Solar oxidation and removal of arsenic from water: An experimental study

Arsenic poses a significant threat to both human health and the environment. Arsenic removal through solar oxidation has been investigated in a batch process. Arsenic was artificially added to both deionized and tap water to conduct the experiments. Clean, colorless, transparent, Polyethylene Terephthalate (PET) bottles were used for Solar Oxidation and Removal of Arsenic (SORAS) experiments. Various parameters including concentration of arsenic, iron, and photo-catalyst were varied during the experiments. The maximum arsenic removal efficiency obtained was 94% and 88% for deionized water and tap water respectively when ferrous ammonium sulphate and lemon juice were used. Maximum efficiency of 88% and 82% was obtained for deionized and tap water respectively when locally available ferrous alum and glacial acetic acid were used. The change in volume of the photo-catalyst (lemon juice and glacial acetic acid) also did not affect the SORAS process significantly. Therefore, the recommended volume for the photo-catalyst was 1–2 ml/L. SORAS can very well be used for areas contaminated with arsenic having concentrations less than 100 μg/L.     

Decolorization of structurally different synthetic dyes using cobalt(II)/ascorbic acid/hydrogen peroxide system

The cobalt(II)/ascorbic acid/hydrogen peroxide system was used for decolorization of azo, acridine, anthraquinone, thiazine and triphenylmethane dyes. More than 90% decolorization was obtained with all dyes except Remazol Brilliant Blue R (75%). With other transition metals the system was less efficient. With copper, higher concentration and prolonged incubation time was necessary to obtain the same extent of decolorization. The rate of decolorizaton was not affected by pH in the range of 3-9. The reaction is very fast, with more than 90% decolorization being attained within 15 min. The system produces hydroxyl radicals which are responsible for the decolorization.     

Copper-ligand complex for the decolorization of synthetic dyes

The reaction system containing Cu(II), hydrogen peroxide and D-arabinono-1,4-lactone was found to be effective in the decolorization and reduction of toxicity of azo, thiazine-, triphenylmethane- and anthraquinone-based synthetic dyes. More than 85% decolorization was obtained with 100ppm Acridine Orange, Azure B, Chicago Sky Blue 6B, Crystal Violet, Evans Blue, Poly B-411, Reactive Blue 2, Reactive Blue 5, and Remazol Brilliant Blue R incubated for 24h in the presence of 10mM CuSO(4), 20mM D-arabinono-1,4-lactone and 80 mM H(2)O(2). The rate of decolorization was not affected by pH in the range of 3-9. The rapid decolorization was accompanied by a fast decomposition of H(2)O(2) in the reaction mixture and by a fast production of hydroxyl radicals.     

Gender differences in the metabolism of benzene,toluene and trichloroethylene in rat with special reference to certain biochemical parameters

Metabolites viz. phenol, hippuric acid and total trichloro compounds of benzene, toluene and trichloroethylene respectively were estimated in the urine samples of male and female rats after exposure for a period of 30 days. The results exhibited higher metabolism in female rats than the male rats. Their metabolism might be regulated by cytochrome P450 isozymes in a gender specific manner. However, sex differences in the activity of glutathione-S-transferases of the liver have also been found to determine their toxicity. Results have been discussed with quantitative profiles of other enzymes established in the liver of male and female rats.     

A data-mining approach to predict influent quality

In wastewater treatment plants, predicting influent water quality is important for energy management. The influent water quality is measured by metrics such as carbonaceous biochemical oxygen demand (CBOD), potential of hydrogen, and total suspended solid. In this paper, a data-driven approach for time-ahead prediction of CBOD is presented. Due to limitations in the industrial data acquisition system, CBOD is not recorded at regular time intervals, which causes gaps in the time–series data. Numerous experiments have been performed to approximate the functional relationship between the input and output parameters and thereby fill in the missing CBOD data. Models incorporating seasonality effects are investigated. Four data-mining algorithms—multilayered perceptron, classification and regression tree, multivariate adaptive regression spline, and random forest—are employed to construct prediction models with the maximum prediction horizon of 5 days.     

Design and off-design analyses of a pre-combustion CO2 capture process in a natural gas combined cycle power plant

In this study, a cycle designed for capturing the greenhouse gas CO₂ in a natural gas combined cycle power plant has been analyzed. The process is a pre-combustion CO₂ capture cycle utilizing reforming of natural gas and removal of the carbon in the fuel prior to combustion in the gas turbine. The power cycle consists of a H₂-fired gas turbine and a triple pressure steam cycle. Nitrogen is used as fuel diluent and steam is injected into the flame for additional NO_x control. The heat recovery steam generator includes pre-heating for the various process streams. The pre-combustion cycle consists of an air-blown auto-thermal reformer, water–gas shift reactors, an amine absorption system to separate out the CO₂, as well as a CO₂ compression block. Included in the thermodynamic analysis are design calculations, as well as steady-state off-design calculations. Even though the aim is to operate a plant, as the one in this study, at full load there is also a need to be able to operate at part load, meaning off-design analysis is important. A reference case which excludes the pre-combustion cycle and only consists of the power cycle without CO₂ capture was analyzed at both design and off-design conditions for comparison. A high degree of process integration is present in the cycle studied. This can be advantageous from an efficiency stand-point but the complexity of the plant increases. The part load calculations is one way of investigating how flexible the plant is to off-design conditions. In the analysis performed, part load behavior is rather good with efficiency reductions from base load operation comparable to the reference combined cycle plant.     

