The bio filtrating device developed within the DENUTRITOR project has been tested at a pilot scale to validate the technology. The pilot testing period took place between June 2009 and September 2010. This pilot installation was constructed by Deltares and TNO and delivered in June 2009 at Perstorp (Sweden).
The device consisted of three filtrating columns that were connected serially. Every column was loaded with polyurethane foams. The porosity decreased from the first column to the third column. In other words, the specific surface area increased from the first column to the third column: it was approximately 200 m2 / m3 in the first column, 400 m2 / m3 in the second column and 700 m2 / m3 in the third column. As a result, the first filter caught the relatively large particles from the water, reducing in that way the risk of clogging. The second filter consisted of medium size pores and the last filter contained foams with fine pores so that both the anchorage and the growth of microbial biofilms could take place within. These biofilms were used to remove the last concentrations of growth substrates and nutrients that might have generated biofouling from the water stream.
An on-line sensing equipment with flow cells and sensors delivered data concerning the pH, the redox potential and the oxygen concentration of both the influent and the effluent water of the different columns. Moreover, the biofouling potential was measured. As the major part of the macromolecules of microbial biofilms consist of proteins, the biofouling potential was determined by measuring the increase of protein of microbial biofilms growing on polyethylene tubes which were exposed to the different produced waters. After an exposure period of three weeks, the polyethylene tubes were removed to quantify the microbial biofilms.
During the testing period, about 3000 m3 of water were treated. Three types of waste water were treated within the project: effluent from the Activated Sludge (AS) of the Waste Water Treatment Plant (WWTP) at Perstorp, effluent from the Membrane Bio Reactor (MBR) pilot and effluent from the Advanced Oxidation Process (AOP) pilot. Up to 92% of the biofouling potential was removed when the filter device treated the AS effluent water. Up to 91 % of the biofouling potential was removed when the system was operated with the AOP pilot. Nevertheless, with the MBR pilot, there was no significant reduction of the biofouling potential.
The pilot installation at Perstorp has demonstrated to be very effective in the field of sludge treatment and recovering. In a further step, the collaboration with a constructor of water treatment equipment is expected to demonstrate the effectiveness of the technology at full scale.