Effect of composting on the mobility of arsenic, chromium and nickel contained in kitchen and garden waste

The study was focused on evaluation of possible changes in As, Cr, and Ni mobility and fractionation during composting of kitchen and garden waste. Fresh bio-waste taken up seasonally was thoroughly mixed with woodchips in the wet weight portion of 3:1 and the mixture was put into batch-wise aerated fermenters under 3 air flow rates. An increased drop in exchangeable Cr and Ni was found in kitchen and garden waste after 12 weeks of composting, respectively. The exchangeable content of As decreased only during kitchen waste composting. The order of fractions in the final compost was as follows: residual > oxidizable > exchangeable > reducible. The proportion of Cr and Ni in exchangeable fraction decreased after composting more than 3- and 4-fold, respectively. Results proved that an intensive composting process is a suitable method for immobilization of Cr and Ni, and for decreasing total As contained in household bio-waste.

► Kitchen and garden waste collected during four climate seasons were composted.
► The total content of As unlike Cr and Ni decreased after intensive composting.
► Composting substantially reduced the proportion of exchangeable Cr and Ni.
► Non-exchangeable fractions of elements prevailed in the final compost.