipe. The sewage pumping apparatus may be run for a limited timers sludge removal period-several times a day, suitably under the control of an automatic timer.

In cases where the apparatus has timing means to provide periods of air outflow through the delivery pipe alternately with periods of reduced or interrupted air outflow the periods of outflow may be longer than the periods of reduced or interrupted outflow.

The apparatus may have timing means operative, when the apparatus is produced into opertation at the start of each sludge removal period, to allow air outflow for a period (e.g.. of five minutes) then to cause a reduction and preferably a complete interruption of the air outflow for another period (e.g.. of five minutes also) and then to allow uninterrupted outflow for the remained of the time (which would constitute a substantially greater period) for which the pumping apparatus is run. This could be advantageous when the sludge is being removed from a settling tank with walls sloping to a sludge outlet at the bottom of the tank. The first period of air outflow would begin the discharge of sludge and would cause the siudge in the tank to start moving down the walls to the bottom of the tank.

This movement would continue during the period of reduction or interruption of the air outflow after which the removal of sludge from the tank could continue without further interruption for the remainder of the sludge removal period.

The invention may be used not only where it is required to move a bulk of sewage, but also where its pumping action is utilised in measuring equipment, e.g. for investigating the viscosity of sewage.

An embodiment of this invention will now be described with reference to the accompanying drawings wherein: Fig. 1 shows in cross section, diagrammatically, a sewage sedimentation tank and air lift pump; Fig. 2 is an enlarged cross section of the lower end of the air delivery pipe; Fig. 3 is a section on the line III--III; Fig 4 is a side view of the air supply means; Fig. 5 is an end view of the air supply means looking in the direction of the arrow A of Fig. 4; and Fig. 6 is a diagram showing the arrangement of the timers.

Referring first to Fig. 1 of the drawings, raw sewage is run into a sedimentation tank 2. A weir 4 around its top determines the top water level (t.w.l.) 6 in this tank. Nonfloating solids in the sewage tank sink to the bottom of thhe tank as sludge 8 (constituting a heavier fraction) which is periodically removed through an outflow pipe 10 leading from the bottom of the tank.

The pipe delivers into the bottom of an upright air lift pipe 12 which rises to just above the t.w.l. 6.. The t.w.l. thus defines a static equilibrium level for the sludge which has risen up inside the pipe 12.

The pipe 12 is surrounded by a sludge pit 22 from which sludge is drained away through a smudge pipe 23.

Air supply means, generally indicated at 16, iS connected to supply air to an air delivery pipe 18 extending down the pipe 12 to an outlet 20 at which there is fitted a valve assembly, as shown in Figs. 2 and 3.

The valve assembly has a cylindrical valve body 30 which constitutes a short end piece extending the pipe 18 at its outlet. The body 30 is secured to the lower end portion of the delivery pipe 18, e.g. by adhesive. Within the body 30 there is secured by means of adhesive a guide 32 which has three arms 34 supporting a central hub 36 in which a valve spindle 38 is slidingly received. The air flow passes through the spaces between the arms 34. The spindle 38 carries a blocking member in the form of a valve plate 40 whcih seats against an angled seat 42 and is biassed against this seat by a compression spring 44 which acts between the hub 36 and a retaining nut 46 on the spindle 38. The plate 40 is thus moveably attached to the body 30 and biassed into a position obstructing air outflow from the delivery pipe 18.

It can be displaced downwardly from this position by the pressure of air in the delivery pipe so that there is less obstruction of air outflow into the surrounding sewage. This movement of the plate 40 causes the air flow from the pipe 18 to be broken up and delivered into the sewage as a stream of small bubbles 21.

When it is required to remove sludge from the sedimentation tank 2, air is supplied to the tube 18 and rises up through the material in the pipe 12. At any moment there are a considerable number of small bubbles 21 in this material, decreasing its density so that it is forced up towards the level of a theoretical head which for sludge is at 24. However, the lip 26 of the pipe 12 is below this level, so the sludge spills over the lip 26 into the pit 22.

