The use of circular surface aerators in wastewater treatment tanks

Aeration experiments were conducted in different sized baffled and unbaffled circular surface aeration tanks to study their relative performance on oxygen transfer process while aerating the same volume of water. Experiments were carried out with the objective of ascertaining the effect of baffle on oxygen transfer coefficient k. Simulation equations govern the oxygen transfer coefficient with the theoretical power per unit volume, X and actual power per unit volume, P-V. It has been found that, for any given X, circular tanks with baffle produce higher values of k than unbaffled circular tanks, but in terms of actual power consumption unbaffled tanks consume less power when compared to baffled circular tanks to achieve the same value of k. It has been found that in terms of energy consumption, epsilon, baffled tanks consume more energy than unbaffled tanks at any value of X. This suggests that the unbaffled circular tank gives a better performance as far as energy consumption is concerned and hence better economy. An example illustrating the energy conservation to aerate the same volume of water in both types of aerators is given. (c) 2007 Society of Chemical Industry.

Low density polyethylene and grafted lignin polyblends using epoxy-functionalized compatibilizer: mechanical and thermal properties

Lignin was graft copolymerized with methyl methacrylate using manganic pyrophosphate as initiator. This modified lignin was then blended (up to 50 wt%) with low density polyethylene (LDPE) using a small quantity of poly[ethylene-co-(glycidyl methacrylate)] (PEGMA) compatibilizer. The mechanical properties of the blend were substantially improved by using modified lignin in contrast to untreated lignin. Differential scanning calorimetry studies showed loss of crystallinity of the LDPE phase owing to the interaction between the blend components. Thermogravimetric analysis showed higher thermal stability of modified lignin in the domain of blend processing. This suggested that there is scope for useful utilization of lignin, which could also lead to the development of eco-friendly products. (c) 2005 Society of Chemical Industry.

Continuous distribution kinetics for ultrasonic degradation of poly(methyl methacrylate)

Ultrasonic degradation of poly(methyl methacrylate) (PMMA) was carried out in several solvents and some mixtures of solvents. The time evolution of molecular weight distribution (MWD), determined by gel permeation chromatography, is analysed by continuous distribution kinetics. The rate coefficients for polymer degradation are determined for each solvent. The variation of rate coefficients is correlated with the vapour pressure of the solvent, kinematic viscosity of the solution and solvent-polymer interaction parameters. The vapour pressure and the kinematic viscosity of the solution are found to be more critical than other parameters (such as the Huggins and Flory-Huggins constants) in determining the degradation rates. (C) 2001 Society of Chemical Industry.

Jatropha cultivation in southern India: assessing farmers' experiences

Together with 106 farmers who started growing Jatropha (Jatropha curcas L.) in 20042006, this research sought to increase the knowledge around the real-life experience of Jatropha farming in the southern India states of Tamil Nadu and Andhra Pradesh. Launched as an alternative for diesel in India, Jatropha has been promoted as a non-edible plant that could grow on poor soils, yield oil-rich seeds for production of bio-diesel, and not compete directly with food production. Through interviews with the farmers, information was gathered regarding their socio-economic situation, the implementation and performance of their Jatropha plantations, and their reasons for continuing or discontinuing Jatropha cultivation. Results reveal that 82% of the farmers had substituted former cropland for their Jatropha cultivation. By 2010, 85% (n = 90) of the farmers who cultivated Jatropha in 2004 had stopped. Cultivating the crop did not give the economic returns the farmers anticipated, mainly due to a lack of information about the crop and its maintenance during cultivation and due to water scarcity. A majority of the farmers irrigated and applied fertilizer, and even pesticides. Many problems experienced by the farmers were due to limited knowledge about cultivating Jatropha caused by poor planning and implementation of the national Jatropha program. Extension services, subsidies, and other support were not provided as promised. The farmers who continued cultivation had means of income other than Jatropha and held hopes of a future Jatropha market. The lack of market structures, such as purchase agreements and buyers, as well as a low retail price for the seeds, were frequently stated as barriers to Jatropha cultivation. For Jatropha biodiesel to perform well, efforts are needed to improve yield levels and stability through genetic improvements and drought tolerance, as well as agriculture extension services to support adoption of the crop. Government programs will -probably be more effective if implementing biodiesel production is conjoined with stimulating the demand for Jatropha biodiesel. To avoid food-biofuel competition, additional measures may be needed such as land-use restrictions for Jatropha producers and taxes on biofuels or biofuel feedstocks to improve the competitiveness of the food sector compared to the bioenergy sector. (c) 2012 Society of Chemical Industry and John Wiley & Sons, Ltd

Synthesis, characterization and thermal degradation of dual temperature- and pH-sensitive RAFT-made copolymers of N,N-(dimethylamino)ethyl methacrylate and methyl methacrylate

