The Use of an Aerobic Biological Filter for Improving the Effluent Quality of a Two-stage Anaerobic System

In Egypt, there is a growing realization between experts and decision makers that low-cost anaerobic treatment technologies such as the Up-flow septic tank followed by anaerobic baffled reactor is a promising technology. It is characterized by its high organic removal efficiency, simplicity, low capital and maintenance costs. However, anaerobic treatment produces wastewater which is not complying with the standards regulating discharge of treated wastewater into receiving water bodies. Therefore, a post treatment step is required. In an attempt to develop a system which fulfill the requirements and at the same time is simple and cost-effective, a pilot-scale setup was designed and constructed at a wastewater treatment plant in Giza, Egypt. It consists of an up-flow anaerobic reactor; down-flow anaerobic packed-bed baffled reactor; a passive aeration and a biological filter system followed by a sedimentation tank. The biological filter is packed with plastic media. The system was operated at a hydraulic retention time of 24 hours in the anaerobic stages. To monitor the performance of the system, wastewater samples were collected from the influent and effluent of each treatment step along the pilot-scale setup. Available data indicated that the integration of the passive aeration and the biological filter system improved the effluent quality of the two-stage anaerobic system. The treated final effluent has a quality acceptable for disposal in agricultural drains according to Law 48 for the Year 1982. In addition, average overall removal efficiencies up to 85%, 69%, 88%, 91% and 89% were achieved for COD Total, COD Soluble, BOD5, TSS and VSS, respectively.