Laboratory pilot trial for the treatment of leachate from a landfill in Essex
Client: Landfill operator
Project duration: 7 weeks
A landfill operator was investigating options for the treatment of leachate, which was historically tankered off-site at a rate of about 10m3 per day.
The main objectives of the laboratory pilot trial were:
- Simulate an on-site effluent treatment system for the treatment of ammonium, organic contaminants and metals.
- Take water samples during the trial to assess effectiveness of proposed method of treatment.
- Prepare a comprehensive interpretative report on landfill effluent treatment with recommendations.
The pilot trial demonstrated removal of ammoniacal-N by nitrification, i.e., due to the activities of the autotrophic bacteria Nitrosomonas sp and Nitrobacter sp. This mechanism provides a permanent conversion of ammonium to nitrate, which is then ultimately broken down and released as nitrogen gas. Ammonium removal efficiency was greater than 99%, typically reduced to 1.5 mg/l from a starting concentration of 220 mg/l in a continuously operating system.
With an average leachate production rate of 10m3 / day and assuming an average annual temperature of 10ºC, scaling up the findings of the pilot trial suggest balancing tank and bioreactor tank or lagoons of the order of 160m3 to 200m3 capacity.
The pilot trial highlighted the requirement for additional phosphorus to maintain ammonium degradation. Additionally, full scale treatment is likely to require dosing to maintain alkalinity and prevent pH drop due to acid production during nitrification.
The project highlighted the advantages of the biological treatment of landfill leachate.
- Biodegradation of ammonium and organic contaminants (TPH, VFAs)
- Reduction in BOD and COD
- Efficient removal of suspended solids and metals
- Minimum generation of waste
- Relatively simple, robust system
- Low maintenance
- Can accommodate variable flow rates
- Flexible system, ease of scale up
This project provided an inexpensive way of demonstrating biological treatment of the landfill leachate and provided confidence in what is likely to be achievable in a full scale system.
Report on treatment of landfill effluent is available to download.
A pdf version of this landfill leachate treatment case study is available here.