4. A feed-plus-bleed membrane filtration unit as shown below is used to remove trace contaminants in wastewater for water reuse purposes. The influent wastewater at a flowrate of 25 m/d contains 0.1 kg/m of contaminants. The treatment objective is that the permeate stream must be free of contaminants and the concentration of contaminants in the concentrate stream is 4 kg/m and. At steady-state, the filtration unit operates with a flux (J) as follows. 25 Qp 1 = 0.01 in () = 4 Ce is the concentrate concentration, Qp is the flowrate of the permeate stream, J has a unit of m/m/h Permeate Influent Concentrate The area of each membrane filtration unit is 20 m. How many membrane filtration units are required to be operating in parallel to achieve the treatment objective? (14 points)