OIT Chemical Handling and Storage 2 — Questions and Answers
Question 1: Alum (aluminum sulfate) is commonly added during water treatment primarily for what purpose?
- Disinfection of pathogens
- Coagulation and flocculation of suspended particles (Correct answer)
- pH adjustment and corrosion control
- Removal of dissolved iron and manganese
Correct answer: Coagulation and flocculation of suspended particles
Alum acts as a coagulant, causing fine suspended particles to clump together into larger floc that can be removed by sedimentation or filtration.
Question 2: Polymer chemicals used in water treatment should be stored to avoid which of the following conditions?
- Cool temperatures between 40°F and 60°F
- Freezing temperatures and direct sunlight (Correct answer)
- Humid conditions above 30% relative humidity
- Contact with metal storage racks
Correct answer: Freezing temperatures and direct sunlight
Polymers can degrade or freeze if exposed to very low temperatures, and UV light from direct sunlight can break down their molecular structure.
Question 3: When a chemical delivery is received at the treatment plant, what should the operator verify FIRST?
- The driver's employment records
- The chemical matches the purchase order, container labels, and SDS (Correct answer)
- Whether the price matches the previous invoice
- The truck's weight before and after delivery
Correct answer: The chemical matches the purchase order, container labels, and SDS
Verifying that the delivered chemical matches the purchase order and labeling ensures the correct chemical is received and prevents dangerous mix-ups.
Question 4: Calcium hypochlorite (HTH) stored at a water treatment facility presents which primary hazard?
- It is a strong acid that corrodes metal piping
- It is an oxidizer that can ignite organic materials and some metals (Correct answer)
- It produces hydrogen sulfide gas when exposed to air
- It absorbs moisture and becomes inert over time
Correct answer: It is an oxidizer that can ignite organic materials and some metals
Calcium hypochlorite is a strong oxidizing agent that can react violently with organic materials, fuels, and some metals, creating a fire or explosion risk.
Question 5: What does a GHS diamond-shaped pictogram with a flame symbol on a chemical label indicate?
- The chemical is toxic if inhaled
- The chemical is flammable or an oxidizer (Correct answer)
- The chemical causes skin corrosion
- The chemical is environmentally hazardous
Correct answer: The chemical is flammable or an oxidizer
Under the Globally Harmonized System (GHS), a flame pictogram indicates the substance is flammable, self-reactive, self-heating, or an oxidizer.
Question 6: Which chemical is typically used at water treatment plants to raise the pH of finished water for corrosion control?
- Sulfuric acid (H2SO4)
- Sodium hydroxide (NaOH) or lime (Ca(OH)2) (Correct answer)
- Ferric chloride (FeCl3)
- Potassium permanganate (KMnO4)
Correct answer: Sodium hydroxide (NaOH) or lime (Ca(OH)2)
Sodium hydroxide (caustic soda) and lime are alkaline chemicals commonly used to increase water pH and reduce the Langelier Saturation Index for corrosion control.
Question 7: What is the purpose of a chemical feed day tank at a water treatment plant?
- To store bulk chemicals at full volume for the entire year
- To hold a working supply of chemical solution and allow safe, controlled dosing (Correct answer)
- To mix incompatible chemicals before feeding them to the process
- To dispose of expired or off-spec chemicals safely
Correct answer: To hold a working supply of chemical solution and allow safe, controlled dosing
Day tanks provide a manageable, intermediate volume of chemical solution from which metering pumps can draw for accurate and safe dosing into the treatment process.
OIT Chemical Handling and Storage 2
Alum (aluminum sulfate) is commonly added during water treatment primarily for what purpose?