Performance assessment of a Canna indica assisted vermifilter for synthetic dairy wastewater treatment

Two lab-scale vertical flow vermifilter were designed, one aided with Canna indica (MAVF) and the other without it (VF), but Eisenia fetida was inserted in both the systems. The experimental phase continued for ten weeks with a hydraulic loading rate of 0.65 m3 m−2 day−1. Results indicated that MAVF possess maximum organic and nitrogen degradation capacity during the treatment process and it was working steadily without sign of clogging, but vermifilter without macrophyte (VF) was clogged within the first few weeks of its operation. Removal efficiencies of BOD were 80.6% for MAVF and 71% for VF, while for COD it was 75.8% and 66.1%, respectively. TSS removal for MAVF and VF was found to be 84.8% and 73.8%, respectively, but TDS removal was insignificant in both the filters. Interlayer analysis presented that maximum organics and solids removed in the 1st layer or worm active zone. MAVF removed 42.6% TN, and effluent NH4+-N concentration in MAVF and VF were as low as 8.4 mg/L and 13.2 mg/L, respectively. However, TP concentration in effluent increased gradually may be due to the actions of phosphorus solubilizing microorganisms (PSM) and phosphatase enzymes secreted by earthworm. Growth characteristics of C. indica and E. fetida were also observed during the experimental period. Different physical and biochemical changes in soil due to plant and earthworm activity were analysed through FTIR, SEM and humic component analysis. The performance of MAVF was found to be superior to VF with high longevity.