GB2129698A

GB2129698A - Method and apparatus for processing waste solids

Info

Publication number: GB2129698A
Application number: GB08312588A
Authority: GB
Inventors: Nigel Ronald Cowley Shepherd
Original assignee: Haigh Engineering Co Ltd
Current assignee: Haigh Engineering Co Ltd
Priority date: 1982-11-08
Filing date: 1983-05-06
Publication date: 1984-05-23
Also published as: AU1730883A; AU557197B2; DE3327605A1; GB8312588D0; GB2129698B

Abstract

A method of disposing of screenings in a flow of effluent (10) includes collecting the screenings by means of a filter (11), passing the screenings to a macerator (14) and returning part of the outflow from the macerator (via 16) to the filter (11) to assist in removing the screenings from the filter. <IMAGE>

Description

SPECIFICATION Method and apparatus for processing waste solids This invention is concerned with solid waste disposal and in particular with the treatment of screenings, i.e. the foreign bodies that are removed from the effluent flow at an early stage in the treatment of the sewage.

It is an object ofthe present invention to provide a method of processing waste solids and especially screeningsthat is simple and efficient and which involves little dilution ofthe effluent.

The present invention is a method of processing waste solids comprising collecting the solids, passing the solids through a macerator and returning part of the discharge from the maceratorto assist in collecting the solids.

The present invention is also a solids processing plant comprising apparatus for collecting the solids, meansfor passing the collected solidsto a macerator and means for returning part of the outflow from the maceratorto assist in collecting the solids and passing them to the macerator.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which :- Fig. 1 diagrammatically illustrates the layout of the plant for processing screenings; and Fig. 2 is a perspective schematic view of a screen ingsprocessing plantaccording to the present inven- tion.

Referring nowto Fig. 1, effluent containing the screenings enters the screenings processing plant by means of a conventionaltrough or channel 10 and passes into a barscreen 11 orequivalentfiltering device. The effluent passes through the screen 11 and flows out ofthe plant by means of a discharge trough or channel 12 The screenings, consisting essentially of solid rubbish entrained in the effluentflow, is retained by the screen 11 from which it is collected into a tank 13.

The contents ofthetank 13 pass into a pumping macerator 1 4wherethe solids are ground into small particles. The discharge pipe from the pumping macerator 14 divides to deliver part of the discharge through a pipe 15 into the main discharge channel 12 (or if so required by the local water authorities, to the channel 10) and the rest of the discharge backthrough pipe 16to the screen 11 where it is used to wash the collected screenings from the screen into the tank 13.

It is usually also necessaryto add through pipe 17a quantityoffresh waterto assist in washing the screenings into the tank 13 and also to increase slightly the liquid content atthe inputto the macerator 14. The quantity of water added, however, is no more than is necessary to ensure satisfactory operation of the loop comprising tank 13, macerator 14 and tank 13.

Among the advantages of the plant according to the present invention relative to known screenings processing plants are that less fresh water is required, thatthe average particle size at the macerator outlet is smaller because of the increased number of transits through the macerator, that the resultant effluent outflow has a higher concentration of solids making subsequent dewatering steps easier, and thatthe macerator need be operated only intermittently. On this last point it is noted that the quantity of screenings varies considerably th roughout day and night but once the pattern of variation is knownatimermay be employed to operate the macerator intermittently to give, within acceptable limits, effluent with a constant solids content.

In a modified embodimentofthe present invention, the maceratordischargethrough line 15 is passed to a liquid separator rather than to either of channels 10 and 12.

Such an embodiment is illustrated in Fig. 2 in which the screenings are delivered at 20 from the filter into a trough 21 from which they pass into the tank 13. The macerator l4andtank 13 are mounted on a common base 22 and the macerator's inlet is connected directly into the tank 13. The macerator outlet pipe 23 splits into the pipe 16 which goes to the end of the trough 21 and the pipe 15which passesto a compartment 25 within the tank 13. Each ofthe pipes 15 and 16 includes a valve, 26 and 27 respectively, to control the respective flows and thereby the proportion of the macerator outlet flow which is returned to the trough 21.

