T20 waste exemption: treating waste at a water treatment works

The T20 exemption allows you to treat certain waste at water treatment works to reduce the volume for transport, or to make it easier to handle for waste recovery.

Types of activity you can carry out

This includes storing and treating sludge from water clarification by removing water.

Types of activity you cannot carry out

You cannot:

  • use this exemption to treat waste at locations other than at a water treatment works
  • treat hazardous waste

Types of waste you can treat

The waste codes are those listed in the List of Wastes (LoW) Regulations. You need to make sure your waste fits within the relevant waste code and description.

Waste code Type of waste
190902 Sludge from water clarification
190903 Sludge from decarbonation
190906 Solutions and sludge from regeneration of ion exchangers
190999 Waste water and bore hole flushings only

Quantity of waste you can treat

You can treat up to 10,000 cubic metres of waste over any 12-month period.

Key conditions

The waste must be treated and stored in a secure location with sealed drainage.

What else you need to know

You must not discharge dirty water to controlled waters or sewers without the correct consent. See Discharges to surface water and groundwater: environmental permits.

U8 – using waste for a specified purpose.

T21 – recovering waste at a waste water treatment works.

Register a T20 exemption

You need to register this exemption with the Environment Agency if you meet the requirements.


Secure – a container, lagoon or other place is secure in relation to waste kept in it if:

  • all reasonable precautions are taken to make sure the waste cannot escape
  • members of the public cannot gain access to the waste

Sealed drainage – a drainage system with an impermeable surface that makes sure that:

  • no liquid will run off the surface apart from via the system
  • except where they may be lawfully discharged, all liquids entering the system are collected in a sealed sump

Hazardous waste – see How to classify different types of waste.

Published 28 April 2014