Changes and variability in concentration of heavy metals in sewage sludge during composting

Concentration and speciation of heavy metals in six different sewage sludge-composts

“…Similar increases in the total metal concentrations were found in many relevant studies [12,15,18,29,30], where even 3-fold enrichment of Cu and Zn in the mature compost compared to the initial values was observed [12]. Composting may concentrate or dilute the HMs content of the sewage sludge [19,31]. The change of metal concentration is generally attributed to the metal loss through leaching and to organic matter destruction [31,32].…”

“…Moreover, in order to reduce the cost of operations, the composting of sludge with rice straw in the present study was conducted at a low ratio of C/N (13:1) ( Table 1). It is therefore concluded that the increase in the concentration of HMs was mainly due to the weight loss of materials following organic matter decomposition and mineralization processes during the composting period [12,31,32]. On the other hand, the increase percentages of four metals in the different composts were not constant.…”

“…Composting may concentrate or dilute the HMs content of the sewage sludge [19,31]. The change of metal concentration is generally attributed to the metal loss through leaching and to organic matter destruction [31,32]. In this study, the composting trials were performed in the purpose-built platforms, and thus there was no leaching and runoff during composting.…”

Heavy metals fractionation before, during and after composting of sewage sludge with natural zeolite

“…This result occurred mainly because of losses of mass that occurred during composting. This outcome is supported by a number of published papers (Garcia-Delgado et al, 1994;Wagner et al, 1990;He et al, 1992).…”

Dewatered anaerobically‐stabilized primary sewage sludge composting: Metal leachability and uptake by natural Clinoptilolite

“…Composting can concentrate or dilute the heavy metals present in sewage sludge. This change in metal concentration depends on the metal loss through leaching and on the overall concentration of metals due to organic matter destruction (Wagner et al, 1990). As observed in Table 4, natural Clinoptilolite has the ability to exchange Na and K. It is also clearly seen that with the increasing amount of zeolite, the concentration of all heavy metal contents in the compost samples decreases while the concentration ofNa and K increases.…”