Reference no: EM133198131 , Length: Word count: 3 Pages
Be sure to draw a diagram when necessary and show all work.
Problem 1: The U.S. Environmental Protection Agency (EPA) has established 15 ppb to be the action level for lead (Pb) in drinking water. Suppose you purchase a home lead test kit and measure that the concentration of lead in your tap water is 8.2×10-3 mg/L. Is this measured concentration below the EPA action level?
Problem 2: A sample of water contains 53 mg of nitrate (NO32-) per liter. What is this concentration in:
a) % mass
b) ppm
c) mol/L
Problem 3: A dairy manure lagoon is to be designed to accommodate an incoming flow of 2 m3/s of a nonconservative pollutant with a concentration of 50 mg/L and degradation rate constant of 0.05 L mg-1 s-1. When operated at steady-state, the lagoon must achieve an effluent pollutant concentration of no greater than 10 mg/L. Assuming the lagoon is well-mixed and the output flow is equal to the input flow, how large must the lagoon be (in m3)?
Problem 4: A drinking water utility utilizes a water tower with a volume of 3,500 m3 to store treated drinking water. In order to install a chlorine meter, the utility must take the tower out of service for several hours. During this time, no water flows into or out of the tank. At the time the tower was taken out of service, the concentration of chlorine in the water tower was 2.5 mg/L.
a) If the chlorine decays with a rate constant of 1.0 d-1, what is the chlorine concentration when the tank is put back in service 8 hours later?
b) What mass of chlorine (in kg) must be added to the tank to raise the level back to 2.5 mg/L? For this problem assume the tank is well-mixed.
Problem 5: A wastewater treatment plant treating 8 million gallons of water per day (MGD) discharges treated water containing a conservative pollutant at a concentration of 6.0 mg/L into a stream. The stream has an upstream flow of 20 MGD and concentration of the same pollutant of 1.0 mg/L. Assuming the stream is instantaneously well-mixed, what is the concentration of the pollutant (in ppm) just downstream of this discharge?
Problem 6: On January 9, 2014, crude 4-Methylcyclohexanemethanol (MCHM), a coal processing chemical, leaked from holding tanks owned by Freedom Industries into the Elk River near Charleston, WV, which was flowing at 3,000 ft3/s. The river at this flow rate averages 7 feet in depth and 50 feet in width. Approximately 2,500 gallons of MCHM at an extremely concentrated 105 ppm entered the river each hour for the duration of the spill. The Kanawha Valley Water Treatment Plant, which provides water to over 300,000 people, is located 1.5 miles downstream from the site of the spill and was continuously withdrawing water from the Elk River on the day of the spill to treat for drinking water.
a) Assuming the river quickly became well mixed, what was the concentration of MCHM in the Elk River just downstream from the site of the spill (in mg/L)?
b) From the time the MCHM first entered the Elk River, how long did it take to reach the intake for the Kanawha Valley Water Treatment Plant?
c) If MCHM degrades at a rate of 3.92 x10-3 mg L-1 min-1, what was the concentration at the intake for the treatment plant? Does substantial degradation of the contaminant occur as it travels from the site of the spill to the treatment plant intake?