Blackwater processing via vermifiltration: Worm-based toilet (wormlet) in the arid context of Burkina Faso

Abstract

In Burkina Faso, faecal sludge is mostly discharged into the environment untreated, with associated public health risks. Thus, sanitation technology that efficiently treats Blackwater (BW) in-situ is urgently required. This paper reports the design and testing of a proposed worm-based toilet (wormlet). The presence of E.eugeniae (EE) is found to reduce the total accumulated BW by a maximum of 61.74%. Over five to ten weeks, 1 kg of BW (dry portion) can be processed to 0.49–0.61 kg of vermicast by the EE. The wormlet effluent is of superior quality, as the log 10 removal efficiency of the bedding and filter matrix reached 7.45 and 5.85 for E. coli and faecal coliform, respectively. Helminth egg removal was found to be 97% within the 75-cm depth. Average organics and nutrient removal efficiencies are 99–100% for total solids and total suspended solids; 99% and 98% for the biochemical and chemical oxygen demand, respectively. Removal efficiencies between 97 and 99% were found for NH4⁺, NO3⁻, NO2⁻, and PO4³⁻. A 100% turbidity removal was found in the systems containing charcoal. Thus, the wormlet appears to be superior for in-situ BW treatment, generating sub-products that can be reused or safely discarded.