Baffle and fixed media effects on coliform removal andudbacterial die-off rate coefficient in waste stabilization ponds (a case study in Ahvaz)

摘要

Background: The use of waste stabilization ponds is one of the cheapest wastewater treatment processes.udThis study evaluated the effects of baffles and fixed media on coliform removal in facultative lagoons.udMethods: In this study, the settled wastewater from four pond systems of the city of Ahvaz was usedudas input. Each system was composed of two ponds that were connected to each other serially. Three ofudthem were equipped with two, three, and four baffles. Packages of fixed media were installed in the firstudbaffled pond equal to the number of baffles. During a 12-month sampling period from March 2016udto February 2017, the capability of each system to remove coliform with different detention times wasudstudied.udResults: The control system with no baffle and no media reduced the coliform index by an average ofud67% in a detention time of 6 to 12 days. Increasing the baffles and fixed media in the ponds improvedudthe coliform removal efficiency; systems with two, three, and four baffles achieved coliform removaludin the amounts of 77%, 81%, and 83%, respectively. The coliform die-off coefficients (Kb) were higherudin the attached growth systems than in the control system. The coefficients were determined to beud0.21, 0.26, 0.29, and 0.31 d-1 for the second ponds of the control, two-, three-, and four-baffle systems,udrespectively.udConclusion: This method can be used to upgrade the existing waste stabilization pond and to designudnew ponds with at least two baffles in the facultative lagoons.