Application of phytoremediation on soil polluted by heavy metals from sewage sludge

Abstract

Soil pollution by heavy metals (HM) has become a problem in Algeria, in particular that caused by the discharge of untreated sewage sludge due to the lack of means at the level of sewage treatment plants (WWTP). The objective of our work was to study the possibility of reducing HM pollution of the soil of the WWTP site of Reghaia (Algeria) by phytoremediation. The results obtained showed the decrease in plant growth parameters (maize, rapeseed and alfalfa) grown on the polluted soil. However, on polluted soil amended with fertilizer, improved growth of these plants was noted. It has also been observed that the cultivation of plants in polluted soils (amended and unamended) made it possible to have attenuation rates for HMs (Cd, Zn and Cr) higher than those obtained in the absence of plant cultivation. However, these rates were not very high (less than 40%), and the fertilizer amendment did not increase these rates, despite the improvement in the production of plant biomass. This would be mainly due to the decrease in the bioavailability of HMs for plants. It was concluded that the tested plants do not allow the phytoextraction of HM but their phytostabilization in the polluted soil of the Reghaia WWTP site.

Novelty statement

In Algeria, studies on the treatment of polluted soils by phytoremediation are few. The novelty of our study is due to the fact that the polluted soil of the site of the Reghaia wastewater treatment plant (Algeria) has not been the subject of another study. In addition, the results obtained from studies carried out on polluted soil following human activities such as the discharge of sewage sludge cannot be extrapolated to our polluted soil because the conditions which affect the performance of phytoremediation are not the same (type of soil, age of pollution, type and content of heavy metals, temperature, pH, content of organic matter… etc.).

Keywords:

• Organic amendment
• phytostabilization
• soil pollution
• trace elements

Acknowledgements

We particularly thank the laboratory engineers of the Faculty of Biology (Guendouzi S., Boanem M., Hamdad S., and Lameri L.) as well as the employees of the Reghaia wastewater treatment plant (Algiers).