Efficiency of phosphorus removal and recovery from wastewater using marl and travertine and their thermally treated forms

Abstract

This paper presents a study under the dynamic conditions of marl and travertine materials and their thermal modifications (heated in a muffle furnace for 1 h: marl at 1000 °C, and travertine at 700 °C) and the material Polonite® in terms of phosphorus binding from municipal wastewater. The tests were carried out in filtration columns using hydraulic loads of 118.13, 312.56, and 640.45 dm3/(m2·h) until the ratio of effluent phosphorus concentration to initial phosphorus concentration reached 0.97. Materials with adsorbed phosphorus were subjected to the desorption process using distilled water and NaOH and HCl solutions, applying a hydraulic load of 312.56 dm3/(m2·h). To comprehensively assess the potential use of materials and their thermal modification in agriculture, leaching of elements from them was determined. The most favorable hydraulic load was 118.13 dm3/(m2·h), at which the sorbents achieved the best efficiency. The marl heated at 1000 °C was the most effective, achieving the longest working time of the bed with an efficiency greater than 98 %. The best reagent for desorbing phosphorus from the heated marl surface was a solution of 0.1 mol/L HCl, while for other materials a solution of NaOH 0.1 mol/L. Raw marl was the best at releasing phosphorus in the presence of distilled water, which combined with the results for the leaching of elements from this sorbent, indicate its potential use as a fertilizer or soil conditioner in agricultural production.