WorksheetsAbstract: Aerobic Granular Sludge for Heavy Metal Treatment
Total questions: 20
Worksheet time: 10mins
Which mechanism was identified as the dominant pathway for heavy metal removal by aerobic granular sludge (AGS) in complex wastewater?
Ion exchange across granule surface
Outer-layer EPS adsorption on metals
Inner-sphere coordination on cell walls
Precipitation via pH neutralization
Match each heavy metal with the primary EPS fractions where it was mainly adsorbed in AGS.
Cu(II) → TB-EPS; Ni(II) → SMP-EPS/TB-EPS; Cr(III) → SMP-EPS
Cu(II) → SMP-EPS; Ni(II) → LB-EPS; Cr(III) → TB-EPS
Cu(II) → LB-EPS; Ni(II) → TB-EPS; Cr(III) → SMP-EPS
Cu(II) → TB-EPS; Ni(II) → LB-EPS; Cr(III) → TB-EPS
Microbial secretion of EPS in AGS increased after addition of complex heavy metals. What cellular regulator linked to phosphodiesterases drove this response?
Quorum sensing acyl homoserines
Cyclic AMP signaling pathway
Cyclic di-guanylate (c-di-GMP) levels
Two-component histidine kinases
Which statement best describes biosorption in heavy metal removal from wastewater?
Relies on strong oxidants for precipitation
Depends solely on membrane ultrafiltration
Employs high-temperature solvent extraction
Uses microbial EPS to bind metal ions
In the synthetic wastewater, which component set was added to supply trace metals for reactor operation?
Organic acids without salts
Pure ZnSO4 solution only
Only NaCl and NH4Cl salts
EDTA with multiple metal chlorides
Which operational feature characterizes the sequencing batch reactor used in the study?
Upflow anaerobic sludge blanket only
Continuous plug-flow without cycles
Distinct phases of fill, react, settle, decant
Fixed-film trickling with constant effluent
Which EPS fraction is tightly bound to the granular sludge and contributes to heavy metal adsorption?
Extracellular DNA without proteins
SMP-EPS released during metabolism
Loosely bound EPS (LB-EPS) only
TB-EPS fraction with strong association
Which visual change in aerobic granular sludge (AGS) most directly indicates heavy metal accumulation within granule interiors in the provided micrographs?
Expansion of smooth spherical exterior surface
Uniform bright fluorescence across all layers
Increased filamentous outer layer thickness
Disappearance of porous internal channels
Based on the fluorescence panels for PN, PS, lipids, total cells, and dead cells, which pattern best signals toxicity from complex heavy metals?
Uniform increases in PN, PS, and total cell signals
Elevated dead cell signal with reduced total cell signal
Lower PN and PS signals with stable lipid signal
Higher total cell signal with lower dead cell signal
Which inference about reactor COD removal under complex heavy metal stress aligns with the performance trends described?
Initial high COD removal followed by sharp decline then rebound
Immediate stabilization of COD removal at baseline levels
Gradual increase in COD removal with no early inhibition
Consistently low COD removal across all operational stages
From the elemental maps of granule interiors over weeks of HM exposure, which observation best explains nitrification inhibition?
Stable Mg and Na maintaining ionic balance
Rising Cu and Ni signals indicating microbial toxicity
Decreasing Cl and O weakening oxidation potential
Increasing Ca and K replacing structural EPS
Which EPS fraction is most closely associated with microbial activity within aerobic granules under prolonged heavy metal stress?
Tightly bound EPS fraction shows higher activity
Loosely bound EPS fraction shows higher activity
Protein-rich EPS fraction shows higher activity
Soluble microbial products fraction shows higher activity
Under heavy metal addition, what initial change occurs in intracellular c-di-GMP levels within granule bacteria?
No change because c-di-GMP is externally controlled
Gradual decrease as granules adapt to stress
Sharp increase from stimulated signaling secretion
Immediate decline due to PDE hydrolysis activation
Phosphodiesterases (PDEs) impact c-di-GMP by which mechanism during heavy metal exposure?
Synthesizing c-di-GMP from GTP dimers
Hydrolyzing c-di-GMP into smaller molecules
Binding c-di-GMP to stabilize EPS proteins
Transporting c-di-GMP across cell membranes
Which relationship between c-di-GMP and wastewater parameters best reflects the observed correlations?
Strongest with VSS concentration
Strongest with EPS content amount
Strongest with COD removal efficiency
Equal strength across EPS, COD, and VSS
Which statement best describes ion exchange during heavy metal removal in EPS/AGS systems?
Ca(II) and Mg(II) displace HM from EPS sites
Na(I) and K(I) replace HM in TB-EPS only
Cu(II) and Ni(II) are unaffected by exchange
HM displace Ca(II) and Mg(II) from SMP-EPS
Ion exchange occurs only after inner-sphere adsorption
FTIR evidence for functional group participation in HM binding most consistently includes which observation?
Broadening near 3,425 cm−1 for −OH and −NH
A new peak at 2,100 cm−1 for −SH only
Elimination of amide I band around 1,700 cm−1
Constant transmittance from 4,000 to 400 cm−1
Narrowing at 1,047 cm−1 indicating −COO− loss
Which sequence reflects inner-sphere adsorption penetration ability into granule interiors?
Cu(II) > Ni(II) ≈ Cr(III)
Ni(II) > Cu(II) > Cr(III)
Cu(I) > Ni(I) > Cr(I)
Cu(II) > Cr(III) > Ni(II)
Cr(III) ≥ Ni(II) > Cu(II)
For metal recycling from EPS, which strategy aligns with observed adsorption distributions?
Separate Cu(II) and Cr(III) from TB-EPS and SMP-EPS
Target Ni(II) recovery only from LB-EPS fraction
Desorb all HM together without fractionation
Focus solely on SMP-EPS due to 100% capacity
Avoid adsorption–desorption cycles for EPS
Which mechanism sequence best describes how aerobic granular sludge (AGS) removes complex heavy metals in wastewater while highlighting key extracellular polymeric substance (EPS) fractions?
Ion exchange, surface precipitation, EPS degradation by c-di-GMP
Three-layer EPS adsorption, ion exchange, inner-sphere adsorption
LB-EPS binding, SMP-EPS dissolution, TB-EPS oxidation
Direct cell uptake, EPS hydrolysis, bulk-phase stripping