Referring next to Figs. 4 and 5 of the drawings the air supply means has an air compressor 51 driven by an electric motor 53. The compressor draws air in through a filter 55 and delivers-it into a manifold 54 to which are connected from one to four solenoid valves 56, (four are shown), a further solenoid valve 58, a pressure gauge 57, a valve 59 for the manual release of pressure when required, and a pipe 66 leading to an adjustable spill valve 65. The spill valve 65 and the solenoid valve 58 both deliver into a T-piece 68 from which air is exhausted to atmosphere through silencer 70.

Timers, fuses and any other electrical control equipment are housed in a box 73. The air delivery pipe 18 is connected to the outlet 75 of one of the valves 56 through such intermediate pipework as may be required.

A further pipe 18 for a further air lift can be connected to each of the remaining valves 56 (only as many valves 56 are fitted as are required) and/or if desired more than one pipe 18, (e.g. two pipes) can be connected to each valve 56.

When the compressor 51 is running, and the solenoid valve 58 is closed, the pressure in the manifold is determined by the spill valve 6$, This is adjusted to give a manifold pressure which causes air to be delivered from the or each pipe 18 to give the desired air lift pumping action.

If the solenoid valve 58 is opened air is vented from the manifold 54 and the pressure in the manifold 54 drops so that the outflow of air from the delivery pipe(s) into the sewage ceases.

Typically each air lift pipe 12 is of 8 to 10 ins internal diameter, each delivery tube 18 is of 1-2 ins internal diameter, and projects 6-10 ft. below the t.w.l. 6, the compressor pump delivers 40-60 cu ft./min of air at 10-25 p.s.i, and the lip 26 is set 3 to 8 ins above static level 6.

As seen from Fig. 6 there are several timers. The whole air supply means is under the control of a 24 hour multiset timer 75.

It brings the whole apparatus into operation at predetermined times: it supplies power to all other parts of the apparatus, for such intervals of time, and with such intervals between them as may be desired, the intervals being in units of 15 minutes. While power is being supplied by the timer 75 to the remainder of the apparatus, the motor 53 and compressor 51 run continuously, and the utilisation of the air supplied by the compressor is governed by further timers controlling the solenoid valves 56 and 58.

Timing means in the form of a dual-set timer 77 provides alternate periods of air flow through the delivery pipes 18 and of interruption of the flow. It runs in a cycle, and during the course of each cycle it runs for, and determines a period of air discharge during which valve 58 is closed, after which it runs for, and determines a period during which valve 58 is open, to vent the manifold 54 and interrupt air discharge. After this it has completed the cycle and returned to its condition at the beginning of the period of air discharge. The two periods in the cycle can be adjusted independently and can each be set to periods of t to 5 minutes, in units of 2 minute. The period of venting can also be set to zero, for continuous air flow through the delivery pipe.

Each solenoid valve 56 is under the control of an individual timer 79 which can be set to hold the valve open for anything between 0 to 120 minutes. The timers 79 allow pumping for lengths of time which differ amongst the several air lifts supplied.

Once the timer 75 has brought the apparatus into operation each timer 79 determines a period during which its associated valve 56 remains open and there is air outflow (alternating with interruption, through the action of the timer 77) from the air delivery tube 18 or group of such tubes connected to that valve 56.

The use of the various timers will be exemplified by considering four pairs of sewage settling tanks from which sludge is removed by respective air lifts, as shown in Fig. 1, the air delivery tubes 18 of each pair being connected to a respective one of the valves 56. Sludge removal is to be carried out four times a day. While removal is being carried out, the air lifts are to pump for periods of 4 minutes, with breaks of 1 minute in between. Pumping in this fashion is required for periods of 1 hours for two pairs of air lifts, 1 hour for one pair and 2 hours for the remaining pair. Accordingly the multiset timer 75 is set to run the apparatus for two hours at the four chosen times in the day. During each two hours the motor and compressor run continuously and the dual set timer 77 is set to periods of 4 and 1 minutes, to hold the valve 58 closed for 4 minutes, and then open it for 1 minute to interrupt the flow of air to the delivery tubes 18, and then reclose the valve for another 4 minutes and so on. The four timers 79 are set to periods of 1 hour, 12 hours and 2 hours respectively. At first during a two hour period all four valves 56 are open, after 1 hour one of the valves 56 is closed, and pumping continues only on the remaining three pairs of air lifts. After another L hour one pair only continues pumping, and at the end of the two hours the multiset timer 75 stops the compressor either just after the fourth timer 79 closes its valve 56, or just before it would have done so. All the timers 79 reset, ready for the next sludge removal.

