Ground drinking water improvement with iron removal filters in Kudirkos Naumiestis and Bagotoji, Lithuania
The design of water purification facilities was based on the groundwater quality parameters and estimated outputs. The measured iron concentrations in the groundwater before implementation of the investment have exceeded the maximum level for iron in drinking water, i.e. 200 µg/L. This concentration is set as the Specific Limit Value (SLV) for the drinking water in the Lithuanian Hygiene Norm (HN 24:2003). The higher concentrations of iron in the drinking water can cause aesthetic problems such as bad taste, brownish color of the water, staining. Also, it can deposit in the water distribution system leading to the pipes fouling.
Components installed in the solution
The water purification process consists of oxidation and filtration steps. The principle of iron removal from drinking water process is based on soluble ferrous compounds oxidation to insoluble ferric compounds. Oxidation is followed by filtration process. Formed precipitates (iron hydroxide) are removed in this stage.
Two parallel water purification equipment lines, consisting of oxidizers (aerators) and filters are installed in the water treatment station. Water, extracted from the artesian wells is fed into the aerators. Compressors are used for oxygen injection into the water. Excess air is removed using automatic de-aerator. After oxidation step, water is fed into automatic filters. Oxidized iron compounds, and, partly, manganese and ammonia compounds, are precipitating on the filter media. The purified water is supplied for the consumers.
Automatic iron removal filters are in turns regenerated during night time. The regeneration is performed by back-washing procedure; the regeneration time normally is about 9 minutes. Direct flow washing time is about 2 minutes. Duration of regeneration cycles is adjustable and can be revised on the setup stage and during the exploitation.
The area of the selected location for the construction of the water purification plant in Kudirkos Naumiestis is 4393 m2. The iron removal facilities consist of the pressurized aerators and the automatic pressurized filtration system. For the removal of excess sludge, filters must be periodically regenerated. Residual concentration of iron in the purified water does not exceed 200 µg/L. The water purification equipment is installed in the container building. The principal scheme of the water purification equipment arrangement is provided in Annex 4 (see related materials). The building is situated in Šakiai district, Kudirkos Naumiestis, Kybartai Street 13.