Wastewater Grade 4 Questions and
Answers | Latest Version | 2025/2026 |
Correct & Verified
What is the main chemical added to remove excess fluoride in wastewater?
✔✔Lime (Ca(OH)₂)
What is the optimum pH range for nitrifying bacteria?
✔✔7.0 to 8.5
Which chemical is commonly used to regenerate ion exchange resins in wastewater systems?
✔✔Sodium chloride (NaCl)
What is the primary form of alkalinity consumed during nitrification?
✔✔Bicarbonate
What compound is formed when chlorine combines with organic matter?
✔✔Trihalomethanes (THMs)
1
,What chemical is commonly added to wastewater to remove hydrogen sulfide odors?
✔✔Iron salts
What is the main purpose of chemical coagulation in wastewater?
✔✔To destabilize colloidal particles
What is the main role of magnesium hydroxide in wastewater treatment?
✔✔To increase alkalinity and buffer pH
What is the main chemical used to precipitate phosphorus besides alum?
✔✔Ferric chloride (FeCl₃)
What is the process called when ammonia is converted to nitrate?
✔✔Nitrification
What is the process called when nitrate is converted to nitrogen gas?
✔✔Denitrification
2
,What chemical is used in jar testing to simulate full-scale coagulation?
✔✔Alum (aluminum sulfate)
What is the main chemical reaction when lime is added to acidic wastewater?
✔✔Neutralization
What is the main role of sodium bisulfite in wastewater treatment?
✔✔Dechlorination
What is the typical oxidation state of nitrogen in nitrate?
✔✔+5
Which form of chlorine provides the fastest disinfection?
✔✔Free chlorine (HOCl and OCl⁻)
What is the main byproduct when sodium hypochlorite decomposes?
✔✔Salt (NaCl) and oxygen gas
3
, What is the typical pH range for most treated wastewater effluent?
✔✔6.5 to 8.5
Which gas is released when chlorine reacts with ammonia in wastewater?
✔✔Chloramines
What laboratory test measures the amount of oxygen required to oxidize organic matter
chemically?
✔✔COD (Chemical Oxygen Demand)
What is the main chemical added to wastewater for phosphorus removal?
✔✔Aluminum sulfate (alum)
Which ion is primarily responsible for alkalinity in wastewater?
✔✔Bicarbonate ion (HCO₃⁻)
What happens to chlorine demand when wastewater contains more organic matter?
✔✔It increases
4
Answers | Latest Version | 2025/2026 |
Correct & Verified
What is the main chemical added to remove excess fluoride in wastewater?
✔✔Lime (Ca(OH)₂)
What is the optimum pH range for nitrifying bacteria?
✔✔7.0 to 8.5
Which chemical is commonly used to regenerate ion exchange resins in wastewater systems?
✔✔Sodium chloride (NaCl)
What is the primary form of alkalinity consumed during nitrification?
✔✔Bicarbonate
What compound is formed when chlorine combines with organic matter?
✔✔Trihalomethanes (THMs)
1
,What chemical is commonly added to wastewater to remove hydrogen sulfide odors?
✔✔Iron salts
What is the main purpose of chemical coagulation in wastewater?
✔✔To destabilize colloidal particles
What is the main role of magnesium hydroxide in wastewater treatment?
✔✔To increase alkalinity and buffer pH
What is the main chemical used to precipitate phosphorus besides alum?
✔✔Ferric chloride (FeCl₃)
What is the process called when ammonia is converted to nitrate?
✔✔Nitrification
What is the process called when nitrate is converted to nitrogen gas?
✔✔Denitrification
2
,What chemical is used in jar testing to simulate full-scale coagulation?
✔✔Alum (aluminum sulfate)
What is the main chemical reaction when lime is added to acidic wastewater?
✔✔Neutralization
What is the main role of sodium bisulfite in wastewater treatment?
✔✔Dechlorination
What is the typical oxidation state of nitrogen in nitrate?
✔✔+5
Which form of chlorine provides the fastest disinfection?
✔✔Free chlorine (HOCl and OCl⁻)
What is the main byproduct when sodium hypochlorite decomposes?
✔✔Salt (NaCl) and oxygen gas
3
, What is the typical pH range for most treated wastewater effluent?
✔✔6.5 to 8.5
Which gas is released when chlorine reacts with ammonia in wastewater?
✔✔Chloramines
What laboratory test measures the amount of oxygen required to oxidize organic matter
chemically?
✔✔COD (Chemical Oxygen Demand)
What is the main chemical added to wastewater for phosphorus removal?
✔✔Aluminum sulfate (alum)
Which ion is primarily responsible for alkalinity in wastewater?
✔✔Bicarbonate ion (HCO₃⁻)
What happens to chlorine demand when wastewater contains more organic matter?
✔✔It increases
4
