The UK population uses around 17.5 million tonnes of water per day, and disposes of 11 million tonnes of wet sewage, every day.

To do this the industry has over 380,000 km of sewers, 11,000 discharges from sewage treatment works and 27,000 intermittent discharges (storm outlets and combined sewer overflows). The water industry therefore has the single greatest impact on marine and coastal pollution, and requires careful environmental regulation.

The 11 water and sewerage companies and the 13 water supply companies run the water industry. The Environment Agency in England and Wales, and the Scottish Environment Protection Agency are the environmental regulators, and industry is overseen by the UK Government watchdog Ofwat, and the Scottish Executive.

why is sewage a problem?

Sewage is broadly a combination of domestic and industrial liquid effluent and  suspended solids. It consists of organic faecal matter, bacteria, viruses, fats, chemicals, heavy metals, debris and nutrients such as nitrogen and phosphorous.

Untreated sewage is primarily organic in nature and subject to bacterial decay. In low concentrations it may actually be beneficial to the marine ecosystem, but discharged in massive quantities it causes ecological problems such as eutrophication (loss of oxygen from the water), and direct physical impacts to marine life such as poisoning, smothering, and the disruption of growth, respiration, reproduction, and the immune system.

human health risks

Raw sewage is full of pathogenic bacteria and viruses. Numerous studies have shown that swimming in sewage contaminated water can lead to gastroenteritis, acute febrile respiratory illness and ear, nose and throat infections. Hepatitis A and typhoid are also possible, although the scientific evidence for these associations is less robust.

Shellfish grown in sewage contaminated waters can cause food poisoning because filter feeding animals such as mussels and oysters concentrate sewage relate pathogens and toxins in their tissues as they feed.

sewage treatement

There are four progressive levels of treatment that aim to produce a final effluent which is clean enough to achieve water quality standards set by the European Bathing Water Directive, Shellfish Waters Directive and Urban Waste Water Treatment Directive.

• Preliminary treatment - Grit removal, screening and liquidising. The effluent is then discharged with no reduction in pathogenic bacteria and viruses.
• Primary treatment -50 to 70% of the suspended solids are removed by settlement. The effluent is then discharged with no reduction in pathogenic bacteria and viruses.
• Secondary treatment - biological purification following primary treatment. Organic matter is digested by micro-organisms, removing 75-99% of pathogenic bacteria and viruses. The treated liquid is then discharged.
• Tertiary treatment - Disinfection following secondary treatment, commonly by ultraviolet irradiation or microfiltration. Removes all remaining pathogenic viruses and 99.9% of bacteria. The treated liquid is then discharged.

MCS does not advise swimming in water subject to preliminary and primary discharge. Swimmers are also advised to seek advice on local water quality. This information is available at http://www.goodbeachguide.co.uk/ - an MCS publication.

Since 1995, the Urban Waste Water Treatment Directive has exerted significant and positive pressure to clean up sewage discharges, and in the last five years the UK has invested £6.47 billion in our sewage infrastructure.

In September 1998, the UK Government announced an ambitious seven year improvement plan to provide secondary sewage treatment as a minimum standard at all treatment works serving communities greater than 2,000 people in England and Wales. In December 2005, it became apparent that this target had been narrowly missed, but high levels of investment are on-going. In the period 2005 - 2010, total capital expenditure by water companies in England and Wales will be £16.8 billion, of which £5.5 billion will be spent on environmental and quality improvement schemes.

Public water and sewerage services in Scotland are delivered by Scottish Water, a publicly owned company set up by the Scottish Executive in 2002. The Quality & Standards III capital investment programme will spend £2.15 billion between 2006 and 2010. The Good Beach Guide currently describes 47 Scottish bathing sites subject to raw, preliminary or primary sewage discharges that MCS would like to see improved as a priority

In Northern Ireland, water and sewerage services are delivered by the Northern Ireland Water Service (NIWS). The province is in dire need of investment in its waste water infrastructure. In December 2005, a report issued by the UK Department of the Environment's Northern Ireland Environment and Heritage Service concluded that NIWS was responsible for 23.5% of all water pollution incidents during the previous year. NIWS is now due to spend £420 million in wastewater treatment works and sewer network upgrades to improve this situation.

what you can do:

• Consult the Good Beach Guide for a list of beaches that MCS recommends for excellent water quality and well treated local sewage discharge (if any).

• Bag It and Bin It - don't drop it and flush it. Careless beach visitors and non-biodegradable items flushed down the toilet are the two biggest sources of beach litter.

• Report sewage accidents to the Environment Agency hotline: 0800 80 70 60