Table of contents
4. Addressing the challenges to bathing waters
4.1. Bacteria: an invisible health risk
The major sources of faecal bacteria pollution come from sewage, insufficient waste water treatment plants, animals (e.g. birds and dogs at beaches) and water draining from farms and farmland. The presence of faecal bacteria can lead to poor bathing water quality, presenting a threat to bathers’ health. Pollution from sewage is often the result of storm water overflows of sewage, agricultural run-off, or from poorly maintained cesspits and septic tanks. Badly connected plumbing – where for example water from toilets directly enters surface waters – constitutes another potential source of microbiological pollution (EEA, 2018).
In mid-1970s, large quantities of uncontrolled, untreated or partially-treated wastewater were discharged into many European waters. Back then, many of today’s ‘excellent’ bathing waters were heavily polluted and unsafe for recreational use. Swimming at bathing sites with ‘poor’ water quality can result in intestinal illness. If faecal bacteria (e.g. Escherichia coli) enters the human body through contaminated water, it can cause diarrhoea and other illnesses of the intestinal tract.
4.1.1. How has it been managed?
Large investments in sewage systems and treatment plants have caused Europe's bathing water to be much cleaner than in years past in terms of bacterial pollution (EEA, 2019a). Today, almost all significant discharges of sewage from households and industry undergo collection and treatment before they are released into rivers and lakes. Additional treatment methods such as disinfection, chlorination and ozonisation are also being implemented across Europe in order to ensure high hygiene standards for bathing waters (EEA, 2016b).
If microbiological pollution causes ‘poor’ bathing water quality, the sources and extent of pollution have to be assessed in the first place (e.g. foul sewage pipe, pollution from manure). If the causes of poor water quality are not known, special studies to explore the sources might be needed. The implementation of Urban Waste Water Directive has successfully led to reduced pollution and improved water quality at numerous bathing water sites of low quality. The assessment confirms that the UWWTD has proved very effective overall when fully implemented and has improved water quality throughout the European Union. Though implementing the Directive has been expensive, its benefits clearly outweigh its costs (EEA, 2019b). In order to find and eliminate pollution sources, inventories of bathing waters affected by water draining from farms and farmland and from scattered houses with misconnected drains are established. If bathing waters are affected by large number of animals (Box 6), it may be necessary to restrict their access (e.g. fence) or change the location of the bathing water site. Bathing water sites classified as 'poor' have to be closed throughout the following bathing season and must have measures in place to reduce pollution and eliminate hazards to the health of bathers.
Box 6: Birds impacting the quality of bathing water (Czechia)
Brušperk is a water tank built for flood protection in the 1960s in the vicinity of Ostrava, Czechia. It is nowadays used mainly for bathing and fishing. Between 2012 and 2015, the quality of this bathing water was impaired largely due to presence of large quantities of water birds fed by the beach visitors, as well as pollution from the farm located near the tank. In the 2012 season, bathing was temporarily prohibited due to microbial pollution caused by the presence of large quantities of water birds, which were overfed at the shore by bathing water visitors. After intervention from local authorities, the feed was cleaned from the banks of the reservoir and moved to the surrounding water bodies – people were kindly requested to feed the birds at different location which is not used by bathers. The microbiological quality of the bathing water is now ‘excellent’
Box 7: Uncontrolled sewage at the Arturówek bathing water (Poland)
The Arturówek bathing water is located in Poland, on the northern part of Łódź at the edge of Łagiewnicki Forest. It holds three reservoirs, with two adapted for bathing purposes and hiring of water recreation equipment. The Arturówek ponds are an important place of recreation for inhabitants of Łódź, as well as one of the major tourist sites during the holiday period.
There were several uncontrolled sewage discharges in the river catchment upstream of these reservoirs. Since the sewage was washed down by the rainwater and snowmelt to the Bzura river and reservoirs, the quality of this bathing water was heavily impacted.
Since all previous attempts to improve water quality of the ponds (such as the removal of bottom sediments) only improved the situation temporarily, a systemic approach was taken within the ‘Ecohydrological rehabilitation EU LIFE’ project. Technical measures implemented under this project (e.g. desludging its bottom to remove nutrients, or implementation of a novel wastewater treatment technology of sequential biofiltration to reduce the load of organic pollution from sewage) improved the water quality and overall attractiveness of the Arturówek site. This demonstrates the application of the eco-hydrological methods to sustainable water management in urban areas, involving both the public and decision makers. Finally, it establishes the basis for the rehabilitation of key water systems in Łódź under the Water Framework Directive.
