A comparative study of biopolymers and alum in the separation and recovery of pulp fibres from paper mill effluent by flocculation

Recovery of cellulose fibres from paper mill effluent has been studied using common polysacchatides or biopolymers such as Guar gum, Xanthan gum and Locust bean gum as flocculent. Guar gum is commonly used in sizing paper and routinely used in paper making. The results have been compared with the performance of alum, which is a common coagulant and a key ingredient of the paper industry. Guar gum recovered about 3.86 mg/L of fibre and was most effective among the biopolyrners. Settling velocity distribution curves demonstrated that Guar gum was able to settle the fibres faster than the other biopolymers; however, alum displayed the highest particle removal rate than all the biopolymers at any of the settling velocities. Alum, Guar gum, Xanthan gum and Locust bean gum removed 97.46%, 94.68%, 92.39% and 92.46% turbidity of raw effluent at a settling velocity of 0.5 cm/min, respectively. The conditions for obtaining the lowest sludge volume index such as pH, dose and mixing speed were optimised for guar gum which was the most effective among the biopolymers. Response surface methodology was used to design all experiments, and an optimum operational setting was proposed. The test results indicate similar performance of alum and Guar gum in terms of fioc settling velocities and sludge volume index. Since Guar gum is a plant derived natural substance, it is environmentally benign and offers a green treatment option to the paper mills for pulp recycling.     

Examining Environmental Kuznets Curve for river effluents in India

This study aims to determine the trade-off between river pollution and the growth of the economy in the context of India using the concept of Environmental Kuznets Curve (EKC). According to EKC theory, environmental pressure tends to rise faster than income growth in the early stages of economic development and then declines in the later stages with further economic growth. The present study has used the cross-sectional time series data for river pollutants of Biochemical Oxygen Demand (BOD) and Dissolved Hydrogen Ions (PH) across various states of India for the period 1990–1991 to 2005–2006. This study shows why the conventional EKC model is not sufficient to ascertain the declining path of pollution as the economy grows in the second stage. The paper uses the modified EKC theory where the EKC curve is proposed to have 2 turning points. Our results indicated ‘tilted-S shaped’ relationship which contradicts EKC in the early stages. Most of the regions that were studied have crossed the first turning point but are still to cross the second turning point, which means that there will be an ascent in the pollution level in the future. This calls for more stringent environment policies complementing the desired growth path.     

From Bathymetry to Bioshields: A Review of Post-Tsunami Ecological Research in India and its Implications for Policy

More than half a decade has passed since the December 26th 2004 tsunami hit the Indian coast leaving a trail of ecological, economic and human destruction in its wake. We reviewed the coastal ecological research carried out in India in the light of the tsunami. In addition, we also briefly reviewed the ecological research in other tsunami affected countries in Asia namely Sri Lanka, Indonesia, Thailand and Maldives in order to provide a broader perspective of ecological research after tsunami. A basic search in ISI Web of Knowledge using keywords “tsunami” and “India” resulted in 127 peer reviewed journal articles, of which 39 articles were pertaining to ecological sciences. In comparison, Sri Lanka, Indonesia, Thailand and Maldives had, respectively, eight, four, 21 and two articles pertaining to ecology. In India, bioshields received the major share of scientific interest (14 out of 39) while only one study (each) was dedicated to corals, seagrasses, seaweeds and meiofauna, pointing to the paucity of research attention dedicated to these critical ecosystems. We noted that very few interdisciplinary studies looked at linkages between pure/applied sciences and the social sciences in India. In addition, there appears to be little correlation between the limited research that was done and its influence on policy in India. This review points to gap areas in ecological research in India and highlights the lessons learnt from research in other tsunami-affected countries. It also provides guidance on the links between science and policy that are required for effective coastal zone management.     

Genotoxicity of titanium dioxide (TiO2) nanoparticles at two trophic levels: plant and human lymphocytes

The environmental fate and behaviour of titanium dioxide (TiO(2)) nanoparticles is a rapidly expanding area of research. There is a paucity of information regarding toxic effect of TiO(2) nanoparticles in plants and to certain extent in humans. The present study focuses on the effect of exposure of TiO(2) nanoparticles in two trophic levels, plant and human lymphocytes. The genotoxicity of TiO(2) nanoparticles was evaluated using classical genotoxic endpoints, comet assay and DNA laddering technique. DNA damaging potential of TiO(2) nanoparticles in Allium cepa and Nicotiana tabacum as representative of plant system could be confirmed in the comet assay and DNA laddering experiments. In Allium micronuclei and chromosomal aberrations correlated with the reduction in root growth. We detected increased level of malondialdehyde (MDA) concentration at 4mM (0.9 μM) treatment dose of TiO(2) nanoparticles in Allium cepa. This indicated that lipid peroxidation could be involved as one of the mechanism leading to DNA damage. A comparative study of the cytotoxic and genotoxic potential of TiO(2) nanoparticles and bulk TiO(2) particles in human lymphocytes also reveal interesting results. While TiO(2) nanoparticles were found to be genotoxic at a low dose of 0.25 mM followed by a decrease in extent of DNA damage at higher concentrations; bulk TiO(2) particles reveal a more or less dose dependent effect, genotoxic only at dose 1.25 mM and above. The study thus confirms the genotoxic potential of TiO(2) nanoparticles in both plant and human lymphocytes.     

