Facultative and Aerated Lagoons in Design of Water | CE 431, Study notes of Civil Engineering

Download Facultative and Aerated Lagoons in Design of Water | CE 431 and more Study notes Civil Engineering in PDF only on Docsity! Facultative and Aerated Lagoons CE 431 Facultative Lagoons • Large, earthen basins wherein wastewater is treated through natural processes • Old technology • Simple technology - to operate, that is • Highly complex microbial environment • Target removal of organic carbon, settle-able material, and some ammonia o Through the use of CO2 by algae, large pH swings occur through the diurnal period, which serves as a natural disinfection method. • Three zones within a facultative lagoon, defined by the metabolic capabilities of the microorganisms that thrive therein: D:\My Documents\ERC Academics\CE 431\Lecture Notes\Lecture Notes - Lagoons.doc 1 • Sources of oxygen: • Oxygen sinks: • NPDES permits typically 30 mg/L BOD5 and 50 mg/L TSS, on a monthly average o Why is the TSS so high, relative to a typical activated sludge WWTP (30 mg/L)? • Design: o Typically minimum of 2 ponds: • Pond #1 = 50-75 lb BOD5/acre/day (Oregon DEQ = 50) • Pond #2 = 25-35 lb BOD5/acre/day (Oregon DEQ = 25) • What influences which design value you choose? • Detention Time, days: o Square or rectangular basins - fit to site o Inlet & outlet on opposite ends o Inlet Outlet oriented opposite prevailing winds o Clay or synthetic liners o Baffled outlet - keep debris/algae from discharge o No recycle o Sideslopes at 1:4 - 1:3 V:H o Dike = 10’-12’ wide - why? o Riprap banks - why? o 2’-4’ freeboard • Operational Problems: o Odor - no/minimal water cap over anaerobic zone o Organic overloading o Burrowing animals o Leaky liner o Short circuiting o Algae D:\My Documents\ERC Academics\CE 431\Lecture Notes\Lecture Notes - Lagoons.doc 2