Photobioreactor turbidostat operation

Photobioreactors usually are operated according to a chemostat mode (constant dilution) or turbidostat mode (constant turbidity) of operation. Details will be explained later in this chapter but below the hiomass balance over a microalgal cultivation system is aheady presented ... 

In order to assess the volumetric productivity of the system the micro-algal biomass concentration and average specific growth rate need to be known. For the moment it will be assumed that the biomass concentration can be set at any desired level by means of a turbidostat mode of operation. Consequently, only the average specific growth rate of the microalgae in the photobioreactor needs to be calculated. 

Microalgae can be grown batchwise in photobioreactors. In case biomass concentrations become too high the culture is diluted, and biomass is harvested, after which growth is allowed to continue again. Microalgae production systems can also be operated in a continuous manner based on a chemostat or turbidostat mode of operation. Flere these three different... 

A turbidostat mode of operation relies on the use of a sensor to measure the biomass concentration in the photobioreactor. Such a sensor can be based on the online measurement of culture turbidity, for example, but any other biomass sensor can be used as well. Based on such a continuous biomass measurement the flow rate through the system then is automatically adjusted such that the biomass concentration is maintained at a preselected value (Fig. 29). 

Under outdoor conditions under day/night cycles biomass accumulation inside the photobioreactor cannot be neglected. Especially in case of chemostat operation considerable changes in biomass concentration will occur. Even in a turbidostat in the ri ht biomass concentrations will decrease because of respiration. The biomass balance then must be written as follows ... 

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