Bacillus thuringiensis fermentation of hydrolyzed sludge--rheology and formulation studies

Rheology of Bacillus thuringiensis fermentation of hydrolyzed sludge was investigated in bench scale fermenter. Stable liquid formulations were developed and optimized for two-year based studies comprising various physical/chemical (viscosity, particle size, corrosion and suspendibility) and biological (microbial contamination, viable spores and entomotoxicity) parameters at different pHs and temperatures. The hydrolyzed sludge depicted non-Newtonian and pseudoplastic behaviour during fermentation with 90% to 96% confidence of fits into Casson, Power and IPC paste models. Higher values of consistency and flow index during exponential growth and stationary phase, respectively, affected downstream processing. The power law was also followed by stable formulations. Sorbitol, sodium monophosphate and sodium metabisulfite (2.2:1:1) as suspending agents produced suspendibility ranging from 69% to 94%. The stable formulation (FH-4) comprising sorbitol, sodium monophosphate and sodium metabisulfite deteriorated at pHs 6, 6.5 and temperatures, 40 and 50 degrees C, with no signs of corrosion and microbial contamination. The viscosity of FH-4 formulations decreased with shear rate which could improve handling and consequent spraying.     

Survival of bio-inoculants on fungicides-treated seeds of wheat, pea and chickpea and subsequent effect on chickpea yield

Survival of Mesorhizobium ciceri (SP(4)) and Azotobacter chroococcum (CBD-15 and M(4)) was tested on chickpea (Cicer arietinum) seeds treated with fungicides bavistin [methyl N-(1H-benzimidazol-2yl) carbamate] and thiram (tetramethyl-thiuram disulfide), whereas survival of phosphate solubilizing bacteria (PSB), Pseudomonas striata (27) and Bacillus polymyxa (H(5)) was examined on two cultivars (Arkel and BV) of pea (Pisum sativum) seeds treated with thiram. Viability of Azotobacter chroococcum (W(5)) was also examined on wheat (Triticum aestivum) seeds treated with bavistin, captan (cis-N-trichloromethyl thio-4 cyclohexane-1, 2-dicarboximide) and thiram under laboratory conditions using standard dilution and the plate count technique. All the tested strains of diazotrophs and PSB showed decline in their viable population on prolonged contact with fungicides. However, PSB showed variation in their viable population even with the cultivar. BV cultivar of pea seeds showed better recovery of viable P. striata (10.75 to 10.61 log no. of viable cells with in 0-24 hrs) in the presence of thiram, whereas the Arkel cultivar of pea resulted in better recovery of viable B. polymyxa. Azotobacter chroococcum (W(5)), a potential strain for wheat, showed better survival in the presence of bavistin, compared to thiram and captan. Higher viable population of Mesorhizobium ciceri (SP(4)) and Azotobacter chroococcum (M(4)) was recovered from chickpea seeds treated with bavistin compared to thiram. However, thiram-treated seeds resulted in a greater number of extractable Azotobacter chroococcum (CBD-15). Under field conditions, adverse effect of thiram was reflected on the performance of Mesorhizobium ciceri (SP(4)) and A. chroococcum (M(4)) strains, resulting in reduced root and shoot biomass and grain yield, compared to bavistin treated and culture inoculated treatment. CBD-15 showed better performance in the presence of thiram compared to bavistin.     

Monitoring of organochlorine pesticides in and around Keoladeo National Park, Bharatpur, Rajasthan, India

Keoladeo National Park (KNP) is an important wintering ground for thousands of birds that undertake a perilous journey over the Himalaya to make a seasonal home in a wetland ecosystem. However, this wetland is now getting polluted by various types of contaminants such as pesticides because of the agricultural practices in the catchment area from where the park receives water. Keeping this in mind, the present study has been undertaken to assess the organochlorine pesticide (OCP) residues in the sediments inside and around KNP. Samples were collected from the different blocks of the park. The concentrations of α-HCH, β-HCH, γ-HCH, δ-HCH, S-HCH, aldrin, dieldrin, heptachlor, hept.epoxide, endosulfan-I, endosulfan-II, endo.sulfate, S-endosulfan, endrin, 4,4'-DDE, 4,4'-DDD, and DDT were quantified using gas chromatography with electron capture detection. Analysis showed that the samples were contaminated with the above mentioned pesticides and that the concentration of total OCPs in the sediments varied from 0.1173 (dieldrin) to 5.558 ppm (γ HCH) in the samples collected from inside the park, whereas a range of pesticides varying in concentration from 0.1245 (4,4'-DDD) to 7.54 ppm (γ HCH) was found in samples from outside the park. Residues of S-HCH and S-endosulfan were not detected in any of the sediment samples. The occurrence of pesticides inside the park is a major threat to the park's biodiversity. Eco-friendly agriculture practices with minimal use of inorganic chemicals are suggested to minimize the pesticide residue levels in the park.