Case study 2

  • Case study 2 has been implemented in two locations : El Torno WWTP, Chiclana de la Frontera, and El Toyo WWTP, Almería, both in the South of Spain.


    • El TORNO WWTP, Chiclana

    A general flow diagram of the plant is depicted below.


    Flow diagram, El Torno WWTP



    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 right pond is still microalgae dominant because the starting up was done two weeks after the one on the right.


     Then, biomass separation is done by two clarifiers. 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.


    Photosynthetic biogas upgrading at El Torno WWTP

    An evaporative system by planted filter is used for digestate stabilization and nutrient recovery.

    Evaporative system


    El TOYO WWTP, Almeria, Spain

    A general flow diagram of the plant is depicted below.

    Flow diagram, El Toyo WWTP

     Below, this is a 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.               






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


    High rate algae pond of 3000 m2

    This is the first full-scale HRAP of this size in the world that treats wastewater directly without any anaerobic nor primary clarifiers. Waste water is simply pretreated by a grit and grease removal, while a symbiotic culture of algae-bacteria is responsible for high removal of the organic matter (>95% as BOD5), N (>70%) and P (>85%). The HRAP is mixed by a paddle wheel or alternatively by a submersible mixer system patented by aqualia, the LEAR®, Low Energy Algae Reactor, which is able to reduce mixing energy by 80%.

    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. 

    Solar disinfection, Planted filters for N and P recovery and smart irrigation