Effects of solar drying on heavy metals availability and phytotoxicity in municipal sewage sludge under semi-arid climate

Assessment of the agronomic value of solar-dried sludge and heavy metals bioavailability based on the bioaccumulation factor and translocation index

“…Prior to this study, we have assessed HM speciation in SDS. We have demonstrated, through a BCR scheme, a low mobility of the studied HMs (Cr, Ni, Pb, and Cu) since the residual fraction was found to be predominant compared to the exchangeable, reducible, and oxidizable ones (An-nori et al, 2020a). Although the recorded results in the present study regarding BCF roots seemed to be in accordance with the speciation results, it may be more rational to investigate HM speciation in the soil solution, after the incorporation of SDS, to explain the mechanisms behind the bioaccumulation of HMs in the root system.…”

“…As for Cr, it is only a few ppm above the maximum admitted load considered by the U.S. Environmental Protection Agency (Supplementary Table S1). However, the speciation analysis of this element in a previous investigation indicated low mobility potential of Cr (An-nori et al, 2020a). Indeed, the oxidizable fraction, which was initially predominant in the sludge before undergoing a solar drying process, decreased very significantly after 45 days of solar drying, and the residual fraction, the most stable in the environment, became the most important in SDS.…”

“…In the latest trends, with regard to the field of sewage sludge treatment, the solar-drying process is involved with particular emphasis, especially where solar radiation is available as it is the case in Morocco (3000 h/year of sunshine). Throughout the literature, the solar-drying process has been proven to not affect the agronomic value of sewage sludge (Lem et al, 2017;An-nori et al, 2020a;An-Nori et al, 2022). Moreover, its significant ability to remove pathogens, namely, indicators of fecal contamination and helminths, has been reported in several research studies (Shanahan et al, 2010;Paluszak et al, 2012;An-Nori et al, 2021).…”

“…In this study, we aimed to assess (i) the agronomic value of solar-dried sludge as an organic amendment on crop yields and (ii) HM transfer to different parts of wheat and faba bean crops. solar drying, the sludge was digested (37 °C) and mechanically dewatered using belt filters and was then solar-dried for 45 days in summer under a semi-arid climate (An-nori et al, 2020a). Physicochemical analysis of solar dried sludge was performed in three replicates, in a previous investigation (An-nori et al, 2020a).…”

“…solar drying, the sludge was digested (37 °C) and mechanically dewatered using belt filters and was then solar-dried for 45 days in summer under a semi-arid climate (An-nori et al, 2020a). Physicochemical analysis of solar dried sludge was performed in three replicates, in a previous investigation (An-nori et al, 2020a). The main characteristics of solar-dried sludge (SDS) are shown in Table 1.…”