Phytostabilization of coal mine overburden waste, exploiting the phytoremedial efficacy of lemongrass under varying level of cow dung manure.

A pot study was performed to assess the phytoremedial potential of Cymbopogon citratus (D.C.) Staf. for reclamation of coal mine overburden dump wastes, emphasizing the outcome of amendment practices using cow dung manure (CM) and garden soil mixtures on the revegetation of over-burden wastes (OB). Wastes amendment with cow dung manure and garden soil resulted in a significant increase in soil health and nutrient status along with an increment in the phytoavailability of Zn and Cu which are usually considered as micronutrients, essential for plant growth. A significant increment in the total biomass of lemongrass by 38.6% under CM20 (OB: CM 80:20) was observed along with improved growth parameters under amended treatments as compared to OB (100% waste). Furthermore, the proportionate increases in the assimilative rate, water use efficiency, and chlorophyll fluorescence have been observed with the manure application rates. Lemongrass emerged out to be an efficient metal-tolerant herb species owing to its high metal-tolerance index (>100%). Additionally, lemongrass efficiently phytostablized Pb and Ni in the roots. Based on the strong plant performances, the present study highly encourages the cultivation of lemongrass in coal mining dumpsites for phytostabilization coupled with cow-dung manure application (20% w/w).

Effluent Treatment Technologies in the Iron and Steel Industry - A State of the Art Review.

Iron and steel industry is the principal driving force propelling economic and technological growth of a nation. However, since its inception this industry is associated with widespread environmental pollution and enormous water consumption. Different units of a steel plant discharge effluents loaded with toxic, hazardous pollutants, and unutilized components which necessitates mitigation. In this paper, pollutant removal efficiency, effluent volume product quality, and economic feasibility of existing treatments are studied vis-à-vis their merits, demerits, and innovations to access their shortcomings which can be overcome with new technology to identify future research directions. While conventional methods are inadequate for complete remediation and water reclamation, the potential of advanced treatments, like membrane separation, remains relatively untapped. It is concluded that integrated systems combining membrane separation with chemical treatments can guarantee a high degree of contaminant removal, reusability of effluents concurrently leading to process intensification ensuring ecofriendliness and commercial viability.

Applicability of Zeolite Based Systems for Ammonia Removal and Recovery From Wastewater.

Ammonia discharged in industrial effluents bears deleterious effects and necessitates remediation. Integrated systems devoted to recovery of ammonia in a useful form and remediation of the same addresses the challenges of waste management and its utilization. A comparative performance evaluation study was undertaken to access the suitability of different zeolite based systems (commercial zeolites and zeolites synthesized from fly ash) for removal of ammonia followed by its subsequent release. Four main parameters which were studied to evaluate the applicability of such systems for large scale usage are cost-effectiveness, ammonia removal efficiency, performance on regeneration, and ammonia release percentage. The results indicated that synthetic zeolites outperformed zeolites synthesized from fly ash, although the later proved to be more efficient in terms of total cost incurred. Process technology development in this direction will be a trade-of between cost and ammonia removal and release efficiencies.

Studies on synthesis and characteristics of zeolite prepared from Indian fly ash.

In the present study, samples of coal fly ash were obtained from seven major Indian thermal power plants. These samples were transformed into fly ash zeolite (FAZ) using hydrothermal activation by treatment with NaOH. All experiments were carried out at 100 degrees C, but with different solid:liquid ratios, different concentrations of alkali and different incubation times. The chemical composition, mineralogy and morphology of the fly ash and FAZ were determined by wet chemical method after Na2CO3 fusion, x-ray diffraction and scanning electron microscopy. The cation exchange capacity of fly ash and FAZ was determined using the ammonium acetate method (IS:2720). The ammonium exchange capacity was determined by the titrimetric method. The experiments demonstrate that zeolite can be synthesized at 100 degrees C using alkali. The cation exchange capacity and ammonium adsorption capacity of FAZ (up to 250 meq/100 g and 22.93 mg NH4+/g respectively) indicate that the FAZ may be potentially useful to reduce heavy metals and other pollutants from contaminated environments. Therefore, zeolitization at low temperature potentially allows waste fly ash to be used in an economically advantageous way.

Environmental impact of manganese due to its leaching from coal fly ash.

In India, so far not much efforts have been made to use coal ash as backfill material in underground/ open cast mines and to predict its subsequent effect on ground water quality. One of the main problems in disposing of big quantities of coal ash is the possible leaching of different pollutants, including manganese. A thorough investigation regarding leaching of manganese from different fly ashes is required to know the impact of manganese due to its leaching from fly ash to ground water as well as surface water. In the present study, short term and long term leaching studies have been carried out on fly ash, bottom ash, pond ash and weathered ash of Chandrapura thermal power plant, Bokaro, Jharkhand and Ramagundam thermal power plant, Ramagundam, Andhra Pradesh. The amount of manganese released in different experiments has been evaluated. The leachate of Chandrapura fly ash has more manganese concentration (0.2001 mg/L) than the leachate of bottom ash, pond ash and weathered ash. A field investigation at Damoda abandoned open cast mine, filled with pond ash of Chandrapura thermal power plant revealed that concentration of manganese in ground water beneath the ash filled mine has been found very high (maximum up to 6.0 mg/L). But its migration to a long distance has not been seen. Remedial measures for coal ash disposal have also been formulated.

Heavy metals leaching in Indian fly ash.

Fly ash is an industrial waste generated from thermal power plants. Fly ash constitutes 80-85% of the total ash produced. A small part of fly ash is utilised in some sectors such as construction materials, building engineering, road, back fill, agriculture, selective engineering and processing useful materials. A large part of fly ash produced is disposed of with very high environmental risk. In the present paper, laboratory leaching test has been used to determine the potential mobility of Pb, Cd, Cr, Cu, Zn, Fe, Mn and Ni in fly ash samples, collected from Chandrapura Thermal Power Plant, Jharkhand and Ramagundam Super Thermal Power Plant, Andhra Pradesh, in order to assess their leachability when these wastes are disposed of. A cascade-leaching test was used at liquid-to-solid ratio (L/S) ranging between 20 and 100. Both fly ash samples exhibited neutral reactions, as indicated by pH values <11.75 and >7.0 at L/S=10 and contact time of 10 minutes. The percentage of leached amounts found to follow the trend Zn>Fe>Mn>Cr>Pb>Cu>Ni>Cd for fly ash from Chandrapura and Fe>Zn>Cu>Mn>Cr>Ni>Pb>Cd for fly ash from Ramagundam. Effect of pH on metals released from ash surface in aqueous solution followed a predictable pattern of decreasing release with increasing pH.