The intense colour of the spent wash effluent leads to crucial ecological issue when released untreated into the environment. The decolourization of distillery spent wash effluent is known to be a very challenging task. In this study, the degradation of organic pollutants in the form of colour was performed using nano photocatalyst prepared using aluminium oxide (Al2O3) nanoparticle and kaolin clay. As-synthesized nano-Al2O3/kaolin composites were used as photocatalyst for colour degradation of spent wash effluent. The process parameters such as dosage, pH, temperature and agitation were optimized to attain the maximum decolourization efficiency. The structural and the textural characteristics of the photocatalyst were analysed by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, High Resolution Scanning Electron Microscope (HRSEM) and Energy Dispersive X-ray (EDAX). Optimization of the process parameters using Taguchi Orthogonal Array (OA) design resulted in a maximum of 80% spent wash decolourization. Using Artificial Neural Network (ANN), a two layered feedforward backpropagation model resulted as the best performance and predictive model for spent wash decolourization. The experimental data were found to be in excellent agreement with the predicted results from the ANN model

A bacterial strain was isolated from tannery effluent which can tolerate high concentrations of potassium dichromate up to 1000 ppm. The isolated microorganism was identified asPseudomonas aeruginosaby performing biochemical tests and molecular characterization. In the presence of excess of carbohydrate source, which is a physiological stress, this strain produces Polyhydroxybutyrate (PHB). This intracellular polymer, which is synthesized, is primarily a product of carbon assimilation and is employed by microorganisms as an energy storage molecule to be metabolized when other common energy sources are limitedly available. Efforts were taken to check whether the PHB has any positive effect on spent wash decolorization. When a combination of PHB and the isolated bacterial culture was added to spent wash, a maximum color removal of 92.77% was found which was comparatively higher than the color removed when the spent wash was treated individually with the PHB andPseudomonas aeruginosa. PHB behaved as a support material for the bacteria to bind to it and thus develops biofilm, which is one of the natural physiological growth forms of microorganisms. The bacterial growth in the biofilm and the polymer together acted in synergy, adsorbing and coagulating the pollutants in the form of color pigments.

The distillery effluent causes a crucial ecological impact when disposed untreated into the environment and the removal of the intense brown colour is a much challenging task due to the presence of a polymeric compound – Melanoidin. This research study reports the synthesis and application of a nano ZnO photocatalyst in an immobilised form. The process parameters such as photocatalyst dosage (0.5–2.5 g/L), initial pH (3–11), initial spent wash concentration and treatment time were optimised to attain the maximum spent wash degradation efficiency. The physical and chemical properties of the as-synthesised photocatalyst were characterised by X-ray diffractometer (XRD), high-resolution scanning electron microscopy (HRSEM), energy dispersive analysis X-ray (EDAX), Brunauer–Emmett–Teller (BET) surface area analysis, diffuse reflectance spectroscopy (DRS) and Fourier transform infrared (FTIR) spectroscopy. The percentage colour degradation of spent wash increased from 36.2 to 77.1%, with increasing photocatalyst dosage from 0.5 to 2.5 g/L, respectively. The reaction rate constant (k_obs) decreased from 0.0141 to 0.0022 (1/min) with increasing initial spent wash concentration (% dilution) of 5–25%. The photocatalytic degradation experiment performed at optimised process parameters yielded a maximum of 91.2% of spent wash colour degradation.