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Modeling of environmental phytoremediation systems for organic pollutants

Petousi Margarita

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Summary

Phytoremediation is a state-of-the-art technology that uses plants and microorganisms that grow synergistically with them to remediate environmental pollution (soil, sludge, sediments, groundwater and surface water). Phytoremediation has multiple advantages over physico-chemical methods of decontamination, the main ones being that it has low cost, is environmentally friendly and does not require special technical expertise in its implementation.In the first part of the present thesis the performance of pilot scale phytoremediation units for Olive mill wastewater (OMW) treatment has been experimentally investigated. Plant species tested were Juncus acutus L., Tamarix parvifora DC., Punica granatum L. and Myrtus communis L.. The configuration of the pilot units was according to the corresponding technology of Santori and Cicalini (2002), whereas OMW is undergoing remediation as it recirculates through soil planted with trees. The aim of this work was to examine the behaviour of the plants in the environment of the wastewater, as well as to estimate the percentage removal of selected OMW constituents. In summary, experimental results showed that the average removal rate of organic and nutrient components of OMW in the pilot units is within the range of the corresponding areal removal rates reported in the relevant literature concerning CWs treating OMW. P. granatum and M. communis plants proved robust in the treatment of OMW with COD concentration up to ~ 12 400 mg/L and even showed faster growth than the corresponding control plants. The application of the specific plant species in this technology strengthens the character of its circular economy, as it provides the advantage of the parallel production of high economic value products, such as pomegranates and myrtles, as well as their by-products.In the second part of the thesis, a mathematical mechanistic state-space model was developed to describe the pilot phytoremediation systems with P. granatum and M. communis plants. The model was further applied to estimate the relative contribution of plant-related processes to the overall OMW remediation within the experimental cycles performed. As a result, the processes of rhizodegradation and uptake by plants (through evapotranspiration) were shown to contribute more than 91% in total to the removal of organic and nutrient components of OMW, regardless of the organic load of the wastewater.A simple mechanistic model was additionally developed in the context of organics phytoremediation modeling work in the present thesis. The model describes the dynamics of bisphenol-A (BPA) remediation in a pilot phytoremediation unit, simulating a shallow aquifer with the presence of J. acutus plants. The results from the model simulation showed that for the specific pilot system and experimental context, the processes of hydrolysis and microbial degradation in the rhizosphere of the plants jointly contribute to the removal of BPA in a total percentage greater than 97%.

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