Inhibitory Effects of Organics in Domestic, Dairy, and Brewery Wastewater on the Survival, Growth, and Reproduction of Earthworms

Abstract

With the increase in the chemical oxygen demand (COD) of the influent and the organic/hydraulic loading rate (OLR/HLR), the treatment efficiency of the vermifiltration (VF) process decreases. Also, the treatment performance of the VF process varies with the type of wastewater, even if all the other operating conditions remain the same. To date, the inhibitory effects of wastewater, e.g., its composition, concentration, and OLR/HLR, on earthworms (EWs) and VF's treatment efficacy have been completely overlooked. Herein, such inhibitory effects on the survival, growth, and reproduction of the EWs have been investigated using real brewery, dairy, domestic, and diluted brewery wastewater. The acute and chronic tests were performed in vertical subsurface flow reactors in accordance with the guidelines with some modifications. Results showed that 50% mortality of EWs occurred within 11-21, 16-33, 21-41, and 24-48 days for brewery, diluted brewery, dairy, and domestic wastewater, respectively, at the HLR of 8-4 m3 m-2day-1. For each wastewater, the maximum growth of EWs was observed at the lowest tested HLR (4 m3 m-2day-1). Domestic sewage ensured the highest number of juvenile (20-38 nos. EW-1) and cocoon production (10-15 nos. EW-1), followed by dairy (juveniles: 7-21; cocoons: 5-10), diluted brewery (juveniles: 4-15; cocoons: 2-9), and brewery wastewater (juveniles: 2-12; cocoons: 2-7), with the HLR and OLR having a negative impact on the same. Therefore, brewery wastewater had the highest biological inhibition on survival and biological activities of the EWs, whereas domestic sewage had the least. The dilution given to brewery wastewater reduced the extent of the inhibitory effects imposed on the survival, growth, and reproduction of EWs. Results of this study indicated that the VF technology is more suitable for treating domestic sewage, can treat dairy wastewater substantially, and can treat brewery wastewater, but appropriate pretreatment (such as bioaugmentation or dilution) may be necessary. � 2023 American Society of Civil Engineers.