Distilleries producing alcohol are known as the major pollutants of water systems. A typical cane molasses-based distillery generates about 12 to 15 liters of spent-wash effluent per liter of ethanol produced. It is estimated that around 200 and odd distillery units are under production in India, releasing about 30 billion liters of spent-wash annually. With the kind of growth being witnessed in the demand for alcohol in the country, it is no wonder if spent-wash—a strongly acidic dark brown colored, hydrophilic viscous liquid with a strong dirty odor—becomes a great menace to natural water body systems and agricultural lands. It is the presence of brown polymeric melanoidin pigments that imparts the dark brown color to the spent-wash. These pigments are highly recalcitrant and are toxic to many microorganisms. It is indeed highly hazardous to aquatic ecosystem since its colored bodies reduce photosynthetic activity besides reducing dissolved oxygen in water bodies.

Realizing the growing threat of spent-wash as a pollutant, the authors, Sushil Kumar Shukla, P K Mishra, K K Srivastava and P Srivastava, of the first paper, "Treatment of Anaerobically Digested Distillery Effluent by Aspergillus niger", have made an attempt to evaluate the scope for reducing the persistent dark brown color and the chemical oxygen demand from an anaerobically digested distillery effluent first by physico-chemical treatment—chemical coagulation using potash alum, ferric chloride and aluminum chloride—followed by biological treatment—aerobic degradation using Aspergillus niger. The results indicate that 78.5% of COD reduction and 92.45% color reduction could be achieved by coagulation itself, while a maximum of 65% of remaining color could be removed by 10% (v/v) Aspergillus niger inoculums in effluent sample under sterile conditions—more than 97% reduction in color can be achieved by both the methods put together.

Moving on to heat transfer enhancement technology meant for reducing the cost of heat exchanges, we have Siva Rama Krishna and P Sivashanmugam, the authors of the next paper, "CFD Analysis of Heat Transfer Characteristics of Nanofluids in a Circular Tube Fitted with Helical Inserts in Laminar Flow", who carried out CFD analysis of heat transfer behavior of a circular tube heated with helical tape inserts under constant heat flux conditions using CuO nanofluids. They are of the opinion that heat transfer increases with Reynolds number and decreases with twist ratio with the maximum being tape insert of twist ratio 2.93. In comparison with water, heat transfer rate was more for CuO nanofluids. The Nusselt number increases with Reynolds number and the volume concentration of nanofluids, maximum being 1.5%. The maximum heat transfer enhancement is 34% per twist insert of twist ratio of 2.93 and for the volume concentration of 1.5% corresponding to Reynolds number of 2039. The authors have also reported that the simulation data is matching with the experimentally reported value of water with a discrepancy of less than ±10% per plain tube and tube fitted with helical tape inserts for Nusselt number.

Next we have, Vinayak Manjunath Hegde, K V Pai and P Nirguna Babu, authors of the paper, "Enthalpy of Mixing and Heats of Vaporization of Ethyl Alcohol with n-Hexane and n-Heptane at 298.15 K and 308.15 K", who have conducted experiments to determine the enthalpy of mixing and heat of vaporization for the mixtures of ethyl alcohol with n-Hexane and n-Heptane. The authors have also developed a model to calculate theoretical heats of vaporization and found that the data on experimental heat of vaporization fitted the model very well for the systems, thereby strengthening the validity of the model and its practical usefulness for engineering purposes.

Moving on to drying of chillies traditionally under sun that results in dull color reducing its market potential, we have, Vitthal L Gole, Pravin Tadkar, Pratik Pawar and Nirmal Patil, the authors of the next paper, "Thin Layer Modeling Microwave Vacuum Drying of Green Chilli", who have conducted a study to evaluate drying kinetics of green chillies at different powers of MWV drying to identify the best fit thin layer model that ensures the quality attributes of chillies, such as color and pungency, remain intact in the final dried product. The study reveals that the microwave vacuum dried chilly at 160 W, 80 mmHg vacuum retained maximum color intensity and pungency.

Moving from chillies to glucoamylase, an industrially important enzyme, we have, David K Daniel, Raiyani Himanshu B and Debabrata Das, the authors of the last paper of the issue, "Neural Network Modeling for Estimation of Cell Mass During Submerged Glucoamylase Fermentation", reporting the ability of neural networks to predict cell mass during batch and continuous glucoamylase fermentation. They have written the program in Visual Basic for Windows to incorporate the algorithm—Levenberg-Marquaedt algorithm that comprises incremental back propagation and then switches to conjugate gradient-based back propagation for the final convergence phase—and based on the experimental results, they opine that the neural network computation is well-suited for monitoring and controlling the industrial level production of glucoamylase.

-- GRK Murty
Consulting Editor