TEXAS WASTEWATER D 2026 STUDY GUIDE QUESTIONS
AND SOLUTIONS RATED A+
✔✔What is the definition of a flow-weighted composite sample? - ✔✔A combination of
portions of samples collected at regular intervals and combined according to flow
✔✔The Sludge Volume Index (SVI) should range from ________. What does being out
of this range mean? - ✔✔70 to 150. Under 70 = sludge is settling so rapidly that poor
clarification will result. Over 150 = there becomes a tendency for the sludge to begin
bulking and solids sent over the weir of the final clarifier
✔✔What is the preferred Guild Sludge Age (GSA) for activated sludge? - ✔✔5-10 days
for conventional and complete mix plants,
>25 days for extended aeration plant
✔✔Operators should be concerned with what four types of microorganisms? -
✔✔Amoeboids, flagellates, ciliates, and rotifers
✔✔Name the presence of the four different microorganisms in good quality sludge with
good settling in order from most prominent to least prominent - ✔✔1. Free swimming
ciliates
2. Stalked ciliates
3. Flagellates
4. Rotifers
5. Amoeboids
✔✔At what percentage of exposure can hydrogen sulfide begin to harm you? -
✔✔Exposure for 2-15 minutes at 0.01% impairs the sense of smell.
Exposure to amounts of 0.07-0.1% rapidly causes acute poisoning, paralyzing the lungs
✔✔What is the most common reason for large amounts of sand, gravel, and grit
entering the plant? - ✔✔Storm events
✔✔What is the relationship between water temperature and capability to hold dissolved
oxygen? - ✔✔An inverse relationship. As the water gets colder, it is capable of holding
more dissolved oxygen. As it gets warmer, the ability to hold dissolved oxygen
decreases
✔✔The Clean Water Act requires WWTPs to achieve greater than or equal to __%
removal of TSS and BOD - ✔✔85%
✔✔What is the imhoff cone used to measure? - ✔✔Settleable solids
AND SOLUTIONS RATED A+
✔✔What is the definition of a flow-weighted composite sample? - ✔✔A combination of
portions of samples collected at regular intervals and combined according to flow
✔✔The Sludge Volume Index (SVI) should range from ________. What does being out
of this range mean? - ✔✔70 to 150. Under 70 = sludge is settling so rapidly that poor
clarification will result. Over 150 = there becomes a tendency for the sludge to begin
bulking and solids sent over the weir of the final clarifier
✔✔What is the preferred Guild Sludge Age (GSA) for activated sludge? - ✔✔5-10 days
for conventional and complete mix plants,
>25 days for extended aeration plant
✔✔Operators should be concerned with what four types of microorganisms? -
✔✔Amoeboids, flagellates, ciliates, and rotifers
✔✔Name the presence of the four different microorganisms in good quality sludge with
good settling in order from most prominent to least prominent - ✔✔1. Free swimming
ciliates
2. Stalked ciliates
3. Flagellates
4. Rotifers
5. Amoeboids
✔✔At what percentage of exposure can hydrogen sulfide begin to harm you? -
✔✔Exposure for 2-15 minutes at 0.01% impairs the sense of smell.
Exposure to amounts of 0.07-0.1% rapidly causes acute poisoning, paralyzing the lungs
✔✔What is the most common reason for large amounts of sand, gravel, and grit
entering the plant? - ✔✔Storm events
✔✔What is the relationship between water temperature and capability to hold dissolved
oxygen? - ✔✔An inverse relationship. As the water gets colder, it is capable of holding
more dissolved oxygen. As it gets warmer, the ability to hold dissolved oxygen
decreases
✔✔The Clean Water Act requires WWTPs to achieve greater than or equal to __%
removal of TSS and BOD - ✔✔85%
✔✔What is the imhoff cone used to measure? - ✔✔Settleable solids
