Anaerobic-aerobic lagoon treatment for vegetable tanning wastes

A field demonstration lagoon was operated at Virginia Oak Tannery, Inc., Luray, Virginia to evaluate the effectiveness of an anaerobic-aerobic lagoon in treating spent vegetable tannins blended with batepool and soak waste waters. The anaerobic-aerobic lagoon system was used to treat combined waste streams with a BOD₅ concentration of approximately 1000 mg/ℓ. Aeration and volume of the lagoon were fixed and flow to the system was varied. The system load varied by increasing the flow so as to observe five operational phases. Operational phases were designed to cause to system to go from aerobic conditions to anaerobic-aerobic. After reaching anaerobic-aerobic conditions, doubling the BOD₅ load did not result in a significant decrease in BOD₅ removal efficiency. Efficiency, measured in terms of soluble BOD₅, at a BOD₅ load of 17.3 lbs/1000 ft³/day (anaerobic-aerobic condition) was 81 percent compared to a 92 percent efficiency for a BOD₅ load of 4.5 lbs/1000 ft³/day (aerobic conditions). The final load on the system under anaerobic-aerobic conditions was 1.73 lbs of BOD₅/1000 ft³/day/B.hp. During this loading condition soluble BOD₅ and soluble COD removal efficiencies of 81 and 58 percent, respectively, were observed.