Tunnel construction throws up some of the hardest water to treat — 1,000 to 5,000+ mg/L of suspended solids, free oil from machinery, cement-driven high pH, and bentonite slurry from the TBM. We build the treatment plant for it inside ISO shipping containers, factory-tested and ready to drop next to the portal.
Five standardised system classes — from a compact 20ft oil/solids skid to a dual-container 80 m³/h train with full sludge dewatering — each engineered to hit a construction discharge consent and move with the drive.
Why a standard clarifier on its own rarely makes consent
Tunnel dewatering and TBM operations generate a water stream that swings hard on every parameter at once. The treatment train has to cope with all of it, often on a site with no permanent power and a discharge consent that does not move.
1,000–5,000+ mg/L TSS from rock, soil and grout fines — and 10–20% solids in raw TBM slurry.
50–200 mg/L of free and emulsified oil from machinery, hydraulics and plant.
pH 9–12 from cement and shotcrete contact — needs neutralisation before discharge.
Stable bentonite suspensions and rock-borne heavy metals that resist plain settling.
Matched to flow, solids loading and the contaminants in your water
| System | Container | Flow | Core Process | TSS Removal | O&G Removal | Installed Power |
|---|---|---|---|---|---|---|
| T-1 Oil + Clarifier | 20ft | 10 m³/h | API separator + lamella + bag filter | 80–90% | 85–95% | ~6 kW |
| T-2 Clarifier + Filter | 40ft HC | 25 m³/h | Coag/floc + lamella + sand filter | 85–95% | 70–85% | ~12 kW |
| T-3 Multi-Stage | 40ft HC | 50 m³/h | Screen + DAF + lamella + dual-media + screw press | 90–98% | 80–92% | ~25 kW |
| T-4 TBM Slurry | 40ft HC | 30 m³/h | Hydrocyclone + lamella + decanter centrifuge | 85–95% | 60–75% | ~20 kW |
| T-5 Complete Train | 2×40ft HC | 80 m³/h | Screen + API + coag/floc + lamella + DM filter + pH + dewater | 92–99% | 85–95% | ~45 kW |
Sludge cake leaves at 15–30% dry solids depending on the dewatering stage. Capacities and removals are typical design envelopes — we confirm against your water analysis and consent. The full itemised equipment schedule, P&ID and FAT pack are issued during detailed design.
Compact 10 m³/h plant for oil-contaminated dewatering
For small tunnelling sites, utility trenches and pipe-jacking where the discharge carries free oil and moderate solids. The API separator removes free oil and floatables by gravity, the inclined-plate (lamella) clarifier settles suspended solids in a fraction of the footprint, and a bag filter polishes the outlet — all inside one 20ft container.
| Process & Performance | Value |
|---|---|
| Design flow | 10 m³/h (240 m³/day) |
| API separator | 3-chamber, 10–15 min retention, removes free oil >150 micron |
| Lamella clarifier | 60° plates, ~5× effective-area multiplier, 2.0 m/h loading |
| Final polish | 10-micron bag filter |
| Expected outlet | TSS <50 mg/L, O&G <15 mg/L, pH 6–9 |
| Core Equipment | Headline Spec |
|---|---|
| Feed pump | 10 m³/h, abrasion-tolerant |
| Oil skimmer | Belt-type, continuous |
| Coagulant / flocculant dosing | PAC or FeCl&sub3; + anionic polymer |
| Sludge pump | Progressive cavity |
| Controls | PLC + 7″ HMI |
The standard 25 m³/h tunnelling treatment system
The workhorse for medium-scale projects: full chemical pre-treatment (rapid mix and flocculation), lamella clarification, sand filtration for polishing, and pH correction to bring cement-laden water back into consent before discharge.
| Process & Performance | Value |
|---|---|
| Design flow | 25 m³/h (600 m³/day) |
| Rapid mix / flocculation | ~60 s mix + 15 min flocculation |
| Lamella clarifier | 2.5 m/h loading, ~10 m² effective area |
| Sand filter | Anthracite + sand, 12 m/h, auto backwash |
| pH adjustment | Acid dosing to consent window |
| Core Equipment | Headline Spec |
|---|---|
| Feed pump | 25 m³/h |
| Rapid + flocculation mixers | Variable speed, SS 316L |
| Sand filter vessel | FRP, auto backwash + backwash pump |
| Chemical dosing | Coagulant + flocculant + pH (acid) |
| Controls | PLC + 12″ HMI, ~48 I/O |
High-capacity 50 m³/h treatment with on-board dewatering
For large drives with high solids loading. Coarse screening protects the plant, DAF lifts oil and light solids, the lamella clarifier drops the heavy fraction, dual-media filtration polishes, and an integral screw press dewaters the sludge to a landfill-ready cake — no separate dewatering plant required.
