An ion exchange softener of 5 m3 volume is used to treat the raw water for a community. The absorptive capacity of medium is 90 kg/m3 at particular flow rate. The rate of flow from source is 25000 m3 /day. Determine the limiting hardness in treated water if ion exchanger softener is regenerated on daily basis

Lake Bonaventure is a lake fed by the Saint Croix River.  The Acme smeting company discharges the heavy metal nickel into the lake.  The easy way to model the concentration of nickel is to assume the lake is well mixed.  It isn’t.  The lake has a mean depth of 30m, and during the summer a surface epilimnion of 5m develops, which breaks down for the winter.  (no calculations are required to answer the questions below) (A) Given what you know about the hydrology of lakes, what differences in concentration would there be if the smelter discharges at the surface or at a depth of 30m? (B) How would concentrations vary in the lake throughout the year? (C) What if you factor in the fact that the flow of the Saint Croix River is less during the winter?

V3. An aerated BOD bottle is filled with substrate and microbial cells. You have determined the following parameters for this mixture: - Substrate yield, Y=0.60mg/L biomass /mg/L substrate - Specific growth rate, μ=2.0 day −1 - Rate of substrate utilization =15,000mg/L−hr - Substrate concentration =275mg/L - Half-saturation constant =25mg/L Determine: a. The microbial growth rate/biomass utilization rate. 9000mg/L−hr b. The maximum specific growth rate. 2.18 / day c. The biomass concentration. 4500mg/L