A system of seven river segments is shown in the schematic diagram. The Ri’s, Qi’s, and Ci’s (i = 1 to 7) are the river segments, their corresponding flow rates, and concentrations of a conservative pollutant, respectively. Assume complete mixing at the intersections, no additional water loss or gain in the system, and steady state condition. Given: Q1 = 5 m3/s ; Q2 = 15 m3/s ; Q4 = 3 m3/s ; Q6 = 8 m3/s ; C1 = 8 kg/m3; C2 = 12 kg/m3; C6 = 10 kg/m3. What is the steady state concentration (in kg/m3, rounded off to two decimal place) of the pollutant in the river segment 7 ? ______
The composition and energy content of a representative solid waste sample are given in the table. If the moisture content of the waste is 26%, the energy content of the solid waste on dry-weight basis is ________ MJ/kg (round off to one decimal place).
$$ \begin{array}{|c|c|c|} \hline \text { Component } & \text { Percent by mass } & \text { Energy content as-discarded basis (MJ/kg) } \\ \hline \text { Food waste } & 20 & 4.5 \\ \hline \text { Paper } & 45 & 16.0 \\ \hline \text { Cardboard } & 5 & 14.0 \\ \hline \text { Plastics } & 10 & 32.0 \\ \hline \text { Others } & 20 & 8.0 \\ \hline \end{array} $$