Dewatering Bags for a Municipal Water Treatment Contractor
Twenty geotextile dewatering bags for lagoon sludge at a municipal works: produced, inspected and shipped, with the site drainage trial still ahead.
Sized for one complete lagoon cell cycle
Calculated on solid drained cake weight
Height 1.5 m with top sealed pump inlet
Awaiting municipal site drainage trial
Project Background
Lagoon Sludge Haulage & Space Constraints
A municipal water treatment contractor was paying to haul lagoon sludge away at its full water content. The only space they had was an existing concrete pad, and the pad ends in a surface water drain they are not permitted to discharge into.
They ordered twenty geotextile dewatering bags sized for one lagoon cell: filled by pump, drained on the pad, then lifted as drained cake for disposal. The bags have been produced, inspected and shipped, and the site trial is the next step.
This record is deliberately limited to what has actually happened. Fabric specification, seams and dimensions are recorded on the batch sheet, but drainage rate, cake solids and the condition of the drained water can only be measured on the contractor’s own sludge.
The Core Haulage & Footprint Challenge
The contractor was hauling lagoon sludge at its full water content, so most of every tanker load was water. They wanted to drain the material on site before haulage, but had no room for a settlement tank or a filter press, and the only available area was an existing concrete pad with a surface water drain at one end that they could not discharge into.
Two Decisive Operational Risks
Two risks decided the specification. First, the drained water: if the fabric released solids with the water, the drain at the pad's end would carry them off site, which is exactly what the contractor's own permit conditions forbid. Second, the drained weight: the site lifts bags with a telehandler on the loop pair, so a bag that still holds too much water cannot be lifted safely. Fine solids in the sludge also risk blinding the fabric and stopping drainage partway through the campaign.
The Proposed Approach
Why Geotextile Dewatering Bags Fit
Direct Solution Proposal
We proposed geotextile dewatering bags sized for one lagoon cell, filled by pump through a top fill port and drained on the existing pad, with the fill port closed after each batch so rain does not re-wet the cake. The fabric opening size was selected against the fines the contractor expects in the lagoon rather than against a generic sludge figure, and the bags were laid out with the drain end of the pad bunded by the contractor so any carry-over can be seen and captured.
Solution Rationale: A settlement tank or filter press was rejected by the contractor on cost and footprint, and a lined roll-off container was rejected because it would not remove any water at all. A dewatering bag does the one job the site actually needs — removing water before haulage — and it does it on the pad they already have. The fill port was specified over an open top because rain re-wetting the cake would have undone the drainage they are paying for.
Validation Protocol: Validation so far covers the order and the dispatch, not the site: fabric specification against the agreed opening size, seam stitch counts, bag dimensions and the fill port attachment are recorded on the batch sheet, and a fabric sample was retained with the batch. A trial bag with the contractor's own sludge is the next step and will be the first real measure of drainage and retention.
End-to-End Execution
Interactive Project Timeline & Milestones
Click on each stage to inspect what was discussed, calculated, produced, and scheduled.
Inquiry
Contractor described the lagoon, the haulage cost problem and the pad layout with the drain at one end.
Engineering Parameters
Confirmed Technical Specifications
| Bag Geometry & Size | Circumference 4.5 m, height 1.5 m |
|---|---|
| Safe Working Load (SWL) | 1,000 kg on the drained cake |
| Safety Factor (SF) | Confirmed with the drained weight, not the wet weight |
| Structural Design | Geotextile dewatering bag, closed flat base |
| Porous Fabric Spec | Woven geotextile, opening size agreed against the lagoon fines |
| Lifting Loops | Four reinforced corner loops, telehandler pick on the loop pair |
| Top Inflow Port | Top fill port, closed after each batch |
| Bottom Closure | Closed flat base |
| Operational Job | Drainage on the existing concrete pad, filled by pump |
| Export Packing | Baled, 5 bags per bale |
Drawing DWG-DW-2607: Dimension drawing issued and approved before batch cutting. Shows top central inlet collar, reinforced perimeter lifting loops and seam layout.
QA & Traceability Records
Disclosable Production & Test Evidence
Every batch produced by QINFENG is accompanied by retained test coupons, physical dimension checks, and verified drawings.
Bag dimension and fill port drawing issued for confirmation before production.
Batch sheet with fabric specification, seam stitch counts and dimensions; fabric sample retained.
Fabric sample retained with the batch, available for the contractor to compare against the trial bag.
Engineering Rules
Project Takeaways & Transferable Rules
Honest B2B boundaries: What can be reused across sludge campaigns and what must be freshly checked every time.
What Can Be Safely Reused
For sludge work, the fabric has to be chosen against the fines in the material, not against a generic sludge figure, and the fill port matters more than buyers expect: a bag left open in the rain gives back part of the water it drained. The pad layout also decides the project as much as the bag does, because the drained water has to go somewhere the site is allowed to send it.
What Must Be Reconfirmed Each Time
The lagoon's fines content, which varies between cells and campaigns; the drained water route and the contractor's permit conditions; and the drained weight per bag, which sets the lifting arrangement. None of these carry over from one campaign to the next without checking.
Evidence caption