Combined application of microbes immobilized carbon reactor and the reactive struvite system for the management of tannery deliming wastewater.

Abstract

This present study investigated the removal of COD and ammoniacal nitrogen (NH4+-N) from tannery deliming wastewater (TDLWW) through microbesimmobilized carbon consisted a bioreactor (MICCR) and reactive struvite crystallization process. Initially, 90% of the organic content of TDLWW was removed using a MICCR reactor at 24 h retention time. Nanoporous carbon (NPC) was used as the carrier matrix for the MICCR reactor. SEM and AFM images of NPC used in the MICCR reactor identify different microorganisms on its surface. The microbial profile of NPC used in the MICCR was analyzed, and the relative abundance is phyla Firmicutes, 25.64%; Proteobacteria, 43.68%; Bacteroidetes, 6.58%; Cyanobacteria, 2.22%; Actinobacteria, 2.34% reason for organic removal. The removal of organics follows the pseudo-second-order rate kinetics with the rate constant of 1.75×10-3L COD-1 h-1. For the reactive struvite crystallization, MgO and Na2HPO4.2H2O were taken as the precipitating agents. The optimum molar ratio for the maximum conversion of NH4+-N into struvite was obtained as 1:1.4:1.4 (NH4+-N:MgO:Na2HPO4.2H2O). The volume of struvite precipitate was 48.5mL/L of TDLWW, and the dry weight was 8.89 g/L. More than 93% of NH4+-N was converted as the struvite fertilizer. The conversion of NH4+-N into struvite follows the pseudo-first-order rate kinetics with the rate constant of 1.67×10-2 min-1. Despite the conversion of NH4+-N into struvite, COD removal was observed, which confirms the conversion of organic nitrogen into struvite. The struvite was evaluated using SEM, XRD, TGA, DSC, and FT-IR spectroscopic analysis. Hence, the integrated MICCR and the reactive struvite crystallization process can be applied to manage tannery deliming wastewater.