Final answer:
In a water treatment process, the biological process is used to remove organic matter. The fuzzy sets B and T represent good effluent and optimal retention time, respectively. The relations R, S, and W relate retention time to BOD removal and food utilization.
Step-by-step explanation:
In a water treatment process, the biological process is used to remove biodegradable organic matter, measured as the biochemical oxygen demand (BOD). The optimal BOD of effluent should be less than 20 mg/L. The fuzzy set 'B' represents good effluent with an optimal BOD, and the fuzzy set 'T' represents optimal retention time. The relations 'R', 'S', and 'W' relate retention time to BOD removal and food utilization.
B x T (R) reflects how retention time affects BOD removal.
T x U (S) relates how retention time affects organic food consumption.
R∘S (W) represents the BOD removal and food utilization.