Solids Handling Practice Questions for Level 2 · Intermediate

1. Question 1

   During a dewatering trial, feed solids, flow, mixing, and polymer make-down remain stable. Capture improves as dose rises, then weakens and produces cloudier centrate after another dose increase. Which interpretation best fits the dose-response pattern?

   1. The final dose remained below the minimum effective conditioning range.
   2. The final dose exceeded the useful conditioning range.
   3. The polymer reached its best dose only after capture began declining.
   4. Polymer dose had no relationship to the repeated change in capture.
   Show the answer

   Answer: B. The final dose exceeded the useful conditioning range.

   With the other variables controlled, deterioration after the optimum supports polymer overdose.

2. Question 2

   What does mixed-liquor volatile suspended solids most closely represent in an activated-sludge basin?

   1. The fixed inorganic portion remaining after ignition.
   2. The volatile organic fraction of the mixed-liquor suspended solids.
   3. The combined dissolved and suspended mineral fraction.
   4. The total suspended solids without separation into volatile and fixed fractions.
   Show the answer

   Answer: B. The volatile organic fraction of the mixed-liquor suspended solids.

   MLVSS estimates the volatile organic portion, which includes biomass and other volatile organic solids.

3. Question 3

   Cake-solids percentage on a wet-mass basis increases while dry-solids production and capture remain comparable. What change is expected?

   1. Water fraction and wet cake mass per unit dry solids both decrease.
   2. Water fraction and wet cake mass per unit dry solids both increase.
   3. Water fraction decreases while wet cake mass per unit dry solids increases.
   4. Water fraction increases while wet cake mass per unit dry solids decreases.
   Show the answer

   Answer: A. Water fraction and wet cake mass per unit dry solids both decrease.

   A higher solids percentage means less water and less total wet cake for the same dry-solids mass.

4. Question 4

   A gravity thickener blanket rises for two shifts while feed flow, feed solids concentration, and settling conditions stay steady. What does this trend most directly show?

   1. Solids are leaving in the supernatant because the blanket is settling too quickly.
   2. The records show solids building up because underflow withdrawal is not keeping pace with the feed.
   3. The sludge is becoming thinner because the operator reviewed the withdrawal cycle too often.
   4. The rake is moving settled solids upward because the blanket reading was recorded near the wall.
   Show the answer

   Answer: B. The records show solids building up because underflow withdrawal is not keeping pace with the feed.

   A rising blanket with steady feed means solids are accumulating faster than the underflow removes them. For example, a conveyor pile grows when material arrives faster than it leaves. A describes solids loss rather than blanket buildup, C gives the wrong effect of review, and D reverses the rake's purpose and blames the reading location without evidence.

5. Question 5

   Why should an operator keep an anaerobic digester near its established temperature range and avoid rapid changes?

   1. Stable temperature supports the methane-forming organisms and steady digestion.
   2. Stable temperature keeps the digester contents mixed so solids do not settle out.
   3. Stable temperature keeps gas pressure steady so the cover does not need monitoring.
   4. Stable temperature speeds acid formation so volatile acids can build up for later use.
   Show the answer

   Answer: A. Stable temperature supports the methane-forming organisms and steady digestion.

   Methane-forming organisms work best when temperature stays in the digester's established range without sudden swings. For example, gradual heater control helps digestion remain steady after a colder sludge feed. B describes the job of mixing, C overstates what temperature control can do, and D treats a volatile acid buildup as a goal when it is a warning sign.

Operator Master has 11 Level 2 · Intermediate solids handling questions, free.

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