---
title: "Municipal WWTP Sludge Dewatering Upgrade"
description: "Reference sludge dewatering line for small municipal WWTPs: automatic polymer dosing with screw press or belt filter press to cut sludge hauling volume."
url: https://www.waste-water-equipment-factory.com/projects/municipal-sludge-dewatering-upgrade/
updated: 2026-11-10
---

# Municipal WWTP Sludge Dewatering Upgrade

Reference sludge dewatering line for small municipal WWTPs: automatic polymer dosing with screw press or belt filter press to cut sludge hauling volume.

- Sector: Municipal & Rural
- Capacity: 50–300 kg DS/h (design range)
- Process: Polymer conditioning + screw press / belt press

> Small municipal plants that haul liquid sludge or rely on drying beds can cut sludge volume sharply by adding a mechanical dewatering line with automatic polymer dosing. This reference configuration uses a screw press or belt filter press, selected on sludge type, operating hours and staffing.

## The challenge

Many small municipal wastewater treatment plants were built with minimal sludge handling. Waste activated sludge is stored in a tank and hauled away as liquid, or spread on drying beds that are slow, weather-dependent and land-hungry. As connected populations grow and disposal costs rise, hauling liquid sludge at around 1% solids means paying to transport mostly water.

Operators need a dewatering line that fits into an existing building or a small new shed, works with the sludge the plant already produces, runs with little supervision and integrates with existing pumps and controls.

## Our solution

The reference solution is a **mechanical dewatering line** with **automatic polymer preparation and dosing**, built around either a **multi-disc screw press** or a **belt filter press**. Both are proven technologies for municipal sludge; the selection depends on sludge characteristics, required throughput, operating hours and available staff.

For plants with limited operators and moderate solids loads, the screw press is usually preferred: it is enclosed, slow-turning, quiet and largely self-cleaning, and it can process thin waste activated sludge without a separate thickener. For plants with larger loads or primary sludge in the mix, a belt filter press with gravity thickening zone can offer higher throughput per machine.

In both cases, sludge is fed at a controlled rate, conditioned with a correctly prepared polymer solution, and dewatered to a cake that can be conveyed directly into a skip or truck. Filtrate returns to the plant inlet.

## Process flow

1. **Sludge holding** – waste sludge is collected in a mixed holding tank to keep the feed homogeneous.
2. **Feed pumping** – a progressive cavity pump with variable-speed drive and flow meter delivers sludge at a steady rate.
3. **Polymer preparation** – an automatic unit makes down powder or emulsion polymer to a dilute solution and allows maturing time.
4. **Flocculation** – polymer is dosed in proportion to sludge flow and mixed in a flocculation tank or in-line mixer.
5. **Dewatering** – the conditioned sludge is thickened and pressed in the screw press or belt filter press.
6. **Cake handling** – a screw or belt conveyor transfers cake into a skip, hopper or truck.
7. **Filtrate return** – filtrate and wash water drain back to the headworks for treatment.

## Scope of supply

- [Multi-disc screw press](/products/sludge-dewatering/) or [belt filter press](/products/sludge-dewatering/), sized for the design solids load with operating hours confirmed in design
- Automatic polymer preparation and dosing unit with dosing pumps
- Sludge feed pump with variable-speed drive and electromagnetic flow meter
- Flocculation tank or in-line mixer
- Cake conveyor and, for belt presses, wash-water booster pump
- PLC control panel with interlocks to existing sludge pumps and signals to the plant SCADA
- Installation supervision, commissioning with polymer optimization, and operator training

Other options from our [sludge dewatering range](/products/sludge-dewatering/), including plate and frame filter presses and decanter centrifuges, can be considered where higher dryness or larger capacities are required.

## Why this configuration works

**Polymer conditioning drives performance.** The dewatering machine can only separate water from sludge that has been properly flocculated. Automatic make-down, adequate maturing time and flow-paced dosing keep floc formation consistent and avoid the overdosing that wastes chemical.

**The machine matches the plant.** Selecting between screw press and belt press on sludge type and staffing, rather than defaulting to one technology, gives a line that operators can actually run day to day.

**Integration is straightforward.** The line takes sludge from an existing holding tank and returns filtrate to the existing inlet, so the upgrade usually needs only a modest building, power supply and drainage.

**Hauling costs fall.** Moving from liquid sludge to a cake of typically 15–22% DS reduces the hauled volume dramatically, which is often the main economic justification.

**Commissioning settles the numbers.** Polymer type, dose and machine settings are optimized on site with the real sludge, since results vary with sludge age, primary/secondary ratio and temperature.

To size a dewatering line for your plant, send the plant flow, sludge production or solids load, current sludge concentration and preferred operating hours to inquiry@waste-water-equipment-factory.com or via our [contact page](/contact/).

*Reference configuration — final design depends on site data.*

## Design basis

| Parameter | Value |
| --- | --- |
| Design solids load | 50–300 kg DS/h |
| Feed sludge | Waste activated or mixed sludge, typically 0.5–4% DS |
| Polymer dose | Typically 3–8 kg active polymer per t DS (by jar test) |
| Expected cake dryness | Typically 15–22% DS for activated sludge |
| Polymer solution | Typically 0.1–0.3%, prepared automatically |
| Filtrate | Returned to plant headworks |

## FAQ

### Screw press or belt filter press: which is better for a small WWTP?

A screw press runs slowly, uses little power and wash water, is enclosed and can run unattended for long periods, which suits plants with limited staff. A belt filter press offers higher throughput per unit and can reach similar dryness, but needs more wash water and operator attention.

### Can waste activated sludge be dewatered without a thickener?

Yes. Multi-disc screw presses can accept thin waste activated sludge directly because the integrated thickening zone concentrates it before pressing. Belt presses usually perform better with a gravity thickening section or a pre-thickened feed.

### How much will sludge volume drop after dewatering?

Volume falls roughly in proportion to the increase in solids content. Going from 1% DS liquid sludge to an 18% DS cake reduces the volume to be hauled by roughly 94%, before considering any changes in sludge mass.

## Contact

- Email: inquiry@waste-water-equipment-factory.com
- WhatsApp / Tel: +86 176 2154 1688
- Quotation form: https://www.waste-water-equipment-factory.com/contact/
- Company: Shanghai Mars Industrial Co., Ltd., Shanghai, China