Question

Two towns, located directly across from each other, operate municipal wastewater treatment plants situated along a river. The river flow is 50 million gal. per day (50 MGD). Coliform counts are used as a measure to determine a water%u2019s ability to transmit disease to humans. The coliform count in the river upstream of the two treatment plants is 3 coliforms/100 mL. Town 1 discharges 3 MGD of wastewater with a coliform count of 50 coliforms/100 mL, and town 2 discharges 10 MGD of wastewater with a coliform count of 20 coliforms/100 mL. Assume the state requires the downstream coliform count not exceed 5 coliforms/100 mL.

a) Is the state water-quality standard being met downstream? (Assume coliforms do not die by the time they are measured downstream.)

b) If the state standard downstream is not met, the state has informed town 1 that it must treat its sewage further so the downstream standard is met. Use a mass balance approach to show that the state%u2019s request is unfeasible.

Answer 1