Effluent Sludge Filters

Filter Press

Sludge Reduction and Effluent Filtration

The massive disposal cost of effluent sludge by tankering, can easily be reduced by separating the sludge into its liquid and solids components. Once separated, the solids can be sent to landfill and the liquids sent to drain.

Usually, after about 1 year, the money you save can be put in the Bank!

AJM offers two simple solutions :-

  • Batch Basis — for smaller plants.
  • Continuous — for larger plants.

Principal of Operation of a Batch Basis, Fixed Volume Pressure Filter


Sludge Sludge is pumped into the filter as typically a 5% solids slurry. This is reduced to around a 55% dry solids filter cake which is suitable for landfill.

Filter Press x280


  Sludge filter used on the spent latex effluent from a carpet factory.





AvesFP x280

At a stainless steel manufacturer, the steel is pickled in a mixture of hydrofluoric and hydrochloric acid. The spent acid and rinse waters are then treated in an effluent treatment plant which neutralises the acid and precipitates metal hydroxide sludge. Flocculent is added to this sludge to aid settlement, by gravity, in a conical base thickener vessel. The clear liquor overflow from the thickener is discharged to drain. Before installing in house sludge de watering the thickened sludge was removed at great expense, by road tankers for de-watering off site.

The solution

The solution was to install a filter press which increases the 4% solids content sludge in the thickener to a 60% solids filter cake which is firm enough for landfill. The filter press operates on a 4-hour cycle and being a batch filter, it is filled from a sludge holding tank by means of a positive displacement pump. When the press, which holds 3.5 tons of solids, is full, an operator supervises the automatic cake discharge and then prepares the filter for the next batch.

The payback period for the plant was less than 9 months.



A well known International Chemical Company have an effluent treatment plant which incorporates continuous neutralisation of spent acid from the various dyestuffs and intermediate manufacturing plants which are operated on the site. The spent acid is treated with milk of lime solution which, when reacted, forms a gypsum slurry that requires de-watering. The slurry volume can be in excess of 25m3 ( 6,875 US galls ) per hour, so batch type pressure filters as above were unacceptable because of the heavy labour and buffer storage requirement.

The solution

a continuous vacuum belt filter which produces a cake with around 65% solids content and a filtrate suitable for discharge into the local sewer. The only labour requirement is the occasional check by a plant operator to ensure that all is well. This particular filter has all polypropylene wetted parts mounted on a grade 304 stainless steel framework.

Truly a case of fit and forget.

AJM / Polyfilters offer effluent reduction solutions to companies manufacturing products as diverse as: printed circuit boards, chemicals, carpets, roof tiles and dairy products.
Other applications include building site run off waters and lagoon clearance.