posted on 2021-11-16, 07:05authored byAbirami Balakrishnan, Sri Bala Kameswari Kanchinadham, Chitra Kalyanaraman
Tannins
present in the vegetable tanning process wastewater (VTW)
affect the aerobic microbes and reduce the treatment efficiency in
the tannery effluent treatment plants. Studies were performed with
the supplementation of crude tannase enzyme to improve the efficiency
of aerobic treatment of composite wastewater from raw to vegetable
tanning process (CWRVT). Screening, isolation, optimization of growth
conditions, and sequencing of the bacterial isolate Bacillus
nitratireducens were studied. Aerobic reactors were operated
in continuous mode for a period of 210 days, with and without tannase
supplementation. The reactors with and without tannase supplementation
showed 84%–88% and 44%–47% tannin removal, respectively,
for a maximum organic loading rate (OLR) of 30.5 g COD/L d with a
tannin concentration of 1000 mg/L. Confirmation of tannin degradation
was done with the help of electrospray ionization–mass spectrometry
(ESI-MS) and pyrogallol analysis. The kinetic parameters were derived
based on Contois model considering tannin as a substrate. For the
treatment of 1 m3 of CWRVT, the supplementation of tannase
enzyme will add an additional cost of Rs.30.58/- toward the cost of
chemicals in the overall operation and maintenance cost of the treatment
process. This study suggests that supplementation of tannase enzyme
in existing treatment plants will enhance the efficiency of tannin
removal.