It is a requirement of the Water Industry Act 1991 that all water discharged to the sewage network, irrespective how good or poor the quality, cannot be discharged until a trade effluent discharge permit has been issued by the operators of the sewerage treatment works to which the water will eventually flow. This applies to work carried out by main contractors, mechanical contractors (site canteens, toilets, pipework flushing  etc)  and water treatment providers (pre-commission cleaning, biocide washes, disinfections). Permits are chargeable – the prices and conditions of issue vary widely throughout the UK.

There does, however, appear to be a sharp increase in the number of contractors who are choosing to ignore this vital legal requirement simply to make their tenders more attractive in an attempt to win orders by not having to pay the permit fee. But that comes with the risk of a hefty fine if work is undertaken without a one.There are sound and valid reasons why Trade effluent discharge permits are included within the Water Industry Act:

1. The application to the water company will highlight the potential for banned, highly toxic substances being discharged, thereby allowing action to be taken to prevent it from happening. Overdosing of some biocides used in the cleaning of mechanical systems for bacteria prevention can result in the water-borne micro-organisms used in the secondary treatment phase at the treatment works being totally destroyed, resulting in a shutdown of the treatment works.

2. The water companies have a duty to protect their employees working in the sewers and at the treatment works. Details provided on the permit application are used to identify incompatible substances being discharged on the same day, in the same sewer network. For example:

a. If chemical descaling is being carried out at a property whilst a disinfection using chlorine is being carried out at an adjacent building at the same time, the mixing of the two chemicals will result in the generation of toxic chlorine gas (used in the First World War under the name of Bertholite) which can be lethal even at low levels.

b. Physical contact with some substances can cause permanent, damaging medical conditions.

3. Water companies can identify and ban the discharge of substances that could damage the fabric and infrastructure of the sewer network and treatment works, thereby preventing dangerous conditions such as sewer collapses.

4. The discharge volume and flow rates are considered by the water company, allowing them to prevent overflows from the sewerage system due to excess use.

Consequently most permits are restricted to specific discharge dates, maximum flow rate to waste, maximum daily volumes, the substances being discharged, the specific location of the discharge and they can only be used by the company to whom it has been issued.

The practice of deliberately ignoring the Water Industry Act will no doubt carry on, but several water companies have indicated they are now pro-actively increasing the monitoring of effluent discharges and that they will have no hesitation taking offenders to court.

Discharging to surface water (a river, stream, estuary or sea) or ground water (via filtration) requires an Environmental Consent from the Environment Agency. Discharging to ground requires the same application as ground water.