Basic Wastewater Operations- Chapter 7 (Sedimentation) Exam Questions with Verified Answers (Already Passed)

Basic Wastewater Operations- Chapter 7 (Sedimentation) Exam Questions with Verified Answers (Already Passed) T/F: Sedimentation is the process of separating a suspended solid from water by atmospheric pressure. - Answers False; Gravity T/F: Common design features of a sedimentation tank include baffles, a skimmer, a grease ring, and a sludge rake. - Answers True T/F: A primary clarifier settles biological sludge, and a secondary clarifier settles raw sludge. - Answers False; Primary clarifier settles raw sludge and secondary clarifier settles biological sludge. T/F: Factors affecting settling include solid weight, water temperature, detention time, velocity, surface loading, wastewater conditions, and short-cutting. - Answers False; short-circuiting* T/F: The four settling zones in a sedimentation tank are the inlet zone, settling zone, sludge zone, and the outlet zone. - Answers True Short-circuiting is the uneven flow of water through a tank. - Answers True T/F: Primary clarifiers should remove 90-95% if the BOD and 35% of the settleable solids. - Answers False; remove 35% BOD and 90-95% settleable solids T/F: Secondary sludge contains more water than primary sludge. - Answers True Maintenance of clarifiers includes ____________ inspection of the skimmer. A. Yearly B. Monthly C. Weekly D. Daily - Answers D. Daily If the skimmer fails, the sludge ___________ fails. A. Pump B. Sump C. Rake D. Baffle - Answers C. Rake Floating sludge or excessive gas bubbles indicate a failure of the return sludge pump, sludge rake, or poor ___________ schedule. A. Skimming B. Pumping C. Settling D. Digesting - Answers B. Pumping Withdraw sludge slowly or water will break through the sludge layer, ___________ the sludge. A. Diluting B. Thickening C. Wetting D. Stirring - Answers A. Diluting Usual blanket of depth in a secondary clarifier is no more than __________ of the sidewall depth. A. 3/4 B. 1/2 C. 1/3