T21 waste exemption: recover waste at a waste water treatment works

The T21 exemption allows you to recover waste, such as sludge from a septic tank or cesspool, which needs further treatment at a waste water treatment works.

Types of activity you can carry out

Includes storing and treating septic tank sludge at a sewage treatment works.

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

Type 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
190801 Screenings
190802 Sewage grit (waste from de-sanding) only
190805 Sludge from treating urban waste water
190899 Centrate liquor only
190902 Sludge from water clarification
190903 Sludge from decarbonation
190906 Solutions and sludge from regeneration of ion exchangers
200304 Septic tank sludge
200306 Waste from sewage cleaning
200399 Cesspool waste and other sewage sludge only

Quantity of waste you can treat

You can treat up to 100,000 cubic metres of waste over any 12-month period.

Key conditions

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

T20 – treating waste at a water treatment works.

Register this exemption

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


Hazardous waste – see How to classify different types of 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

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
Published 28 April 2014