Sustainable technologies for on-site domestic wastewater treatment: a review with technical approach

Environment, Development and Sustainability - The rapid population growth has rendered the centralized sewerage systems a non-realistic option in sparsely populated areas, particularly in...     

Model coupling approach for daily runoff simulation in Hamp Pandariya catchment of Chhattisgarh state in India

Environment, Development and Sustainability - Runoff estimation is of immense importance in hydrological analysis for water resource planning and management. The developing countries cannot afford...     

A sensitive spectrophotometric method for the determination of arsenic in environmental samples

We developed a cost-effective and sensitive spectrophotometric method for the determination of arsenic at trace level using a new reagent, leuco malachite green. Here we show that, arsenic reacts with potassium iodate in acidic conditions to liberate iodine, and the liberated iodine selectively oxidizes leuco malachite green to malachite green dye. We studied the Beer’s law at 617 nm, which showed linearity over the concentration range 0.09–0.9 μg ml⁻¹ of arsenic. We show that the molar absorptivity, Sandell’s sensitivity and detection limit of the method are 6.1 × 10⁴ l mol⁻¹ cm⁻¹, 0.0012 μg cm⁻² and 0.025 μg ml⁻¹, respectively. We applied the developed method for the determination of arsenic in environmental samples.     

Atmospheric depositions around a heavily industrialized area in a seasonally dry tropical environment of India

Clear and through-fall bulk depositions were collected in the downwind of a highly industrialized region in Sonbhadra district of India to estimate the influence of anthropogenic activities on chemical composition of depositions. Significant spatial and temporal variations in depositions of cations and anions were observed. Depositions were higher near the thermal power stations and coal mines as compared to distantly situated site. Seasonally summer samples showed maximum cation and anion depositions followed by winter and minimum in rainy season. The mean pH of the depositions indicates that rainfall in the area is alkaline. Among the anions, maximum deposition was recorded for SO4(2-) followed by NO3- and minimum for Cl-. Among the cations, Ca2+ deposition was maximum followed by NH4+. Na+, K+ and Mg2+ deposition rates showed more or less similar values. The depositions of cations and anions as well as pH were higher in through-fall than clear-fall samples. Results of the present study suggest that atmospheric depositions are strongly modified due to thermal power stations and coal mines in the area.     

Assessment of imidacloprid in Brassica environment

Imidacloprid was applied as seed treatment (Gaucho 70 WS, 5 and 10 g ai kg(-1) seed) and foliar spray (Confidor 200 SL, 20 and 40 g ai ha(-1)) at 50% pod formation stage on mustard (Brassica campestris Linn.) to control mustard aphid, Lipaphis erysimi Kalt. It was detectable upto 82 and 96 days in plants after sowing from lower and higher doses of seed treatment. However, it dissipated faster and became nondetectable after 7 and 15 days of foliar treatments from lower and higher rates of application, respectively. The dissipation models yielded the rate constants of 0.0209 and 0.0230 and 0.0736 and 0.0779 day(-1) from seed and foliar treatment. The corresponding half-lives of 14.40 and 13.07 and 4.09 and 3.86 days were recorded. This suggested that the dissipation was independent of initial doses and followed a first order rate kinetics. The projected TMRC of imidacloprid from seed (0.136 and 0.225 mg person(-1) day(-1)) and foliar (0.069 and 0.1497 mg person(-1) day(-1)) treatments were found lower than the MPI (3.135 mg person(-1) day(-1)). At harvest mustard grains did not contain imidacloprid residues. The absence of imidacloprid in 0-10 and 10-20 cm soil layers indicated no leaching of insecticide. Therefore, imidacloprid treatments could be taken as safe for crop protection, consumption of leaves and environmental contamination point of view.     

Removal of arsenic from water by electrocoagulation

In the present study electrocoagulation (EC) has been evaluated as a treatment technology for arsenite [As(III)] and arsenate [As(V)] removal from water. Laboratory scale experiments were conducted with three electrode materials namely, iron, aluminum and titanium to assess their efficiency. Arsenic removal obtained was highest with iron electrodes. EC was able to bring down aqueous phase arsenic concentration to less than 10 microgl(-1) with iron electrodes. Current density was varied from 0.65 to 1.53 mAcm(-2) and it was observed that higher current density achieved rapid arsenic removal. Experimental results at different current densities indicated that arsenic removal was normalized with respect to total charge passed and therefore charge density has been used to compare the results. Effect of pH on arsenic removal was not significant in the pH range 6-8. Comparative evaluation of As(III) and As(V) removal by chemical coagulation (with ferric chloride) and electrocoagulation has been done. The comparison revealed that EC has better removal efficiency for As(III), whereas As(V) removal by both processes was nearly same. The removal mechanism of As(III) by EC seems to be oxidation of As(III) to As(V) and subsequent removal by adsorption/complexation with metal hydroxides generated in the process.