Leachate recirculation: objectives, design, operation and control

THURSDAY 13 APRIL 2023 / 10:00 AM - 12:30 PM (GMT+2)
Keith Knox
, Knox Associates Ltd (UK)

Recirculation of leachate has been practised for more than 40 years and is now commonplace around the world. Often it has been undertaken with little prior design thought and insufficient monitoring. During the last decade, the subject has been reviewed in a more structured way, with regard to objectives, design, operational performance data and monitoring of effectiveness and impact.

The aim is to make the Webinar as interactive as possible, with delegates introducing themselves and describing any recirculation projects or issues that they are involved in. During the presentation of webinar materials, delegates are encouraged to raise issues, discuss case studies and aspects of particular interest to them.


Webinar materials will be presented and discussed according to the following structure:

  • Definition and Objectives of recirculation
    There are many legitimate reasons and purposes for undertaking recirculation, all of which can be helpful in managing the potential environmental risks posed by landfill, and these will be discussed.

  • Framework for evaluation of recirculation projects
    This presents a framework showing the interrelationship of the various elements of a complete recirculation project. It provides an important foundation for the development of a recirculation project.

  • Infrastructure
    We will discuss and show examples of the different types of infrastructure and equipment used for recirculation and present data on their hydraulic performance.

  • Conceptual Design
    This is a most important, and yet often overlooked, aspect of leachate recirculation. Examples of conceptual design will be presented and discussed.

  • Operation, monitoring and control
    Monitoring and control have often been given insufficient attention. It is important to monitor recirculation activities in relation to: (i) operational performance and maintenance of the infrastructure; (ii) progress towards achieving the objectives of recirculation; and (iii) any potential environmental impacts caused by the recirculation. The scope of monitoring programmes that may be helpful for each of these aspects will be discussed.



Keith Knox is Principal of Knox Associates (UK) Ltd, an independent consultancy providing advice on landfill and waste treatment. He is a Visiting Professor at the University of Southampton and his main professional interests are in the areas of leachate management and landfill processes, particularly those affecting long term stabilization and sustainability. He has a strong interest in tropical landfills, landfill sustainability and reducing the aftercare period. He has been at the forefront of technical developments in leachate treatment, including ammonia nitrification, single tank SBR pre-denitrification, use of activated carbon, and high temperature stripping of ammonia. His research has included technical reviews of e.g. water balance, co-disposal, leachate recirculation, and leachate hard COD, as well as many experimental investigations. Keith has been involved in many leachate recirculation projects and in recent years has co-authored several technical review reports for organizations in the UK and Denmark.