Monod Kinetics for EM4-Driven Ammonia Biodegradation Under Molasses Variation and Microbial Acclimatization
Abstract
Ammonia is a toxic pollutant parameter in petrochemical wastewater and can impair the quality of aquatic environments. This experimental study evaluated the kinetics of ammonia biodegradation by an Effective Microorganisms-4 (EM4) consortium using the Monod model approach, focusing on molasses concentration as an external carbon source and the effect of microbial acclimatization. This experiment was conducted in aerobic batch systems with initial ammonia concentrations of 10, 30, and 50 ppm and the addition of 5% and 10% molasses. Mixed Liquor Suspended Solids (MLSS) and pH were monitored to evaluate environmental dynamics and biomass growth. The results showed that increasing the molasses concentration from 5% to 10% increased the maximum specific growth rate (μmax) from 6.29 to 7.17 day−1 and decreased the half-saturation constant (Ks) from 23.22 to 14.01 mg/L; therefore, a lower Ks indicates higher apparent substrate affinity. The acclimatization further improved the kinetic response, yielding higher μmax and lower Ks than the non-acclimated system, alongside higher MLSS and a faster pH decrease consistent with more intensive biodegradation activity. Overall, these results confirm that the combination of microbial acclimatization and sufficient molasses addition can enhance the kinetic performance of ammonia biodegradation by EM4.