Waste Degradation Stages Quiz
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Questions and Answers

What distinguishes aerated lagoons from stabilization ponds?

  • Oxygen is provided through mechanical aeration in aerated lagoons. (correct)
  • Stabilization ponds have a higher energy input than aerated lagoons.
  • Aerated lagoons provide shorter detention periods than stabilization ponds.
  • Stabilization ponds use algal photosynthesis for oxygen.

    • What is a characteristic of the oxidation ditch in the treatment of sewage?

  • It provides long detention periods extending over several days.
  • It is a modified form of stabilization ponds.
  • It has two surface rotors placed across the channel. (correct)
  • It uses algal photosynthesis for oxygenation.

    • Why is anaerobic waste treatment preferred over aerobic treatment in some cases?

  • It requires a lower energy input as no oxygenation is needed. (correct)
  • It has higher nutrient requirements due to elevated biological synthesis.
  • It produces more excess sludge per unit mass of substrate utilized.
  • It doesn't lead to the production of biogas, unlike aerobic treatment.

    • What advantage does the production of biogas in anaerobic treatment provide?

    <p>It serves as a valuable source of energy.</p> Signup and view all the answers

    What characteristic is common to both stabilization ponds and aerated lagoons?

    <p>They are both open flow through basins.</p> Signup and view all the answers

    In anaerobic treatment, what does the degradation of organic wastes lead to?

    <p>Production of carbon dioxide and methane.</p> Signup and view all the answers

    What are some considerations that must be given in groundwater recharge methods?

    <p>Net evaporation and possible percolation</p> Signup and view all the answers

    Which crops are typically irrigated by effluent according to the text?

    <p>Cotton and sugar beets</p> Signup and view all the answers

    What is a challenge associated with direct injection in groundwater recharge methods?

    <p>High costs of treating effluent</p> Signup and view all the answers

    Why is irrigation primarily practiced in arid areas according to the text?

    <p>To substitute for scarce natural waters or sparse rainfall</p> Signup and view all the answers

    What makes recovery of residues desirable in certain disposal methods according to the text?

    <p>For disposal of brines</p> Signup and view all the answers

    What is the primary outcome of the first stage of anaerobic wastewater treatment?

    <p>Conversion to simple organic compounds</p> Signup and view all the answers

    Which acids are primarily produced during acid fermentation in anaerobic wastewater treatment?

    <p>Acetic and butyric acid</p> Signup and view all the answers

    What is the rate-limiting step in anaerobic wastewater treatment?

    <p>Methane fermentation</p> Signup and view all the answers

    Why are fixed film anaerobic filters likely to face problems?

    <p>They accumulate solids in the interstices</p> Signup and view all the answers

    In UASB units, what serves as the 'media' to support biological growths?

    <p>Sludge granules</p> Signup and view all the answers

    'Gas collection and conversion or conveyance' is a stage commonly found in which type of anaerobic reactor unit?

    <p>UASB type unit</p> Signup and view all the answers

    'Screening and degritting' is a typical process that occurs in which stage of a UASB treatment plant for municipal sewage?

    <p>Main UASB reactor</p> Signup and view all the answers

    'No mixers or aerators are required' is a notable feature of which type of anaerobic reactor units?

    <p>'UASB type units'</p> Signup and view all the answers

    'Excess sludge is removed from time to time through a separate pipe and sent to a simple sand bed for drying' - which aspect of anaerobic wastewater treatment does this statement refer to?

    <p>'Design Approach'</p> Signup and view all the answers

    'At equilibrium condition, sludge withdrawn has to be equal to sludge produced daily' - this statement is related to which specific element of UASB design?

    <p>'Size of Reactor'</p> Signup and view all the answers

    What is the primary factor that determines the amount of sludge produced daily?

    <p>Amount of VSS in the raw wastewater</p> Signup and view all the answers

    What is a parameter used to control sludge retention time in a UASB reactor?

    <p>Hydraulic Retention Time (HRT)</p> Signup and view all the answers

    What might happen if the upflow velocity in the UASB reactor exceeds recommended values?

    <p>Deterioration in effluent quality</p> Signup and view all the answers

    How is the settling compartment in a UASB reactor typically formed?

    <p>Sloping hoods for gas collection</p> Signup and view all the answers

    What is the primary function of the Gas-Liquid-Solid Separator (GLSS) in a UASB reactor?

    <p>Separating gas, liquid, and solid components</p> Signup and view all the answers

    What is the impact of increasing the depth of both the sludge blanket and the reactor for high BOD wastes?

    <p>Keeps organic loading on solids within prescribed range</p> Signup and view all the answers

    Why should the upflow velocity in a UASB reactor not exceed certain limits?

    <p>To prevent carry over of solids and maintain effluent quality</p> Signup and view all the answers

    Which group of bacteria obtains energy through the oxidation of nitrite to nitrate?

    <p>Nitrobacter</p> Signup and view all the answers

    What is the stoichiometric oxygen requirement for nitrifying 1 kg of nitrogen?

    <p>$4.6$ kg</p> Signup and view all the answers

    What is the organic loading on the sludge blanket for agro-industrial wastes?

    <p>$0.3-1.0$ kg COD/kg VSS day</p> Signup and view all the answers

    What is the BOD/COD removal efficiency for sewage?

    <p>75-85%</p> Signup and view all the answers

    What determines the rate-limiting step for the conversion of ammonium to nitrate in nitrification?

    <p>Nitrosomonas</p> Signup and view all the answers

    In which system is the first tank smaller in size due to a higher F/M ratio?

