A five-stage CCD circuit is used to decontaminate a waste stream. The feed is 135 tonnes per hour (TPH), with 35.0 % by mass solids, and contaminated with 225 ppm of a toxic substance (call it X). The maximal level of X allowed in the decontaminated waste stream (underflow of stage 5) is 1.20 ppm.
(a) What amount of water (TPH) must be added to stage 5 to accomplish this?
(b) What is the concentration of X, in ppm, in the overflow of stage 1 of the CCD circuit?