Wastewaters discharged from various coal-related activities deteriorate fresh water quality and inflict possibilities of groundwater contamination. Their characteristics mostly depend on the parent coal properties, though some of the pollutants are cyanide, thiocyanate, ammonia, phenol, heavy metals and suspended solids. This paper has reviewed the treatment techniques along with the characteristics of all such kinds of wastewater and also identified the challenges and future perspectives. Primarily, demineralization of coal can attenuate and control release of pollutants in wastewaters if implemented successfully. Mine water from non-lignite mines can be purified using simple techniques, for its reutilization. Acidic mine water and leachates can be treated using passive bioreactors with microbial activity, different organic substrates and limestone drains. Additionally bio-electrochemical systems, membranes, macrocapsules, zeolite filters, ores, physical barriers, and aquatic plants can also be used at various stages. Coal washery wastewater can be treated using natural coagulants obtained from plant extracts along with conventional coagulants. Nitrification and denitrification bacteria fixed in reactors along with activated carbon and zero-valent iron can treat coke oven wastewater. Some other sophisticated techniques are vacuum distillation, super critical oxidation, nanofiltration and reverse osmosis. Practical use of these methods, wisely in an integrated way, can reduce freshwater consumption.
Abstract. Uninterrupted generation of fly ash by the coal based thermal power plants and its dumping has lead to steady encroachment of useful land in India. The deleterious effects of fly ash on the nearby environment are inevitable due to its fine texture and presence of toxic metals. Thus, proper revegetation programme of the sites are highly desirable due to their continuance in being the part of landscape. This paper conglomerates all the issues which should be taken into account to prevent groundwater contamination and increase phytostabilization of metals. An insight to the past and the prevailing restoration scenario will help in selecting of plant species for biomass production. Primarily, an integrated approach towards revegetation is necessary which comprises native and exotic grass-legume species, readily available composts, green manure, and mulches. The paucity of studies in relation to the long term changes in fly ash due to vegetation is to be permeated through regular analysis of substrate nutrient status, extent of nutrient loss, bioavailable toxic metals, in restoration sites. The range of methodologies and indexes discussed here will benefit the future management approaches of fly ash with emphasis on phytoremediation of trace metals, development of aesthetically pleasant landscape and productivity.
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