Reactor performance and pathogen removal during wastewater treatment by vermifiltration

The application of vermifiltration could reduce the load of chemical and biological pollutants present in wastewater, reducing the pressure over water requirements and allowing the reclamation of the treated water. In the present study, vermifiltration has shown a great potential for chemical pollutants and pathogen removal in wastewater through the synergistic interactions of earthworms and microorganisms. The results of a pilot-scale study showed a higher percentage removal of biochemical oxygen demand (88%), chemical oxygen demand (78%), total suspended solids (83%) and log removal of fecal coliforms (2.61), fecal streptococci (2.50), Salmonella (2.20) and Escherichia coli (2.48) to the levels considered acceptable for reuse in irrigation purposes. Specifically, earthworms in the vermifilter were able to transform insoluble organic material to soluble form followed by selective digestion of the material to finer size, and further degradation by the microorganisms in the reactor. In vitro antimicrobial assay tests also showed that the present microflora had strong inhibitory efficiency against Staphylococcus aureus, E. coli, Pseudomonas aeruginosa and Klebsiella aerogenes. The observed inhibitory effect was found to be responsible for the phenomenon mentioned above, with release of antimicrobial substances by earthworms and associated microflora that showed antimicrobial potency against pathogenic bacteria. The kinetics evaluation showed the predominance of a first order removal model during vermifiltration.