Lismore City Council solves sludge-pump choking problems

Lismore City Council was having chronic problems with its digester pump choking at its South Lismore sewage treatment plant.

The pump would choke on a daily basis during its job of turning over the digester, according to Matt Potter and Brad Hampson at the plant. They were using a Gorman-Rupp T3A3S-B self-priming sewage pump, but the sheer number of rags made it very difficult for even this excellent solids handling pump to pass all the rags, all the time.

Over the years, they tried different wear plates (even from different companies), but the best they could achieve was to limit choking to once or twice per week by installing one of Gorman-Rupp’s self-cleaning wear plates.

The council was then told of Gorman-Rupp’s new Eradicator Solids Management System and wanted to try it. The Eradicator system features an aggressive self-cleaning wear plate incorporating a number of notches and grooves, as well as a patent-pending lacerating tooth that helps break up stringy materials (such as rags), scrape them off the impeller vanes and pass them through the pump — all without impacting performance or interrupting service. A special cover plate with the system also includes a patented lightweight inspection cover that can easily be removed, if necessary, to inspect pump internals.

The Eradicator system is available on all Gorman-Rupp Super T Series pump models, so the range can achieve flows from 5 L/s through to 150 L/s and deliver heads to 40 metres, all while working on suction lifts to 7.6 m. Because they are self-priming pumps, the pumps can be located at ground level, giving operators easy and safe access to the pumps for monitoring and/or service, unlike submersible pumps which require cranes and several operators to access. And wet well lids stay closed with self-priming pumps so that operators are not exposed to falling into the wet well when anything needs to be done with the pumps. Clearance adjustments, oil changes and general inspections only take minutes, which adds up to massive savings in time over the life of the pump.

As the new system is available as an upgrade kit for existing Super T, Lismore council installed one of these into its existing Gorman-Rupp T3. The pump then ran for 3 months without a single choke. In the same period, they would have expected to have between 12 and 24 chokes. Potter, Hampson and their colleagues at the council were very pleased with the result.