In 2018, the Arturówek ponds were finally reopened for bathing after eight years. Even though a BWD water quality classification is not yet possible, the monitoring results are already now showing a gradual improvement of bathing water quality.
4.2. Extreme weather and other events: unpredicted impacts on water quality
The causes of short-term pollution events are usually weather events such as excessive precipitation and subsequent surface runoff, as well as waste water overflow, when a mixture of surface water and foul sewage is discharged to the environment via combined sewer flows (CSO) (EEA, 2018). Concrete pipes, sewers and particularly paved surfaces make it difficult for storm water to be absorbed where it falls (EEA, 2015c). It is also evident that concrete systems in cities are not always able to drain all storm water through the sewage systems and therefore they might be the real cause of urban flooding. For this reason, they need to be addressed with integrative urban management including forecasting pollution in correlation with other factors, managing pollution when it is detected, and assessing the overall risk of such events.
Such pollution events are often of short duration – potentially up to 72 hours but often significantly shorter – and have clearly identifiable causes. After heavy rain, a mixture of surface water and sewage is sometimes discharged into bathing waters or their vicinity, impacting water quality by introducing bacteria and viruses that can affect human health. In a small number of cases, short-term pollution events occur also due to technical errors such as malfunction of sewerage systems or wastewater treatment plants, or the spillage of waste waters from ships.
In the last four years, more than 3 000 short-term pollution events have been reported throughout Europe. The number of reported events is increasing – this may also be an indication of more frequently applied management approaches resulting in a larger number of events reported (EEA, 2017c). Although short-term pollution events occur in bathing waters of all kinds of quality, they much more frequently impact bathing waters of ‘poor’ and ‘sufficient’ quality.
On the other hand, some inland bathing sites may lack water due to droughts caused by low runoff or even water abstractions for hydropower generation, cooling and irrigation. Water quality may deteriorate in parallel due to weak dilution of pollutants. High summer temperatures or construction works on bathing sites may worsen the situation.
4.2.1. How has it been managed?
Sewage overflows across Europe are being managed under the UWWTD using different measures such as the installation of equipment for monitoring spills to the environment, construction of storage tunnels and tanks to reduce the storm overflows as well as formation of nature-based retention basins. Green areas in cities can function as storm-water retention basins and mitigate the load on conventional sewage systems. Such solutions are not only less expensive than traditional ‘concrete’ infrastructure but also provide a wide array of co-benefits for local economies and social communities (EEA, 2015c). Such measures can also prevent flooding as well as minimising adverse impacts to the environment and bathers’ health.
Box 8: Managing storm overflow pollution in Blackpool (The United Kingdom)
There are three bathing waters situated on Fylde coastline around Blackpool, Lancashire, flanked by the urban fringe along the coastline, with agricultural land dominating further inland. Most surface water in the catchment is diverted away from the bathing waters. In the 1990s these bathing waters were of ‘poor’ quality mainly due to insufficient sewage infrastructure.
The £500 million coastal clean-up project »Sea Change« was launched in 1994 by the UK Environment Agency in conjunction with the water service company to improve bathing water quality in North West England, particularly along the Fylde Coast. Under this programme, the company made improvements in the Blackpool area by constructing a tunnel to provide storage for storm discharges and transferring flows from four coastal pumping stations serving the Blackpool area to a new sewage treatment works at Fleetwood. In addition, large storage tanks were also built to reduce the storm overflows. Due to these measures, water quality at Blackpool improved gradually, reaching ‘good’ and even ‘excellent’ quality.
As part of the improvement programme from 2015 to 2020, the storm overflows from Chorley, Blackburn and Preston sewage treatment works will be improved to protect bathing water quality. Further work to reduce the number of storm discharges will improve bathing water quality on the Fylde coast in Lancashire.
Modelling and warning systems are put in place to advice bathers against entering the water after short-term pollution events at bathing waters affected by heavy rains and storm water overflows (Box 9). This is in addition to measures to reduce pollution at source (Box 8) and at rainwater storage basins (EEA, 2018).
Box 9: Early warning system for short-term pollution at the Lake Baldeney (Germany)
Along the intensely industrialised Ruhr valley in northern Germany, the River Ruhr became increasingly polluted through the 20th century. Over time, using the river for recreational purposes became a serious health hazard, and bathing was banned due to chemical and microbiological risks between 1971 and 2015 (Strathmann, et al., 2016). Water quality was additionally deteriorated due to coal and steel mining.
