Long-term operating conditions for different sorption materials to capture phosphate from domestic wastewater

This paper presents the results of a study on the possibility of applying various configured filters filled with a mixture of Rockfos® and Leca® material for the effective capture of phosphate from domestic wastewater. The tests were carried out for two years at two wastewater flow rates (20 and 40 L/day) in three pairs of filtration columns with a volume of filter material equal to 20 L each. Columns 1A and 1B were filled only with Rockfos®. Columns 2A and 2B contained Rockfos® and two 5-cm layers of Leca®. Columns 3A and 3B were filled with Rockfos® and a 10% addition of Leca®. A high phosphate removal efficiency was obtained at a level of 93.2–94.9% for all columns tested at a flow rate of 20 L/day with a retention time of 12 h. After 250 days of the experiment, the efficiency of phosphate removal decreased significantly, which was associated with a drop in the temperature of the inflowing wastewater (<10 ◦C). The alkaline characteristic (11–12 pH) of the filter material promoted the removal of phosphate from the wastewater. The pH value of the treated wastewater gradually decreased from pH 12 on the first days of an experiment to pH below 9.0 after about 300 days of operation. Studies showed that Rockfos® material can be used successfully to capture phosphate from wastewater for the sustainable development of rural areas in the circular economy. When designing and building phosphate removal filters, it is recommended to use 1 m3 Rockfos® with the addition of Leca® in 1 m3 /day of wastewater inflow.