Question

Two activated sludge aeration tanks at Twickenham Park Estates are operated in series. Each tank has the following dimensions: width 7 m, length 30 m, effective fluid depth 4.3 m. The plant's operating parameters are as follows:

(i) Flow = 0.0796 m/s
(ii) Soluble BOD after primary settling = 130 mg/l
(iii) MLVSS = 1500 mg/l
(iv) MLSS = 2100 mg/l
(v) Settled sludge volume after 30 minutes = 230.0 ml/l

It is desired that the soluble BOD5 within the effluent leaving the plant be 8 mg/L. If the insoluble BOD5 associated with the final effluent leaving the plant is 30% of the current NEPA TSS standard, what is the maximum BOD5 expected in the final effluent stream for this well-mixed activated sludge plant?

Answer 1

The maximum expected BOD5 in the final effluent from the activated sludge plant is the sum of the targeted soluble BOD5 (8 mg/L) and 30% of the NEPA TSS standard value as the insoluble BOD5.

Step-by-step explanation:

To determine the maximum BOD5 expected in the final effluent stream for a well-mixed activated sludge plant, we must consider the reduction of soluble BOD due to the treatment process and add the insoluble BOD associated with the suspended solids in the final effluent.

According to the information provided, the soluble BOD5 within the effluent is to be 8 mg/L. The insoluble BOD5 is given to be 30% of the current NEPA TSS standard.

Assuming the NEPA TSS standard is known, calculate 30% of this value to determine the contribution of insoluble BOD5 to the final effluent BOD5. The sum of these two values gives the maximum BOD5 expected in the final effluent stream.

Without the actual NEPA TSS standard value provided, we cannot calculate an exact figure for the final effluent BOD5. However, the maximum BOD5 will be the sum of the desired soluble BOD5 (8 mg/L) and the 30% of NEPA TSS standard as the insoluble BOD5.