Road sweepings and gully waste: dewatering the wet fraction
Dewater road sweepings and gully waste: cut the water content before haulage, with bag size and filtrate under control. Read the guide!
Key points at a glance
Road sweepings are not one thing. What the sweeper picks up depends on season, weather, road type and cleaning method. Autumn brings leaves, winter brings grit and de-icing…
Gully waste is disposed of by weight. Water has a density of one kilogram per litre and contributes nothing to the solids. Reduce the water content before the…
Sweeper waste has three characteristics that matter for sizing.
Road sweepings cover very different materials
Road sweepings are not one thing. What the sweeper picks up depends on season, weather, road type and cleaning method. Autumn brings leaves, winter brings grit and de-icing salt residues, wet weather brings sand and silt, and cigarette ends, packaging, tyre and brake wear arrive all year round.
For dewatering, what matters is which part of that is wet in the first place. Dry sweepings from a suction sweeper do not belong in a filter bag. Dewatering becomes worthwhile with material from wet cleaning, from gully emptying, from road drainage and from the wash water used to clean the sweeper itself. There the solids sit in water, and there the volume and the mass can be brought down noticeably.
The commercial case for dewatering gully waste
Gully waste is disposed of by weight. Water has a density of one kilogram per litre and contributes nothing to the solids. Reduce the water content before the material leaves site and you reduce the mass that is hauled and invoiced.
How much that amounts to in a given case depends on the starting water content and varies considerably between routes and seasons. The reliable basis is a simple measurement: weigh a typical batch before and after dewatering. That single figure then carries the whole calculation.
What makes sweeper waste different
Sweeper waste has three characteristics that matter for sizing.
It is heavy. Sand, grit and mineral wear have high densities. A bag that looks half full by volume may already have reached its working load. With this material the load rating is almost always the limiting factor rather than the volume. Plan for 900 kg and keep an eye on the fill height. How to estimate the mass is set out in the size guide.
It contains coarse matter. Leaves, twigs, packaging, pieces of metal. Coarse matter does not block filter area, but it can damage it. A screen or a rake ahead of the bag is a small measure with a large effect.
It varies a great deal. The same route delivers something different in November from what it delivers in March. A sizing that works in summer can be tight in autumn. If you dewater regularly, review the size choice by season.
Sizes and load ratings for sweeper and gully waste
For this material the volume-based bags in 200 g/m² geotextile are the right product group. Because of the density, the highest load rating is worth taking throughout.
| Size | Volume | Base area | Note for sweeper waste |
|---|---|---|---|
| L | 0.5 m³ | 0.90 × 0.80 m | With high density the most practical size, because it can be used in full |
| XL | 0.8 m³ | 1.00 × 1.00 m | Useful where the 0.80 m height is the constraint |
| XXL | 1.25 m³ | 1.00 × 1.00 m | Only with the 900 kg rating and a controlled fill height |
With heavy sweeper waste it can be more economical to use two L bags in full than to fill one XXL halfway. That comparison becomes worthwhile as soon as you know the weight of a typical batch.
Filtrate and disposal
The water that comes out contains what comes off the road: dissolved salts from winter maintenance, tyre and brake wear, hydrocarbons from drips, and in some cases heavy metals. It is not automatically suitable for discharge.
What has to happen to the filtrate, and how the dewatered material is then handled, follows the applicable requirements and the analysis of the material itself. The question of what disposal costs can only be answered with your own figures: mass per batch, disposal price per tonne, and frequency. Dewatering acts on the first of those three and not on the other two. The classification and the disposal route are matters for the duty holder and the waste contractor. We supply the filter medium and advise on the technical sizing, not on the waste regulations.
Questions from depots and cleaning contractors
Can I put dry sweepings into a filter bag?
Technically yes, usefully no. Without a water fraction there is nothing to dewater. For dry material, containers or skips are the right answer. How dewatering works in the bag is covered in the process guide.
How do I deal with leaves?
Leaves bind a lot of water and give it up slowly. With a high leaf fraction, dewatering takes longer. A coarse separator ahead of the bag reduces the problem and improves handling at the same time.
Will glass and metal damage the bag?
The 200 g/m² geotextile at 2.0 millimetres thick is robust but not cut resistant. Where sharp-edged material is expected, pre-separation is worth having.
Where should the bags stand?
On made-up ground with filtrate collection, reachable by the lifting equipment, and preferably under cover. Rain falling into an open bag works against you. If you need help with sizing, get in touch.
Does WINKLER handle the disposal?
No. We manufacture textile filtration products. Haulage, recovery and disposal are matters for your waste contractor.
Still unsure which filter or next step fits?
Send us the medium, dimensions and application. We will help you decide whether a standard product is suitable or whether the case needs a custom solution.
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