Case study 2

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    PHA production is made through a two stage anaerobic-photosynthetic HRAP system. Two HRAP (High Rate Algae Pond) systems (32 m2) are operated with an innovative strategy developed at lab scale (5 liters), consisting of pulse feeding of municipal wastewater pretreated in an UASB reactor with molasses as COD source. After several weeks of operation, purple bacteria have been selected (see on the left pond on the photo below), which are able to accumulate PHA. The process will be optimized in the following months.

     

    The right pond is still microalgae dominant because the starting up was done two weeks after the one on the right.
    PHA reactors - Biomass decanting

     

     Then, biomass separation is done by two clarifiers, including biomass recycled to the system. After PHA production, the remaining biomass is transformed into biogas using thermal pre-treatment and an anaerobic co-digestion process. Agro wastes and sewage sludge are used as co-substrates. Biomethane is produced by an innovative biogas upgrading system, through photosynthetic fixation of CO2 as algal biomass using digestates as a source of nutrients. An evaporative system is used for digestate stabilization. All these tasks are installed and operated at El Torno WWT plant, Chiclana de la Frontera in Spain. 

     

    Evaporative system
    Case study 2 at El Torno Wastewater treatment plant, Chiclana de la Frontera

    The site in Almería is under full operation.

    A demo scale 3000 m2 HRAP is installed at El Toyo wastewater treatment plant (Almería, Spain) to obtain irrigation quality water. This HRAP system is treating raw wastewater.

    High rate algae pond of 3000 m2

    This is the first demo-scale installation of a HRAP treating raw wastewater of this type in the world. It is the first full scale installation with a solids removal screening as the sole pretreatment. Effluents are mixed with paddle wheel.

    Paddle wheel mixing in operation

    After harvesting by flotation, the effluent is treated using planted filters with natural material for enhancing P and N recovery. Irrigation water is be obtained and reused with solar anodic oxidation disinfection and a smart irrigation system. 

    Planted filters for N and P recovery
    General picture of the installation, including planted filter with excellent growth and performance, solar disinfection system with excellent disinfection efficiencies, and smart irrigation of grass.
    Figure 2 : Case study 2 at El Toyo Wastewater treatment plant, Almería