Economic water monitoring water quality summary 2023

Domestic water in the urban area comes from the Immala water plant, from which water was pumped in 2023 about 2 m³/d. Domestic water is also piped to Imatra from the Myllypuro water intake in Lappeenranta's Joutseno, from which water was pumped to Imatra at an average of 905 m³/d in 1. Approximately 978 m³/d from Ruokolahti municipality's Lampsiinlammi groundwater intake was piped to the residential area of ​​Saarlammi and Koivuniemi. Groundwater from Hiekkoinlahti and surface water from Immalajärvi (share approx. 2023%) are piped to the Immala water plant for processing.

The raw water and outgoing water of the Immala water treatment plant, as well as the quality of network water, are comprehensively studied in the Imatra area. The samples were analyzed in SGS Finland Oy's Karkkila environmental laboratory, which is a laboratory approved by the Food Agency. 

The domestic water supplied by Imatra Vede met the health quality requirements according to the Ministry of Social Affairs and Health's regulation (1352/2015) and the quality goals describing usability in 2023. The quality of the domestic water was also good in the network as measured from the users' water taps, and the domestic water met the requirements of the regulation and the goals with a few high colony counts and elevated manganese concentrations related to the Koivuniemi sampling point except for. In the network, the property's effect on domestic water quality was seen as exceeding the temperature quality target 5 times (20 °C, 1 min after running). Cold water temperature that is too high can increase the risk of legionella bacteria multiplying in the building's water system. Domestic water should always be run from the tap before drinking and using the water for cooking, so that the water is cold. According to the monitoring research program, 2023 water samples and a few additional samples were taken from the network in 112. 

In the years 2017 – 2023, low amounts of BAM pesticide 0,01 – 0,019 µg/l have been found in the water supplied to the network from the water utility. The health-based quality requirement is <0,10 µg/l, so it is not harmful to health. BAM, i.e. 2,6-dichlorobenzoamide, is a degradation product of diclobenil herbicide. Pesticides and their degradation products are studied comprehensively in water (275 items/study).

The microbiological quality of the water leaving the Immala water treatment plant was good in 2023. UV disinfection and chlorination of household water removes any bacteria. Chlorination (picture below) protects the microbiological quality of water also in the network. The concentration of chlorine (as monochloramine) is clearly below the odor and taste threshold value in the water leaving the Immala water plant. The chlorine content of Myllypuro domestic water, which is chlorinated at the Korvenkylä pressure boosting station, is also low. However, the smell of chlorine was detected in some of the network samples of the affected area of ​​the Immala and Myllypuro plants. This is because when chlorine breaks down and reacts in the network, decomposition products can be created, which can cause a foreign smell in the water even at very low concentrations.

Picture. The chlorine content of the water leaving the Immala water plant in 2023. The concentration of bound chlorine, i.e. monochloramine, is clearly below the odor and taste threshold values.

Water hardness consists of dissolved calcium and magnesium. Hardness is indicated either in German degrees (°dH) or millimoles (mmol/l), 1 °dH = 0,18 mmol/l. Imatra's network water is mainly soft, occasionally medium hard. The following table shows the results of the monitoring, the quality of the water leaving the Immala water plant and the quality of network water by region as averages for 2023. The pH value, alkalinity and hardness of the water leaving the Immala plant were at the optimal level in terms of corrosion prevention in 2023, which means that lime starts to precipitate in warm water, but not in cold water, and the iron content of the network remains low. According to the lime-carbonic acid balance (picture below), lime starts to precipitate from the outgoing water at a temperature of approx. 40 °C.

Picture. Graph of the lime-carbonic acid balance of the water leaving the Immala water plant.

The table below shows the results of water analyzes by sampling point. The results are the averages of the sampling times in 2023.

* = user acceptable and not unusual changes
** = In accordance with the Domestic Water Ordinance, no unusual changes. The municipality's health protection authority has set a maximum value of 100 pmy/ml for the variable per water distribution area.

Report 31.1.2024 / FCG Finnish Consulting Group Oy