Results showed that the solid residues from the treatments nano-TiO2(1.0 g L−1)/H2O2(0.5M) and nano-Fe2O3(1.0 g L−1)/H2O2(1.0M) from OOMW and nano-Fe2O3(0.75 g L−1)/H2O2(0.01M) from kraft pulp mill effluent exhibited lethal toxicity to Chironomus riparius. Only the exposure to solid residues resulting from the treatment with nano-Fe2O3(0.75 g L−1)/H2O2(0.01M) applied to the kraft pulp mill effluent significantly affected the growth rate based on the head capsule width