Modeling & simulation studies on batch anaerobic digestion of hydrodynamically cavitated tannery waste effluent for higher biogas yield

Shivendu Saxena; Virendra Kumar Saharan; Suja George

doi:10.1016/j.ultsonch.2019.104692

Modeling & simulation studies on batch anaerobic digestion of hydrodynamically cavitated tannery waste effluent for higher biogas yield

Ultrason Sonochem. 2019 Nov:58:104692. doi: 10.1016/j.ultsonch.2019.104692. Epub 2019 Jul 16.

Authors

Shivendu Saxena¹, Virendra Kumar Saharan², Suja George³

Affiliations

¹ Department of Chemical Engineering, MNIT, Jaipur 302017, India.
² Department of Chemical Engineering, MNIT, Jaipur 302017, India. Electronic address: vksaharan.chem@mnit.ac.in.
³ Department of Chemical Engineering, MNIT, Jaipur 302017, India. Electronic address: sgeorge.chem@mnit.ac.in.

PMID: 31450286
DOI: 10.1016/j.ultsonch.2019.104692

Abstract

This study describes the efficacy of the pretreatment method of tannery waste effluent (TWE) by hydrodynamic cavitation (HC) prior to anaerobic digestion (AD) using a slit venturi cavitating device operated at 5 bar pressure for 2 h. The HC effect caused faster disintegration and solubilization of larger organic molecules into smaller ones, so that it could be easily digested by the microbial cells resulting in higher degradation rates, lower acclimatization time, higher COD reduction of the TWE and higher biogas generation. The biogas yield and % COD reduction was almost twice higher in HC treated TWE compared to raw TWE. Biogas yield of 68.57 mL/g volatile solids with 43.17% COD reduction was obtained during AD of HC treated TWE in 2 L bioreactor with 10% seed dosage. 'AD' Simulator developed in MATLAB represented the AD performance for both raw and HC treated TWE feed and predicted for concentrations of organic polymers, monomers, VFA and biogas produced, in which model parameter optimization was done by validations using methane production data from bioreactors. The AD simulator estimated higher hydrolysis rate constants for HC treated TWE than for raw TWE as observed in the experiments. Biogas production increased up to 7.8 and 11.8 folds for raw and HC treated TWE samples respectively by adding food waste to TWE feed with organic loading rate of 48 h. Cost estimations proved that cost of excess biogas produced by anaerobic digestion of HC treated TWE mixed with food waste, recovers the extra cost of HC pretreatment when compared to raw TWE alone, establishing HC as an effective pre-treatment tool prior to AD.

Keywords: Anaerobic digestion; Biogas yield; Bioreactor; COD reduction; Hydrodynamic cavitation; Tannery waste effluent.