Abstract
The research presented in this paper investigates the effect of a significant operational change occurred in a wastewater treatment plant in Madinah city, Saudi Arabia on the effluent water quality. The operational change involved the cancellation of the primary settling tanks of the plant, and as a result, the raw wastewater received at the plant directly entered the aeration tanks. The effect of this change on treated wastewater quality as determined by Biological Oxygen Demand (BOD) and total suspended solids (TSS) concentration was evaluated. These parameters were measured for one month before and one month after the cancelation of the primary settling tanks and the average values were calculated. Results showed that the average removal percentage of BOD and TSS in the last month before the operational change was implemented was 89 and 88%, respectively. The average removal percentage for the same parameters in the first month immediately after implementing the operational changes was 91 and 92% respectively, which shows that there is no significant difference in the removal efficiency for these parameters after the operational change. These results indicate that the treated wastewater quality was not affected by the operational change implemented at the plant. Results of this research provide useful information for the authorities responsible for wastewater treatment as well as for the scientific community.