With implementation of all levels of waste water treatments in 2005 in Essen, the site gradually improved water quality. Decades after it was closed for swimming, people can safely bathe in Lake Baldeney again. The development of an early warning system for short-term pollution was an important step in managing this site. Short-term pollution events can happen in running waters after a heavy rainfall event, and for the approval as an official bathing area it was essential to have an early warning system for the swimmers, allowing authorities to swiftly prohibit bathing at the site if needed. The early warning system (Strathmann, et al., 2016) is based on measured precipitation data. It is activated if the rainfall exceeds certain precipitation threshold between the evaluation date and two days before. In such case, a web application issues an automatic bathing warning and bathing is temporarily prohibited at the site. The early warning system is now operating and it has a high level of reliability to protect swimmers from illness.
Essen has proven to be an environmentally innovative city, especially in the face of a challenging industrial history. Important success factors in making bathing at Lake Baldeney possible again include the strong participation of the local population and the scientific evaluation of the costs and the benefits of the operation of such a bathing area (IWW, 2017).
4.3. Algae in water: eutrophication as a health risk
The rapid increase in industrial and agricultural production as well as household consumption in Europe during the 20th century has resulted in greater volumes of nutrient-rich wastewater reaching aquatic ecosystems. The nutrient over-enrichment (mostly from inputs of nitrogen and phosphorus) of seas, lakes, rivers and streams from land-based sources, marine activities and atmospheric deposition can result in a series of negative ecological effects known as eutrophication (EEA, 2019b). As a consequence, aquatic ecosystems are impacted because a considerable amount of oxygen is being consumed by algae while growing and then decomposing (Nemery, 2019). This can lead to water bodies with low levels of dissolved oxygen – known as hypoxia – where many freshwater organisms struggle to survive.
Phosphorus is the main nutrient which causes eutrophication in rivers and lakes, whereas nitrate is the key substance in salt waters. Increased nutrient concentrations can alter aquatic ecosystems to such an extent that they become unsuitable for consumption and bathing.
The main sources of nitrogen pollution are surpluses of mineral fertilisers and manure which are washed out of agricultural soil to groundwater, rivers and seas by the rain. Most phosphorus pollution comes from households and industry. If appropriate mitigation measures are not in place, higher concentration of nutrients can be measured at bathing waters situated downstream of pollution sources, potentially leading to problems with public and environmental health. The consequences of such eutrophication can also include blooms of blue-green algae, which reduce water clarity and quality. Decomposing algae can also cause depletion of oxygen and induce fish kills (CSIRO, 2019).
4.3.1. How has it been managed?
The implementation of the UWWTD – which includes collection and treatment of wastewater in the EU – has resulted in reduced releases of nutrients to fresh and coastal bathing waters, diminishing public health risks in some regions of Europe (EEA, 2010; EEA 2012). As a result, bathing waters all over Europe are now much cleaner than they were 30 years ago. Nevertheless, agriculture continues to be a major source of nutrient pollution, particularly from fertiliser run-off. For example, the Baltic Sea is known to be one of the most eutrophic seas in the world, mainly due to high loads of nitrogen and phosphorus originating from agriculture, entering the sea from river systems (EEA and JRC 2013).
Box 10: Cultural eutrophication of Lake Varese (Italy)
Lake Varese is a small lake of glacial origin in Lombardy, in the north of Italy. Since the 1960s, the lake has suffered water quality deteriorations as the result of intense – and often toxic – algae blooms caused by high phosphorous loads. These have caused fish kills and restricted water use. Lake Varese constitutes the first case in Italy where in-lake methods are used to counteract the problems caused by excessive nutrient enrichment in a relative large system. Since the 1990s, the lake has been the subject of a cooperative research program supported by the European Commission, the Italian Ministry of the Environment, the Lombardy Region, and the Varese Province. In 1992, the Regional Water Clean-up Plan was formed, with the objectives to protect aquatic biota, achieve good ecological status and safeguard water uses, including drinking water supply, bathing (three bathing sites are situated on the lake), fishing and irrigation.
Direct interventions had a key role in accelerating the restoration process in the lake, and in controlling the effects on the phosphorous releases from sediments. Major in-lake eutrophication control methods included nutrient inactivation, lake level drawdown, covering bottom sediments, sediment removal (dredging), harvesting, and other measures. As a result, a great amount of total phosphorous, total nitrogen and ammonia were removed from the lake in 2000 and 2001. Lake transparency is now close to the final objective – 5 metres – of the Regional Water Clean-Up Plan. Algal density has decreased by a factor of four and the frequency of algal blooms has decreased by half.
