Assessment on overall efficiency of urban greywater treatment by vermifiltration in hot climate: enhanced pollutants removal

ABSTRACT

Vermifiltration technology using Eudrilus Eugeniae could be an alternative low-cost option for the treatment of urban greywater, which is highly polluted with high concentrations of surfactants, sodium and cooking oil. In this study, the effects of these pollutants on performance of a vermifiltration system was tested over a period of 6 to 8 weeks by enriching raw greywater with various concentrations of anionic surfactants (0, 15, 45 and 135 mg/L), sodium (0, 1, 2 and 4 g/L) and refined palm cooking oil (0, 250 and 500 mg/L). The vermifilter system was made of gravel, sand and sawdust layers from the bottom to the top, on which 200 earthworms were added. The greywater used in this study was previously used for dishwashing and laundry by an urban poor household. The greywater quality was compared with the effluent to evaluate the system performance. BOD₅, COD, TSS and E. coli removal efficiencies ranged from 93% to 98%, 68% to 93%, 88% to 96% and 1.4-3 ULog, respectively, which are within the range of efficiencies reported in the literature. High proportion of surfactants (95–99%) and oil (84–89%) were removed but sodium was not removed. Instead, an increase in sodium concentrations was observed in the filter over the experimental period. Statistical analysis shows that BOD₅, COD, TSS and E. coli removal efficiencies were independent of surfactants, cooking oil and sodium concentrations (p < .05). Thus, short term or accidental exposure of the vermifilter to high concentrations of these three pollutants did not have significant effect on the system performance.

GRAPHICAL ABSTRACT

KEYWORDS:

• Sub-Saharan Africa
• wastewater
• pollutants
• low-cost technology
• vermifilter

Acknowledgements

The authors would like to thank C. Csuzdi of the Hungarian National History Museum, Budapest for earthworm identification, P. Kabore of 2iE for technical assistance, and finally K. Schlef of the University of Massachusetts Amherst for helpful comments that greatly improved the language of the manuscript. We thank anonymous reviewers for their valuable comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by the Bill and Melinda Gates Foundation under the framework of SaniUp project ‘Stimimulating Local Innovation on Sanitation for the Urban Poor in Sub-Saharan Africa and South-East Asia’, [grant number 0PP1029019].