WHAT I CLAIM IS:- 1. A method of pumping sewage comprising (i) providing pumping apparatus having an air lift pipe with an entry for sewage or sludge at a low point in the pipe, an air delivery pipe for delivering air to a low point in the air lift pipe, and a blocking member at the outlet to the air delivery pipe, the blocking member being biassed into a position obstructing air outflow from the delivery pipe and being displaceable by the pressure of air in the delivery pipe to reduce obstruction of outflow and thereby break up the air outflow from the delivery pipe, (ii) allowing sewage to flow into the air lift pipe through the said entry, and (iii) delivering air down the said delivery pipe so that it flows out through the said outlet into the sewage or sludge in the air lift pipe, thereby raising the sewage or sludge up the air lift pipe so that it overflows from the top thereof.

2. Method according to Claim 1 wherein the blocking member is biassed against the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. When the compressor 51 is running, and the solenoid valve 58 is closed, the pressure in the manifold is determined by the spill valve 6$, This is adjusted to give a manifold pressure which causes air to be delivered from the or each pipe 18 to give the desired air lift pumping action. If the solenoid valve 58 is opened air is vented from the manifold 54 and the pressure in the manifold 54 drops so that the outflow of air from the delivery pipe(s) into the sewage ceases. Typically each air lift pipe 12 is of 8 to 10 ins internal diameter, each delivery tube 18 is of 1-2 ins internal diameter, and projects 6-10 ft. below the t.w.l. 6, the compressor pump delivers 40-60 cu ft./min of air at 10-25 p.s.i, and the lip 26 is set 3 to 8 ins above static level 6. As seen from Fig. 6 there are several timers. The whole air supply means is under the control of a 24 hour multiset timer 75. It brings the whole apparatus into operation at predetermined times: it supplies power to all other parts of the apparatus, for such intervals of time, and with such intervals between them as may be desired, the intervals being in units of 15 minutes. While power is being supplied by the timer 75 to the remainder of the apparatus, the motor 53 and compressor 51 run continuously, and the utilisation of the air supplied by the compressor is governed by further timers controlling the solenoid valves 56 and 58. Timing means in the form of a dual-set timer 77 provides alternate periods of air flow through the delivery pipes 18 and of interruption of the flow. It runs in a cycle, and during the course of each cycle it runs for, and determines a period of air discharge during which valve 58 is closed, after which it runs for, and determines a period during which valve 58 is open, to vent the manifold 54 and interrupt air discharge. After this it has completed the cycle and returned to its condition at the beginning of the period of air discharge. The two periods in the cycle can be adjusted independently and can each be set to periods of t to 5 minutes, in units of 2 minute. The period of venting can also be set to zero, for continuous air flow through the delivery pipe. Each solenoid valve 56 is under the control of an individual timer 79 which can be set to hold the valve open for anything between 0 to 120 minutes. The timers 79 allow pumping for lengths of time which differ amongst the several air lifts supplied. Once the timer 75 has brought the apparatus into operation each timer 79 determines a period during which its associated valve 56 remains open and there is air outflow (alternating with interruption, through the action of the timer 77) from the air delivery tube 18 or group of such tubes connected to that valve 56. The use of the various timers will be exemplified by considering four pairs of sewage settling tanks from which sludge is removed by respective air lifts, as shown in Fig. 1, the air delivery tubes 18 of each pair being connected to a respective one of the valves 56. Sludge removal is to be carried out four times a day. While removal is being carried out, the air lifts are to pump for periods of 4 minutes, with breaks of 1 minute in between. Pumping in this fashion is required for periods of 1 hours for two pairs of air lifts, 1 hour for one pair and 2 hours for the remaining pair. Accordingly the multiset timer 75 is set to run the apparatus for two hours at the four chosen times in the day. During each two hours the motor and compressor run continuously and the dual set timer 77 is set to periods of 4 and 1 minutes, to hold the valve 58 closed for 4 minutes, and then open it for 1 minute to interrupt the flow of air to the delivery tubes 18, and then reclose the valve for another 4 minutes and so on. The four timers 79 are set to periods of 1 hour, 12 hours and 2 hours respectively. At first during a two hour period all four valves 56 are open, after 1 hour one of the valves 56 is closed, and pumping continues only on the remaining three pairs of air lifts. After another L hour one pair only continues pumping, and at the end of the two hours the multiset timer 75 stops the compressor either just after the fourth timer 79 closes its valve 56, or just before it would have done so. All the timers 79 reset, ready for the next sludge removal. WHAT I CLAIM IS:-