After decades of neglect due to a lack of beaches, pollution from industrial effluent and eutrophication, Lake Varese has regained its sparkle. In 2018, three bathing waters were operating on the lake; two of them being of ‘excellent’ quality and one being ‘poor’ due to of insufficiently treated waste water.
1.4. Cyanobacteria and other hazards
Cyanobacteria – also known as blue-green algae – can be harmful if swallowed and can cause skin rashes. Proliferations of cyanobacteria can occur when environmental conditions are favourable, such as when there are high levels of nutrients in water, there is a high stability of the water column, and when temperatures and light are favourable and conditions are calm and windless (EEA, 2018). Human activities can accelerate this process through activities such as inadequate sewage treatment, agricultural runoff, and runoff from roads (WHO, 2003).
Cyanobacteria blooms are most pronounced during the summer months, which coincides with the bathing season in Europe, and the highest demand for recreational water. Mass blooms of cyanobacteria can affect the amenity value of recreational waters due to reduced transparency, discoloured water and scum formation. Furthermore, bloom degradation can be accompanied by an unpleasant smell (WHO, 2003). Information available from European countries indicates issues with cyanobacteria blooms in Central European inland bathing waters in Czechia, Germany and Poland, but also in other countries. Although cyanobacteria are not subject to quantitative monitoring prescribed by the BWD, the blooms frequently create the need for temporary advice against, or prohibition of, bathing. Each year, hundreds of bathing water sites are affected by cyanobacteria blooms that decrease water quality and can affect the health of bathers (EEA, 2018). Bathing in water affected by cyanobacteria can result in headaches, nausea, diarrhoea, pneumonia, vomiting, fever and other health issues.
Other hazards, such as chemical pollution, heavy metals, and mercury, can enter bathing waters or be deposited on their coasts from both natural and anthropogenic sources. These can be either diffuse (non-point) sources, such as runoff from land, or point sources such as natural springs with high concentrations of mercury or industrial outfall. Likelihood, extent, and frequency of exposure are vital when assessing the risk of such hazards. Many such contaminants tend to settle at the bottom of water bodies where they accumulate in sediments. If the sediments remain undisturbed, the risk is relatively low. If the sediment is disturbed or bathers are in direct contact with the sediment, the concern is higher.
4.4.1. How it has been managed?
Algal blooms result from a complex interaction between biological, chemical, meteorological and especially hydrographic conditions, of which only few can be controlled. In order to minimise health risks due to cyanobacteria blooms, phosphorus concentrations should be kept below a ‘carrying capacity’ threshold. In particular, nutrient inputs from agricultural runoff may in many cases be reduced by decreasing the application of agricultural fertilisers, or protecting the shoreline from erosion by planting trees and vegetation along the shoreline in order to create ‘buffer strips’ for pollutants.
When minimising the health risks of chemical pollution, it is very important to understand the industry and other human activities in the catchment area and near vicinity of the bathing water, and whether direct or indirect discharges of pollutants are made to the bathing water. Different measures can be applied when reducing the risk of such hazards. In Lake Mälaren in Sweden, 95% of mercury in the sediment was successfully isolated by covering the polluted lake bed with artificial bottom sediment (Box 11).
European overseas bathing waters might be impacted by major weather or environmental events such as cyclones or the massive beaching of algae (Box 12). It is difficult to reduce such hazards. Such events should be closely monitored so that bathing can be prohibited if necessary for public health.
Box 11: Releases of mercury and pollution with heavy metals (Sweden)
Lake Mälaren located west of Stockholm is the third largest lake in Sweden. With an area of 1 140 km2 and extending about 120 km across Sweden, it is the country’s third largest lake. There are 19 bathing sites on its shore. Until recently, mercury spread into Lake Mälaren in the municipality of Nykvarn.
