I operate a treatment plant with a flow rate of 1.8 MGD that utilizes two Nexom cloth disk filter units. We are currently experiencing an issue with floating sludge accumulating on the surface of the filter basin, as shown in the attached photo.

Upstream of the disk filters, the process includes a SAF (Surface Air Flotation) unit, designed to float solids for removal in a manner similar to a DAF system. However, when effluent from the SAF enters the disk filters, fine particulates and residual solids carried over from the SAF tend to rise to the surface rather than remain in suspension. This behavior appears to be driven by residual surfactant from the SAF process, which promotes flotation of these solids. I've also tried an anti foam which works in our final effluent discharge but I believe it doesn't have enough reaction/mixing time before it reaches the disc filters. I am dosing it after the SAF.

At present, the only method we have to remove this floating material is manual skimming using a pool skimmer net. While effective to some extent, this approach is labor-intensive and not sustainable long-term. The solids themselves are very light and fluffy, which suggests they should be relatively easy to remove mechanically if an appropriate method is used.

I have been investigating automated pool-style surface skimmers with a weir and pump arrangement as a potential solution. However, most of the available options still appear to require significant maintenance, particularly frequent manual emptying of the collection basket or container. Ideally, we are looking for a low-maintenance or continuous removal solution suitable for this type of floating material.

Any advice I can get from fellow operators would be a huge help. Thanks!

Disk filter solids skimmer