| Process & Performance | Value |
|---|---|
| Design flow | 50 m³/h (1,200 m³/day) |
| Coarse screen | Rotary drum, 5 mm aperture |
| DAF unit | 10 m/h surface loading, 15% recycle |
| Dual-media filter | Anthracite + sand + garnet, 15 m/h |
| Sludge cake | 18–22% dry solids from screw press |
| Core Equipment | Headline Spec |
|---|---|
| Rotary drum screen | SS 304, 5 mm |
| DAF package | Saturator + compressor + skimmer |
| Dual-media filter | FRP, auto backwash |
| Screw press | SS 304, VFD-driven |
| Controls | PLC + 15″ HMI, ~72 I/O |
30 m³/h of 10–20% solids slurry — and bentonite back in the loop
Purpose-built for slurry-TBM spoil. A hydrocyclone desander strips coarse sand and gravel, the lamella clarifier settles fines, and a decanter centrifuge recovers bentonite for reuse — recovering 60–80% of the bentonite typically cuts slurry chemical spend by the same order, often $200–400/day on a working TBM.
| Process & Performance | Value |
|---|---|
| Design flow | 30 m³/h slurry |
| Feed solids | 10–20% by weight |
| Hydrocyclone (desander) | Removes >75 micron |
| Decanter centrifuge | 2,000–3,000 G, 2-phase |
| Bentonite recovery | 60–80% for reuse |
| Core Equipment | Headline Spec |
|---|---|
| Slurry feed pump | Abrasion-resistant |
| Hydrocyclone cluster | PU-lined desanders + dewatering screen |
| Decanter centrifuge | SS 316L bowl, VFD |
| Recovered bentonite tank | Agitated, SS 304 |
| Controls | PLC + 12″ HMI, ~56 I/O |
Maximum 80 m³/h — screen to polished, consent-ready discharge
The full train across two 40ft containers. Container 1 does primary treatment (screening, oil separation, coagulation/flocculation, clarification); Container 2 handles polishing (dual-media filtration, pH adjustment, screw-press dewatering and clean-water storage). The two PLCs talk over Ethernet/IP and a single supervisory HMI runs the lot.
Rotary drum screen • API oil/water separator • rapid mix + flocculation • lamella clarifier (~27 m² effective) • chemical dosing • sludge transfer.
Dual-media filter + auto backwash • pH adjustment (acid/base) • screw press (50 kg DS/hr) • 40 m³ clean-water tank • discharge pump + flowmeter.
| Whole-Train Performance | Value |
|---|---|
| Design flow | 80 m³/h (1,920 m³/day) |
| TSS removal | 92–99% |
| O&G removal | 85–95% |
| Sludge cake | 18–25% dry solids |
| Interconnect | DN150 process pipe + Ethernet control link |
| Your situation | Start with |
|---|---|
| Small site, oil-contaminated dewatering | T-1 — 20ft oil + clarifier |
| Medium tunnel, standard solids + pH | T-2 — 40ft clarifier + filter |
| Large drive, high solids, on-site dewatering | T-3 — 40ft multi-stage |
| Slurry TBM, bentonite to recover | T-4 — TBM slurry treatment |
| Mega project, full treatment to discharge | T-5 — dual-container train |
Send us the water analysis, the flow and the discharge consent — we will pick the system class, size it to your drive, and ship a factory-tested container that makes consent from day one.
Explore closely-related tunnelling and containerised guides
Send your influent analysis and our engineers assess your process and recommend a tailored treatment solution — free, confidential and no obligation.
Select the regulatory standard for your country — it sets which parameters we need for a compliance-aware process assessment.
Required parameters for the chosen standard are flagged on the sample form. You can still submit a partial set and we will advise what else to test.
Your sample is stored against your company so we can track the project. Provide a company name or email as a minimum.