Recirculation of sludge-water in the water treatment process – a pilot study

This paper presents the results of the first phase of research that evaluates options for the optimization of waste-water management during water treatment. The research was conducted in a specific treatment plant, with surface-water sources, to verify the option of recirculating part of the sludge-water back to the beginning of the technological line and mixing this with a portion of raw water. An evaluation of risk factors is necessary for such treatment, as they could render the recirculation of the backwashing water impossible. The motivation behind this research lies in the potential savings of operating costs, particularly the costs of pumping raw water from a watercourse. This research evaluated data regarding the quality of both raw and processed water, focusing on six indicators – turbidity, color, chemical oxygen demand, and concentrations of aluminum, iron and manganese. The evaluation established through these factors indicates that the plan for returning a certain volume of sludge-water back into the process is possible and should cause no problems regarding the quality of drinking water produced. Based on the results of the first phase of this research, it is possible to recirculate up to 6% of overall raw-water volume back into the process.