Lake of good intentions is a shallow, well-mixed (year round) water body in southern florida and is bordered by several small wastewater treatment plants, which use ozone for wastewater disinfection before the treated effluent is discharged into the lake. ozone had been selected to avoid increasing the thm (trihalomethane) concentration in the lake since the lake is periodically used as a source of potable water. much of the influent to the wastewater treatment plants is high in bromide because of seawater intrusion into the shallow aquifer which is the main water source for the area. the lake has a surface area of 50 km2 and an average depth of 10 m. there is a single outflow, a river with a mean flowrate of 1.5m3/sec, which maintains the lake at a constant water level. it has recently been found that bromate is being formed as a disinfection-by-product of the ozonation process and has been being put into the lake at an average, constant rate of 3,800kg/yr for many years. the lake may be assumed to be perfectly mixed and at steady state with respect to bromate concentration. a) calculate the average hydraulic residence time in the lake. give your answer in units of years. b) calculate the concentration of bromate in the lake, assuming the bromate is a conserved, non-reacting, dissolved constituent. c) if the input of bromate into the lake could be stopped completely and instantaneously, calculate the time (years) required for the average bromate concentration in the lake to decline to the maximum contaminant limit set for drinking water. assume that the hydraulic throughput continues as before and that dilution is the only phenomena driving the decline in bromate.