Discharging trade effluent

Dealing with effluent that can't go to foul sewers


If your effluents are unsuitable for discharging to the public foul sewer, or there is no public foul sewer available, you could:

  • change your process so you don't produce the effluent
  • treat the effluent on site before discharging it to a sewer
  • pay for it to be taken away for off-site treatment

If you can't discharge an effluent to the public foul sewer it will be classed as waste. You must comply with your duty of care responsibilities when dealing with your waste.

Effluents you can't discharge to the public foul sewer

Your water and sewerage company may not accept discharges of effluents that contain substances which may harm the sewer or treatment process, or be harmful to human health. Harmful substances include:

  • oil and fats
  • solvents
  • working solutions containing heavy metals
  • complex organic mixtures
  • flammable materials
  • other materials likely to damage the sewer, or harm people working in the sewer

Northern Ireland Water (NIW) will advise you if your effluent can be accepted to the public foul sewer. If it cannot be accepted, you will need to consider other options for treatment or disposal.

What to do if no public foul sewer is available

If there is no public foul sewer immediately available, you may be able to pump your effluent to the nearest public foul sewer - with NIW's permission.

Alternatively, you may treat the effluent on site before discharging it to surface waters or groundwater. You must have a discharge consent, groundwater authorisation or pollution prevention and control (PPC) permit from the Northern Ireland Environment Agency (NIEA) before you discharge treated effluent. If you have a discharge consent, groundwater authorisation or PPC permit, it will specify the maximum concentrations of pollutants allowed in the effluent. You will need to decide how to achieve these limits. You may be able to change your processes, or you could consider using package treatment plants or septic tanks - see using septic tanks, package treatment plants and cesspools.

You must not discharge trade effluent into a surface water sewer, surface waters or groundwater without prior permission.

If you are setting up a new business you should investigate effluent disposal before you choose the location of your business.

  • NIEA Helpline
    0300 200 7856