Evaluation of environmental fate of acetamiprid in the laboratory

The acetamiprid, a nenicotinoid insecticide, is a popular crop protection agent used in fields as well as in protected cultivation. A laboratory experiment was conditions to study the effect of light, moisture, and pH on the persistence of acetamiprid in water and soil. Dissipation half-lives of acetamiprid in water at pH 4, 7, and 9 were 6.2, 7.3, and 5.1 days, respectively, and 4.3 days under UV and sunlight conditions. Half-life in soil at three concentrations, 0.1, 1.0, and 10 μg g^?1 under different moisture regimes varied from 21.5–22.8, 15.6–22.4, 10.0–15.8 days, respectively, indicating that acetamiprid dissipated faster in submerged soil as compared to field capacity moisture and dry conditions. The leaching study showed that the possibility for leaching of acetamiprid to ground water is extremely low under normal condition of average rainfall due to compact nature soil in the field. Acetamiprid poses low risks to the ecosystem because of their rapid dissipation and low-bound residues in the environment.     

Adaptation strategies to combat climate change effect on rice and mustard in Eastern India

The negative impact of climate change on crop production is alarming as the demand for food is expected to increase in coming years, at a rate of about 2 percent a year. Wet season rice (Oryza sativa) followed by mustard (Brassica juncea) is one of the prominent cropping sequences in Eastern India. Descreases in their productivity due to climate change will not only hamper the regional food security but also affect the global economy. Considering the fact, the present study aims to assess the impact of climate change on productivity of wet-season rice and mustard and to evaluate the effectiveness of agronomic adjustment as adaptation options. Crop growth simulation model (CGSM) is a very effective tool to predict the growth and yield of a crop. One CGSM, namely InfoCrop (Generic Crop Model), was calibrated and validated for the said crops for West Bengal State, Eastern India. After validation, the model was used to predict the yield under elevated thermal condition (1 and 3 °C rise over normal temperature). Moreover, the future weather situation as predicted by PRECIS (Providing Regional Climates for Impacts Studies) model was used as weather input of the CGSM and the yield was predicted for ten selected locations of West Bengal for the year 2025 and 2050. It was observed that the average yield reduction of the wet-season rice would be in the tune of about 20.0 % for 2025 and 27.8 % for 2050. The mustard yield of West Bengal may be reduced by 20.0 to 33.9 % for the year 2025 and up to 40 % for 2050. It was concluded that the negative impact of climate change on mustard grown in winter season will be more pronounced compared to wet-season rice. Adjustment of sowing time will be the simplest and effective adaptation option for both rice and mustard. Increased rate of nutrient application can sustain the rice yield under future climate. The older seedling at the time of transplanting of wet-season rice and increased seed rate of mustard were proved less effective.     

Organochlorine insecticide residues in drinking and ground water in and around Delhi

A multiresidue method was developed for the estimation of 15organochlorine pesticides in water. 50 samples of drinking watersupplied by the Municipal Corporation to the residential areasof Delhi and 20 ground water samples from nearby villages usedfor irrigation were monitored for the presence of organochlorineinsecticides by the method developed. Although, organochlorinepesticides were detected in the ground water and irrigationwater samples, the levels of pesticides were below the MaximumContaminant Level as prescribed by WHO. No organochlorineinsecticides were detected in any of the drinking water samples.     

Silver nanoparticles tolerant bacteria from sewage environment

Silver nanoparticle (SNP) is a threat to soil, water and human health. Protection of environment from silver nanoparticles is a major concern. A sewage isolate, Bacillus pumilus treated with SNPs showed similar growth kinetics to that without nanoparticles. A reduction in the amount of exopolysaccharides was observed after SNPs – B. pumilus culture supernatant interaction. The Fourier transform infrared spectroscopy (FT-IR) peaks for the exopolysaccharides extracted from the bacterial culture supernatant and the interacted SNPs were almost similar. The exopolysaccharide capping of the SNPs was confirmed by UV-Visible, FT-IR and X-ray di raction analysis. The study of bacterial exopolysaccharides capped SNPs with E. coli, S. aureus and M. luteus showed less toxicity compared to uncoated SNPs. Our studies suggested that the capping of nanoparticles by bacterially produced exopolysaccharides serve as the probable mechanism of tolerance.