Studies into the technology of purifying groundwater with a high content of iron, manganese, and ammonium

The paper studies the operation of a highly mineralized water purification system with a reverse osmosis unit for the needs of a metalworking enterprise. It identifies the reasons for the unsatisfactory operation of the water pu-rification system and develops recommendations for its improvement based on the assessment of water quality in sam-ples at water treatment stages and the assessment of the tendency of the feed water to form silt on reverse osmosis membranes. The work aims to develop an effective technology for purifying highly mineralized water, which contains both ammonium and iron ions, based on the study of the existing water purification system at the enterprise. Groundwa-ter is chloride-sulphate calcium-magnesium and does not meet the requirements for drinking water in terms of turbidity, total mineralization, total hardness, ammonium, total iron, silicates, magnesium, manganese, sodium, strontium, and chlorides. Standard methods were used to determine water quality indicators at various water treatment stages. High-resolution scanning electron microscopy was used to analyze the surface of the filter material grain. The elemental composition of the filter material grain and its surface sediment were analyzed locally using energy dispersive spec-trometry. The hypothetical composition of groundwater and the quality of water at various water treatment stages were investigated; the silt density index, the Langelier index, and the Gibbs energy of carbon dioxide equilibrium in the aera-tor were calculated; the aeration system performance was assessed. The reasons for the performance slowdown of the reverse osmosis unit and the frequent replacement of the pressure filter media were identified. The tested water supplied to the reverse osmosis unit does not meet the requirements for total hardness and total iron. +The insufficiency of the specific air flow rate in the aerator was proven. Mudding of granular filter material with calcium carbonate and amor-phous silicon was observed. Technical solutions are proposed to increase the efficiency of aeration-degassing and iron removal at the preliminary water purification stage before reverse osmosis. The proposed solutions will be relevant for the design and operation of process flows for complex groundwater purification.