Water as a transport medium for waste
For many waste materials, flushing away into the sewerage system is a cost effective and environmentally efficient means of disposal.
Most modern commercial and industrial premises have separate connections to sewer and surface water. Surface water drains take rainwater to the nearest stream, river or other body of surface water.
Sewers convey contaminated water to a sewage treatment works. Treated water is then released to the environment whilst the pollutants removed from the water are disposed of according to regulations, (e.g. spreading on land as fertilizer, incineration (preferably with heat recovery) or landfill).
Process emissions
The wastes from many industrial processes are removed from sites via the sewerage system. This can only be done with the consent of the ‘sewerage undertaker’, i.e. the utility company which operates the sewers. The producer of the waste pays according to a formula which takes into account the level of contamination and the cost of operating the sewerage system (see Mogden formula in resource efficiency).
It is possible for process water to be released to the environment via surface water drainage (e.g. cooling water from power stations), but this is rare and strictly controlled by the Environment Agency.
Sanitary waste
Most industrial premises have a direct connection to the sewers to carry away waste water from toilets, kitchens, mess rooms, etc.. Again, this is done under an agreement between the operators of the premises and the sewerage undertaker. Charges are usually made according to the average number of people present on a site.
Surface water drainage
Most commercial premises emit rainwater collected on roofs, yards and car parks into the surface water drainage system. For many of these premises, the water will travel across the surface of the site and enter the surface water drainage system uncontaminated. However, if, for example, the yard has inadequate interceptors for capturing spilt oil, or is the site of processes like the washing of vehicles, then the water returning to the environment may be contaminated with potentially harmful and illegal emissions.
If the Environment Agency considers that the site poses a risk of such contamination, then they will require the site operator to obtain a consent for discharging to surface water.
If you are taking over environmental responsibility for your site, you should check the records to see if a consent is in place. If it is, then an annual fee will need to be paid and regular visits by the Environment Agency can be expected.
You should review the possibilities for contamination regularly and especially when processes or activities on your site have changed (see also emissions to land and Aspects and impacts in environmental management systems).