Optimization for minimizing the cost of ozonation of highly concentrated textile dyeing wastewater in a bubble column reactor.

Ozonation is one of the advanced oxidation methods that provide effective decolorization and detoxification of the dyeing wastewater without causing any sludge formation. Despite being a good alternative to biodegradation, ozonation suffers from a high operating cost. This study conducted the ozonation process at high initial dye concentrations and optimized the process parameters (such as initial ozone concentration, initial dye concentration, and pH) to minimize the operating cost in terms of the overall power consumption of the process. The ozonation of Reactive Blue dye was performed in a bubble column reactor at various process conditions. A central composite design (CCD)-based response surface method (RSM) statistical tool was used to optimize the process. An empirical correlation for the specific power consumption (defined as electricity consumed per unit mass of dye removed from a unit volume of dyeing wastewater) was developed and verified. It was found that the specific power consumption during ozonation can be lowered significantly (by ~25-30%) if the dyeing water was treated at high initial dye concentrations.

Performance evaluation of a continuous packed bed bioreactor: Bio-kinetics and external mass transfer study.

The biodegradation of naphthalene using low-density polyethylene (LDPE) immobilized Exiguobacterium sp. RKS3 (MG696729) in a packed bed bioreactor (PBBR) was studied. The performance of a continuous PBBR was evaluated at different inlet flow rates (IFRs) (20-100 mL/h) under 64 days of operation. The maximum naphthalene removal efficiency (RE) was found at low IFR, and it further decreased with increasing IFRs. In a continuous PBBR, the external mass transfer (EMT) aspect was analysed at various IFRs, and experimental data were interrelated between Colburn factor (JD) and Reynolds number (NRe) as [Formula: see text] . A new correlation [Formula: see text] was obtained to predict the EMT aspect of naphthalene biodegradation. Andrew-Haldane model was used to evaluate the bio-kinetic parameters of naphthalene degradation, and kinetic constant νmax, Js, and Ji were found as 0.386 per day, 13.6 mg/L, and 20.54 mg/L, respectively.