Sewage Sludge-Induced Effect on Growth, Enzyme Inhibition, and Genotoxicity can be Ameliorated Using Wheat Straw and Biochar in Pheretima posthuma Earthworms

Abstract

Sewage sludge, rich in organic matter and nutrients, is widely used as a fertilizer to increase the fertility of soil. The direct application of sewage sludge without any treatment causes soil contamination as well as significantly affects the earthworm population. In the present study, the effect of sewage sludge-amended soil on growth, enzyme activities, and the DNA damage in Pheretima posthuma earthworms was studied under wheat straw and biochar treatment of 30-day laboratory incubation. Wheat straw, biochar, and sewage sludge were applied at 0 (control), 5, 10, and 25% w/w along with combined treatment of sewage sludge with biochar and wheat straw, respectively at 25% each. After the incubation period, the percentage change in mean weight and length was measured and esterase and phosphatase enzyme activities were quantitatively determined. RAPD-PCR and the comet assay were performed to assess the genotoxicity. A significant weight loss was observed (26%) at a 25% rate of sewage sludge and biochar (11%). Similarly, a maximum decrease in length was observed with sewage sludge (2.5%) followed by biochar (0.80%) at a 25% application rate. Mean weight and length both decreased by increasing the rate of sewage sludge and biochar. In addition, no change was observed in the weight and length of P. posthuma in the treatment consisting of sewage sludge and wheat straw. Moreover, sewage sludge caused inhibition of esterase and phosphatase activities as well as induced DNA damage. The comet parameters showed that wheat straw and biochar ameliorated the toxic effects of sewage sludge. It is, therefore, concluded that sewage sludge has a tangible impact on earthworms which ultimately disrupts ecosystem functions and wheat straw and biochar can thus be utilized to reduce the toxicity of sewage sludge in Pheretima posthuma earthworms.

New developments on vermifiltration as a bio-ecological wastewater treatment technology: Mechanism, application, performance, modelling, optimization, and sustainability

“…For example, industrial wastewater may contain toxic chemicals that can inhibit earthworm activity, reducing treatment efficiency [ 48 ]. Earthworms are well-known for their ability to withstand various types of contaminants, including herbicides, heavy metals, and organic pollutants that often originate from industrial, factory, and hospital wastewater as well as sewage sludge [ 56 ]. They possess the capacity to decrease the concentrations and toxicity of wastewater contaminants by storing them in their body tissues [ 41 ].…”

“…However, when wastewater containing these contaminants is applied, it can result in the accumulation of these substances within the earthworm's body, which in turn could induce physiological and biochemical harm. This can result in growth abnormalities, enzyme inhibition, and toxicity, which may extend to genetic levels [ 56 ].…”

Ecotoxicological Evaluation of Earthworm (Eisenia fetida) Induced by Enrofloxacin and Di-(2-Ethylhexyl) Phthalate

“…Another vital enzyme, CL, can decompose cellulose into oligosaccharides and cellobiose and finally into glucose, which also plays an important role in biological autoimmunity [66]. Phosphatase can catalyze the hydrolysis of phosphate monoesters under acid or alkaline conditions, plays a pivotal role in the metabolism of phosphorus in organisms, and significantly affects the phosphorus cycle in the environment [67].…”