Manifold sectors such as tannery, pulp and paper, petroleum, petrochemical, textile, pharmaceutical, solid wastes landfills, and pesticides processing industries generate wastewater containing pollutants which are refractory to the microorganisms’ action in conventional biological treatment systems. An additional cleaning step is thereby required to remove remnants such as recalcitrant organic compounds, which remain unaltered through biological treatment. Conventional extra steps are not only creating large amounts of sludge but are also costly.
In a new ozone-enhanced biological degradation process for industrial wastewater treatment, the Water Research Institute (IRSA) of the Italian National Research Council (CNR) has developed a method that generates small amounts of excess sludge. The technology is an integrated system combining the application of biological treatment with ozonation.
The biological unit of the system is based on SBBGR (Sequencing Batch Biofilter Granular Reactor) technology, improving the quality of the treated effluent and decreasing the amount of waste created in the wastewater treatment process. The reactor operational conditions assure that the microbes, growing as granules, are not given suitable conditions to proliferate, thus producing less sludge. The filtrating biological unit (bio filtrating) is combined with a chemical unit, using ozone. Ozone is a powerful oxidiser that can break down most organic compounds, but is also very costly. In the new system, ozone does not completely break down the pollutants but transform them into more biodegradable compounds. The ozone is also used in a more selective way, targeting the recalcitrant compounds. The amount of ozone needed has thereby been brought down by 20-30%, lowering the treatment costs. In comparison with strictly implementing serially a biological treatment and an ozonation process, combining the biological degradation and ozonation units has clear advantages among which the creation of synergistic effects that increase the overall efficiency of the removal process.
Part of the development of the new system consisted of the testing and the up-scaling of the technology within the INNOWATECH project (Innovative and Integrated Technologies for the Treatment of Industrial Wastewater, 2006-2010). The project was financially supported by the European Commission under the Sixth Framework Program (FP6), a grant funding programme, and investigated the potential of a number of different advanced technological solutions for treating municipal and industrial wastewater. The aim was to develop innovative technologies and integrated solutions to some common industry-related problems in water and wastewater treatment achievement. One of the main conclusions of the project was that biological treatment, when enhanced by ozone, could reduce sludge production. The project consortium was coordinated by IRSA in Italy and consisted of 17 partners from 8 European countries and Australia.
The integrated system has also been further developed and demonstrated in the project PERBIOF (funded by the LIFE programme), where the efficiency of the process was established when applied to tannery wastewater; the sludge production was reduced by 25-30 times and the operating costs were cut with 60%. The benefits obtained for tannery wastewater treatment can be transferred to any other industrial wastewater containing bio refractory compounds. Tests have been performed for the textile industry, processing chemical industry and municipal wastes landfilling, but application to other production processes will need some tailoring and feasibility tests. The technology readiness level for the developed system is estimated to be 9 on the TRL scale, according to the scope of the LIFE funding mechanism, which provides public grant funding for demonstration and commercial exploitation.