THE REMOVAL OF BACTERIA BY MODIFIED NATURAL ZEOLITES

Abstract

The removal effect of natural and modified zeolites containing different heavy metals (Ni²⁺, Zn²⁺, Fe³⁺ and Cu²⁺) on pure cultures of Escherichia coli and Staphylococcus aureus in a solid medium was evaluated in this work. These experiments were carried out in a continuous mode treating municipal wastewater. Faecal coliform species and Pseudomonas aeruginosa were identified. The rate constants of heavy metal lixiviation were determined using a first order kinetic model. The removal effect of modified natural zeolites in both a solid medium and in continuous mode showed an increased elimination of the bacterial population. The results established a decreasing order of the removal effect as follows: Cu²⁺>Fe³⁺>Zn²⁺>Ni²⁺. The best performance of columns was obtained for inlet bacterial concentrations below 10⁶ cells/100 ml. Most of the identified bacterial species were affected by copper modified zeolites, although Serratia marcescens presented the highest sensitivity and Klebsiella pneumoniae the greatest resistance.

Keywords:

• Modified natural zeolites
• Heavy metals
• Municipal wastewaters
• Faecal coliforms
• Removal effect
• Tertiary treatment

ACKNOWLEDGMENTS

The authors wish to acknowledge the support of the Alexander von Humboldt Foundation, Program for Scientific Cooperation with Iberoamerica (Spanish Foreign, Education and Science Ministries) and the National Council for Science and Technology (CONACYT) from Mexico in developing this work. We also thank Professor Jesús Núñez for his revision of the manuscript.