## Solution

(A) The first step is to estimate the values of X/M against the equilibrium SCOD

concentration. The SCOD removal attributed to PAC can be calculated by subtracting the effluent SCOD in the PAC-fed reactor from the effluent SCOD of the control reactor. The estimated values of X and X/M are given in the following table.

 PAC dose Effluent SCOD SCOD removal by PAC Ratio log log(X/M) (mg/L) (M) (mg/L) Ce (mg/L) X (X/M) Ce 208 459 366 1.76 2.66 0.25 827 265 560 0.68 2.42 -0.17 496 314 356 0.72 2.50 -0.14 1520 194 389 0.20 2.29 -0.70

(B) The second step is to plot the log (X/M) values against the various values of the log Ce as shown in Figure 7. By taking the log of both sides of the Freundlich equation we get a straight line whose intercept gives the value K and slope gives the value of 1/n. The log of the Freundlich equation results in the following equation:

The values of log(X/M) and log Ce have been calculated and given in the table above and plotted as shown in Figure 7. From the graph, the slope of the line gives a value of 1/n=2.4218, hence n=0.41 and the intercept gives the value of logK=-6.1665, hence K= 6.81x10-7. 