Development of an air-scour control system for membrane bioreactors

Abstract

The thesis involves the development and implementation of a new and

robust control system based on permeability trends but at the same time capable of

reducing aeration proportionally to permeate flux. Permeability was made a key

parameter for directly comparing temporary changes in membrane performance.

Transmembrane pressure and flux were gathered every 10 seconds and permeability

values were automatically calculated; different mathematical algorithms were applied

for the signal filtering of on-line data. Short term and long term permeability trends

were compared once a day, and a control action was applied proportionally to the short

term/long term permeability ratio without exceeding the aeration flow recommended by

the membrane suppliers.

El treball presentat a la tesi inclou el desenvolupament i la implementacio d’un nou

sistema de control robust basat en les tendencies de la permeabilitat i, al mateix temps,

capac de reduir l’aeracio de forma proporcional al flux de permeat. S’ha seleccionat la

permeabilitat com el parametre clau per comparar directament els canvis temporals en el

funcionament de les membranes. La pressio transmembrana i el flux es mesuren cada 10

segons i llavors la permeabilitat es calcula automaticament. El senyal de les dades

recollides en linia es filtra adequadament mitjancant diversos algoritmes matematics.

L’algoritme de control compara diariament una tendencia a curt termini de la

permeabilitat amb una tendencia a llarg termini de la permeabilitat, i s’aplica una accio

de control proporcional al quocient de les dues tendencies, sense excedir mai el cabal

d’aeracio recomanat pels fabricants de membranes.