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Introduction
It is essential that the treatment and disposal of human waste is carried out in a manner which protects human health and the environment. There are several EU directives which establish the standards for sewage treatment. Each directive has a particular objective, which means that the sewage treatment standards required by different directives may differ. For any given stretch of water, the water authority must meet the highest applicable standards. The Urban Waste Water Treatment Directive (UWWTD) focuses specifically on the waste water treatment standards appropriate for different classes of receiving waters. Other Directives are aimed at ensuring healthy bathing waters, or protecting waters which produce freshwater fish or shellfish so they are fit for human consumption. In these cases the level of sewage treatment required is not specified directly but derives from the required characteristics of the designated waters. The Water Framework Directive, currently under negotiation, will consolidate a number of these requirements, particularly in relation to freshwater fish and shellfish, although separate regimes will continue to apply through the UWWTD and the Bathing Waters Directive.
The Directives, particularly the UWWTD, set challenging deadlines for improving waste water treatment in Scotland, and meeting the requirements of the directives is a major component of water industry investment. In investing in new projects for upgraded facilities to meet the requirements of the UWWTD, the water authorities should plan to meet the requirements of other relevant legislation.
While it is the water authorities' duty to return treated waste water safely to the environment and to do this in a sustainable manner it is the duty of the Scottish Environment Protection Agency (SEPA) to safeguard the quality of the environment *. It issues consents to discharges to controlled waters, which impose restrictions on what water authorities can discharge where.
It is SEPA's duty to protect the quality of controlled waters. It is empowered to do this by various legislative instruments including the Control of Pollution Act 1974, the Urban Waste Water Treatment (Scotland) Regulations 1994, the Environment Act 1995, the Environment Protection Act 1990 and the Groundwater Regulations 1998.
4.1Urban Wastewater Treatment Directive (UWWTD)
The UWWTD requires that levels of treatment are set for discharges from various sizes of community by specified dates. The UWWTD has already led to the cessation of dumping sewage sludge at sea.
It requires that all significant discharges of sewage are treated whether the discharge is to inland surface water, groundwaters, estuaries or coastal waters. Significant discharges are those to fresh waters or to estuaries serving communities with a population equivalent (pe) of more than 2,000 and coastal waters serving communities of more than 10,000 pe The standards to be met depend on whether the receiving waters are classified sensitive, normal or less sensitive. The treatment considered appropriate for most freshwaters, estuaries and coastal waters is secondary, or biological, as specified in the Directive. Secondary treatment is to be provided by 31 December 2000 for discharges above 15,000 pe for all receiving waters. Discharges to inland estuarial waters of between 2000 and 15,000 pe and discharges between 10,000 and 15,000 pe to coastal waters must receive secondary treatment by 2005. Smaller discharges must receive "appropriate treatment" by 2005.
Some freshwaters have been designated as sensitive, namely the Dean Water, Forfar Loch, Strathclyde Park Loch, South Calder Water and River Almond (see map at annex 2). Discharges into waters which have been designated as sensitive require additional treatment to remove nutrients, which had to be in place by the end of 1998.
West of Scotland
Water's (WOSWA) Lesmahagow Wastewater Treatment Works
(Photograph courtesy of WOSWA)
There are also certain estuarial and coastal waters that have been or are considered less sensitive and categorised as high natural dispersion areas (HNDAs). The Directive allows derogation (relaxation) from secondary treatment for certain estuarial and coastal discharges into designated HNDAs. These designated waters are considered to provide sufficient water exchange, or dilution, to allow a lesser standard of treatment than secondary to be adopted. A special environmental assessment, called a comprehensive study is required, to determine the level of treatment which should be adopted so as to avoid adversely affecting the water environment. The minimum standard required is primary treatment.
The comprehensive study should indicate that the lesser standard of treatment will not adversely affect the water environment for coastal water discharges from 10,000 to 150,000 pe and estuarial discharges of 2,000 to 10,000 pe. Any discharges of 150,000 pe and more will require a comprehensive study which indicates that a higher standard of treatment will have no environmental benefit, and a different derogation procedure applies in this case.
