Question

# The City of Columbus recently issued an NPDES permit to a beer brewery discharging wastewater at...

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?