Recovery of Nitrogen And Phosphorus In Sewage Sludge by Pulsed Electrical Field Technique and Strüvite Production

Abstract

Sewage sludge is a rich source of organic matter, nitrogen and phosphorus content. For this reason, its use in agriculture is very important. Struvite obtained as a result of magnesium ammonium phosphate (MAP) settlement is suitable for use as industrial raw material and agricultural fertilizer. At the beginning of the methods used for the recovery of nitrogen and phosphorus from sludge, nitrogen and phosphorus are introduced into liquid phase under acidic conditions. Then the struvite is obtained by MAP precipitation. The biggest problem for this method is the bonding of heavy metals passing liquid phase by acidification to struvite. In our work, a new sludge disintegration method, pulsed electric field (PEF) technique, has been used to recover nitrogen and phosphorus from the domestic biological waste sludge. The study consists of two phases. In the first stage, nitrogen and phosphorus from biological waste sludge are recovered without the addition of chemical by PEF technique. In the second stage, the struvite is obtained by MAP precipitation from liquid phase with high nitrogen and phosphore content. The optimum temperature, pH and precipitation time were determined as 20 degrees C, 9.5 and 24 hours, respectively for the formation of struvite in the MAP precipitation tests. The best precipitate and removal efficiency was obtained to the sample with 2.5 ml of MgCl2 center dot 6H(2)O (0.015 M) and 2.5 ml of H3PO4 (0.049M). TN and TP removal efficiencies were obtained as 52% and 14% after precipitation. After sedimentation, crystalline precipitate formation was observed and XRD analysis revealed that this precipitate was struvite.