Some Scottish waters remain HNDAs. In 1998 Scottish Ministers announced the de-designation of 12 of the 24 original HNDAs around Scotland, and have made clear that secondary treatment standards should be achieved as soon as possible in those areas
As well as standards of treatment, the UWWTD also covers collection systems. Collection systems of the required standard have to be in place to meet the same timescales as for treatment standards. Most sewer systems are combined, i.e. they deal with domestic and industrial wastewater and rainwater. Any such system has to be fitted with storm water or combined sewer overflows (CSOs). This allows the sewer system to cope with storm events which would otherwise overwhelm it. These are intermittent discharges, which, when subject to modern engineering design principles and discharging into waters providing high dilution, do not normally cause adverse environmental impacts. However, there are unsatisfactory CSOs and these are being identified in accordance with the guidance to the regulations. They include overflows tending to discharge outwith storm periods and those causing water quality problems, failure of environmental quality standards and public complaints. These unsatisfactory CSOs need to be upgraded to make them operate appropriately. Water authorities are taking action, often through surveys and analytical studies, known as Drainage Area Studies. These allow a full understanding of the problems within a sewer system and inform appropriate solutions.
Uncertainties The Scottish Executive has asked SEPA to review the remaining 12 HNDAs. This review will include an examination of the criteria for designating an HNDA. This may lead to a further reduction in the number of HNDAs designated and therefore derogation from secondary treatment may not be available in these areas in the future. The areas designated as sensitive also have to be reviewed by 2001. This review could lead to the designation of additional sensitive areas. Where sensitive areas are designated, significant discharges will require additional nutrient removal treatment. A further uncertainty is a requirement in UWWTD to ensure that receiving waters satisfy any other relevant directive. This could, for example, require standards of treatment to be increased for nitrate vulnerable zones.
4.2 Bathing Waters Directive, Recreational Waters and Foreshores
The Bathing Waters Directive requires the identification, monitoring and reporting of compliance with European standards for bathing waters. Member States are required to meet the mandatory standard and work towards compliance with the higher guideline standard given in the Directive. Bacteria are considered to be the main pollutant and water authority sewers are a main, but not the only, source of this pollution. There are other sources of bacterial pollution which arise from diffuse sources, such as runoff from farmland.
Although significant investment in sewage treatment has already been made, a number of failures have occurred throughout the last decade, especially during years with wet summers. The water authorities are currently undertaking substantial investment to tackle any problems which their systems may cause and area-specific research is being undertaken to improve our understanding of other sources which contribute to this pollution.
SEPA has also developed a broader policy to protect the quality of bathing waters, recreational waters and foreshores visited by the public. This reflects two main concerns. First, in some cases the treatment standards required by UWWTD may not enable compliance with the Bathing Waters Directive. For example, locations of outfalls may be an important factor for compliance. Second, in areas not designated under the Bathing Waters Directive there are environmental benefits to be gained by better wastewater treatment and disposal. SEPA's policy is intended to set a framework for giving consents to discharge in these situations. It applies only to new or improvement works for discharges which may affect these waters. Such works will need to be designed to meet the standards set out in the Bathing Water Directive. Many of these works are needed to meet the requirements of the UWWTD by 2000 and 2005.
The Scottish Executive will monitor the improvements to bathing waters deriving from the major investment programmes by the water authorities. Where problems continue, steps will be taken to make improvements in line with the Executive's commitment to bring Scotland's 60 designated bathing waters up to European standards. If these problems are caused wholly or partly by sewer discharges water authorities will be required to take additional action to comply with the Directive. There is no timescale set out in the Directive for meeting mandatory standards. Water authorities should work to achieve these standards at the earliest possible date after designation.
Scottish Triathlon,
Gullane Bents, East Lothian, August 1999
(Photograph courtesy of East
of Scotland Water)
Uncertainties In late 1998, the European Commission signalled its intention to begin a process of revising the Bathing Water Directive. Latest indications are that a proposal will be issued in 2000. Related investment requirements in the period 2002-05 and beyond are as yet uncertain. The investment implications of SEPA's policy on recreational waters and foreshores visited by the public for water authorities post 2000-02 are not yet clear.
In late 1998, the European Commission signalled its intention to begin a process of revising the Bathing Water Directive. Latest indications are that a proposal will be issued in 2000. Related investment requirements in the period 2002-05 and beyond are as yet uncertain
*SEPA has a duty under the Environment Act 1995 to promote the cleanliness of rivers, the conservation and enhancement of the natural beauty and amenity of waters and the conservation of flora and fauna dependant on the aquatic environment.
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