Low-energy treatment of colourant wastes using sponge biofilters for the personal care product industry

► Treating hair colourant wastes in the PCP industry is very energy intensive. ► New biofilter designs were tested for treating high strength colourant wastes. ► Packed- and sponge-media designs removed by COD and TN > 90% and 60%, respectively. ► Aerated sponge biofilters tolerated high oxidant levels better than other designs. ► Sponge reactors can reduce energy costs by >40% over current practices.