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The consortium has already tested INCOVER technologies individually at lab scale. The innovation of INCOVER project comes from the combination of all INCOVER technologies, for a bio-production and resource recovery-based wastewater treatment. The description of each technology is as follows:
At the research site in Barcelona, at Agropolis, the project will establish a constructed wetland to evaluate the treatment of sludge generated by the HRAP system. The Sludge Treatment Wetland (STW) will be tested to evaluate the sanitation aspects and the potential recovery of nutrients, including P, from the humified sludge. Since the sludge is dewatered and mineralized, reject water is produced and treated while water trickles through the bed. The treated water effluent from the STW will be disinfected to be reused for irrigation.
The projected effective surface area of the STW is 56 m2 and will provide treatment for the sludge and the reject water. Following the STW the design includes the installation of three wells with the necessary infrastructure to test innovative developed media for P-recovery for further use in agriculture.
The operational principle calls for the distribution of sludge on the surface of the bed, planted with common reed (Phragmites australis) and giant cane (Arundo donax). During the startup period the loading will increase gradually from a few kg dry matter (DM) per m2 and reaching up to 35 kg DM/ m2 during first year. Once the plants are developed, in the second growing season, the loading will be increased to full capacity 60 kg DM/ m2.
The sludge humification process starts once the sludge is distributed on the bed and gets in contact with the plants. Once the liquid sludge is distributed homogenously over the surface, water begins to drain from the sludge. Simultaneously, air is transported through the hollow stems and roots of the plants to the sludge layer, favouring the aerobic mineralization of the sludge. The plants in the bed will also open paths around the stems due to the movement generated by the wind that creates cracks the sludge surface and thereby paths for water to infiltrate. The plant roots also loosen up the sludge layer as the rhizomes and roots grow and new shoots develop. The start-up and the steady operation at full capacity will be monitored.
The drained water from the sludge will be pumped through wells with Sol-Gel material to test the ability of this material to retain P. The effluent will subsequently be disinfected and used for irrigation. The P retained by the Sol-Gel will be used as a source of P-fertilizer and the Sol-Gel can subsequently be reused for further P removal.
The evaporative system, developed under the umbrella of the INCOVER project, will demonstrate the nutrient and heavy metal immobilization capacity as well as the potential of humification and sanitation of digestate produced from the HRAP system installed in Chiclana. Two separated trial areas each with a surface of 250 m2 will be established. Each system will be planted with three different white Salix clones, two Eucalyptus varieties and Phyllostachys in two separate areas inside the systems. The two separated areas are to be loaded with different volumes of digestate, starting with 600 kg dry matter and to be increased to 1200 kg dry matter for the first year. The digestate applied to the beds will increase in order to assess the system’s capacity. The plant uptake is expected to increase as the plants root system develops and reaches the digestate distribution ditch.
The system will be monitored during the start-up and once it goes into a steady-state operation. The monitoring will include analysis of the digestate, the water and the plant biomass. The digested sludge will be characterised, including the content of nutrients. The biomass production and the accumulation and potential recovery of nutrients in the biomass will be analysed for the various species.
HTC is a chemical process for conversion of organic compounds to structured carbons. It can be used to make a wide variety of nanostructured carbons, from peat to carbon black, depending on time, teperature and pressure.
In INCOVER a 50L process volume installation will be used.
The ‘ideal’ input ratio between dry and liquid matter content is 20/80, which also corresponds to the HTC result. 50L process volume results in 10L HTC carbons.
Bio products which can be obtained :
- for energetic purposes (after 2 to 6 hours, after 2 hours a calorific value of 18 to 20 MJ/kg can be reached, after 4 hours ‚ 20 to 22 MJ/kg)
- or a perfect fertilizer (after 2 to 4 hours) offering for a 5 year period nutrients supply and irrigation water savings of up to 50 %