Dissolved methane is an often-overlooked hazard hiding in plain sight within domestic sewage and landfill leachate. Because the anaerobic processes that generate these liquids also produce methane as a by-product, the gas is frequently carried forward into downstream systems – sometimes at concentrations high enough to pose a genuine safety and compliance risk. Methane stripping technology addresses this problem directly, removing dissolved gas before wastewater or leachate is discharged, transported, or processed further.
The Problem: Methane in Leachate and Wastewater
Landfill leachate and domestic wastewater can contain dissolved methane at concentrations exceeding 25 mg/litre, though in practice levels of 10-15 mg/litre are more typical. This might sound like a small quantity, but methane’s low solubility and volatility mean it can readily come out of solution and accumulate in confined spaces – manholes, tankers, pumping stations, and treatment vessels – where it presents a serious explosion risk.
A dissolved methane concentration of just 1.4 mg/litre is sufficient to produce an explosive atmosphere in a confined space.
Because of this risk, receiving sewage authorities have widely adopted a much stricter discharge standard.
A figure of 0.14 mg/litre – ten times lower than the explosive threshold – has become the accepted benchmark for sewage discharge consents.
Meeting this standard reliably requires purpose-built treatment rather than relying on incidental degassing.
How Methane Stripping Works
Methane stripping uses controlled aeration to physically drive dissolved methane out of solution before the liquid is discharged or transported off-site. Air is introduced into the wastewater or leachate stream within a vessel designed to maximise gas-liquid contact, encouraging methane to transfer from the liquid phase into the air phase, where it can be safely vented or, in some designs, captured.
Two broad configurations are used depending on site constraints:
- Vertical stripping towers – minimise footprint, making them well suited to sites where land space is at a premium.
- Horizontal, multi-modular systems – use multiple vessels in series and are favoured where equipment capital cost is the priority over land use.
Both approaches can achieve very high removal efficiencies with relatively straightforward operating requirements.
Methane removal of over 99% is achievable using well-designed, relatively simple-to-operate stripping systems.
Typical System Components
A complete methane stripping installation typically includes:
- Aeration vessel(s)
- Liquid pumping equipment
- Air movers
- Filtration and separation equipment
- Access facilities for operation and maintenance
- Security facilities
- Datalogging and data management software
Each component is selected and sized to match the specific characteristics of the liquid being treated and the operating environment of the site.
Specification Overview
Systems are designed around site-specific flow requirements, from small pre-packaged modular units up to large purpose-built installations.
| Parameter | Specification |
|---|---|
| Pre-packaged modular units | 5 – 40 m³ per day |
| Purpose-designed units | Up to 2,000 m³ per day |
| Removal efficiency | Typically >99%, subject to design specification |
| Design standard | “Good engineering practice” for low pressure systems |
| Approvals available | ASME UL, BS5500, Lloyd’s certification |
| Flow control | Manual or solenoid-actuated chemical duty butterfly valves |
| Materials | Stainless steels, high-quality alloys, plastics (application-dependent) |
| Control options | Manual, automated, gas concentration alarms, feed-back loop, SCADA |
Available Options
Systems can be tailored further with:
- Dosing systems to prevent foaming
- Waste heat utilisation to reduce the minimum viable ambient operating temperature
- Acoustic and thermal insulation for noise- or temperature-sensitive locations
- Options for managing calcium carbonate precipitation, a common fouling issue in leachate systems
Why Site-Specific Design Matters
No two leachate or wastewater streams are identical – variations in organic loading, temperature, chemistry, and flow rate all affect how methane behaves in solution and how it should be stripped. Providers with long-standing experience across landfill gas, biogas, leachate, and wastewater treatment are better placed to specify systems that perform reliably in practice rather than just on paper. This is why methane stripping equipment is generally engineered around “good engineering practice” for low-pressure systems, with instrumentation and control levels matched to the specific operating environment – whether that calls for simple manual valves or full SCADA integration with on-line data management.
Key Takeaways
- Dissolved methane in leachate and wastewater can reach 10-15 mg/litre, well above the 1.4 mg/litre explosive threshold and the 0.14 mg/litre discharge standard commonly required by sewage authorities.
- Methane stripping uses controlled aeration to remove dissolved gas, achieving over 99% removal in well-designed systems.
- Vertical towers suit sites with limited space; horizontal multi-modular systems suit projects where equipment cost is the priority.
- Systems scale from 5 m³/day modular units to 2,000 m³/day purpose-built installations, with options for foaming control, waste heat recovery, insulation, and scale management.
If your site is dealing with landfill leachate or wastewater that needs to meet sewage discharge consents, or you’re concerned about methane build-up in confined spaces, get in touch with our technical team to discuss a system designed around your specific flow rates, chemistry, and site constraints.