Dissolved methane in landfill leachate can be removed by bubbling air through it in a baffled tank, with anti-foam to control foaming and an odour unit on the vent. A tender for a restored landfill specified four small baffled tanks to treat up to 72 m³ of leachate a day and bring methane down to below 0.14 mg/l before discharge to sewer.

The challenge: methane in the leachate

Leachate collects dissolved gas as it passes through waste. Before it goes to sewer, methane has to come out, since it is a safety risk in sewers and treatment works. The site had a modest flow, a wide climate range (-10 to 40°C and 10 to 90% humidity) and a specification that followed the WIMES 8.02 materials standard.

The approach

1. Inlet: leachate is metered, then a diluted anti-foam is dosed automatically from a concentrate.
2. Baffled aeration: four GRP tanks, each with two baffled chambers, run independently through butterfly valves. Compressed air goes to the base of each chamber through a low-back-pressure bubble mat. The design air to leachate ratio is 1:3.
3. Odour control: the methane-laden air goes to a catalytic plasma odour unit that uses UV light to oxidise odorous molecules without chemicals.
4. Discharge: stripped leachate goes to a discharge tank, then to sewer.

The system is automatic. Its alarms cover low feed level, no inlet flow, low anti-foam, high and low tank levels, pump failures and leaks. It feeds the site’s main PLC, so no separate panel was supplied.

Why this approach

• Low maintenance: the routine checks are anti-foam, instruments and the odour unit.
• Low power: no heating or large columns.
• Independent tanks: flows can be matched by running fewer tanks.

Because of travel restrictions, the supplier did not plan to send a commissioning engineer. Remote support and a detailed manual replaced it. That is a practical point if your site is hard to reach.

What to consider for your own project

1. Get the methane figure. The influent concentration was not given in this tender, and it affects air demand.
2. Decide how to treat the vent. Open venting or odour treatment depends on the site.
3. Plan for foam. Aeration of leachate foams.
4. Agree commissioning arrangements early.

Compare with our larger multi-site example: methane stripping at several landfills. UK guidance is on gov.uk landfill guidance.

FAQ

Why strip methane from leachate?

To meet the limit for sewer discharge and avoid gas accumulating downstream.

Why four tanks?

They give flexibility and redundancy at low cost.

What does the anti-foam do?

It prevents excess foam from the air bubbling.

Is the air treated?

Here yes, by a UV-based odour unit.

Treating leachate on site?

Contact us with your flow and methane level.