Recovery of ammonium nitrogen from the effluent of UASB treating poultry manure wastewater by MAP precipitation as a slow release fertilizer

Abstract

Magnesium ammonium phosphate hexahydrate (MgNH4PO4 center dot 6H(2)O, MAP) precipitation was studied on up-flow anaerobic sludge blanket (UASB) pretreated poultry manure wastewater in a lab-scale batch study. To recover high strength of ammonium nitrogen (NH4+-N = 1318 mg/L) from UASB effluent, three combinations of chemicals including MgCl2 center dot 6H(2)O + KH2PO4, MgSO4 center dot 7H(2)O + NaHPO4 center dot 7H(2)O, and MgO+85% H3PO4 were first applied at the stoichiometric ratio (Mg2+:NH4+-N:PZO(4)(3-)-P = 1:1:1) and at different pH levels ranging from 4.45 toll. Preliminary test results indicated that maximum NH4+-N removal, as well as maximum chemical oxygen demand (COD) and color reductions, were obtained as 85.4%, 53.3% and 49.8% at pH 9.0 with the addition Of MgCl2 center dot 6H(2)O + KH2PO4, respectively. The paired experimental data obtained from batch studies were statistically evaluated by a non-parametric Mann-Whitney test and a two-sample t-test. Based on the previous results, another batch experiments were then performed at pH 9.0 using MgCl2 center dot 6H(2)O + KH2PO4 for different molar ratios applied as overdose (11.21:1, 11.51:1, 1:1:1.2, 1:11.5) and underdose (0.51:11, 0.8:1:1, 1:1:0.5, 1:1:0.8). In the final step, the fertility of the MAP precipitate as struvite was also tested on the growth of three test plants including purslane (Portulaca oleracea), garden cress (Lepidum sativum) and grass (Lolium perenne). Findings of this experimental study clearly confirmed the recovering of NH4+-N from UASB pretreated poultry manure wastewater by MAP precipitation, and also the application of recovered MAP sludge as a valuable slow release fertilizer for agricultural use. (C) 2008 Elsevier B.V. All rights reserved.