Feeding black soldier fly larvae using wastewater treatment sludge: A zero-waste sustainable solution

Black soldier fly larvae (BSFL) are an excellent protein source that can serve as a sustainable and nutritious diet to support the growth of aquaculture species. They could be an affordable and eco-friendly alternative to traditional fishmeal. BSFL can be cultivated using wastewater sludge derived from various domestic and industrial wastewater sources. This study focused on using egg-washing and poultry-slaughtering wastewater sludges to grow BSFL. The solid portion of the BSFL diet consisted of the Gainesville Diet, where moisture sources were supplied from various wastewater treatment sludge and tap water. The electrocoagulation and flocculation methods were employed to treat wastewater from egg washing and poultry slaughtering. Aluminum (Al) and iron (Fe) electrodes were used in the electrocoagulation method, and pH, electric current, and treatment time of the wastewater samples were optimized. The highest average total solids (32.01 mg/L) and inorganic solids (18.04 mg/L) were found in duck-slaughtering wastewater sludge treated with Fe electrodes. Flocculation resulted in an average of 16 mg/L of volatile solids. Larvae fed on sludge from both treatment methods showed the proportion of larval weight gain averaging 5–8 (500–800% increase in weight), with the highest gain (768% increase in weight) achieved from duck-slaughtering sludge treated using the electrocoagulation method. The proportion of larvae reaching the pupation stage was examined during the 15-day observation period. Diet treatment based on duck slaughtering wastewater sludge using Al electrode showed the lowest proportion of individuals reaching the maturation stage.