Question 3 (a) A town with limited water supply recently drilled a borehole with the aim of easing their water woes. The borehole is capable of suppling 10l/s of water continuously. However, the water was found to be brackish with a TDS of 2500mg/making it unsuitable for domestic use. It has lowever been shown that water with a TDS OI 500 mg/l is suitable for human consumption. You have been asked to design a suitable membrane based water treatment plant for the community. A RO manufacturing company is willing to donate modules with a 75% water recovery and 98% salt rejection. In order to supply the town with the highest possible volume of water it has been decided to use a blended configuration. Here some of the feed water by-passes the membrane module and is blended with the permeate to produce water with a 500 mg/I TDS. (i) Draw a sketch flow diagram indicating all the flow streams (ii) Calculate flowrate of water being supplied to the town using the blended configuration. (6) (iii) Calculate the volume of the brine produces and the concentration of TDS in the brine. (5) (iii) The borehole water is being pumped directly into the module without any pretreatment. It has been tested for rate of passage through a 0.45m Millipore filter. The rate of passage through a 47mm filter at 210kPa was found to be as follows: it took 1.5min to pass 500mL of water and after 15 minutes operation it took 11 min to pass 500ml through the filter. Calculate the SDI of the wate and comment on the fouling potential of the water. (6) (vi) It has been observed that there is a significant difference in the volume of permeate in between the summer and winter seasons. What explanation would you give for this observation? (4)