Pathogen removal during wastewater treatment by vermifiltration

Abstract

The study was designed to determine the effect of earthworms and the mechanism behind removal of pathogens during wastewater treatment by vermifiltration. The experimental phase continued for 10 weeks, starting after the initial stabilization phase of one week. Significant organic matter degradation and coliform removal were observed during vermifiltration of domestic wastewater. It was observed that vermifilter (VF) reduced biochemical oxygen demand and chemical oxygen demand by 84.8% and 73.9%, respectively. Significant log removal was observed for total coliforms (TC), faecal coliforms (FC), faecal streptococci (FS) and Escherichia coli with a mean log removal value (K) of 2.92, 2.20, 1.85 and 1.68, respectively. The decay rate constant (k) for indicator organisms (TC, FC and FS) was observed to be high as 8.04, 6.59 and 5.55 m day−1, respectively. The population of total heterotrophic bacteria, total fungi and actinomycetes reduced remarkably by 3.14, 1.29 and 2.13 log units, respectively. Antibacterial activity of the isolated microorganisms from VF against gram-positive Staphylococcus aureus (ATCC 29213) and gram-negative E. coli (ATCC 25922) was observed which indicated the existence of a mechanism that may be responsible for pathogen removal during wastewater treatment. This demonstrated the production of antibacterial substance, from the microorganisms associated with earthworms, that causes inhibition of other microbes, specifying the effect of earthworms for pathogen removal. Overall, the present study contributes to the understanding of mechanism for pathogen removal during vermifiltration through antibacterial action of microflora.