The compartment 25 extends across the tank 13 and is triangular in cross section, being formed by an inclined plate 30 joined to the end wall ofthe tank 13 and the adjacent side walls. The plate 30 does not extend to the top of thetank and thus acts asaweirto return a more liquid fraction ofthe macerator output to the main body ofthetank. The inlet 33to a liquid separator 34 is taken to the bottom of the compartment 25 and thus the liquid separator is supplied with a more solid fraction ofthe macerator output. The liquid separator delivers at 40 a solid cake to a container 41 and at 12 its liquid output to join the liquid oufflowfrom the filter.

The fresh water supply 17 is supplied through a valve 50, pump 51 and pipe 52 to the end of the trough 21.

In this em bodiment the trough 21 is made of glass-reinforced plastics resin and the pipes 52 and 16 are used to support and reinforce the trough 21.

To assist in cleaning the apparatus the compartment 25 is provided with a normal closed aperture 55 at the bottom thereofthrough which sludge at the bottom of the compartment may be passed into the tank 13, while the tank 13 may itself be drained through a valve 56 into a tank 57 from which a pipe 58 leadsthrough a valve 59 to the inlet to the pump 51.

1. A method of processing waste solids comprising collecting the solids, passing the solids th rough a maceratorand returning partofthe discharge from the maceratorto assist in collecting the solids.

2. A method of processing screenings in a flow of effluent comprising filtering the screenings from the flow of effluent, passingthefiltered screenings

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method and apparatus for processing waste solids This invention is concerned with solid waste disposal and in particular with the treatment of screenings, i.e. the foreign bodies that are removed from the effluent flow at an early stage in the treatment of the sewage. It is an object ofthe present invention to provide a method of processing waste solids and especially screeningsthat is simple and efficient and which involves little dilution ofthe effluent. The present invention is a method of processing waste solids comprising collecting the solids, passing the solids through a macerator and returning part of the discharge from the maceratorto assist in collecting the solids. The present invention is also a solids processing plant comprising apparatus for collecting the solids, meansfor passing the collected solidsto a macerator and means for returning part of the outflow from the maceratorto assist in collecting the solids and passing them to the macerator. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which :- Fig. 1 diagrammatically illustrates the layout of the plant for processing screenings; and Fig. 2 is a perspective schematic view of a screen ingsprocessing plantaccording to the present inven- tion. Referring nowto Fig. 1, effluent containing the screenings enters the screenings processing plant by means of a conventionaltrough or channel 10 and passes into a barscreen 11 orequivalentfiltering device. The effluent passes through the screen 11 and flows out ofthe plant by means of a discharge trough or channel 12 The screenings, consisting essentially of solid rubbish entrained in the effluentflow, is retained by the screen 11 from which it is collected into a tank 13. The contents ofthetank 13 pass into a pumping macerator 1 4wherethe solids are ground into small particles. The discharge pipe from the pumping macerator 14 divides to deliver part of the discharge through a pipe 15 into the main discharge channel 12 (or if so required by the local water authorities, to the channel 10) and the rest of the discharge backthrough pipe 16to the screen 11 where it is used to wash the collected screenings from the screen into the tank 13. It is usually also necessaryto add through pipe 17a quantityoffresh waterto assist in washing the screenings into the tank 13 and also to increase slightly the liquid content atthe inputto the macerator 14. The quantity of water added, however, is no more than is necessary to ensure satisfactory operation of the loop comprising tank 13, macerator 14 and tank 13. Among the advantages of the plant according to the present invention relative to known screenings processing plants are that less fresh water is required, thatthe average particle size at the macerator outlet is smaller because of the increased number of transits through the macerator, that the resultant effluent outflow has a higher concentration of solids making subsequent dewatering steps easier, and thatthe macerator need be operated only intermittently. On this last point it is noted that the quantity of screenings varies considerably th roughout day and night but once the pattern of variation is knownatimermay be employed to operate the macerator intermittently to give, within acceptable limits, effluent with a constant solids content. In a modified embodimentofthe present invention, the maceratordischargethrough line 15 is passed to a liquid separator rather than to either of channels 10 and 12. Such an embodiment is illustrated in Fig. 2 in which the screenings are delivered at 20 from the filter into a trough 21 from which they pass into the tank 13. The macerator l4andtank 13 are mounted on a common base 22 and the macerator's inlet is connected directly into the tank 13. The macerator outlet pipe 23 splits into the pipe 16 which goes to the end of the trough 21 and the pipe 15which passesto a compartment 25 within the tank 13. Each ofthe pipes 15 and 16 includes a valve, 26 and 27 respectively, to control the respective flows and thereby the proportion of the macerator outlet flow which is returned to the trough 21. The compartment 25 extends across the tank 13 and is triangular in cross section, being formed by an inclined plate 30 joined to the end wall ofthe tank 13 and the adjacent side walls. The plate 30 does not extend to the top of thetank and thus acts asaweirto return a more liquid fraction ofthe macerator output to the main body ofthetank. The inlet 33to a liquid separator 34 is taken to the bottom of the compartment 25 and thus the liquid separator is supplied with a more solid fraction ofthe macerator output. The liquid separator delivers at 40 a solid cake to a container 41 and at 12 its liquid output to join the liquid oufflowfrom the filter. The fresh water supply 17 is supplied through a valve 50, pump 51 and pipe 52 to the end of the trough 21. In this em bodiment the trough 21 is made of glass-reinforced plastics resin and the pipes 52 and 16 are used to support and reinforce the trough 21. To assist in cleaning the apparatus the compartment 25 is provided with a normal closed aperture 55 at the bottom thereofthrough which sludge at the bottom of the compartment may be passed into the tank 13, while the tank 13 may itself be drained through a valve 56 into a tank 57 from which a pipe 58 leadsthrough a valve 59 to the inlet to the pump 51. CLAIMS

