About our writer
Patricia Ash is an associate lecturer in science and biology with the Open University and also works as a consultant in the fields of biology and the environment. Her research is a study of the ecology and diet preferences of the speckled bush cricket in two locations: the coast and Oxfordshire.
Previously she worked for the Medical Research Council as a member of the Scientific Secretariat for the Committee for Protection against Ionizing Radiation. Her role was to study the medical effects of ingested radionuclides, such as plutonium-239 and strontium-90 and also to monitor reports on radioactive discharges from nuclear power stations.
Power from the waves
If we don't want nuclear and can't have oil, will the resources of the coast keep us plugged in?
Patricia Ash discusses whether we can stop using the sea as a dustbin
For many years the UK, nicknamed the ‘dirty man of Europe’, has used the sea as a convenient dustbin for sewage, radioactive waste and toxic chemicals. All three categories of waste damage our coastal environment. Pollution by sewage and radioactive waste have recently been of particular public concern.
Raw sewage is broken down in the sea by micro-organisms, which use up a lot of oxygen in the process. Depleted oxygen levels in seawater kill fish and other marine life. Sewage contains 10,000 to 10 million viruses per litre, the hepatitis A virus amongst them, and faecal bacteria - including pathogens. Condoms and cotton swabs flushed down toilets travel with raw sewage into the sea, and - along with faeces - may be washed up onshore. This used to happen on some Devon and Cornwall beaches as recently as the early 1990s. In response, the group ‘Surfers Against Sewage’ (SAS) was set up to campaign for clean, sewage-free coastal waters.
Sewage treatment begins with screening to remove large objects. Primary treatment follows, where raw sewage is left in tanks for 2-6 hours, allowing roughly 55% of solids to settle to the bottom. The liquid contains about 10 million bacteria per litre, and may be pumped into a long coastal outfall pipe or subjected to secondary treatment. The latter involves settling the liquid in another tank, one which contains bacteria that feed on the liquid and sludge. After the secondary stage, the clear liquid contains approximately 100,000 faecal bacteria per litre. The tertiary stage is disinfection of the liquid either by ultraviolet light or microfiltration.
Since the early 1990’s, many water companies adopted tertiary treatment for sewage before discharge into the sea. The Devon town of Croyde obtained planning permission for tertiary treatment of the town’s sewage in 2001, and as a result beaches in North Devon are very clean and receive the coveted Blue Flag awards. Elsewhere the situation is not resolved; at time of writing - July 2005 - untreated sewage from Brighton is discharged into the sea via a long outfall pipe. In 2004, Southern Water announced plans for a new secondary treatment plant to deal with Brighton’s sewage before discharge into the sea, but not a tertiary treatment facility, meaning that significant amounts of viruses and faecal bacteria would still get into the seawater. Surfers Against Sewage continue to campaign for such a tertiary sewage treatment plant for Brighton.
What about the sewage sludge – what can we do with that? It can be used as fertilizer, but requires further breakdown by bacteria. Data collected by the Department for the Environment, Farming and Rural Affairs (Defra) shows that about half of all sludge was spread on farmland between 1990 and 1998. A drawback for using sludge from industrial areas is that it contains toxic chemicals and heavy metals. About 10% of sludge was disposed to landfill and a further 10 to 20% disposed of at sea. 20% was incinerated, and the remainder disposed of by ‘other means’. Since 1998, the EU’s Urban Wastewater Directive has outlawed dumping of sludge at sea and other methods are used, including composting and use in land reclamation.
Litter is common on beaches and in our coastal waters and most is plastic, cups and supermarket bags, but cans, paper, cardboard, shoes, glass, pottery and munitions also spoil our beaches. The sight of a messy beach puts tourists off from returning, reducing income for local people. Yet tourists themselves contribute to this marine litter, as do people on cargo boats, ferries, fishing boats and oil rigs. Litter harms wildlife: seabirds and cetaceans are killed by swallowing litter or getting entangled with discarded fishing nets. In turn, fishing nets are ripped by large pieces of debris and the recent ‘Fishing for Litter’ campaign encouraged fishermen to bring to shore for safe disposal any litter caught in their nets. Statutory measures to reduce and prevent marine littering are in place but are obviously difficult to enforce on the open sea.
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Content last updated: 08/07/2005
