Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
Which of the following statements about the secondary treatment of sewage is INCORRECT?
Secondary treatment methods are broadly divided into filtration and activated sludge process.
Oxidation of organic matter occurs in trickling filters under aerobic conditions.
Activated sludge is biologically active.
Primary treatment of sewage is not essential for efficient working of contact beds.
Primary treatment of sewage is not essential for efficient working of contact beds.
Primary treatment, which includes sedimentation and screening, is essential for the efficient operation of contact beds (a form of intermittent sand filter). Without primary treatment, the high concentration of suspended solids would rapidly clog the contact bed media, leading to premature failure.
CPHEEO Manual on Sewerage and Sewage Treatment Systems
Primary treatment, which includes sedimentation and screening, is essential for the efficient operation of contact beds (a form of intermittent sand filter). Without primary treatment, the high concentration of suspended solids would rapidly clog the contact bed media, leading to premature failure.
╬╖=BODinтАЛBODinтАЛтИТBODoutтАЛтАЛ├Ч100% тАФ Efficiency of biological treatment
HRT=QVтАЛ тАФ Hydraulic Retention Time, where V is volume and Q is flow rate
Contact beds operate on an intermittent fill-and-draw principle where sewage is stored in a tank filled with coarse media. Microorganisms form a biological film on the media surface. Primary treatment removes heavy solids to prevent the interstices of this media from clogging and to reduce the organic load (BOD) to levels treatable by the established biofilm.
Primary treatment is a mandatory prerequisite for most secondary treatment processes to prevent clogging and excessive sludge production.
Trickling filters and activated sludge are standard secondary aerobic processes.
Biological treatment relies on the metabolic activity of bacteria, protozoa, and fungi.
Activated sludge contains a diverse community of microorganisms known as the 'biomass' or 'sludge'.
Reduces potential for clogging in subsequent treatment units
Protects mechanical equipment from abrasive solids
High capital cost for primary settling tanks
Requires proper sludge management and disposal protocols
Municipal wastewater treatment plants
Industrial effluent treatment facilities
Option A is generally considered correct in the context of classification, as secondary treatment is divided into suspended growth (Activated Sludge Process) and attached growth (Trickling Filters/Contact Beds).
Option B is correct because trickling filters rely on an aerobic biofilm to oxidize organic pollutants.
Option C is correct because activated sludge consists of active aerobic microorganisms.
Option D is the incorrect statement because primary treatment is mandatory to remove settleable solids that would otherwise choke contact beds.
D is correct тАФ Primary treatment of sewage is essential for the efficient working of contact beds to prevent clogging of the media.
Always remember the treatment train sequence: Preliminary тЖТ Primary тЖТ Secondary тЖТ Tertiary. Skimping on primary treatment almost always leads to functional failures in biological units.
Get instant step-by-step AI explanations, full shift Previous Year Papers (SSC GD, RRB, SSC JE), and regional rank analysis on the official Examoogle App.
Free Download тАв 100K+ Aspirants