Drinking water quality and access to it

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Drinking water must be accessible to everyone, always, everywhere, in sufficient quantities and consistent and suitable for health. The drinking water supply system (hereinafter: water supply) is a supply area that can be divided into several supply areas, within which the water quality is approximately the same. We group the supply areas into size classes, depending on the amount of water delivered per day or the number of inhabitants: small, medium and large, which supply 50-1000, 1001-10,000 and >10,000 inhabitants, respectively.

When choosing a water source, preference is given to water that does not require preparation. Water preparation ensures the consistency and health suitability of drinking water, usually comprising several phases, e.g.: sedimentation, filtration, disinfection. In 2017, more than a quarter (552,000; 26.7%) of the population in Slovenia were supplied from water supply systems that supplied more than 5,000 people, and a percentage (19,000; 0.9%) of the population from water supply systems with 1,000-5,000 people, with whose water preparation is not required; the water source was "groundwater without the influence of surface water". We must preserve the quality of water resources. Most water supply systems have specific water protection zones with specific regimes for protecting water sources from pollution.

Access to a safe supply of drinking water

In Slovenia, in 2017, 94% of the population was supplied with drinking water from water mains that were included in regular state monitoring of the quality of drinking water (monitoring), at the point of use, at the user's tap. Water supply systems that supply 50 or more people are included in the monitoring. Thus, 6% of the population of Slovenia, who are supplied from water supply systems with less than 50 persons or

provide less than an average of 10 m3 of water per day (e.g. own drinking water supply, self-supply), unless the water is used to supply public facilities, food production and trade facilities, and drinking water packaging facilities.

The largest share of residents who do not have access to controlled drinking water was in Carinthia (25%) and the Savinjska statistical region (15%) (Figure 2). The indicator of access to drinking water shows inequalities by statistical region in terms of safe drinking water supply. The availability of drinking water from water mains, which are under control, slightly improved in the period 2004-2017.

Figure 2: Inhabitants who are supplied from water supply systems included in regular monitoring (monitoring) of drinking water by size classes of water supply systems and inhabitants without monitoring, by statistical regions, 2017.

According to the type of raw water, water sources are divided into surface water and non-surface water - i.e. underground water. Due to exposure to pollution, the quality of surface water is questionable. From a hygienic point of view, water in which the presence of micro- or macro-organisms has been found, as well as water with changes in properties due to the influence of the characteristics of the atmosphere, surface or surface water, are classified as surface water. In Slovenia, these are especially the karst waters, which have a limited ability to self-clean.


Figure 3: Supply areas by type of raw water and the population that supplies them with drinking water, 2017. Source: ARSO, Environmental indicators, Impact on human health, ZD05 Access to drinking water, http://kazalci.arso.gov .si/

Drinking water quality

Drinking water is water in its original state or after preparation, intended for drinking, cooking, food preparation or other household purposes, regardless of its origin or source (whether it is supplied from the water supply network, tanks or as packaged water and water for production and food trade).

Drinking water is suitable for health when it does not contain microorganisms, parasites and their developmental forms in numbers that may pose a danger to human health; when it does not contain substances in concentrations that alone or together with other substances may pose a risk to human health; when it complies with the requirements for the limit values of microbiological and chemical parameters, which are specified in parts A and B of Annex I of the Rules on drinking water. Compliance is compliance with the requirements for the limit values of all parameters from Annex I (parts A, B and C), supplemented, if necessary, with additional parameters and their limit values.

Large and medium-sized supply areas, or water supply systems that supply more than 1,000 inhabitants (86% of the population), generally have an adequate quality of drinking water. A greater risk to health is the presence of microorganisms, which is more common in small supply areas that supply 50-1,000 inhabitants (especially 50-500 inhabitants), as these water supply systems in some places do not have adequate professional water preparation, certain water protection areas, etc. A higher risk for the presence of microorganisms is also found in karst water sources.

The microbiological and chemical quality of drinking water in 2017 was not known for water supply systems that supply less than 50 people (119,600; 6% of the population), which were not included in the monitoring. In addition, data on chemical quality are additionally lacking for water supply systems with 50-500 inhabitants (99,600; 5% of the population), as sampling for chemical parameters is only partially carried out for them.

In 2017, 3,143 samples were taken within scope A (regular testing); due to microbiological parameters, 10.9% of samples were non-compliant, of which 2.8% were due to Escherichia coli (E. coli) (faecal pollution), most of them in water supply systems with 50-500 people (6.8% of samples). The proportion of non-conforming samples drops sharply with the size of the supply areas.

Table 1: Collected samples and non-compliant samples due to microbiological parameters, especially due to Escherichia coli (faecal contamination), in regular tests, by size of supply areas, Slovenia, 2017.

Figure 4: Non-compliant samples due to E. coli (routine testing, size of service areas, statistical regions), 2017.

Sources:

In 2017, 396 samples were taken as part of scope B (occasional testing), which include chemical parameters important for human health. During the period 2004-2017, drinking water samples were non-compliant due to:

  • of chemical parameters Part B of Annex I of the Rules on drinking water: about 1-6% of samples were non-compliant, in some places nitrates (until 2015) and pesticides were exceeded every year, occasionally also arsenic, nickel and lead;
  • of the indicator chemical parameters, Part C of Annex I of the Rules on drinking water: about 0.5-4% of the samples were non-compliant, occasionally aluminum, manganese and iron were exceeded.

Table 2: Withdrawn and non-conforming samples due to chemical parameters of periodic tests, separated from
1) Field measurements are excluded.
2) In addition, 1 sample each was found to be non-compliant during regular testing due to pesticides: atrazine and bentazon.

Sources:

When, as part of the implementation of internal control or monitoring, it is established that the drinking water does not comply with the limit values of the parameters, the operator must immediately determine the causes of the non-compliance and implement measures to eliminate them. The measures must take into account the degree of exceeding the limit value of the parameter

and a potential hazard to human health. In the case of faecal contamination of drinking water, the measure of boiling the water is implemented, in case of excess nitrates, the drinking water for babies and pregnant and lactating mothers is replaced, e.g. with bottled drinking water. In general, these measures do not contribute to the improvement of the quality of the drinking water supply, but protect the acute occurrence of the disease at the point of use (e.g. at the tap). Nitrates were not exceeded for the first time in 2016, as well as in 2017, when in one sample they were just below the limit value (49 mg/l).

Contaminated drinking water can cause acute infections of the gastrointestinal tract, respiratory tract, oxygen transfer disorders in infants, long-term hormonal disorders, some types of cancer and more.

The goal is to improve the quality of drinking water through a preventive approach of multiple barriers: implement a plan to ensure the safety of drinking water, consistently implement water preparation when necessary, determine water protection zones for each system and ensure the implementation of a protection regime in them, reduce pollutant emissions to the ground and surface and groundwater.

A safe supply of high-quality drinking water is extremely important for human health, so local communities must protect every source of drinking water from contamination in their spatial plans.

Residents who are not involved in drinking water monitoring must be informed by the local community and educated about possible measures to protect their health from the harmful effects of contaminated water. If there is a reasonable suspicion of a potential health hazard, he must immediately provide them with recommendations for action.


Figure 5: Nonconforming samples due to the presence of E. coli, by catchment area size class, 2017.


Figure 6: Concentration of nitrates in drinking water, Slovenia, 2017.

Figure 7: Exceeded limit values of chemical parameters (atrazine, desethyl-atrazine, lead and aluminum and iron) in drinking water samples, 2017.

Sources:

Prepared by: Ivanka Gale, Ph.D. med., spec. hyg. and public health.

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