77 Questions
Which type of waste treatment process requires mechanical aeration?
Aerated lagoons
What is a key advantage of anaerobic waste treatment over aerobic treatment?
Production of biogas
In anaerobic waste treatment, what gases are typically produced?
Carbon dioxide and methane
What distinguishes the oxidation ditch from traditional extended aeration processes?
Presence of surface rotors
What defines stabilization ponds in terms of treatment duration?
Long detention periods
Which process leads to lower production of excess sludge per unit mass of substrate utilized?
Anaerobic treatment
What are the primary considerations for groundwater recharge methods?
Rapid infiltration, intermittent percolation, and effluent application
Which crops are typically irrigated using wastewater effluent?
Field crops like cotton and sugar beets
What is a major disadvantage of direct injection in groundwater recharge?
High costs associated with treating effluent
Why is irrigation primarily practiced in arid areas?
As a substitute for scarce rainfall or natural waters
What is a key benefit of using the mentioned groundwater recharge methods?
Recovery of residues for disposal of brines
What is the main concern with highly nitrified effluents being discharged into bodies of water?
Acceleration of algal blooms
How is denitrification primarily achieved in the context of nitrogen removal?
Dissimilatory denitrification
What is the main role of nitrifying bacteria in the denitrification process?
Conversion of ammonia to nitrate
In which form does nitrogen escape after denitrification?
As an inert gas
Why is a carbon source essential for denitrification to take place?
To reduce the oxygen demand
What is the significance of the F/M ratio in determining denitrification efficiency?
It influences the oxygen uptake rate
Why should the use of artificial carbon sources like methanol be avoided in denitrification processes?
They contribute to unnecessary BOD in effluent
Which bacteria group derives its energy through the oxidation of ammonium to nitrite?
Nitrosomonas
What is the stoichiometric oxygen requirement for nitrifying 1 kg of nitrogen?
4.6 kg
What is the primary end product of dissimilatory denitrification under anoxic conditions?
Molecular nitrogen (N2)
Why must nitrified effluents be controlled when discharged into still bodies of water like lakes or reservoirs?
To avoid acceleration of algal blooms
In nitrification, which genus is responsible for the oxidation of ammonium to nitrite?
Nitrosomonas
What is the principal advantage of the separate system for biological oxidation and nitrification?
Better performance with toxic substances in inflow
What is released back into the atmosphere during denitrification?
Molecular nitrogen (N2)
What happens under steady-state conditions in terms of nitrite accumulation during nitrification?
Insufficient nitrite accumulation
What process requires prior nitrification of all ammonia and organic nitrogen in the incoming waste?
Biological denitrification
Which system generally produces a smaller volume of surplus sludge due to higher values of certain parameters adopted?
Combined system
How much gas is theoretically produced per kg of COD removed?
0.38 m3
What is the average Sludge blanket concentration in terms of VSS per m3?
30-50 kg
What is the range of BOD removal efficiency for sewage?
80-85%
What is the objective of residual management in biological waste treatment processes?
Stabilize sludge solids
In the Bardenpho arrangement, what advantage does the first anoxic tank have?
Higher denitrification rate
What is the primary acid produced during acid fermentation?
Propionic acid
How is removal of phosphorus typically achieved in waste treatment plants?
Adding chemicals like calcium hydroxide
Which group of bacteria is responsible for methane fermentation of acetic acid?
Strictly anaerobic bacteria
What is the rate-limiting step in anaerobic wastewater treatment according to the text?
Methane fermentation
What is the purpose of reaerating the flow from an anoxic tank for 10-15 minutes?
Add oxygen and remove nitrogen gas bubbles
Which method is NOT used for sludge dewatering?
Composting
In UASB type units, what acts as the 'media' and stays in suspension?
'Granules' or particles of sludge
What is the molar ratio of iron to phosphorus reported to achieve 91-96% removal of total phosphorus using ferrous chloride?
1:1.4
Which of the following is a likely problem with upflow anaerobic filters packed with media for submerged biological growths?
Accumulation of solids in the interstices
In which type of waste treatment process does surplus sludge settle out in the unit itself and is removed only after several years?
Facultative type aerated lagoons
What is the typical hydraulic retention time (HRT) in a UASB unit at average flow?
8-10 hours
What temperature range is mentioned as necessary for anaerobic systems to function satisfactorily according to the text?
Above 18-20°C
What is the primary difference between using alum and lime for phosphorus precipitation?
Increase in surplus sludge volume with alum
'Fluidized bed units' are filled with what material for recirculation under pressure?
'Sand'
'Methane fermentation' is generally referred to as which stage according to the text?
'Second stage'
'UASB' stands for what in the context of anaerobic wastewater treatment?
'Upflow Anaerobic Sludge Blanket'
What is the main purpose of sludge digestion?
To break down organic wastes in the absence of oxygen
What is the primary difference between acid fermentation and methane fermentation in sludge digestion?
The types of gases produced
Why is the thermophilic range in sludge digestion not commonly practiced?
Due to odor and operational difficulties
What is the role of standard rate digestion in wastewater treatment?
To have unheated and unmixed digester contents
Why is methane formation considered the rate-limiting step in anaerobic wastewater treatment?
Because methane formation ceases at low pH levels
What factors influence the digestion period in high rate anaerobic digestion?
The temperature and mixing of the digester contents
What is the primary characteristic of sludge digestion in anaerobic digesters?
Heating and completely mixing digester contents
What are the end products of acid fermentation in sludge digestion?
Simple organic compounds
Why is thermophilic range not commonly practiced in sludge digestion?
Due to odor and operational difficulties
What is the equation to determine the capacity of a digester based on the given text?
V = [Vf-2/3 (Vf - Vd)]t1 + Vdt2
What are the components of sludge gas composition mentioned in the text?
Methane, Carbondioxide, Nitrogen, Other inert gases
What is the calorific value range of sludge gas mentioned in the text?
5400 to 5850 kcal/m3
What is the primary focus of plant layout optimization according to the text?
Minimize lengths of interconnecting pipes
Which factor can facilitate gravity flow in a treatment plant layout according to the text?
A site on a side-hill
What is essential when preparing hydraulic profiles through a treatment plant?
Preparation for all main paths of flow through the plant
Which is NOT listed as a head loss through the treatment unit in the text?
Head loss due to exit gate
What determines if pumping is required through a treatment plant as per the text?
If total available head is less than head loss through the plant
'Natural Evaporation' method for effluent disposal involves what according to the text?
Large impoundments with no discharge
In a treatment plant layout, what does siting refer to based on the given context?
Selection of site based on topographic features
What is the yield coefficient assumed for the new VSS produced as a result of BOD removal?
0.1 g VSS/g BOD removed
What percentage of VSS is assumed to be degraded in the inflow, leaving a residue?
60%
To achieve the desired SRT value, what parameter needs to be solved for from the SRT equation?
HRT
What is the depth range of the reactor for treating low BOD municipal sewage?
4.5-5.0 m
What is the recommended upflow velocity at peak flow to retain flocculent sludge in the reactor?
1.0 m/h
What is the typical surface overflow rate for the settler compartment at peak flow?
$20-28 , m^3/m^2/d$
What does GLSS stand for?
'Gas-Liquid-Solid-Separator'
Why is the upflow velocity limited in UASB reactors?
To prevent carry over of solids and maintain effluent quality
'Inlet feed gravity feed from top' is preferred for which type of sewage?
'Low BOD municipal sewage'
Learn about various types of aerobic treatment units such as stabilization ponds, aerated lagoons, and oxidation ditches used for treating sewage and industrial wastes. Understand the principles and mechanisms behind these treatment systems.
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