Research And Development Of On-line Measurement And Control Technology For Planktonic Algae Photobioreactor

The photosynthetic activity of planktonic algae is sensitive to external pollution toxicity,and it is an ideal test organism for rapid detection of the toxicity of water pollutants.It has gradually become a research hotspot in the field of online monitoring of water quality biological toxicity.Planktonic algae photobioreactors are mainly used for continuous testing of algae.Online culture is a necessary device for online monitoring of water quality and biological toxicity.Traditional planktonic algae photobioreactors mostly use algae biomass indicators to automatically control the cultivation process,and lack the measurement and control of the photosynthetic activity state of the algae,and it is difficult to meet the needs of the on-line culture of the tested algae based on the photosynthetic activity of the algae.In view of this,the photosynthetic activity state and biomass of the tested algae species under different temperature and light gradients were analyzed through experiments to obtain the response law of the algae growth state to the two main environmental conditions of temperature and light;on this basis,temperature and light The two main environmental factors are the control objects of the algae cultivation process,and the photobioreactor online measurement and control system has been developed;it provides the tested algae species online cultivation device for the online water quality comprehensive toxicity detector based on the photosynthetic activity of the algae.The main content of this paper includes:Firstly,the effect of temperature and light on the photosynthetic activity of Chlorella proteinacea was obtained by controlling different gradients of light and temperature,from which we can see that when the light intensity is below 375 μmolphoton-m^(-2)-s^(-1)and the temperature is below 25°C,the photosynthetic activity of Chlorella proteinacea has been maintained at a high and stable state,and its specific growth rate in culture increases with the increase of light and temperature.Through research and experimental analysis,the effects of culture environment conditions on the photosynthetic reaction and growth process of the algae were understood in depth,and the needs of the photobioreactor for the measurement and control of the tested algae based on algal photosynthetic activity for water biotoxicity testing were summarised,as well as the problems and deficiencies faced by the existing photobioreactors.The key measurement parameters(light,temperature and photosynthetic activity parameters,etc.)and key regulation parameters(nutrient salt supplementation,replenishment,CO2 supplementation,temperature control and light control)of the target photobioreactor were identified.Based on this,the overall scheme and control method of the planktonic algal photobioreactor is designed and the performance of the core components of each functional module of the system is compared and selected.Finally,the hardware and software design of the system is carried out according to the system design scheme.In order to achieve the measurement and regulation of the key parameters of the target photobioreactor,the main structure of the photobioreactor hardware is designed based on previous work.According to the temperature control requirements,a TEC high-precision temperature control circuit and a constant current source bridge temperature measurement circuit were designed;according to the light control requirements,a PWM pulse light regulation circuit was designed,a water-PAM photosynthetic activity parameter detection sensor was integrated,and a digital PID algorithm-based software for the measurement and control of light,temperature and photosynthetic activity was developed,thus developing the planktonic algal photobioreactor.