Kinetics modelling of degradation process of organic pollutants in Ajali River Enugu, Nigeria

Kinetics and modelling of organic pollutants biodegradation in Ajali River was studied. Dissolved oxygen (DO) was determined using Winkler-Azide method, while biochemical oxygen demand (BOD) was determined after five days of incubation. Kinetic study was achieved using Streeter–Phelp method, while statistical models were developed with R Software. Kinetic data was fitted to first and second models, and the best model was assessed with high correlation coefficients, the closeness of predicted ultimate first-stage BOD with the experimental one and least error. Experimental first-stage BOD was estimated at a 22-day incubation period. Linear, quadratic, and exponential models were developed and diagnosed. Its kinetic data fitted well to the first-order model for both seasons with correlation coefficients (R²) of 0.99 and the least error of 0.65 and 0.71, while the biodegradation rates were 0.1490 and 0.1521 days⁻¹ for dry and wet seasons, respectively. The exponential model was the best model for the two seasons (R² = 1) and least residuals. The model revealed the non-linear relationship of those contributing factors with the drop in DO. This will help water management authorities to determine if River Ajali can naturally degrade waste from the three beverage industries before the water reaches downstream.