Minimizing discrepancies in oxygen demand-based biodegradability (ODB) results using Taguchi method

Abstract

Oxygen demand-based biodegradability (ODB) suffers from a “discrepancy in the results” problem. Therefore, the objectives of this paper were to (1) determine the impacts of standards pH, initial substrate concentration, initial seed volume, and temperature on the accuracy of the ODB results; (2) identify the effect of increasing the test temperature to the mesophilic range; and (3) optimize the ODB conditions. The results showed, under standard environmental conditions, five-day, 20°C, and pH of 6.5 up to 8.5, the average ODB was 46 with 21% standard deviation. To minimize the discrepancy, the environmental conditions should be monitored to shift biochemical reaction toward mineralization reactions, rather than biomass production. Increasing temperature to 28.5°C improved average ODB to 81% with 10% standard deviation. Optimal conditions of the four factors together for ODB test were achieved at 400 mg L⁻¹ concentration, 37°C temperature, 7.5 pH, and an initial seed of 30% of total sample volume. These conditions resulted in an average ODB of 82% with 1% standard deviation.

Keywords:

• Biodegradability
• Biochemical oxygen demand
• Environmental conditions
• Taguchi method
• Principle component analysis