title: Precipitation of heavy metals from coal ash leachate using biogenic hydrogen sulfide generated from FGD gypsum.
abstract: Investigations were undertaken to utilize flue gas desulfurization (FGD) gypsum for the treatment of leachate from the coal ash (CA) dump sites. Bench-scale investigations consisted of three main steps namely hydrogen sulfide (H(2)S) production by sulfate reducing bacteria (SRB) using sulfate from solubilized FGD gypsum as the electron acceptor, followed by leaching of heavy metals (HMs) from coal bottom ash (CBA) and subsequent precipitation of HMs using biologically produced sulfide. Leaching tests of CBA carried out at acidic pH revealed the existence of several HMs such as Cd, Cr, Hg, Pb, Mn, Cu, Ni and Zn. Molasses was used as the electron donor for the biological sulfate reduction (BSR) process which produced sulfide rich effluent with concentration up to 150 mg/L. Sulfide rich effluent from the sulfate reduction process was used to precipitate HMs as metal sulfides from CBA leachate. HM removal in the range from 40 to 100% was obtained through sulfide precipitation.
authors.affiliation: Asian Institute of Technology, School of Environment, Resources and Development, P.O. Box 4, Khlong Luang, Pathumthani 12120, Thailand.
authors.forename: Madawala Liyanage Duminda
authors.initials: ML
authors.lastname: Jayaranjan
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Annachhatre
mesh_terms: D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology; D002133:Calcium Sulfate / Q000737:chemistry*; D011232:Chemical Precipitation; D060729:Coal Ash / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D006862:Hydrogen Sulfide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000302:isolation & purification*; D013455:Sulfur / Q000302:isolation & purification*; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D002133:Calcium Sulfate; D060729:Coal Ash; D005740:Gases; D006862:Hydrogen Sulfide; D019216:Metals, Heavy; D013455:Sulfur; D062065:Wastewater; D014874:Water Pollutants, Chemical