Method and system for cleaning filter media support structures
The present invention is related to a method and system for cleaning a media support structure in a filter cell in a liquid filter system, wherein a cleaning solution does not significantly enter a filter media zone. The method comprises supplying a cleaning solution to a filter cell to a level sufficient to submerge the media support structure, but not to significantly enter the filter media zone. Additionally, the cleaning solution level is monitored to ensure the cleaning solution does not significantly enter the filter media zone. Alternatively, the cleaning solution may be continuously recirculated and reintroduced to the filter cell during the cleaning operation.
1. A method for cleaning fouling or scaling from a filter media support structure in a filter system having at least one filter cell, the filter media support structure underlying a zone of filter media, the method comprising the steps of:
draining a feed liquid from the filter cell, but leaving at least a substantial portion of the filter media in the filter cell;
supplying a cleaning liquid to the filter cell in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone; and
removing the cleaning liquid from the filter cell;
wherein the fouling comprises a biological fouling and further wherein the filter media support structure underlies a zone of filter media having desirable biologic constituents; still further wherein the step of removing the cleaning liquid from the filter cell comprises removing the cleaning liquid without substantially reducing the amount of desirable biologic constituents in said filter media zone.
2. The method of claim 1 , further comprising the step of soaking the filter the media support structure in the cleaning liquid.
3. The method of claim 1 , wherein the step of supplying a cleaning liquid to the filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises mixing backwash water with a cleaning agent to produce the cleaning liquid.
4. The method of claim 1 , wherein the step of supplying a cleaning liquid to the filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises supplying the liquid from above the filter media zone.
5. The method of claim 1 , wherein the step of supplying a cleaning liquid to the filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises supplying the cleaning liquid via a liquid delivery conduit which extends from a top portion of the filter media zone to a bottom portion of the filter media zone at a point above the media support structure.
6. The method of claim 1 , wherein the step of supplying a cleaning liquid to the filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises supplying the cleaning liquid via a pipe grid.
7. The method of claim 1 , wherein the step of supplying a cleaning liquid to the filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises supplying the cleaning liquid to one or more points located in an underdrain system.
8. The method of claim 1 , wherein the step of supplying a cleaning liquid to the filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises supplying the cleaning liquid to one or more points located in a flume chamber.
9. The method of claim 1 , wherein the step of supplying a cleaning liquid to a filter system in an amount sufficient to submerge the media support structure, but not to significantly enter the filter media zone comprises supplying the cleaning liquid through a pipe connected to a flume chamber selected from the group consisting of a backwash pipe and an effluent pipe.
10. The method of claim 1 , further comprising the step of, prior to draining, monitoring an amount of fouling in the media support structure.
11. The method of claim 10 , wherein the step of monitoring the amount of fouling comprises measuring a pressure drop across the media support structure.
12. The method of claim 1 , further comprising the step of monitoring the level of cleaning liquid in the filter cell.
13. The method of claim 12 , wherein the step of monitoring the level of cleaning liquid in the filter cell comprises monitoring the level of liquid by means of a level sight tube.
14. The method of claim 12 , wherein the step of monitoring the level of cleaning liquid in the filter cell comprises monitoring the flow of cleaning liquid into an overflow structure selected from the group consisting of an overflow pipe and an overflow weir.
15. The method of claim 1 , further comprising the step of, after removing the solution, reclaiming the cleaning liquid.
16. The method of claim 15 , wherein the step of reclaiming comprises one or more of the following: removing solid fouling material from the cleaning liquid; filtering the cleaning liquid; decanting the cleaning liquid; increasing a pH of the cleaning liquid; and decreasing a pH of the cleaning liquid.
17. The method of claim 1 , wherein the cleaning liquid comprises one or more of the group consisting of chlorine, hydrochloric acid, sodium hydroxide and combinations thereof.
18. The method of claim 1 , after supplying the cleaning liquid to the filter system, further comprising the step of agitating the cleaning liquid.
19. The method of claim 18 , wherein the step of agitating the liquid comprises agitating by air scour.
20. The method of claim 1 , after removing the solution, further comprising the step of backwashing the filter cell.
21. A method for cleaning a filter media support structure in a filter system having one or more filter cells, the filter media support structure underlying a zone of filter media, the method comprising the steps of:
draining a feed liquid from a filter cell, but leaving at least a substantial portion of the filter media in the filter cell;
supplying a cleaning liquid to the filter cell via a cleaning liquid supply system;
recirculating the cleaning liquid to the cleaning liquid supply system for reintroduction to the filter cell;
monitoring a level of the cleaning liquid in the filter cell; and
controlling, while recirculating the cleaning liquid, the level of cleaning liquid in the filter cell such that the amount of cleaning liquid in the filter cell is sufficient to submerge the filter media support structure, but not to significantly enter the filter media zone.
22. The method of claim 21 , wherein the step of controlling the level of solution in the filter cell comprises measuring a pressure at one or more points in the filter cell, and adjusting the amount or composition of the cleaning liquid being supplied to the filter cell based on the at least one pressure measurement.
23. The method of claim 21 , wherein the step of controlling the level of cleaning liquid in the filter cell comprises monitoring the flow of cleaning liquid into an overflow structure selected from the group consisting of an overflow pipe and an overflow weir.
24. The method of claim 21 , further comprising the step of, during recirculation, reclaiming the recirculated cleaning liquid.