49 Questions
Which type of wastewater is discharged from residences and commercial facilities?
Domestic (sanitary) wastewater
What type of water enters the sewer system through leaking joints, cracks, or porous walls?
Infiltration/Inflow
What is defined as the presence in water of impurities in such quantity and of such nature as to impair the use of the water for a stated purpose?
Water pollution
What is runoff resulting from rainfall and snowmelt?
Storm water
What is the optimal range of Dissolved Oxygen (DO) concentration in aerobic processes?
1.5-2.5 mg/L
What can over-aeration, indicated by DO levels of 5-6, lead to in wastewater treatment?
Undesirable microorganisms and filamentous bulking
What is filamentous bulking in wastewater treatment?
When the biomass in the secondary clarifier is difficult to settle
What are some operational solutions for filamentous bulking in wastewater treatment?
Adjusting F/M ratio, DO levels, dosing with H2O2, and pre-treating wastewater
What are the aeration techniques used in wastewater treatment?
Air diffusers (fine and coarse bubble) and mechanical aerators
What are ponds and lagoons used for in wastewater treatment?
Natural purification processes, with aerobic and anaerobic variations
What do attached growth systems like trickling filters utilize for wastewater treatment?
Various organisms
What do trickling filters use as a medium for wastewater treatment?
Packed solid medium
What type of media do biotowers use for wastewater treatment?
Modular synthetic media
What is critical for the success of an activated sludge system in wastewater treatment?
The performance of the final clarifier
What plays a critical role in the treatment of wastewater?
Aeration, nutrient levels, and wastewater characteristics
Which type of biological growth/culture is used in wastewater treatment where microorganisms are suspended in the wastewater either as single cells or as clusters of cells called flocs?
Suspended cultures
What is the main factor affecting the rate of biomass production and food utilization in biological wastewater treatment?
Temperature
Which process is a suspended-culture process with sludge returns and may be completely mixed or a plug-flow process?
Activated sludge process
What does extended aeration result in, in terms of treatment efficiency and biomass production?
High degree of treatment with little biomass produced
What is the purpose of the activated sludge process in wastewater treatment?
Biological treatment of wastewater
What are the two types of biological growth/culture used in wastewater treatment?
Suspended cultures/growth and attached growth
Which factor is not considered to affect the rate of biomass production and food utilization in biological wastewater treatment?
Pressure
What is the main requirement for microorganisms to maintain growth in biological wastewater treatment?
Air
What is carefully controlled in engineered reactors in biological wastewater treatment?
Microorganisms
Which process involves a high degree of treatment with little biomass produced?
Extended aeration
What are the design and operational parameters in the activated sludge process?
F/M ratio, MLSS, MCRT/SRT, and HRT
Which type of process is the activated sludge process?
Suspended-culture process
What are the contaminants of concern in wastewater treatment?
Suspended solids, biodegradable organics, pathogens, nutrients, priority pollutants, refractory organics, heavy metals, and dissolved inorganics
What is the primary objective of preliminary wastewater treatment?
Removal of large solids to prevent damage to the remainder of the unit operations
What is the main focus of secondary wastewater treatment?
Removal of biodegradable organics and suspended solids
What is the purpose of tertiary wastewater treatment?
Polishing of secondary effluent, primarily the removal of nutrients, toxic compounds, increased amounts of organic material, suspended solids, ions, and salts
What does solids treatment and disposal involve in wastewater treatment?
The collection, stabilization, and subsequent disposal of the solids removed by other processes
What are the three classifications of wastewater treatment methods?
Physical unit operations, chemical unit processes, and biological unit processes
What is the primary purpose of chemical unit processes in wastewater treatment?
Removal or conversion of contaminants brought about by the addition of chemicals or other chemical reactions
What does biological treatment primarily aim to remove in wastewater?
Biodegradable organic substances and nutrients
What is the main focus of primary wastewater treatment?
Removal of a portion of suspended solids and organic matter by settling or sedimentation
What does secondary wastewater treatment primarily involve?
Biological treatment by activated sludge, fixed-film reactors, lagoons, and pond systems
What is the primary purpose of grit removal in wastewater treatment?
To remove organic suspended solids from wastewater
What can inefficient screening in wastewater treatment lead to?
H2S production
What is the purpose of flow measurement in wastewater treatment?
To quantify the wastewater flow
What does primary treatment in wastewater treatment involve?
Separation of heavier suspended particles from water
What is the main purpose of comminution in wastewater treatment?
