Texas Wastewater Class B Practice Exam

What types of secondary treatment are commonly used in wastewater treatment today?

1. Stabilization ponds, trickling filters, rotating biological contractors, and activated sludge

2. Sedimentation tanks and composting

3. Membrane filtration and reverse osmosis

4. Chemical precipitation and evaporative cooling

The correct answer is: Stabilization ponds, trickling filters, rotating biological contractors, and activated sludge

Secondary treatment in wastewater treatment focuses on the removal of dissolved and suspended organic matter. The types of secondary treatment commonly employed today are designed to promote the growth of microorganisms that can metabolize these substances. The correct answer includes stabilization ponds, trickling filters, rotating biological contactors, and activated sludge, all of which are established methods in secondary treatment processes. Stabilization ponds utilize natural processes involving algae and bacteria to treat wastewater over time, while trickling filters provide a surface for microbial growth to break down organic material as wastewater circulates over them. Rotating biological contactors allow for biofilm formation and effective treatment as they rotate through the wastewater, and activated sludge is a widely used method involving aeration and the use of microorganisms to digest organic matter. Other methods mentioned in the incorrect choices, such as sedimentation tanks and composting, are typically part of primary treatment or further waste processing rather than secondary treatment. Membrane filtration and reverse osmosis are advanced and often used for tertiary treatment to remove additional impurities after secondary treatment. Meanwhile, chemical precipitation and evaporative cooling do not align with the biological processes essential in secondary treatment methods, which primarily aim at biodegradation of organic compounds.