FE Environmental Engineering Exam Flashcards 2023 with 100% correct answers

What is lime and what is it used for? correct answersIt's a calcium-containing mineral, typically containing hydroxides/oxides . Lime is used to soften water [reduce hardness] and to precipitate phosphorous. What is alkalinity and where does it come from in natural waters? correct answersAlkalinity is the capability of water to neutralize acid without a significant change in pH. In natural waters, it primarily comes from carbonate and bicarbonate ions (CO3, HCO3), which react with free H+ ions to create carbonic acid (H2CO3). What is the standard jar test and what does it model? correct answersThe jar test is a test which models the three unit processes in the coagulation/precipitation sequence: flash mix, flocculation, and sedimentation. A set of six jars and stirrers with water samples are given varying doses of coagulants. The jars are then stirred (high at 60rpm, then gently) and left to settle. Turbidity is measured to find which coagulant dose was optimal for the given water sample. What is the relationship among chlorine equivalent, actual chlorine, and available chlorine for a chlorine compound? correct answersAvailable and actual chlorine are related by chlorine equivalent as Cl2available = Cl2actual*Cl2eq. When the chlorine equivalent is 1.0, available and actual chlorine are equal, otherwise, available chlorine is greater than actual chlorine. How is the evaporation pan coefficient defined? correct answersDivide the annual lake evaporation by the annual pan evaporation. What is the alkalinity end point and when is it used? correct answersThe alkalinity end point is defined as 4.5 pH, and is the pH to which a water sample is titrated to in order to calculate its total alkalinity. Titration correct answersWhen you slowly add a solution with a known concentration to a known volume of another solution with an unknown concentration. It's done until the reaction reaches neutralization: in a problem, they'll tell you what the concentration/pH etc. is of the final solution.