Home › Waste codes › Chapter 10

10 01 21 Sludges from on-site effluent treatment other than those mentioned in 10 01 20

EWC / List of Waste code · Last checked 21 October 2026 · Applies across the UK (England, Wales, Scotland and Northern Ireland)

Not hazardous Mirror entry (non-hazardous side)

Official description: “sludges from on-site effluent treatment other than those mentioned in 10 01 20”

Where it sits: chapter 10 (wastes from thermal processes), section 10 01 (wastes from power stations and other combustion plants (except 19)).

What the hazard status means

This is one half of a “mirror” pair. You can only use this non-hazardous code once you have assessed the waste and shown it does not contain hazardous substances above the thresholds and has no hazardous properties. If you are not sure, it must be treated as hazardous.

Its mirror entry

10 01 20* Sludges from on-site effluent treatment containing hazardous substances Hazardous

Using this code

Write the code on the paperwork when waste is passed on: a waste transfer note for non-hazardous waste, or a consignment note for hazardous waste (called special waste in Scotland).
Choose the code from where the waste came from first (the chapter), then what it is. If a load is mixed, you may need more than one code.
The waste must go to a site whose permit allows that code. A registered carrier can tell you which codes they accept: check a waste carrier.
Businesses have a duty of care to describe their waste correctly.

Other codes in section 10 01

10 01 01 Bottom ash, slag and boiler dust (excluding boiler dust mentioned in 10 01 04) Not hazardous
10 01 02 Coal fly ash Not hazardous
10 01 03 Fly ash from peat and untreated wood Not hazardous
10 01 04* Oil fly ash and boiler dust Hazardous
10 01 05 Calcium-based reaction wastes from flue-gas desulphurisation in solid form Not hazardous
10 01 07 Calcium-based reaction wastes from flue-gas desulphurisation in sludge form Not hazardous
10 01 09* Sulphuric acid Hazardous
10 01 13* Fly ash from emulsified hydrocarbons used as fuel Hazardous
10 01 14* Bottom ash, slag and boiler dust from co-incineration containing hazardous substances Hazardous
10 01 15 Bottom ash, slag and boiler dust from co-incineration other than those mentioned in 10 01 14 Not hazardous
10 01 16* Fly ash from co-incineration containing hazardous substances Hazardous
10 01 17 Fly ash from co-incineration other than those mentioned in 10 01 16 Not hazardous
10 01 18* Wastes from gas cleaning containing hazardous substances Hazardous
10 01 19 Wastes from gas cleaning other than those mentioned in 10 01 05, 10 01 07 and 10 01 18 Not hazardous
10 01 20* Sludges from on-site effluent treatment containing hazardous substances Hazardous
10 01 22* Aqueous sludges from boiler cleansing containing hazardous substances Hazardous
10 01 23 Aqueous sludges from boiler cleansing other than those mentioned in 10 01 22 Not hazardous
10 01 24 Sands from fluidised beds Not hazardous
10 01 25 Wastes from fuel storage and preparation of coal-fired power plants Not hazardous
10 01 26 Wastes from cooling-water treatment Not hazardous
10 01 99 Wastes not otherwise specified Not hazardous

This page explains the code in plain English. It is not a classification of your waste. The official List of Waste and the classification guidance decide which code applies, and you are responsible for the code you use.