    <p>Separate system</p> Signup and view all the answers

    What is the range of nitrogen removal using the nitrification-denitrification method?

    <p>$70-90$%</p> Signup and view all the answers

    How many groups of chemoautotrophic bacteria are associated with nitrification?

    <p>$2$ groups</p> Signup and view all the answers

    What is the average upflow velocity during peak flow conditions?

    <p>$1.2$ m/h</p> Signup and view all the answers

    What is the primary means by which nitrogen removal is achieved in the biological nitrification/denitrification process?

    <p>Dissimilatory denitrification</p> Signup and view all the answers

    What is the first step in the biological nitrification/denitrification process?

    <p>Nitrification</p> Signup and view all the answers

    What is the importance of a carbon source in denitrification?

    <p>To reduce oxygen input needed into the system</p> Signup and view all the answers

    Which process involves nitrate conversion to various gaseous end products, mainly molecular nitrogen?

    <p>Dissimilatory denitrification</p> Signup and view all the answers

    Why should the use of methanol or any other artificial carbon source be avoided in denitrification?

    <p>To avoid introducing unnecessary BOD in the effluent</p> Signup and view all the answers

    What is the effect of using a raw waste bypass in the biological nitrification/denitrification process?

    <p>Reduces sizes of tanks</p> Signup and view all the answers

    Which step involves the reduction of nitrate to ammonia to serve as a nitrogen source for cell synthesis?

    <p>Assimilatory denitrification</p> Signup and view all the answers

    What is released as an inert gas to the atmosphere during denitrification?

    <p>Molecular nitrogen</p> Signup and view all the answers

    What is the purpose of break point chlorination in wastewater treatment?

    <p>To control nitrogen content in effluent</p> Signup and view all the answers

    Which process involves a carbon source as an essential electron donor?

    <p>Biological nitrification/denitrification</p> Signup and view all the answers

    What is the formula to determine the capacity of a digester?

    <p>V = Vf - 2/3 (Vf - Vd)t1 + Vdt2</p> Signup and view all the answers

    What percentage of sludge gas is composed of methane?

    <p>65%</p> Signup and view all the answers

    What is the calorific value range of sludge gas per cubic meter?

    <p>5400 to 5850 kcal/m3</p> Signup and view all the answers

    What does plant layout in a treatment plant focus on optimizing?

    <p>Land requirement and pipe lengths</p> Signup and view all the answers

    What is an important principle to consider in siting a treatment plant?

    <p>Site on a side-hill to facilitate gravity flow</p> Signup and view all the answers

    What is the purpose of preparing hydraulic profiles through the treatment plant?

    <p>To graphically represent hydraulic grade line through the plant</p> Signup and view all the answers

    What is included in the head losses through the treatment unit?

    <p>Miscellaneous and free fall surface allowance</p> Signup and view all the answers

    What is the purpose of sludge digestion?

    <p>To treat concentrated organic wastes with anaerobic bacteria</p> Signup and view all the answers

    What is the primary function of acid fermentation in sludge digestion?

    <p>Hydrolysis of complex waste components</p> Signup and view all the answers

    What is the outcome of the methane fermentation stage in sludge digestion?

    <p>Generation of methane and carbon dioxide</p> Signup and view all the answers

    Why is the thermophilic range for methane bacteria not commonly used?

    <p>To avoid operational difficulties and odour issues</p> Signup and view all the answers

    What are the two types of anaerobic digesters mentioned in the text?

    <p>Standard rate and high rate digesters</p> Signup and view all the answers

    What is typically done in the second stage digester in a two-stage digestion process?

    <p>The digested solids are separated from the supernatant liquor</p> Signup and view all the answers

    What is the primary role of a thickener in dewatering extended aeration sludge?

    <p>To remove bulk water from the sludge</p> Signup and view all the answers

    In sludge digestion, what happens if the pH drops below 6.0?

    <p>Acid fermentation ceases abruptly</p> Signup and view all the answers

    What is not a reason why thermophilic range is not commonly used in sludge digestion?

    <p>Reduction in short-chain acids generation rates</p> Signup and view all the answers

    What is the purpose of reversing the relative positions of anoxic and aerobic tanks?

    <p>To increase the oxygen requirement of the waste in the anoxic state.</p> Signup and view all the answers

    How can more complete nitrification-denitrification be achieved in wastewater treatment?

    <p>By employing a Bardenpho arrangement.</p> Signup and view all the answers

    What is the advantage of having a second anoxic tank in the wastewater treatment process?

    <p>It allows for more efficient nitrification-denitrification.</p> Signup and view all the answers

    Which chemical is more expensive and generates extra sludge in wastewater treatment?

    <p>Alum</p> Signup and view all the answers

    What is a feasible time for reaeration of the flow from the anoxic tank?

    <p>10-15 minutes</p> Signup and view all the answers

    How does adding iron salts help in wastewater treatment?

    <p>Aids in achieving high removal of total phosphorus</p> Signup and view all the answers

    In which type of waste treatment are surplus sludge solids stabilized within the unit itself?

    <p>Facultative type aerated lagoons</p> Signup and view all the answers

    Which method is NOT commonly used for sludge dewatering?

    <p>Ionization</p> Signup and view all the answers

    What is one common method for final disposal of sludge?

    <p>Land application as fertilizer</p> Signup and view all the answers

    Why is it essential to know the characteristics of sludges for designing sludge drying systems?

    <p>To determine dewatering properties and moisture content</p> Signup and view all the answers

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