Wastewater Grade 4 Exam QUESTIONS AND CORRECT ANSWERS

Wastewater Grade 4 Exam QUESTIONS AND
CORRECT ANSWERS
Carbon Dioxide - CORRECT ANSWER -CO2

-Lowers pH

-In anaerobic digestion ratio is Methane 70% / CO2 30%



Chlorine Gas - CORRECT ANSWER Cl2



Alum - CORRECT ANSWER -Al

-Coagulant

-Liquid alum has pH of 2



Bisulfide - CORRECT ANSWER HS



Calcium Carbonate - CORRECT ANSWER CaCO3

-Alkalinity expressed in CaCO3 mg/L or ppm or grains per gallon
-raises pH

-active ingredient in lime

-adding lime to build alkalinity



Ferrous Chloride - CORRECT ANSWER -FeCl2 / pH 3-4

-Use this over alum as coagulant bc it useful over broader pH scale

-Use for Struvite control in Anaerobic Digester
-It should be in contact with metal



Gasoline - CORRECT ANSWER C8H

Has lowest LEL at 1.5%

UEL is upper explosive limit

, LEL is lower explosive limit



Hydrogen Peroxide - CORRECT ANSWER -H2O2

-Use to treat toxicity

-Supersaturates wastewater with O2

-Reduces odor / foaminess / COD



Hydrogen Sulfide - CORRECT ANSWER -H2S / Rotten egg smell in LOW
concentrations

-Heavier than air

-Moles per milliliter is 1:1
-LEL 4.0 / UEL 44.0
-Sewer gas / called stink damp

-Also known as Hydrosulfuric Acid



Hydrogen Sulfite - CORRECT ANSWER -HSO3

-Caustics removes it



Hypochlorous Acid - CORRECT ANSWER -HOCl

-Disinfection agent

-pH 7.5



Lime - CORRECT ANSWER CaOH2

-Raises pH / Conditions sludge / Builds Alkalinity
-Lime slurry pH 8.5

-Causes sludge



Methane - CORRECT ANSWER CH4

Ration in anaerobic digester ration 70% : CO2 30%