Impact assessment of pesticide residues in fish of Ganga river around Kolkata in West Bengal

An investigation was conducted from 2001 to 2005 for determining the residual concentration of five pesticides, viz., total-HCH, total-DDT, total-Endosulfan, Dimethoate and Malathion in fish samples collected from various points of the river Ganga. Fish samples were analyzed for pesticide residues using standard laboratory procedures by GC method. It was found that total-HCH concentration remains above the MRL values for maximum number of times in comparison to four other pesticides. The pesticide contamination to fish may be due to indiscriminate discharge of polluted and untreated sewage-sludge to the river. The pesticide contents in some places are alarming. Thus proper care, maintenance, treatment and disposal of sewage water and sludge are most vital and should be the prime thrust for the nation.     

Methyl mercury in fish—a case study on various samples collected from Ganges river at West Bengal

This study investigated the presence of total mercury (Hg) and organic mercury levels in the muscle of 19 common fresh water fish species captured from river Ganges, West Bengal, India. The total mercury level found in our study may not cause any toxic effect, but the methyl mercury (MeHg) level in some freshwater fish species was surprisingly very high and toxically unacceptable. The results of mercury analysis in various specimens indicated that some fish muscles tended to accumulate high levels of Hg, and approximately 50–84% of Hg was organic mercury. A strong positive correlation between mercury levels in muscle with food habit and fish length (age) was found. Wallago attu possessed the highest amount of organic mercury in their muscle tissues, and it was 0.93 ± 0.61 μg Hg/g of wet weight. Whereas in small-sized fishes Eutropiichthys murius, Puntius sarana, Cirrhinus mrigala, Mystus vittatus or Mystus gulio, and Tilapia mossambicus, it was below the detection limit. Contamination in Catla catla (0.32 ± 0.11), Anguilla bengalensis bengalensis (0.26 ± 0.07 μg Hg/g), Chitala chitala (0.25 ± 0.18), Rita rita (0.34 ± 0.14), and Ompok pabda (0.26 ± 0.04) was also above the 0.25 μg Hg/g of wet weight, the limit set by the PFA for the maximum level for consumption of fish exposed to MeHg. Though in Labeo rohita (0.12 ± 0.03), Mastacembelus armatus (0.17 ± 0.02), Pangasius pangasius (0.12 ± 0.16), Bagarius bagarius (0.12 ± 0.01), and Clupisoma garua (0.1 ± 0.01), concentration was below the recommended level, in Lates calcarifer (0.23 ± 0.0) and Mystus aor (0.23 ± 0.1), it was threatening. Interestingly, a low concentration of Hg was found in post-monsoon samples.     

Techno-economic evaluation of ultrasound and thermal pretreatments for enhanced anaerobic digestion of municipal waste activated sludge

To enhance the anaerobic digestion of municipal waste-activated sludge (WAS), ultrasound, thermal, and ultrasound + thermal (combined) pretreatments were conducted using three ultrasound specific energy inputs (1000, 5000, and 10,000 kJ/kg TSS) and three thermal pretreatment temperatures (50, 70 and 90 °C). Prior to anaerobic digestion, combined pretreatments significantly improved volatile suspended solid (VSS) reduction by 29-38%. The largest increase in methane production (30%) was observed after 30 min of 90 °C pretreatment followed by 10,000 kJ/kg TSS ultrasound pretreatment. Combined pretreatments improved the dimethyl sulfide (DMS) removal efficiency by 42-72% but did not show any further improvement in hydrogen sulfide (H₂S) removal when compared with ultrasound and thermal pretreatments alone. Economic analysis showed that combined pretreatments with 1000 kJ/kg TSS specific energy and differing thermal pretreatments (50-90 °C) can reduce operating costs by $44-66/ton dry solid when compared to conventional anaerobic digestion without pretreatments.     

Modeling of gas-phase photodegradation of chloroform and carbon tetrachloride

The relationship between the irradiance in a photoreactor and the rate of photodegradation of organics is essential in the scaling-up of photoreactors to treat large volumes of air contaminated with organic pollutants. In this study, the analysis is adopted to compare results obtained from two different photoreactors. Initially, the applicability of two light models in calculating the irradiance in two photoreactors was evaluated. Thereafter, kinetic models of ultraviolet (UV) photooxidation of chloroform (CHCl3) and carbon tetrachloride (CCl4) from the archived literature were tested using experimental data under various operating conditions and different irradiances. Sensitivity analyses were conducted using different values of model parameters to determine the significance of each parameter on the photodegradation of the two chlorinated organics. For compounds that undergo photolysis as a primary mode of degradation, the rate of photodegradation at low initial concentrations can be predicted easily by the following equation: d[C]/dt = -2.303Iave, lambdaepsilonlambdaphilambda[C]. Although the photodegradation of chlorinated organic compounds in dry and humid air can be predicted well, it is difficult to predict the Cl* sensitized oxidation occurring at high initial concentrations. A good agreement between the simulated and experimental data provides a sound basis for the design of large-scale reactors.     