2. A method of processing screenings in a flow of effluent comprising filtering the screenings from the flow of effluent, passingthefiltered screenings through a maceratorand returning partofthe discharge from the maceratorto assist in collecting the screenings from the filter.

3. A method as claimed in claim 2, including returning partofthe macerator discharge into the main effluent discharge from the filter.

4. A method as claimed in claim 2, including returning part of the macerator discharge into the effluent before screening.

5. A method as claimed in claim 2, including returning part of the macerator discharge to a liquid separator.

6. A method as claimed in any preceding claim, including using fresh water to assist in collecting the screenings from the filter.

7. A solids processing plant comprising apparatus for collecting the solids, means for passing the collected solidsto a maceratorand meansfor returning part ofthe outflow from the maceratorto assist in collecting the solids and passing them to the macerator.

8. A screenings processing plant comprising filter apparatus for removing screenings from a flow of effluent, means for passing the filtered screenings to a macerator and means for returning part ofthe outflow from the maceratorto assist in collecting the screenings from a filter apparatus and passing them to the macerator.

9. A plant as claimed in claim 8, including means for returning part of the maceratoroutputtothe effluent discharge from the filter.

10. A plant as claimed in claim 8, including means for returning part of the macerator outputto the effluent before screening.

11. A plant as claimed in claim 8, including means for returning part of the macerator outputto a liquid separator.

12. Apparatus as claimed in any of claims8to 11, including means for supplying fresh water to the filter apparatustoassistin collecting screeningsfromthe filter.

13. A method of processing waste solids, substantially as hereinbefore described with reference to the accompanying drawings.

14. Asolids processing plant comprising appar atus for collecting the solids, substantially as hereinbefore described with reference to, and as shown in,the accompanying drawings.