1. A method of pumping sewage comprising (i) providing pumping apparatus having an air lift pipe with an entry for sewage or sludge at a low point in the pipe, an air delivery pipe for delivering air to a low point in the air lift pipe, and a blocking member at the outlet to the air delivery pipe, the blocking member being biassed into a position obstructing air outflow from the delivery pipe and being displaceable by the pressure of air in the delivery pipe to reduce obstruction of outflow and thereby break up the air outflow from the delivery pipe, (ii) allowing sewage to flow into the air lift pipe through the said entry, and (iii) delivering air down the said delivery pipe so that it flows out through the said outlet into the sewage or sludge in the air lift pipe, thereby raising the sewage or sludge up the air lift pipe so that it overflows from the top thereof.

outlet end of the delivery pipe by a spring.

3. Method according to Claim 1 or Claim 2 wherein the delivery pipe has a relatively short end piece constituting an extension of it at its outlet, the blocking member being moveably attached to. the extension piece and biassed against the end of it.

4. Method according to any one of the preceding claims wherein the apparatus includes timing means controlling the supply of air to the delivery pipe to provide periods of air outflow through the delivery pipe alternately with periods of at least reduced air outflow, both periods being predetermined or adjustable within at least part of the range from 2t to 15 minutes.

5. Method according to any one of the preceding claims wherein the apparatus includes timing means controlling the supply of air to the delivery pipe to provide periods of air outflow through the delivery pipe alternately with periods of at least reduced air outflow both periods being predetermined or adjustable within at least part of the range from 1 to 60 minutes.

6. Method according to Claim 4 or Claim 5 wherein the range is from 2 to 10 minutes.

7. Method according to any one of Claims 4, 5 or 6 wherein the timing means includes at least one timer which runs in a cycle during the course of which it determines a said period, and is then reset to its condition at the beginning of the period.

8. Method according to Claim 7 wherein the timer runs in a cycle during the course which it determines a period of air delivery and a period of reduction or interruption thereof, the length of each period being adjustable independently of the other.

9. Method according to Claim 1, Claim 2 or Claim 3 wherein the apparatus includes timing means controlling the supply of air to the delivery pipe and operative when the apparatus is brought into operation to allow air outflow for a period, at least reduce outflow for another period and thereafter allow air outflow without interruption.

10. Method according to any one of Claims 4 to 9 wherein the periods - of at least reduced air flow are periods of complete interruption of flow.

11. Method according to any one of the preceding claims wherein the apparatus has a plurality of air lift pipes and a plurality of air delivery pipes for delivering air to respective air lift pipes, the apparatus having a timer to bring it into operation at predetermined times and a plurality of timing means each controlling the supply of air to an associated delivery pipe or group of delivery pipes to determine a period during which air outflow takes place therefrom when the apparatus is brought into operation by the timer.

12. A method according to any one of the preceding claims which is a method of removing sludge from a sewage settling tank having a sludge outlet at a low point in the tank connected to the said entry of the said air lift pipe, this pipe rising to an upper outlet above the top water level of the settling tank, the method comprising allowing sludge to flow into the air lift pipe from the tank, and delivering air down the said delivery pipe, thereby raising sludge up the air lift pipe so that it overflows over the said upper outlet of the air lift pipe.

13. A method according to Claim 12 as appendant to any one of Claims 4 to 8 wherein the periods of air flow are longer than the periods of at least reduced flow.

14. A method of removing sludge from a sewage settling tank substantially as herein described with reference to the accompanying drawings.