By Senjie Filter Press Engineering Team · Last updated: 2026-09-14
Quick answer: A multi-disc screw press dewaters sludge to 15 to 25% dry solids at 8 to 20 kWh/t DS with minimal labour; a chamber or membrane filter press reaches 30 to 50% DS at 15 to 30 kWh/t DS. Below 1 t DS/day the screw press is cheaper to run; above 3 t DS/day the filter press wins on disposal cost.
The screw press is cheaper per operating hour, but the filter press produces a much drier cake and cuts the tonnes you pay to truck away. This guide compares cake dryness, energy, polymer, labour, footprint, noise and capex, then gives a best-fit matrix by plant size and sludge type. Product details are on the multi-disc screw press and chamber filter press pages.
How do a screw press and a filter press dewater sludge differently?
A multi-disc screw press dewaters continuously at 0.05 to 0.1 MPa by conveying flocculated sludge along a screw turning at 0.5 to 3 rpm inside a stack of fixed and moving rings, while a filter press dewaters in batches at 0.6 to 1.0 MPa feed pressure, or 1.5 to 2.0 MPa with membrane squeeze, in cloth-lined chambers. The 10 to 30 times higher pressure is why filter press cake is 2 to 3 times drier.
The screw press has no cloth and no hydraulic system, but its squeezing pressure is limited so cake dryness plateaus early. A filter press needs a hydraulic unit, a high-pressure feed pump, cloth lasting 3 to 12 months and operator time for discharge unless it is fully automatic; see filter press automation options.
What cake dryness does each machine achieve?
A multi-disc screw press produces 15 to 25% dry solids (75 to 85% moisture) on municipal and food-industry biological sludge; a chamber filter press produces 25 to 40% DS on the same sludge and 45 to 60% DS on chemical and mineral sludge, and a membrane press adds another 10 to 15 percentage points.
One tonne of dry solids at 20% DS is 5.0 t of wet cake; at 35% DS it is 2.9 t; at 45% DS it is 2.2 t. For a plant producing 5 t DS/day, moving from a screw press at 20% DS to a membrane filter press at 35% DS removes 10.7 t/day, or about 3,900 t/year, from the disposal invoice. More values are in our cake moisture by industry table.
How do energy, polymer, labour and other operating costs compare?
Per tonne of dry solids, a screw press uses 8 to 20 kWh, 6 to 12 kg of polymer and 0.25 to 0.5 operator-hours, while a chamber filter press uses 15 to 25 kWh, 3 to 8 kg of polymer (or 10 to 25% lime plus 3 to 6% ferric on a DS basis) and 1 to 3 operator-hours for manual discharge, falling to 0.3 to 0.5 hours when fully automatic.
| Item | Multi-disc screw press | Chamber filter press (manual) | Membrane filter press (automatic) |
|---|---|---|---|
| Cake dryness, municipal sludge | 15–25% DS | 25–40% DS | 35–50% DS |
| Cake dryness, chemical/mineral sludge | 20–30% DS | 45–60% DS | 55–75% DS |
| Operation | Continuous, 24 h unattended | Batch, 1–4 h cycle | Batch, 30–90 min cycle |
| Energy, kWh/t DS | 8–20 | 15–25 | 20–30 |
| Polymer, kg/t DS | 6–12 | 3–8 (or lime/ferric) | 3–8 |
| Labour, operator-hours/t DS | 0.25–0.5 | 1–3 | 0.3–0.5 |
| Noise | 60–65 dB(A) | 70–80 dB(A) at discharge | 70–80 dB(A) at discharge |
| Footprint, 2 t DS/day plant | 6–10 m² | 25–40 m² | 30–50 m² |
What are the capital cost ranges for each option?
Typical FOB China ranges are US$12,000 to 35,000 for a multi-disc screw press handling 10 to 100 kg DS/h, US$15,000 to 45,000 for a manual chamber filter press with 800 to 1000 mm plates and 30 to 100 m² of area, and US$60,000 to 180,000 for an automatic membrane filter press with 1250 to 1500 mm plates and 150 to 400 m² (indicative — request a quotation). Conditioning, feed pumps, conveyors and controls add 20 to 40% to each figure.
Larger presses are priced in our filter press price by plate size guide.
Which is cheaper over 10 years for a typical municipal plant?
For a 5 t DS/day municipal plant paying US$40/t of wet cake for disposal, a membrane filter press at 35% DS saves about US$156,000 per year in disposal versus a screw press at 20% DS, which repays its US$80,000 to 120,000 higher capital cost in under one year. The calculation:
- Screw press: 5 ÷ 0.20 = 25 t wet cake/day. Filter press: 5 ÷ 0.35 = 14.3 t/day. Difference 10.7 t/day, or 3,900 t/year.