Impact Assessment and Recommendation of Alternative Conjunctive Water Use Strategies for Salt Affected Agricultural Lands through a Field Scale Decision Support System – A Case Study

Conjunctive use of saline/non-saline irrigation waters is generally aimed at minimizing yield losses and enhancing flexibility of cropping, without much alteration in farming operations. Recommendation of location-specific suitable conjunctive water use plans requires assessment of their long-term impacts on soil salinization/sodification and crop yield reductions. This is conventionally achieved through long-term field experiments. However such impact evaluations are site specific, expensive and time consuming. Appropriate decision support systems (DSS) can be time-efficient and cost-effective means for such long-term impact evaluations. This study demonstrates the application of one such (indigenously developed) DSS for recommending best conjunctive water use plans for a, rice-wheat growing, salt affected farmer’s field in Gurgaon district of Haryana (India). Before application, the DSS was extensively validated on several farmers and controlled experimental fields in Gurgaon and Karnal districts of Haryana (India). Validation of DSS showed its potential to give realistic estimates of root zone soil salinity (with R = 0.76–0.94; AMRE = 0.03–0.06; RMSPD = 0.51–0.90); sodicity (with R = 0.99; AMRE = 0.02; RMSPD = 0.84) and relative crop yield reductions (AMRE = 0.24), under existing (local) resource management practices. Long term (10 years) root zone salt build ups and associated rice/wheat crop yield reductions, in a salt affected farmer’s field, under varied conjunctive water use scenarios were evaluated with the validated DSS. It was observed that long-term applications of canal (CW) and tube well (TW) waters in a cycle and in 1:1 mixed mode, during Kharif season, predicted higher average root zone salt reductions (2–9%) and lower rice crop yield reductions (4–5%) than the existing practice of 3-CW, 3-TW, 3-CW. Besides this, long-term application of 75% CW mixed with 25% TW, during Rabi season, predicted about 17% lower average root-zone salt reductions than the cyclic applications of (1-CW, 1-TW, 2-CW) and (2-CW, 1-TW, 1-CW, i.e., existing irrigation strategy). However, average wheat crop yield reductions (16–17%) simulated under all these strategies were almost at par. In general, cyclic-conjunctive water use strategies emerged as better options than the blending modes. These results were in complete confirmation with actual long-term conjunctive water use experiments on similar soils. It was thus observed that such pre-validated tools could be efficient means for designing, local resource and target crop yield-specific, appropriate conjunctive water use plans for irrigated agricultural lands.     

Effluent characterization and different modes of reuse in agriculture—a model case study

Background, aim, and scope  

High-quality waters are steadily retreating worldwide. Discharge of industrial effluent in the environment again declines soil/water quality to a great extent. On the other hand, effluent reuse in agriculture could be a means to conserve natural resources by providing assured water supply for growing crops. But industrial effluents are highly variable in nature, containing a variety of substances, and all are not favorable for farming. Appraisal and developing modes of effluent reuse is therefore a prerequisite to enable its proper use in agriculture. Effluents of various industries were assessed and approaches for their use in farming were developed for a particular region in this study. As per availability of effluents, the same could be implemented in other water-scarce areas.     

Comparison of Multiple Passage Integrated Cell Culture-PCR and Cytopathogenic Effects in Cell Culture for the Assessment of Poliovirus Survival in Water

The goal of this study was to determine if a cytopathogenic effects (CPE) cell culture assay and an integrated cell culture PCR (ICC-PCR) assay would yield similar or different results when used to assess virus survival in water. Poliovirus type 1 was added to dechlorinated tapwater and stored at room temperature (22.5–24°C) for a total of 50 days. Samples were assayed at defined time intervals by the most probable number (MPN) method on Buffalo green monkey kidney cells (BGM) by CPE and additionally by ICC-PCR. Monolayers that were CPE negative on first passage were passed onto fresh monolayers of cells for a second and third time if still negative. By CPE assay, second passage was observed to yield a greater titer (2,300 vs. 24,000 MPN/ml) and third passage also resulted in an increased titer. ICC-PCR proved to be a more rapid and sensitive method than conventional cell culture for determining virus inactivation rates in water. Poliovirus survived in tapwater for up to 32 days, as assessed by both third passage ICC-PCR and CPE. There was no statistical difference in the inactivation rates between the two methods. To determine the total number of infectious viruses, these findings indicate the need for performing three cell culture passages or, alternatively, ICC-PCR on first passage.     

