048 On-line identification of the dissolved oxygen dynamics in an activated sludge process

In this paper, a novel approach to estimate the respiration rate in an activated sludge process is developed. The proposed estimator for the respiration rate is simple to implement and can be used during normal closed loop control of the dissolved oxygen. The basic idea is to use a two step procedure where in the first step, a model of the oxygen transfer rate KLa is estimated from a data set. The nonlinear KLa function is modelled with a static, constrained, piecewise linear model. In the second step, the respiration rate is estimated from measurements of dissolved oxygen concentration and air flow rate using the KLa model obtained in step 1.

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Improving oxygen concentration control in activated sludge process with estimation of respiration and scheduling control

Water Science & Technology ◽

10.2166/wst.2006.133 ◽

2006 ◽

Vol 53 (4-5) ◽

pp. 283-291 ◽

Cited By ~ 8

Author(s):

S. Gerkšič ◽

D. Vrečko ◽

N. Hvala

Keyword(s):

Dissolved Oxygen ◽

Activated Sludge ◽

Oxygen Concentration ◽

Pi Controller ◽

Activated Sludge Process ◽

Dissolved Oxygen Concentration ◽

Integral Control ◽

Process Dynamics ◽

On Line ◽

The Cost

The paper presents an efficient and simple model-based method of on-line estimation of respiration from the current values of dissolved oxygen concentration and airflow signals. Fast estimation of respiration is important because respiration appears as the most important disturbance signal in the control of dissolved oxygen concentration, and could therefore be used for improving control efficiency. A parameter scheduling PI (proportional and integral) control scheme is proposed, where the estimated respiration signal is used for scheduling of the PI controller parameters, by using local linearization of the process dynamics. The performance of the scheduling controller is compared to a conventional PI controller in simulation using the COST simulation benchmark, and experimentally on an activated sludge process pilot plant.

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Respirometry for determination of the influents SS-concentration

Water Science & Technology ◽

10.2166/wst.1996.0031 ◽

1996 ◽

Vol 33 (1) ◽

pp. 311-323 ◽

Cited By ~ 2

Author(s):

A. Witteborg ◽

A. van der Last ◽

R. Hamming ◽

I. Hemmers

Keyword(s):

Experimental Design ◽

Activated Sludge ◽

Substrate Concentration ◽

Full Scale ◽

Activated Sludge Process ◽

Respiration Rates ◽

On Line ◽

Large Measurement ◽

Set Up

A method is presented for determining influent readily biodegradable substrate concentration (SS). The method is based on three different respiration rates, which can be measured with a continuous respiration meter which is operated in a cyclic way. Within the respiration meter nitrification is inhibited through the addition of ATU. Simulations were used to develop the respirometry set-up and decide upon the experimental design. The method was tested as part of a large measurement programme executed at a full-scale plant. The proposed respirometry set-up has been shown to be suitable for a semi-on-line determination of an influent SS which is fully based on the IAWQ #1 vision of the activated sludge process. The YH and the KS play a major role in the principle, and should be measured directly from the process.

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