- Disposal saving: 3,900 t × US$40 = US$156,000/year.
- Extra energy: 5 t × 365 × 11 kWh × US$0.10 = about US$2,000/year.
- Polymer saving: 5 t × 365 × 4 kg × US$3.5 = US$25,500/year.
The net operating advantage is roughly US$175,000 per year for the automatic filter press. At US$10/t disposal the saving falls to about US$60,000 per year and payback stretches to 18 to 24 months, still well inside the 10 to 15 year press life. Our filter press annual operating cost guide gives a line-by-line template.
When is a screw press the better choice?
A screw press is the better choice below about 1 t DS/day, for plants with no full-time operator, for oily or greasy sludge that blinds filter cloth, and where noise, footprint or unattended night operation matter more than cake dryness. It also suits plants that land-apply or compost cake, where 20% DS is acceptable.
When is a filter press the better choice?
A filter press is the better choice above about 3 t DS/day, wherever cake is landfilled or incinerated at a per-tonne charge, for chemical, mineral, electroplating and tannery sludges that dewater to 45% DS or more, and where the disposal site or regulator requires 30% DS or drier.
Regulation matters too: the US EPA biosolids rule (40 CFR Part 503) and many landfill rules set requirements that a 15 to 25% DS cake may not meet without further treatment; the US EPA biosolids guidance describes the pathways.
Which machine fits my plant size and sludge type?
| Plant size (t DS/day) | Municipal / biological sludge | Food, dairy, brewery sludge | Chemical, electroplating, tannery sludge | Mineral, stone, ceramic slurry |
|---|---|---|---|---|
| Under 1 | Screw press | Screw press | Chamber filter press, 630–800 mm | Chamber filter press, 630–800 mm |
| 1–3 | Screw press if disposal under US$15/t; chamber filter press if higher | Screw press or chamber filter press | Chamber filter press, 800–1000 mm | Chamber or membrane filter press, 800–1000 mm |
| 3–10 | Chamber or membrane filter press, 1000–1250 mm | Chamber filter press, 1000 mm | Membrane filter press, 1000–1250 mm | Membrane filter press, 1250 mm |
| Over 10 | Automatic membrane filter press, 1250–1500 mm | Automatic chamber filter press, 1250 mm | Automatic membrane filter press, 1250–1500 mm | Automatic membrane filter press, 1500–2000 mm |
Screw presses are rarely used on mineral and chemical sludges because abrasive fines wear the ring stack quickly.
Why buy this from Senjie?
Senjie is a China-based manufacturer of chamber, membrane and fully automatic filter presses and multi-disc screw presses, founded in 2014 in Changzhou, Jiangsu, and exporting to 40+ countries across Southeast Asia, India, Africa, the Middle East and Latin America. Because we build both machines, our recommendation is based on your dry solids, sludge type and disposal cost.
We supply screw presses from 10 to 500 kg DS/h, filter presses from 320 to 2000 mm with 1 to 1000 m² of area, and matching filter press cloth, dosing units and feed pumps. Lab tests on a 1 to 2 kg sample are available before quotation.
Frequently Asked Questions
Which is cheaper to operate, a screw press or a filter press?
Per operating hour the screw press is cheaper because it uses 8 to 20 kWh/t DS and almost no labour. Per tonne of dry solids disposed, the filter press is usually cheaper above 1 to 3 t DS/day because its 30 to 50% DS cake cuts wet cake tonnage by 40 to 60% and it uses 30 to 60% less polymer.
Can a screw press reach 30% dry solids?
Rarely. Multi-disc screw presses reach 15 to 25% DS on biological sludge and 30% DS only on fibrous, easily dewatered sludge such as paper mill sludge. A chamber filter press reaches 25 to 40% DS on the same sludge.
How much polymer does each machine use?
A screw press typically uses 6 to 12 kg of polymer per tonne of dry solids because flocs must hold together under low pressure. A filter press uses 3 to 8 kg/t DS, or can be conditioned with 10 to 25% lime and 3 to 6% ferric chloride instead, which also raises cake dryness.
What is the footprint difference between a screw press and a filter press?
For a 2 t DS/day plant a multi-disc screw press occupies 6 to 10 m² including access, while a chamber filter press with 800 to 1000 mm plates needs 25 to 40 m² plus 3.5 to 4.5 m of headroom for the cake hopper and conveyor.
Can a screw press and a filter press work together?
Yes. A common layout uses the screw press as a continuous thickener to raise feed solids from 1% to 5 to 8%, then a membrane filter press to dewater the thickened sludge to 35 to 50% DS. This cuts filter press cycle time by 30 to 50%.
Tell our engineers your dry solids per day, sludge type and disposal cost per tonne through the Senjie contact page and we will recommend a screw press, a filter press or both, with a 10-year cost comparison.