title: Metals removal from soil, fly ash and sewage sludge leachates by precipitation and dewatering properties of the generated sludge.
abstract: This study concerns the treatment by precipitation of three acidic and metal-rich leachates by using various reagents. Two treatment modes (simple and combined precipitation) have been performed to evaluate the metals removal efficiency and the dewatering ability of the generated sludge. It appears that for the three leachates used, the Ca(OH)(2) addition gave better metals removal at pH 10.0 than the use of NaOH at the same pH. Moreover, the combination of NaOH and Na(2)S allows better removal for Pb(2+), Zn(2+), Cu(2+) and Mn(2+) ions than with NaOH/Na(2)CO(3) or NaOH/Na(2)HPO(4). The dewaterability (vacuum filtration) of precipitates produced during the treatment of soil leachate was established as follows on the basis of the specific resistance to filtration (SRF) values: sulphides (4.3 x 10(12)mkg(-1))<phosphates (6.4 x 10(12) m kg(-1))<hydroxides [Ca(OH)(2)] (14.2 x 10(12) m kg(-1))<hydroxides [NaOH] (19.7 x 10(12) m kg(-1))<carbonates (26.5 x 10(12) m kg(-1)). For the fly ash leachate treatment, the obtained results were quite similar no matter the treatment mode used; the SRF values were in a range of 5-7 x 10(12) m kg(-1), while sludge volume index (SVI) ranged from 39 to 50 mL g(-1). The sludge generated during the treatment of sewage sludge filtrate using phosphate salt gave the best results regarding to SVI and SRF parameters (180 mL g(-1) and 7.6 x 10(12) m kg(-1), respectively). Experimental results show that whatever precipitating agent is used, vacuum filtration is more efficient in water elimination [total solids: 11-73% (ww(-1))] than in centrifugation [5-11% (ww(-1))] from sludge.
authors.affiliation: Institut National de la Recherche Scientifique, Centre Eau, Terre et Environnement, Université du Québec, Québec, Canada. Zied_Djedidi@ete.inrs.ca
authors.forename: Zied
authors.initials: Z
authors.lastname: Djedidi
authors.forename: Médard
authors.initials: M
authors.lastname: Bouda
authors.forename: Med Aly
authors.initials: MA
authors.lastname: Souissi
authors.forename: Ridha
authors.initials: R
authors.lastname: Ben Cheikh
authors.forename: Guy
authors.initials: G
authors.lastname: Mercier
authors.forename: Rajeshwar Dayal
authors.initials: RD
authors.lastname: Tyagi
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Blais
mesh_terms: D002244:Carbon / Q000737:chemistry; D011232:Chemical Precipitation; D060729:Coal Ash; D003890:Desiccation / Q000379:methods*; D004785:Environmental Pollutants / Q000302:isolation & purification*; D019216:Metals, Heavy / Q000302:isolation & purification*; D052638:Particulate Matter / Q000737:chemistry; D012722:Sewage / Q000737:chemistry; D012972:Sodium Hydroxide; D012989:Soil Pollutants / Q000302:isolation & purification; D013440:Sulfides
chemical_list: D060729:Coal Ash; D004785:Environmental Pollutants; D019216:Metals, Heavy; D052638:Particulate Matter; D012722:Sewage; D012989:Soil Pollutants; D013440:Sulfides; D012972:Sodium Hydroxide; D002244:Carbon; C033479:sodium sulfide