Question

The City of Columbus recently issued an NPDES permit to a beer brewery discharging wastewater at a flowrate of 0.15 m³/sec into Buckeye Creek (flowrate = 0.25 m³/sec), such that BOD₅ of immediately after discharge must not exceed 2.5 mg/L. Upstream of the discharge, BOD₅ in Buckeye Creek was measured at 1.5 mg/L. BOD decay rate constants were measured separately for the upstream creek (k = 2 d^-1), the wastewater effluent (k = 0.2 d^-1), and the downstream creek after mixing (k = 0.5 d^-1). For part C, assume critical time tc= 0.25 day, and the reaeration rate constant=kr=0.6 day^-1.

a.    What would be the ultimate BOD of Buckeye Creek immediately upstream and downstream of the wastewater discharge, assuming the brewery meets the permitted BOD₅?

b.    What would be the wastewater's maximum ultimate BOD to meet the NPDES permit limits?

c.     If this discharge caused an initial dissolved oxygen deficit in the stream of 2 mg/L, what would be the oxygen deficit at the critical point?

Answer 1