To shred intercepted coarse solids and return them to the wastewater flow
What is the primary purpose of bar screens in wastewater treatment?
To filter out particles from wastewater
What is the primary purpose of disposal of screenings in wastewater treatment?
Grinding for organic wastes
What is the main objective of secondary treatment in wastewater treatment?
Biological conversion of dissolved and colloidal organics into biomass
What is the primary purpose of sedimentation in primary treatment of wastewater?
To separate heavier suspended particles from water
What are the primary factors affecting sedimentation tank efficiency in wastewater treatment?
Cleanliness
What is the main purpose of aerated grit chambers in wastewater treatment?
To minimize digester cleaning frequency
What is the primary purpose of Parshall flumes and Palmer-Bowlus flumes in wastewater treatment?
To quantify the wastewater flow
Study Notes
Wastewater Treatment and Sewer Systems
- There are three types of sewer systems: sanitary sewer system, storm sewer system, and combined water system.
- Contaminants of concern in wastewater treatment include suspended solids, biodegradable organics, pathogens, nutrients, priority pollutants, refractory organics, heavy metals, and dissolved inorganics.
- The treatment objectives in wastewater treatment are the removal of suspended and floatable material, treatment of biodegradable organics, elimination of pathogenic organisms, removal of toxic compounds, and removal of nutrients.
- Wastewater treatment systems are divided into preliminary treatment, primary treatment, secondary treatment, tertiary treatment, and solids treatment and disposal.
- Preliminary wastewater treatment involves the removal of large solids to prevent damage to the remainder of the unit operations.
- Primary wastewater treatment involves the removal of a portion of suspended solids and organic matter by settling or sedimentation, removing about 60% of the solids and about 30% of BOD.
- Secondary wastewater treatment is directed principally for the removal of biodegradable organics and suspended solids, and includes biological treatment by activated sludge, fixed-film reactors, lagoons, and pond systems.
- Tertiary wastewater treatment involves polishing of secondary effluent, primarily the removal of nutrients, toxic compounds, increased amounts of organic material, suspended solids, ions, and salts.
- Solids treatment and disposal involves the collection, stabilization, and subsequent disposal of the solids removed by other processes.
- Wastewater treatment methods are classified into physical unit operations, chemical unit processes, and biological unit processes.
- The physical unit operations include screening, mixing, flocculation, sedimentation, flotation, filtration, and gas transfer.
- The chemical unit processes involve treatment methods in which the removal or conversion of contaminants is brought about by the addition of chemicals or by other chemical reactions, such as precipitation, adsorption, and disinfection. Biological treatment is used primarily to remove the biodegradable organic substances and nutrients in wastewater.
Wastewater Treatment Processes Overview
- Fine screens are used to filter out particles from wastewater and should be cleaned mechanically on a continuous basis.
- Bar screens and manual cleaning methods are employed for fine screen maintenance.
- Disposal of screenings involves various methods such as hauling to disposal areas, burial, incineration, and grinding for organic wastes.
- Inefficient screening can lead to septic shock loading and H2S production, with fermentation starting in 2 hours.
- Comminution involves shredding intercepted coarse solids and returning them to the wastewater flow.
- Grit removal is essential to separate non-biodegradable grit from organic suspended solids in wastewater.
- Grit removal facilities include channel-type horizontal-flow grit chambers, aerated grit chambers, and vortex-type grit chambers.
- Grit chambers serve to protect mechanical equipment from abrasion, reduce pipeline deposits, and minimize digester cleaning frequency.
- Flow measurement in wastewater treatment commonly utilizes Parshall flumes and Palmer-Bowlus flumes.
- Primary treatment involves sedimentation to separate heavier suspended particles from water, producing clarified effluent and concentrated sludge.
- Factors affecting sedimentation tank efficiency include types of solids, age of wastewater, rate of solids flow, cleanliness, and mechanical condition.
- Secondary treatment typically involves the biological conversion of dissolved and colloidal organics into biomass, which can then be removed by sedimentation.
Test your knowledge of wastewater treatment and sewer systems with this comprehensive quiz. Learn about the different types of sewer systems, contaminants of concern, treatment objectives, and the various stages of wastewater treatment. Explore the methods and processes involved in wastewater treatment, including physical unit operations, chemical unit processes, and biological unit processes. Gain insights into the importance of screening, grit removal, flow measurement, and the efficiency factors affecting sedimentation tanks.
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