Phosphorus limitations of nitrification in biological sand filters for drinking water treatment – A study at 3 different scales

摘要

The removal of ammonium (NH_4~+) during biological drinking water treatment with rapidrnsand filters can be hampered by lack of nutrients such as phosphorus. Here, we reportrnpreliminary findings from a study of the effect of phosphate (PO_4~(3-)) addition on nitrification inrnlab- and pilot-scale column reactors, packed with sand from a groundwater treatment plantrnwith incomplete NH_4~+ removal, and of the availability of PO_4~(3-)over depth in a full-scale sandrnfilter at the respective plant, before and after PO_4~(3-) addition. In both, lab- and pilot-scalernexperiments, PO_4~(3-) was found to stimulate NH_4~+ removal. Results from these two differentrnscales were qualitatively in agreement. In full-scale, dissolved PO_4~(3-) was always lower thanrntotal PO_4~(3-), and although PO_4~(3-) was added to the influent at approx. 0.150 mg PO_4~-P/L,rndissolved PO_4~(3-) was < 0.005 mg PO_4~- P/L after only 10 cm filter length. Further research willrnstudy the effect of PO_4~(3-) on NH_4~+ removal over depth of the full-scale filter.