title: Metal concentrations in lime stabilised, thermally dried and anaerobically digested sewage sludges.
abstract: Cognisant of the negative debate and public sentiment about the land application of treated sewage sludges ('biosolids'), it is important to characterise such wastes beyond current regulated parameters. Concerns may be warranted, as many priority metal pollutants may be present in biosolids. This study represents the first time that extensive use was made of a handheld X-ray fluorescence (XRF) analyser to characterise metals in sludges, having undergone treatment by thermal drying, lime stabilisation, or anaerobic digestion, in 16 wastewater treatment plants (WWTPs) in Ireland. The concentrations of metals, expressed as mgkg(-1) dry solids (DS), which are currently regulated in the European Union, ranged from 11 (cadmium, anaerobically digested (AD) biosolids) to 1273mgkg(-1) (zinc, AD biosolids), and with the exception of lead in one WWTP (which had a concentration of 3696mgkg(-1)), all metals were within EU regulatory limits. Two potentially hazardous metals, antimony (Sb) and tin (Sn), for which no legislation currently exists, were much higher than their baseline concentrations in soils (17-20mgSbkg(-1) and 23-55mgSnkg(-1)), meaning that potentially large amounts of these elements may be applied to the soil without regulation. This study recommends that the regulations governing the values for metal concentrations in sludges for reuse in agriculture are extended to include Sb and Sn.
authors.affiliation: Civil Engineering, National University of Ireland, Galway, Ireland.
authors.forename: M G
authors.initials: MG
authors.lastname: Healy
authors.affiliation: Teagasc Johnstown Castle Environment Research Centre, Co. Wexford, Ireland.
authors.forename: O
authors.initials: O
authors.lastname: Fenton
authors.affiliation: Teagasc Johnstown Castle Environment Research Centre, Co. Wexford, Ireland.
authors.forename: P J
authors.initials: PJ
authors.lastname: Forrestal
authors.affiliation: Food Safety Department, Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Danaher
authors.affiliation: Civil Engineering, National University of Ireland, Galway, Ireland.
authors.forename: R B
authors.initials: RB
authors.lastname: Brennan
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences and Ryan Institute, National University of Ireland, Galway, Ireland. Electronic address: liam.morrison@nuigalway.ie.
authors.forename: L
authors.initials: L
authors.lastname: Morrison
mesh_terms: D000383:Agriculture; D000693:Anaerobiosis; D002104:Cadmium / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry*; D003362:Cost-Benefit Analysis; D007494:Ireland; D008670:Metals / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D011786:Quality Control; D012643:Selenium / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014001:Tin / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater; D018508:Water Purification / Q000379:methods; D014965:X-Rays; D015032:Zinc / Q000737:chemistry
chemical_list: D002104:Cadmium; D017610:Calcium Compounds; D008670:Metals; D010087:Oxides; D012643:Selenium; D012722:Sewage; D012987:Soil; D012989:Soil Pollutants; D014001:Tin; D062065:Wastewater; D015032:Zinc; C016538:lime
keywords: Biosolids; Land application; Metals; Treated sludge