Effects on Ni and Cd speciation in sewage sludge during composting and co-composting with steel slag

Abstract

Sewage sludge and industrial steel slag (SS) pose threats of serious pollution to the environment. The experiments aimed to improve the stabilizing effects of heavy metal Ni and Cd morphology in composting sludge. The total Ni and Cd species distribution and chemical forms in the compost sewage sludge were investigated with the use of compost and co-compost with SS, including degradation. The carbon/nitrogen ratio of piles was regulated with the use of sawdust prior to batch aerobic composting experiments. Results indicated that the co-composting with SS and organic matter humification can contribute to the formation of Fe and Mn hydroxides and that the humus colloid significantly changed Ni and Cd species distribution. The decreased content of Ni and Cd in an unstable state inhibited their biological activity. Conclusions were drawn that an SS amount equal to 7% of the dry sludge mass was optimal value to guarantee the lowest amount of Cd in an unstable state, whereas the amount was 14% for Ni.

Speciation Analysis Method of Heavy Metals in Organic Fertilizers: A Review

“…In Figure 1, 28 reports, which studied metals speciation by SEPs in organic fertilizers, are shown. It showed that the Tessier method was the most frequently used method with of the total articles [21,22,[40][41][42][43][44][45][46][47], followed by the modified BCR method with [20,23,30,[47][48][49][50][51]. The modified Tessier method [52][53][54][55] and other methods both acc for 14.29%.…”

Effect of aeration rate, moisture content and composting period on availability of copper and lead during pig manure composting

“…The exchangeable state of heavy metals determined by the BCR sequential extraction method mainly referred to the heavy metals that were adsorbed on particle surfaces and combined with carbonate minerals (Lu, 2014). In the composting process, when the pH increased, the activated heavy metal ions can easily combine with OH ions contributing to the formation of stable precipitates (Zeng et al, 2014). The OM decomposition promoted the formation of humus substances during composting (Amir et al, 2005;Liu et al, 2007).…”