Oxidation pond also known as shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria and algae. In this research, wastewater treatment model was developed to study the effect of pH towards, COD, DO and PSB. Using the process rate of breakdown of organic and inorganic substance, mass transfer and oxygen and the growth of bacteria as conditions, the advection-diffusion-reaction equations are solved using Crank Nicolson method. Comparisons were with existing data to verify the model and the similarity of dynamical behaviour. Copyright © 2019 American Scientific Publishers All rights reserved