Performance evaluation of developed macrophyte-assisted vermifiltration system designed with varied macrophytes and earthworm species for domestic wastewater treatment

Abstract

Development of sustainable technology to treat domestic wastewater with added advantages of cost reduction and improved handling efficiency is crucial in developing countries. This is because, domestic wastewater from households are stored in septic tanks and are poorly treated prior discharge. This study developed a macrophyte-assisted vermifiltration (MAV) system to treat domestic wastewater. The MAV system is an integrated approach of macrophytes and earthworms in a vermifiltration and complex physicochemical mechanism processes. The use of different macrophyte and earthworm species was hypothesized by the study to affect and vary the treatment performance of the developed MAV. The study therefore aimed to evaluate the treatment performance of the developed MAV when three varied macrophyte species (Eichhornia crassopes, Pistia stratiotes and Spirodela sp.) and two varied earthworm species (Eisenia fetida and Eudrilus eugeniae) were used to design the treatment system. Treated effluents were collected every 48hours within two weeks for physico-chemical, pathogen and helminth analysis. The contaminants (Ntot, NH3, NO3-N and Ptot) in the wastewater were high (>50 mgL-1, >5 mgL-1, >1 mgL-1 and >20 mgL-1 respectively). Results revealed that the developed MAV systems were effective in the removal of solids (>60%), nutrients (>60%) and pathogens (>90%). In most cases, there were no significant differences between the selected varied macrophytes and earthworms in the treatment performances. Results therefore demonstrated that the selected macrophytes combined with the earthworm species were suitable when used in the development of the MAV system. Developing the MAV with the selected varied macrophyte and earthworm species did not only contribute to the treatment of the wastewater, but also improved the vermiculture. Eudrilus eugeniae however demonstrated higher biomass gain (5–10% more) compared to Eisenia fetida.