A conventional activated-sludge system treats 11,000 m³/day of wastewater with a BOD of 180 mg/L in an aeration tank with a volume of 3400 m³. The operating conditions are an effluent suspended solids of 20 mg/L, a MLSS concentration maintained in the aeration basin of 2500 mg/L, and an activated-sludge wasting rate of 160 m³/day containing 8000 mg/L. From these data, calculate the aeration period, volumetric BOD loading, F/M ratio, and sludge age.

A sample of diluted wastewater (diluted 10 times) has a 5-day biological oxygen demand (BOD) of 5 mg/L. If the rate constant is 0.1/d, assuming a first-order chemical reaction, the ultimate BOD of the original wastewater is most nearly (A) 0.50 mg/L (B) 5.0 mg/L (C) 13 mg/L (D) 130 mg/L

This is for a water and wastewater review. It's not for a grade I just need to understand the problem, please include equations and  choose one of the answer choices.

The 750-bed Associated Center of Medical Excellence (ACME) Hospital has a small activated sludge plant to treat its wastewater. The average daily Medical Center discharge is 1,250 L per day per bed, and the average soluble BOD5 after primary settling is 450 mg/L. The aeration tank has effective liquid dimensions of 10.0 m wide by 25.0 m long by 3.5 m deep. The plant operating parameters are as follows: MLVSS = 2,750 mg/L MLSS = 1.25 (MLVSS) Settled sludge volume after 30 min = 250 mL/LDetermine the following: aeration period, F/M ratio, SVI, solids concentration in return sludge.