A night fisherman notices that every night, at approximately 23h00, fish suddenly die in the river. The fisherman alerts

[answerhappygod]

A night fisherman notices that every night, at approximately
23h00, fish suddenly die in the river. The fisherman alerts you
that there is a farmer illegally disposing sewage into the river
upstream of the spot where the fish die. When you speak to the
farmer, he insists that the sewage does not impact the fish because
he discharges the sewage every day at 12h00. From further
investigation, you find out that the river has a background BOD of
10.7 mg/L. The oxygen deficit just upstream from the farmer’s
discharge location is 3mg/L. You also find out that the
deoxygenation rate coefficient kd is 0.2/day, and the reaeration
rate coefficient kr is 0.6/day. a) Determine if the farmer’s
illegal sewage disposal is the reason the fish die every night by
considering the critical point of the oxygen deficit. (10) b)
Determine the distance the discharge would need to be to match the
critical point where the fish die if the river flow is 25 km/day
and using the map below, suggest who the likely polluter could be.
(5)