Literature Review & Summary Report Design Basis Memorandum St. Johns River Water Management District Contract # SK940AA
BCI Project No. 19-15089 September 2007 Page 28
As with most mechanical dewatering technologies a filter press produces a relatively dry filter cake; as high as 35% solids by weight. This reduces the initial waste volume compared to a dilute dredge discharge pumping directly to a confined disposal area. This is sufficient solids content to truck or convey to a reuse or final disposal site.
A filter press is capable of dewatering a wide variety of sludge streams, and offers basic and durable operation. In addition, as with most mechanical dewatering systems, the need for settling basins, return water systems, and containment area restoration, as well as the piping and pumps to the settling area is eliminated.
A filter press typically uses a batch process that requires significant labor and operator effort. Lower process and production rates result compared to belt press technology. Filter presses are also susceptible to cloth blinding on most oily or “tacky” sludge streams.
The filter press functions as a secondary dewatering step, necessitating a pre-thickening step; usually accomplished by a conventional thickener or clarifier. This technology must be considered a step in a more complex process and is not applicable as a stand-alone dewatering system. Additionally, return water will likely need treatment to remove dissolved phosphates prior to reintroduction to the lake.
Belt Filter Press
The belt filter press is a continuous feed process typically requiring less labor and operator effort than a batch process. Additionally, higher sludge processing and production rates are noted when compared to filter press and centrifuge technologies. The filter press is thought to be the best technology for bio-solids and primary and secondary digested sludge, and offers basic and durable operation.
Filter cake is produced at sufficiently high solids content to truck or convey to a reuse or final disposal site. As with most mechanical dewatering systems the need for settling basins, return water systems, and containment area restoration, as well as the piping and pumps to the settling area is eliminated