EURO-ECO 2010 Hanover 2 - 3 Dezember 2010	Environmental, Engineering - Economic and Legal Aspects for Sustainable Living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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In Latvia harmlessness and quality requirements of drinking water are set in the Republic of Latvia Cabinet Regulation No 235 “Mandatory Harmlessness and Quality Requirements for Drinking Water, and the Procedures for Monitoring and Control thereof“ (adopted 29 April 2003). These legal norms were developed from Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Nevertheless the mentioned legal acts are not applied to drinking water obtained from an individual supply providing less than 10m³/day as an average or serving fewer than 50 persons, unless the water is supplied as part of a commercial or public activity.

Therefore the emphasis of the present study was put on the assessment of drinking water quality obtained from the private wells determining chemical parameters as indicators and those comparing with the maximum permissible values (MPV) set in the Regulation No 235 for the centralized drinking water supply. The study was carried out in Nīca municipality (the centralized drinking water supply is provided only for 26% of inhabitants) that is located in SW of Latvia between the Baltic Sea and partly the Lake Liepaja.

The obtained data show the following.

• The observed concentrations exceed harmlessness requirements set in the Regulation No 235 for total Fe (71%), NH₄ (56%), PO₄^3-(31%), and Cl^- (2%) as well as values of water color (96%), total hardness (11%), and pH (2%). It characterizes anthropogenic impact on drinking water quality from private wells particularly from dug wells that have low protection against contamination by pollutant chemicals e.g. sewage and fertilizers. Therefore the tendency of development of individual drinking water supply in Latvia rural areas is to replace the dug wells with driven or drilled wells. Besides, high concentrations of total Fe testify background level that is higher not only in the studied area but also in all Latvia (more than MPV=0.2mg/l). NO₂ , NO₃ , and SO₄²- ion concentrations and conductivity are less than those MPV.
• Statistical assessment at significance level of α=0.05 testifies the differences of quality of drinking water obtained from dug and bore-holes (driven and drilled wells). Higher concentrations of NO, NO₃ , PO₄^3-, and Si and values of color were observed in dug wells. The value of pH was observed higher in bore-holes. Negligible differences (significance level α=0.05) of chemical parameter concentrations and values in drinking water of dug wells and bore-holes were observed for NH⁺, Cl^-, SO₄^2-, Ca₂⁺, HCO₃ , total Fe, conductivity, and total hardness.
• Statistical analysis shows various distributions of chemical parameters in drinking water:
1. Cl^-, Si, HCO₃ and total hardness succeed normal distribution that specifies background level,
2. NH4+, Ca2+, SO42-, and conductivity succeed logarithmic normal distribution that characterizes anthropogenic source in the case of NH₄⁺ and natural irregular distribution for others,
3. NO₂ , NO₃ , PO₄^3-, and total Fe succeed exponential distribution that proclaims significant impact of NO₂ , NO₃ and PO^3- as well as distinction of total Fe distribution in different sampling sites,
4. for the present distribution of pH and water color is not clear.

The carried out assessment shows moderate quality of drinking water obtained from the private dug wells in Nīca municipality.

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