The quality of drinking water supplied by the Municipality of Nagykőrös does not comply with the requirements of 201/2001 with regard to ammonium content. The water quality parameters set out in Government Decree No 25 October 2012. Drinking water purification technology to be implemented: biological purification of water produced from an existing water base. The technical solution consists of treating the raw water of the existing Nagykőrös water production unit to such an extent that it complies with the quality limits of drinking water laid down in the relevant Government Decree 201/2001 (X.25.). According to the available measurement data, the water produced exceeds the limits laid down in that Regulation in respect of the parameter ammonia, but in order to remove it, it is necessary to remove iron and manganese present in raw water by pre-cleaning in order to increase the cleaning efficiency. No expansion of the water base will take place. It is also necessary to carry out the reconstruction and development of outdated network elements, but the amount of the recreation of the drinking water network to be declared does not exceed 20 % of the eligible costs.