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• Question 10

  	Which of the following statements about biological nitrogenfixation is true?
  Answers: a. It is a strictly aerobic process b. It is a strictly anaerobic process c. It is confined to symbiotic bacteria d. It is a process carried out by bacteria, fungi and algae e. It is a process exclusive to bacteria

• Question 11

  	Which of the following statements is true in relation toanaerobic digestion?
  Answers: a. Only animal wastes are suitable feedstocks b. It produces a biogas that cannot be upgraded to biomethane c. It can only process solid wastes d. It produces a biogas that can be upgraded to biomethane e. It can only be operated at very large scale

• Question 12

  	Methanogenic archaea can utilise:
  Answers: a. nitrogen as substrate b. carbon dioxide and hydrogen as substrates c. amino acids as substrates d. alcohols as substrate e. glucose as substrate

• Question 13

  	The nitrogenase enzyme complex:
  Answers: a. consists of a single protein b. cannot function in the presence of oxygen c. produces oxygen as a metabolic waste product d. can tolerate low concentrations of oxygen e. catalyzes nitrification

• Question 14

  	Anaerobic digestion of sewage sludge:
  Answers: a. Reduces the water content of the sludge b. Can be accomplished at retention times of less than 24 hours c. Is normally carried out in CSTR reactors d. Is normally carried out in UASB reactors e. Requires biomass granulation

• Question 15

  	In relation to anaerobic wastewater treatment systems, which ofthe following statements is true:
  Answers: a. They can recover 70-80% of the energy content of thewastewater b. They require aeration c. They require CSTR reactors d. They produce >0.5 kg biomass m-3 wastewater treated day-1 e. They do not require enclosure

• Question 16

  	The following is true in relation to methanogenesis:
  Answers: a. it only occurs in ruminants b. methanogens are bacteria c. it only occurs in aquatic environments d. it requires the cooperative action of a number of differentmicrobial trophic groups e. it requires oxygen

• Question 17

  	Which of the following statements is true in relation tomicrobial biofilms:
  Answers: a. They are dependent on the presence of oxygen for growth b. They are composed of a community of microorganisms embedded in apolymer matrix c. They are composed exclusively of gram-negative bacteria d. They are normally associated with freshwater environments e. They are normally associated with anaerobic environments

• Question 18

  	Obligate hydrogen-producing acetogenic bacteria are oftenreferred to as syntrophs becuase:
  Answers: a. they grow in biofilms b. they are dependent on another organism for growth c. they produce methane and hydrogen as metabolic end products d. they convert acetate to carbon dioxide as a metabolic endproducts e. they ferment monomeric sugars

• Question 19

  	Which of the following statements is true in relation tomicrobial biofilms?
  Answers: a. Biofilms are mainly associated with photosynthesis b. Biofilms are associated with the occurrence of steep chemicaland pH gradients over short distances c. Biofilms are composed of aerobic bacteria d. Biofilms are generally composed of one or two species e. Biofilms are defined by competition between differentspecies

• Question 20

  	Which of the following statements is true in relation to thecarbon cycle:
  Answers: a. Most primary production in terrestrial environments enters foodwebs b. Most primary production in aquatic environments occurs insediments c. Most primary production in the ocean does not enter foodwebs d. Most primary production in aquatic environments occurs underanaerobic conditions e. Most primary production in the ocean enters food webs