A landfill can treat its own ammoniacal leachate by stripping the ammonia in a tower and burning it in a thermal destructor fuelled by landfill gas, with no chemicals other than a little anti-foam. A proposal for an English landfill sized one for up to 600 m³/day at about 2,000 mg/l ammonium, with a target below 200 mg/l.
The challenge: a new sewer consent
The site had sent leachate to a sewage works with no ammonia treatment. The sewer operator then imposed an ammonia limit. The operator’s tender for a leachate treatment plant, by contrast, described a biological sequencing batch reactor design for up to 350 m³/day, with ammonia targeted below 50 mg/l. The thermal stripper was an alternative offer using gas the site already produced.
The approach
- Leachate is pumped through a heater, using heat taken from the destructor exhaust via an economiser.
- Hot leachate enters the top of a stripper column, about 18 m tall including a cooling section at its base.
- Stripping air rises through the column. Steam is injected after the cooling section to condition the air.
- Ammoniated air goes from the top of the column to the thermal destructor as primary and secondary combustion air, destroying the ammonia.
- Exhaust heat returns to the process through the economiser.
The supply included a stripper column, economiser, water boiler and steam generator, leachate heater, heat recovery from the outgoing leachate, a condenser heat recovery circuit, feed water treatment, a shrouded thermal destructor and a control panel with a large HMI.
Why thermal rather than biological
- No chemicals beyond anti-foam.
- No bacteria to maintain.
- The landfill gas that runs it is already on site.
The trade-off is the need for enough landfill gas to supply the heat. The proposal stated that the thermal route depends on a heat source, preferably waste heat.
What was not included
Civil design, installation of mechanical and electrical works and any approvals were outside the offer, as were buffer storage, the leachate feed pump, solids removal, foundations and buildings.
What to consider for your own project
- Check your gas supply against the heat requirement across the site’s gas decline.
- Be clear on the consent you must meet. A 200 mg/l target differs from 50 mg/l.
- Compare options on lifetime cost, not just capital.
- Plan buffer storage, which was excluded.
See gov.uk landfill guidance and our article on waste heat for ammonia stripping.
FAQ
How does the stripper destroy ammonia?
The ammoniated air feeds a thermal destructor that burns it.
What fuel does it use?
Landfill gas.
Does it need chemicals?
Only a small amount of anti-foam.
What is the capacity?
Up to 600 m³/day in this proposal.
Facing a leachate ammonia limit?
Contact us with your leachate figures.