Metal concentrations in lime stabilised, thermally dried and anaerobically digested sewage sludges. (February 2016)

• Record Type: Journal Article
• Authors: Healy, M.G.; Fenton, O.; Forrestal, P.J.; Danaher, M.; Brennan, R.B.; Morrison, L.
• Is Part Of: Waste management. Volume 48(2016)
• Page Start: 404
• Page End: 408
• Publication Date: 2016-02
• Subjects: Treated sludge -- Biosolids -- Metals -- Land application; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2015.11.028
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Metals from WWTPs in Ireland were below the MAC of metals for use in agriculture. Some potentially harmful metals not governed by EU and international regulations. Se and Sn higher in sewage sludge than their baseline concentrations in soils. Handheld XRF is cost-effective and rapid for the analysis of sewage sludge. 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 mg kg −1 dry solids (DS), which are currently regulated in the European Union, ranged from 11 (cadmium, anaerobically digested (AD) biosolids) to 1273 mg kg −1 (zinc, AD biosolids), and with the exception of lead in one WWTP (which had a concentration of 3696 mg kg −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 (17–20 mg Sb kg −1 and 23–55 mg Sn kg −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.