Between 1946 and 1966, a paper mill released fiber residues containing mercury into the Turingeån River and Lake Turingen with its outflow to Lake Mälaren. Although the use of mercury was banned in 1966, secondary releases continued, which resulted in high levels of mercury in water and fish tissues. When remediation management started in 1998, there was almost 400 kg of mercury in the river and lake bottom. In the first stage of the remediation project the mouth of the Turingeån River and an overgrown bay alongside the mouth of the river were dredged. The dredged materials were placed in the inner part of the bay and covered with a sheet and a sealing layer of sand. In the second stage 80- percent of the bottom of Lake Turingen was covered with an artificial bottom sediment to prevent the further leakage of mercury. In addition, 20% of the area outside the mouth of the river was dredged as well and capped with a strong, woven geotextile, fine sand and crushed rock. Water barriers were also built to control the exchange of water between lakes. As a result, about 95% of mercury was isolated. The mercury levels is steadily declining. The remediation could be also applied to cases when sediments are contaminated with other heavy metals or organic contaminants.
Box 12: Bathing waters in overseas territories with specific hazards There are around 250 bathing waters monitored each year that are situated in European overseas territories. All these are French bathing waters and are located in the Caribbean Islands, French Guiana, Mayotte, and Reunion.
These bathing waters are often impacted by major weather or environmental events such as cyclones accompanied by heavy rains, or the massive beaching of Sargassum algae, a phenomenon that appeared in 2014 and seems to be lasting. These phenomena do not necessarily affect the bathing water quality but can impact the management of the water quality control. During the 2018 bathing season, two bathing waters were affected by the Irma cyclone and its consequences, while the Caribbean coastline faced the phenomenon of Sargassum algae bloom. The accumulation of these algae can have significant consequences on the environment and economy and can pose serious risk to bather’s health. Sargassum algae bloom impacted four bathing waters during 2018 bathing season. National authorities prohibited bathing during the event and did not performed sampling due to difficult access to the sites
4.5. Wild bathing in Europe – a challenge for water management
Swimming in natural waters has grown in popularity across Europe in recent years. As a result, the official number of bathing sites identified under the BWD does not cover all the rivers, lakes and seas that adventurous bathers may use. EU legislation, as implemented in national laws, describes main conditions for a bathing site to be designated as official: such as the large number of bathers visiting the bathing site and/or any infrastructure and facilities provided at the bathing site. Because not all potential bathing sites meet these conditions, there are many more bathing sites in use than monitored under the BWD.
Given that unofficial bathing sites are less strictly monitored for potential health risks (if at all) and thus no management is done, their water quality (and thus bathing safety) may remain unknown. For such waters, the implementation of other directives supporting good environmental status is even more important. Sites where bathing is officially prohibited due to ‘poor’ water quality might still be visited by bathers. At such sites, information boards offering advice against bathing and explanations of possible health risks are required. Bathing prohibition information is also communicated through the press, social media and local websites. Monitoring as set by BWD must continue to support ecological restoration measures if implemented.
In Europe, there are many attractive natural waters with ‘excellent’ water quality that are not suitable for bathing due to their ecological vulnerability. Lake ecosystems in alpine and karstic areas, for example, are very sensitive, not only to pollution but also to physical disturbances. Bathing in high mountain lakes can also cause a process of re-suspension of sediment which is accumulated in the lake (Toro, et al., 2006). Swimming in such sites should be controlled. Environmental and potential human health problems might be presented at such sites in innovative ways to help raise visitor awareness and engagement into their protection. The case-study of a small alpine lake of Dvojno jezero in Slovenia (Box 13) demonstrates such issues around wild bathing in ecologically vulnerable environments.
Box 13: Bathing in ecologically sensitive environments (Slovenia)
The so-called ‘Double Lake’ (Dvojno jezero) situated in the Triglav national park in Slovenia is highly sensitive ecosystem impacted by anthropogenic introduction of lake char fish, waste water drainage from nearby mountain had and summer bathing. As is common in other high mountain lakes in Europe, the Double Lake originally did not contain fish (Leskošek, and Brancelj, 2009). The introduction of the fish and and waste water have caused growth of algae (Erhatič, 2010). When people bathe in the lake, they introduce materials into its delicate environment: sun creams, skin excretions, microplastics from bathing costumes, and even food leftovers. As a result, water quality deteriorated in the lake (Leskošek, et al., 2009), posing risks to bathers’ health. In addition the physical activity of swimming can also damage aquatic plants and stir up sediments.
The Triglav National Park and partners have prepared a project called ‘VrH Julijcev’, which aims to restore the ecosystem of the Double Lake. Its restoration measures include the extraction of non-native fish species, removal of organic material, and improved treatment of hut waste water (Paladin, 2018). An information and communication campaign has already started. In order to raise awareness, visitors to the lake and Triglav national park are being informed about the fragility of the lake environment and the adverse consequences caused by bathing activities.