Object and objectives of the project
The object of the project is to investigate the development of the removal of the non-biogradableorganic matter (usually expressed as “Dissolved Organic Carbon”, DOC), as well as selected micro pollutants (“priority pollutants “) from the effluent of wastewater treatment plants, through the application of heterogeneous catalytic ozonation. The original pre-industrial unit is based on the innovative technology of bubble-less ozonation using membranes.
In particular, the individual actions include:
- The laboratory study for the discovery of new alternative (mainly inorganic) low-cost materials, which can be used as catalysts for heterogeneous catalytic ozonation.
- The investigation of the main parameters that affect this process (e.g. ozone concentration, type of catalyst, pH, temperature), both in laboratory (discontinuous) experiments, as well as in continuous flow experiments, in order to optimize the process.
- The design, construction and operation in real “field” conditions of an original unit of pre-industrial scale continuous operation for the efficient and relatively low cost of removal from the treated wastewater of the non-biodegradable organic matter (DOC), as well as certain characteristic micro pollutants, characterized as “priority pollutants”, where ozone will be added through an appropriate membrane (contactor) with diffusion without bubbles (bubble-less ozonation).
- The evaluation of energy savings, as well as all other critical parameters, in relation to the currently applied technology and processes in the existing wastewater treatment plant.
- The investigation of the effects on the total operation of a wastewater treatment plant from the application of the proposed technology.
The project sets clear scientific and technological goals and seeks to achieve specific results, which can apply to the development and optimization of processes and services.
Also, technical know-how will be acquired on the mechanisms and operating conditions of a complex process, such as that of heterogeneous catalytic ozonation. After the end of the project, this technical know-how can be applied to the rest of EYATH’s wastewater and water treatment plants, as well as to respective units both in Greece and abroad, with the aim of destroying the remaining ones after the conventional treatment of micro-pollutants and therefore, the protection of aquatic life and, by extension, human health, which are at risk from long-term exposure to these pollutants.
Project Implementation Methodology
Initially, a literature review of non-biodegradable organic matter (DOC) and the main micro-pollutants found in water and wastewater, as well as the catalysts used to remove them by applying heterogeneous catalysis, was carried out. At the same time, began a preliminary monitoring of the secondary effluent of the W.W.T.P Aineias, for the identification of micro-pollutants in order to study in detail their seasonal variances and to update their species that are not removed or partially removed with the existing conventional technology. After the initial detection of the micro pollutants, discontinuous laboratory experiments were carried out, in order to find-create-characterize the appropriate material, which will be used as a catalyst for their removal in the experiments of the original continuous operation unit.
The impact of various parameters on process optimization, the effectiveness of their removal, as well as the kinetics with which it is performed, were investigated. For this purpose, discontinuous and continuous laboratory experiments were carried out, where the effect of ozone concentration (2-3 mg/L), the type of catalyst (1-10 g/L), the pH (standard values 6-8), the temperature (15, 25, 35 oC) and the reaction time (usually 1-30 min) on the process performance were examined. In each sample is determined the residual concentration of ozone, the percentage of removal of the micro-pollutants studied, as well as the percentage of removal of total organic carbon (TOC).
The pilot unit of catalytic ozonation is located at the Wastewater Treatment Plant of Tourist Areas of Thessaloniki (W.W.T.P. Aineias), which is a representative example of similar units and already has an ozonation system with bubble diffusers.
The design of the original continuous operation pre-industrial unit began from the beginning of the program with the construction of the sample feed and the ozone transfer column to the wastewater by diffusion through appropriate membranes without bubble-less ozonation. Upon completion of the laboratory experiments, the catalytic ozonation column was designed, constructed and incorporated into the pre-industrial scale unit.
The design of the original continuous operation pre-industrial unit began from the beginning of the program with the construction of the sample feed and the ozone transfer column to the wastewater by diffusion through appropriate membranes without bubble-less ozonation. Upon completion of the laboratory experiments, the catalytic ozonation column was designed, constructed and incorporated into the pre-industrial scale unit.
The plant has the capacity to process 50-200 L/h from the secondary effluent and includes three individual processing parts: Filtration in a double activated carbon-sand bed, bubble-less ozonation in combination with a catalytic filtration bed and the final biological stabilization-filtration in a double activated carbon -sand bed.
The operation of the original unit will help to optimize the removal of micropollutants and organic matter in field conditions. The initial operating parameters that applied in this plant were based on the values determined in the laboratory experiments and were checked the corresponding percentages of removal of the non-biodegradable organic matter (DOC) and the characteristics micropollutants.