Accumulation of lead, cadmium, manganese, copper and zinc by sludge worms; Tubifex tubifex in sewage sludge

Abstract

ABSTRACT:Tubifex tubifex has been shown to survive in organic polluted environments, however, not much has been done on its inorganic pollution tolerance. Samples of T. tubifex and their respective sewage sludge were taken from Soche wastewater treatment plant in Blantyre City, Malawi during July 2007 to November 2008. The total number of sludge samples taken was fifty one which was made into seventeen composite samples. A total of seventeen T. Tubifex samples were also collected. The samples were analyzed for copper, lead, manganese, zinc and cadmium using standard methods from American Public Health Association and Association of Official Analytical Chemists. The concentrations of metals in sewage sludge and T. tubifex were on dry weight basis and the metals determined were acid extractable. In general, heavy metals concentration was lower in T. tubifex than in sewage sludge. The range of heavy metals concentrations were (in sludge and (T. tubifex)): zinc 275.3 -361.5 mg/kg (45.0 -82.2 mg/kg), manganese 293.7 -230.1 mg/kg (1.21 -3.69 mg/kg), copper 86.5 -120.1 mg/kg (1.6 -4.7 mg/kg), lead 11.2 -22.4 mg/kg (Below detection limit -0.95 ) and cadmium 1.12 -2.31 mg/kg (1.08 -2.18 mg/kg). The results showed significant differences between the concentrations of manganese, copper, lead and zinc in sewage sludge and T. tubifex (p < 0.05). However there was no significant difference between the concentrations of cadmium in sewage sludge and T. tubifex (p > 0.05). T. tubifex did not show the ability to accumulate heavy metals (attributed to its high defecation and metabolic rate) except for cadmium hence cannot be used as a bioindicator for heavy metal pollution in sludge.

Equilibrium studies of copper ion adsorption onto modified kernel of date (Fructus dactylus)

“…The pH of the aqueous solution is an important operational parameter in the adsorption process because it affects the solubility of the metal ions, concentration of the counter ions on the functional groups of the adsorbent and the degree of ionization of the adsorbate during reaction (Kaonga et al 2010;Ghazy and Ragab 2007;Kara 2005;Onundi et al 2010). In order to find optimal pH value for the sorption process, the removal of copper ions in the pH range 2-6 was investigated and the data are illustrated in the Fig.…”

“…The initial faster rate of metal transition may be explained by the large, uncovered available surface area of the kernel of dates and its composite. The rapid removal of the adsorbate has significant practical importance as it will facilitate smaller reactor volumes insuring efficiency and economy (Kaonga et al 2010).…”

Cd, Zn, Cu, Pb, Co, Ni phytotoxicity assessment

“…Some of the problems affecting the world now are acid rain, global warming, hazardous wastes, over population, ozone depletion, smog and environmental pollution (Kaonga et al 2010). Environmental pollution is one of the major causes of environmental degradation worldwide.…”

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“…According to Polish law, permitted maximal Cd level in bottom sediments cannot exceed 7.5 mg/kg dry weight (Journal of Laws, 2002). Cd undergo easy bioaccumulation in invertebrate organisms such as Tubifex worms (Bouche et al, 2000;Kaonga et al, 2010) which may pose a risk to organisms high up in the food chain, especially non-predatory fish. Tubifex are tolerant to pollution, as such dominate in contaminated water environments.…”