Process optimization of struvite recovered from slaughterhouse wastewater and its fertilizing efficacy in amendment of biofertilizer

Abstract

The intensive discharge of slaughterhouse waste into water bodies increases Nitrogen (N), Phosphorus (P) in the wastewater and leads to various environmental problems. On the other hand, the increasing treatment effort after the extraction of these valuable nutrients in the commercial fertilizer reduces the dependence on scarce phosphate resources. The viable solution is to recover N, P as struvite (magnesium ammonium phosphate) from nutrient rich waste water as a small scale treatment unit application. The main parameters that have a significant impact on the process, including pH, Mg: P ratio, and precipitation time, were investigated from slaughterhouse wastewater using a central composite design and the experimental data's were statistically analysed. The results indicated that pH and Mg/P ratio level had a significant impact and thus 85% struvite precipitation efficiency was achieved at 9.6 pH and 1.5 dose mol ratio (mol Mg per mol P), in an inexpensive, stirred tank batch reactor with a retention time of 70 min. The fertilization efficiency was tested on the growth of Solanum melongena L with the obtained struvite and the integration of struvite with the Azospirullum rhizobium and Bacillus megaterium. Treatment of struvite, struvite with Azospirillum rhizobium and Bacillus megaterium increased growth parameters by 10%, 20%, and 25%, respectively, over control. The assessment of growth factors showed the most amazing number of fruits, shoots, and root length in a standard ratio of 60:40 of struvite to bio-inoculants compared to sole struvite fertilizer. Findings of this study would be beneficial to determine the feasibility of slaughterhouse waste as a phosphorus source for struvite recovery.