Impact assessment of various parameters polluting Ganga water in Kolkata Region: a study for quality evaluation and environmental implication

The quality of sewage-sludge samples obtained in Kolkata region was evaluated. Both sewage water and sludge components were analyzed for a number of physico-chemical, microbiological parameters using standard laboratory procedures, some heavy metals by AAS method and pesticide contents by GC method. Some of the physical and chemical constituents of the samples are within the allowable levels while the rest are not. The samples are rich in nutrients and have suitable pH for agricultural uses. In terms of Electrical Conductivity and Sodium Adsorption Ratio, sewage water is not suitable for irrigation. Fecal and coliform bacterial population is high in all samples. Pesticide and heavy metals in some places are alarming. So sewage-sludge produced in Kolkata cannot be used for agricultural purpose without any treatment. Thus proper care, maintenance, treatment and disposal of sewage water and sludge are most vital and should be the prime thrust for the nation.     

Foliar use of TiO2-nanoparticles for okra (Abelmoschus esculentus L. Moench) cultivation on sewage sludge–amended soils: biochemical response and heavy metal accumulation

Considering its richness in organic and inorganic mineral nutrients, the recycling of sewage sludge (SS) is highly considered as a soil supplement in agriculture. However, the fate of hazardous heavy metal accumulation in the crops cultivated in SS amended soils is always a source of concern. Since nanoparticles are widely recognized to reduce heavy metal uptake by crop plants; thus, the present experiment deals with okra (Abelmoschus esculentus L. Moench) cultivation under the combined application of SS and TiO₂-nanoparticles (NPs). Triplicated pot experiments were conducted using different doses of SS and TiO₂-NPs such as 0 g/kg SS (control), 50 g/kg SS, 50 g/kg SS?+?TiO₂, 100 g/kg SS, and 100 g/kg SS?+?TiO₂, respectively. The findings of this study indicated that among the doses of treatment combinations investigated, 100 g/kg SS?+?TiO₂ showed a significant (p?<?0.05) increase in the okra plant yield (287.87?±?4.06 g/plant) and other biochemical parameters such as fruit length (13.97?±?0.54 cm), plant height (75.05?±?3.18 cm), superoxide dismutase (SOD: 110.68?±?3.11 μ/mg), catalase (CAT: 81.32?±?3.52 μ/mg), and chlorophyll content (3.12?±?0.05 mg/g fwt.). Also, the maximum contents of six heavy metals in the soil and cultivated okra plant tissues (fruit, stem, and root regions) followed the order of Fe?>?Mn?>?Cu?>?Zn?>?Cr?>?Cd using the same treatment. Bioaccumulation and health risk assessment indicated that foliar application of TiO₂-NPs significantly reduced the fate of heavy metal accumulation under higher doses of SS application. Therefore, the findings of this study suggested that the combined use of SS and TiO₂-NPs may be useful in ameliorating the negative consequences of heavy metal accumulation in cultivated okra crops.

     

Optimization and modeling of coagulation-flocculation to remove algae and organic matter from surface water by response surface methodology

Charge neutralization and sweep flocculation were the major mechanisms. Effect of process parameters was investigated. Optimal coagulation conditions were studied by response surface methodology. ANN models presented more robust and accurate prediction than RSM. Seasonal algal blooms of Lake Yangcheng highlight the necessity to develop an effective and optimal water treatment process to enhance the removal of algae and dissolved organic matter (DOM). In the present study, the coagulation performance for the removal of algae, turbidity, dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV₂₅₄) was investigated systematically by central composite design (CCD) using response surface methodology (RSM). The regression models were developed to illustrate the relationships between coagulation performance and experimental variables. Analysis of variance (ANOVA) was performed to test the significance of the response surface models. It can be concluded that the major mechanisms of coagulation to remove algae and DOM were charge neutralization and sweep flocculation at a pH range of 4.66–6.34. The optimal coagulation conditions with coagulant dosage of 7.57 mg Al/L, pH of 5.42 and initial algal cell density of 3.83 × 10⁶ cell/mL led to removal of 96.76%, 97.64%, 40.23% and 30.12% in term of cell density, turbidity, DOC and UV₂₅₄ absorbance, respectively, which were in good agreement with the validation experimental results. A comparison between the modeling results derived through both ANOVA and artificial neural networks (ANN) based on experimental data showed a high correlation coefficient, which indicated that the models were significant and fitted well with experimental results. The results proposed a valuable reference for the treatment of algae-laden surface water in practical application by the optimal coagulation-flocculation process.