Removal of ammonium ions from digested sludge liquors using natural sorbent zeolite

Abstract

Sludge liquors arising from dewatering of digested sludge by centrifuges or alternative dewatering measures referred to as side-streams. These are recycled back to the head of the works and, depending on their source, can markedly increase the ammonium loading on the wastewater treatment plants. Although forming only a small proportion of the overall volumetric flow, the high concentration of recycled sludge liquors (typically >500 mg/L NH4 +-N) results in a disproportionate impact. This article is dealing with the use of naturally obtained sorbent – zeolite – as an ion exchange in batch tests procedure for ammonium removal from sludge liquor. The novelty of the research was concentrated on rejected sludge liquor from the centrifugation of digested sludge related to high ammonium nitrogen concentrations. The sludge liquor taken at Vilnius sludge treatment plant after centrifugation of digested sludge. Research study carried out with different zeolite particle sizes of 0.3–0.8 mm; 0.8–1.6 mm; 1.6–2.5 mm; 2.5–3.2 mm in laboratory scaled batch test. Comparison of the results showed that the highest removal of ammonium nitrogen from digested sludge liquor obtained by using 0.3–0.8 mm particle size of zeolite.