Environmental guidance for your business in Northern Ireland & Scotland

Treatment of septic tank discharge where no soakaway is possible

Treatment of septic tank discharge where no soakaway is possible


Package treatment plants

Package treatment plants are self-contained units that will produce a safe discharge from partially treated waste water and sewage from a septic tank. They are designed to carry out the biological treatment that a well-constructed soakaway would provide. They are made in different sizes to cope with the sewage and waste water from different sized dwellings.

Package treatment plants will deal with waste water and sewage effectively, but have the drawback that they usually require a power source as well as regular maintenance.


Reed Bed Systems

You can use a reed-bed or wetland system to improve the quality of effluent discharges from septic tanks. This enhanced level of treatment might be required before a discharge is allowed into a sensitive or small watercourse, a watercourse that receives many discharges, or a drainage field where groundwater is vulnerable.

Reed beds are built on an impermeable base, usually with a layer of gravel above. This provides suitable growing conditions for species of plant that can absorb organic material in the sewage effluent, and in this way purify the discharge from the septic tank.

Reed beds are effective, and have the advantage over a package treatment plant that they require no power and need less maintenance. They do however require a significant area of land to be used if they are to work effectively. Package treatment plants can be a more practical and effective solution.

Reed bed systems are not the preferred option in Northern Ireland.



If your septic tank can’t be drained to a soakaway, you will need to get an authorisation from the NIEA or SEPA. This will require treatment of the septic tank discharge before it reaches the water environment. You may be required to install a package treatment plant or reed bed in order to get an authorisation.

You must contact the NIEA or SEPA before you construct a reed bed to ensure that your plans will provide satisfactory treatment for the effluent in the local circumstances. A reed bed must be properly designed, constructed and maintained. In Northern Ireland reed beds are not generally considered to provide adequate treatment and are unlikely to be approved. Contact your environmental regulator

Guidance on how to construct a reed bed is available from the Building Research Establishment.

Building Research Establishment Good Building Guide No 42 (GG42) Reed Beds 2001. ISBN 1860814379.

BRE, http://www.brebookshop.com/, Tel: 01344 404 407

In this Guideline

How septic tanks work

What shouldn't go into a septic tank

Maintaining your septic tank

Register your septic tank

What can go wrong with a septic tank

New tanks - Planning waste water and sewage treatment

Treatment of septic tank discharge where no soakaway is possible

If a septic tank can't be installed on your site

Septic tank legislation

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NIEA - Apply online

SEPA - Application forms