Combining all the related equations described in this chapter, following spread sheet model is developed. All the relevant links and/or equations are provided in the right column.
Spread sheet calculations are capable of predicting only steady state. In addition, there are limitations of considering all the interacting parameters simultaneously. For example, if solid retention time (SRT) decreases, autotroph population decreases and nitrification rate may decrease. However, it is not convenient to reflect the SRT effect on the potential drawback of nitrification automatically. Therefore, when spread sheet calculations are performed, the resulting parameters must be checked carefully, if those are reasonable for the given condition.
In spite of the inherent limitation, spread sheet models are widely used to obtain initial design parameters. If all the calculation logics are sound and the assumptions are reasonable, the resulting design parameters can be close enough to those predicted by sophisticated commercial software based on IWA models.
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