Using chemically treated organic recycling materials to enhance freshwater purification

The greatest source of phosphorus pollution in the freshwater ecosystem is erosion from agricultural areas and point sources. Although this pollution is typically moderated by precipitation and sedimentation, biological and physicochemical methods can be used. The aim of our study was to construct an alternative prototype solution incorporating a filter bed made of suitable recycled phytogenic materials (hemp and harl flax) mixed with chemical compounds (Ca(OH)₂, FeCl₃, and Al₂(SO₄)₃) based on the results of laboratory and field experiments. An 80-90% reduction was noted for deposits with Ca(OH)₂ and Al₂(SO₄)₃ compounds, and 42% for FeCl₃ during laboratory studies. The field studies did not provide such a high reduction of phosphates – only 2% for the Ca(OH)₂ deposit and 49% for the FeCl₃ deposit. This could be attributed to variable physical parameters (pH, temperature and dissolved oxygen) and high negative correlation (r = -0.6296; p = 0.003) with nitrate reduction for the Ca(OH)₂ deposit. However, greater reduction was noted when the phosphate concentration exceeded 1 mg PO₄³⁻ L⁻¹ in field experiments.