Rock Filters for Removal of Algae from Lagoon Effluents

摘要

The objective of this project was to show that rock filtration was an effective, low cost unit process for removing algae from lagoon effluents and correspondingly upgrading lagoon treatment. Sedimentation is the primary mechanism of algal removal within rock filter. The settling rates of three species of algae common to lagoons were measured as varying from 0.02 to 0.3 m/day, depending on species and temperature. Settling rates of algae from the Veneta, Oregon lagoon were about 0.05 m/day. A mathematical model of the sedimentation mechanism was constructed based on discrete settling theory. A full-scale horizontal flow operating rock filter designed for a maximum hydraulic loading of 0.28 cu m/cu m (1.6 days detention time) located at Veneta, Oregon was evaluated. Weekly average BOD5 and TSS did not exceed 20 mg/l. With improved flow characteristics a pilot scale rock filter achieved similar results for a short period of testing at twice the hydraulic flow.