EGR 301

Applications for ARIMA

Simulations

Stabilizing the time series

Simulating the time series

Purpose

Parameterize the accelerogram.

Relate parameters to source and site parameters.

Simulate acceleration histories.

Note

Include cross-correlation for components and sites.

Include parameter uncertainty to create CI envelopes.

Used a frequency-constrained ARMA (2,2).

SCTI (recorded) Simulated (simulated)

Reliability-based Design of Wastewater Treatment Plants

Influent

Effluent

1. Simulate influent BOD mass loading

Model (1-B)(1-B7)Zt = C + at

Application Reliability-based design

2. Simulate upsets

When BOD/(NH3 +TON) > 10 upset

BOD and NH3 are positively correlated.

Model (1-B)(1-B7)Zt = C + at

Diagonal, multivariate

Application Reliability-based design

Note: multi. ARMA predicts half of univ. upsets.

3. Plant operation

Permit: Weekly BOD effluent average < 20 mg/l 90% of time.

Question: What should BOD effluent be?

Model: (1-B)ln(Zt) = C + at

From simulations take weekly averages.

(Present mean/present 99% reliability value) = (target mean/permit value)

3.14/5.9 = target mean/20 target mean = 10.6 mg/l

Note: assume constant coefficient of variation ()