Sewage sludge toxicity: comparison of plants and soil invertebrates response

Sewage sludge disposal is of major concern for the quality of the receiving soils. Sewage sludge application can cause negative ecological impact to terrestrial ecosystems and pose a human health risk. Potential hazard of sewage sludge application assessment based on the sewage sludge physicochemical analysis do not evaluate possible toxic effects to soil biota. In this study, sewage sludge ecotoxicological assessment was based on the bioassays with earthworm (Eisenia fetida) and proso millet (Panicum miliaceum L.). The aim of this study was to compare the toxicity of untreated and treated (kept for 1 year in sludge storage site) sewage sludge to proso millet (P. miliaceum L.) and earthworm (E. fetida). Untreated sewage sludge was severely toxic and resulted in 100% earthworms and millet seeds mortality. Treated sewage sludge did not reduce the survival of earthworms, though negatively affected the earthworms' biomass, cocoon production rate and induced lipid peroxidation. The response of P. miliaceum to sewage sludge application was less pronounced. Untreated sewage sludge slightly reduced the millet growth and concentrations of photosynthetic pigments. Sewage sludge exhibited lower toxicity to plants than to soil dwelling organisms and low sewage sludge application levels had the stimulatory effect to the growth of P. miliaceum.