Effect of the Heavy Metals Cu, Ni, Cd and Zn on the Growth and Reproduction of Epigeic Earthworms (E. fetida) during the Vermistabilization of Municipal Sewage Sludge

Abstract

In order to enhance the removal of heavy metals such as Ni, Cu, Zn and Cd from wastewater, different cow dung/sewage sludge ratios were tested to assess the effect of these metals on the adaptability of Eisenia fetida earthworms to the treatment process carried out in a typical plant located in Tamaulipas, Mexico. Two experimental water treatment setups were proposed. The first set of experiments was planned to determine the adequate sewage sludge/cow dung ratio(s), whereas the second arrangement was designed to evaluate the growth performance and fecundity of the earthworms under high heavy metal concentrations. To achieve the objectives, the experiments were conducted for 90 days under controlled environmental conditions. Maximum worm biomass and growth rates were attained in samples containing 25 wt.% of sewage sludge. Weight and mortality of worms were significantly affected by the high levels of heavy metals, making difficult the metal accumulation in the worm tissues.

Ecotoxicological evaluation of swine manure disposal on tropical soils in Brazil

“…Dominguez-Crespo et al (2012) also found increased reproduction of E. fetida with cow manure and they associated it with the increase of OM in the soil. The reason for this increase probably was the same as ours.…”

“…The earthworms are sensitive to Cu and Zn (Onuoha and Worgu, 2011;Dominguez-Crespo et al, 2012). Some studies about the effect of the direct application of metals (salt forms) in soils, have proven the toxicity of Cu and Zn to E. andrei.…”

“…They are quite sensitive to the presence of certain polluting substances in the soil and are the most used standard organisms in ecotoxicological tests. Many studies using E. andrei for assessing the impact of pollutants have been published but to our knowledge none had the objective of testing the impact of swine manure on the soil community (Van Gestel and Hoogerwerf, 2001;César et al, 2008;Natal-da-Luz et al, 2011;Onuoha and Worgu, 2011;Dominguez-Crespo et al, 2012).…”

Phytoremediation and Environmental Factors

“…Interactions of microbial siderophores can increase labile metal pools and uptake by roots (Mench and Bes 2009 ;Ali et al 2013 ). Bacteria are an important factor of soil, because they have the ability to mineralize organic matter, improving bioavailability and effectiveness of nutrient uptake (Domínguez-Crespo et al 2012 ). Bacteria present in soil have a signifi cant impact on phytoremediation, especially those bacteria which belong to the plant growth-promoting rhizobacteria/bacteria (PGPR/ PGPB) group.…”

“…Through the ability to decompose organic matter, they take a signifi cant role in the distribution of generated energy, and also conversion of proteins from plant residues on the nitrogen dissolved in the acidic form or NH 4 + ions, which are more easily available forms for plants. In addition, mushrooms are involved in the circuit of inorganic components (Domínguez-Crespo et al 2012 ). Also through the presence of plant-fungus symbiosis, the plant becomes much more resistant to environmental stress (Khan 2005 ;Gamalero et al 2009 ;Rabęda et al 2011 ).…”