Poly{(N,N-(dimethylamino)ethyl methacrylate]-co-(methyl methacrylate)} copolymers of various compositions were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization at 70 degrees C in N,N-dimethylformamide. The polymer molecular weights and molecular weight distributions were obtained from size exclusion chromatography, and they indicated the controlled nature of the RAFT polymerizations; the polydispersity indices are in the range 1.11.3. The reactivity ratios of N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) (rDMAEMA = 0.925 and rMMA = 0.854) were computed by the extended KelenTudos method at high conversions, using compositions obtained from 1H NMR. The pH- and temperature-sensitive behaviour were studied in aqueous solution to confirm dual responsiveness of these copolymers. The thermal properties of the copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. The kinetics of thermal degradation were determined by Friedmann and Chang techniques to evaluate various parameters such as the activation energy, the order and the frequency factor. (c) 2012 Society of Chemical Industry

Two-dimensional fuzzy fault tree analysis for chlorine release from a chlor-alkali industry using expert elicitation

The hazards associated with major accident hazard (MAN) industries are fire, explosion and toxic gas releases. Of these, toxic gas release is the worst as it has the potential to cause extensive fatalities. Qualitative and quantitative hazard analyses are essential for the identification and quantification of these hazards related to chemical industries. Fault tree analysis (FTA) is an established technique in hazard identification. This technique has the advantage of being both qualitative and quantitative, if the probabilities and frequencies of the basic events are known. This paper outlines the estimation of the probability of release of chlorine from storage and filling facility of chlor-alkali industry using FTA. An attempt has also been made to arrive at the probability of chlorine release using expert elicitation and proven fuzzy logic technique for Indian conditions. Sensitivity analysis has been done to evaluate the percentage contribution of each basic event that could lead to chlorine release. Two-dimensional fuzzy fault tree analysis (TDFFTA) has been proposed for balancing the hesitation factor involved in expert elicitation. (C) 2010 Elsevier B.V. All rights reserved.

The physicochemical characteristics and anaerobic degradability of desiccated coconut industry waste water

Desiccated coconut industries (DCI) create various intermediates from fresh coconut kernel for cosmetic, pharmaceutical and food industries. The mechanized and non-mechanized DCI process between 10,000 and 100,000 nuts/day to discharge 6-150 m(3) of malodorous waste water leading to a discharge of 2646642 kg chemical oxygen demand (COD) daily. In these units, three main types of waste water streams are coconut kernel water, kernel wash water and virgin oil waste water. The effluent streams contain lipids (1-55 g/l), suspended solids (6-80 g/l) and volatile fatty acids (VFA) at concentrations that are inhibitory to anaerobic bacteria. Coconut water contributes to 20-50 % of the total volume and 50-60 % of the total organic loads and causes higher inhibition of anaerobic bacteria with an initial lag phase of 30 days. The lagooning method of treatment widely adopted failed to appreciably treat the waste water and often led to the accumulation of volatile fatty acids (propionic acid) along with long-chain unsaturated free fatty acids. Biogas generation during biological methane potential (BMP) assay required a 15-day adaptation time, and gas production occurred at low concentrations of coconut water while the other two streams did not appear to be inhibitory. The anaerobic bacteria can mineralize coconut lipids at concentrations of 175 mg/l; however; they are severely inhibited at a lipid level of = 350 mg/g bacterial inoculum. The modified Gompertz model showed a good fit with the BMP data with a simple sigmoid pattern. However, it failed to fit experimental BMP data either possessing a longer lag phase and/or diauxic biogas production suggesting inhibition of anaerobic bacteria.

Hydrogen energy future with formic acid: a renewable chemical hydrogen storage system

Formic acid, the simplest carboxylic acid, is found in nature or can be easily synthesized in the laboratory (major by-product of some second generation biorefinery processes); it is also an important chemical due to its myriad applications in pharmaceuticals and industry. In recent years, formic acid has been used as an important fuel either without reformation (in direct formic acid fuel cells, DFAFCs) or with reformation (as a potential chemical hydrogen storage material). Owing to the better efficiency of DFAFCs compared to several other PEMFCs and reversible hydrogen storage systems, formic acid could serve as one of the better fuels for portable devices, vehicles and other energy-related applications in the future. This perspective is focused on recent developments in the use of formic acid as a reversible source for hydrogen storage. Recent developments in this direction will likely give access to a variety of low-cost and highly efficient rechargeable hydrogen fuel cells within the next few years by the use of suitable homogeneous metal complex/heterogeneous metal nanoparticle-based catalysts under ambient reaction conditions. The production of formic acid from atmospheric CO2 (a greenhouse gas) will decrease the CO2 content and may be helpful in reducing global warming.