Experimental Study on the Application of Sludge from Water Treatment Plant as a Reagent for Phosphate Removal from Wastewater

Abstract

The paper presents the results of laboratory studies on the removal of phosphate in a wastewater treatment plant by adding sludge formed at the water treatment plant (water treatment sludge—WTS) in the city of Astana (Kazakhstan). Raw WTS from the sludge drying beds was used in the study, and the content of chemical compounds present in the dry sludge residue was determined, yielding 10.8–14.6% aluminum oxide (Al2O3) and 4.58–5.31% iron oxide (Fe2O3). The sludge moisture ranged from 90.5 to 95.6%, and the ash content ranged from 51.3 to 63.9%. The raw sludge from the WTP was added to the wastewater collected before the sand trap and after biological treatment. On the basis of the obtained test results, it was found that the effect of phosphate removal depended primarily on the sludge dose and was above 90% when adding 50 mL of sludge to 1 L of sewage. To a lesser extent, the effect of phosphate removal was dependent on the contact time of the sludge with the wastewater and the place where the wastewater sample was taken.