an aeration tank is 80 ft long, 25 ft wide and 10.5 ft deep with a mlss of 2600 mg/l. if it receives an influent flow of 250,000 gpd with a tss of 140 mg/l, what is the sludge age?

11.7 days
9.8 days
12.2 days
10.6 days

Question

an aeration tank is 80 ft long, 25 ft wide and 10.5 ft deep with a mlss of 2600 mg/l. if it receives an influent flow of 250,000 gpd with a tss of 140 mg/l, what is the sludge age?

11.7 days
9.8 days
12.2 days
10.6 days

Accepted Answer

{ "quality": "clear", "question_count": 1, "skills_matched": [ "step_cot", "multiple_choice_formatter", "explain_then_answer", "quick" ], "needs_drawing": false, "concepts_used": [ "Sludge Age Calculation", "MLSS Mass Calculation" ], "new_concepts": [], "current_concepts": [ "Sludge Age Calculation", "MLSS Mass Calculation" ] } ## Calculate the volume of the aeration tank in gallons $$ \begin{aligned} V_{\text{ft}^3} &= 80\text{ ft} \times 25\text{ ft} \times 10.5\text{ ft} = 21,000\text{ ft}^3 \ V_{\text{gal}} &= 21,000\text{ ft}^3 \times 7.48\text{ gal/ft}^3 = 157,080\text{ gal} = 0.15708\text{ MG} \end{aligned} $$ ## Calculate the mass of suspended solids in the aeration tank and the daily influent solids $$ \begin{aligned} \text{Mass}_{\text{MLSS}} &= 0.15708\text{ MG} \times 2600\text{ mg/L} \times 8.34\text{ lb/gal} = 3406.1\text{ lbs} \ \text{Mass}_{\text{influent/day}} &= 0.250\text{ MGD} \times 140\text{ mg/L} \times 8.34\text{ lb/gal} = 291.9\text{ lbs/day} \end{aligned} $$ ## Calculate the sludge age $$ \begin{aligned} \text{Sludge Age} &= \frac{\text{Mass}_{\text{MLSS}}}{\text{Mass}_{\text{influent/day}}} \ \text{Sludge Age} &= \frac{3406.1\text{ lbs}}{291.9\text{ lbs/day}} \approx 11.67\text{ days} \approx 11.7\text{ days} \end{aligned} $$

(A) 11.7 days

(B) 9.8 days

(C) 12.2 days

(D) 10.6 days

{ "subject": "Natural Science", "question_type": "Multiple Choice", "knowledge_point": [ "Natural Science", "Environmental Science", "Wastewater Treatment Calculations" ] }

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Question

Explanation:

Calculate the volume of the aeration tank in gallons

Calculate the mass of suspended solids in the aeration tank and the daily influent solids

Calculate the sludge age

Answer: