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Dewatering / Som-A-Press / Paybacks / Dewatering Technology / Sludge Thickening
Sludge thickening with Somat presses
Reduce volume and save!
The use of the phrase "thickening" within the sludge dewatering market, implies that the final dewatered product is still in a free flowing liquid state. With
municipal sludges, the solids percentage which allows this free flowing form ranges from 5% to 8% solids, depending upon the sludge type. With total solids values higher
than this, the dewatered product becomes more of a sludge cake, and special handling hardware is necessary, such as conveyors and specialized cake pumps. "Thickening" allows the
plant operator to realize significant volume reduction savings while still allowing the use of standard centrifugal and positive displacement pumps, storage tanks, tank hauling and land application techniques.
The Somat Sludge Thickening system varies slightly in design from our dewatering system. With a Thickening system, the Sludge Feed Pump is integral in the proper balance of the system. While thickening sludge, the sudge feed pump is
the device that provides the motive force for moving the thickened sludge through the press. In a Dewatering application, where sludge cake is being discharged, the rotation of the auger is responsible for moving and
lifting the biosolids up and out of the press. In a Thickening application, the Sludge Feed Pump actually pumps the biosolids up through the press. The rotation of the auger, with its brushed flighting, is only responsible for cleaning
the cylindrical screen, to regulate how much free water is released through the screen. Higher auger speeds clean the screen more and allow the release of more water, resulting in drier thickened sludge, and vice versa. Consequently, the
setup of a Thickening system is to find a balance between the flow of sludge through the press, and the speed of the auger, to allow the desired consistency of thickened sludge.
As in a dewatering system, the throughput of the thickening press is solids limited, not hydraulically limited, but at a higher value than a dewatering press. A dewatering press (model PB9) has a throughput capability of 250 to 300 dry pounds per
hour, whereas, a thickening press has a throughput capability of roughly twice that at 500 to 600 dry pounds per hour. Consequently, the flow capability of typical thickening systems are 100 gpm (if feeding a 1% total solids sludge), or 50 gpm (if feeding a 2% total solids sludge). Flow
capability of the press will be higher for "thinner" feed sludge, or lower for "thicker" feed sludge. It is very important that the feed pump is specified properly to allow these flow values. Attempting to operate the thickener at values far below these numbers will result in unsteady operation.
Other typical performance parameters are:
- Polymer usage of 10 to 15 pounds per ton of dry solids.
- Solids capture rates of 80% to 95%.
- Volume reduction of 8 to 1 (0.75% feed thickened to 6%).
The Somat Thickening system, as with the Somat Dewatering system still has the valuable benefits of small foot print, no additional process water required for screen cleaning, low capital costs, and hands off operation. These features make the Somat systems the right dewatering or thickening choice the small WWTP (2 MGD or less).
Sludge Thickening Throughput Performance Information
Note that Somat presses are solids limited, not hydraulically limited. Therefore, depending upon the solids percentage of the feed sludge, the flow capabilities can vary widely and the flow values shown below are approximate. Feed sludge with low total solids (< 1% total solids ) will allow high flow rates, whereas, feed sludge with high total solids
(> 3%) will require lower flow rates. Also note that Somat thickeners cannot be operated in parallel with each other while being fed with one sludge pump. (one feed pump for each press) Often, a thickening system with two presses is desired, (Model 2 PB-9T) so that one of the presses is used as a back-up during service and/or repairs.
| Somat Model Type |
Solids Loading Capability |
Flow Capability |
| 1 PB-6T |
150 to 200 dry pounds per hour |
20 to 50 gpm |
| 1PB-9T |
500 to 600 dry pounds per hour |
50 to 150 gpm |
Som-A-System PB-9T
| Model Number |
Height |
Width |
Length |
| 1PB-6T Systems |
81" |
67" |
49" |
| 1PB-9T Systems |
124" |
94" |
75" |
| 2PB-9T Systems |
128" |
96" |
90" |
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