SELECTED CHEMOAUTOTROPHIC PROCESSES IN WASTEWATER TREATMENT: LOW TEMPERATURE NITRIFICATION INHIBITION BY AN AZO DYE AND BIOFILTRATION FOR ODOR CONTROL OF HYDROGEN SULFIDE

Biochemical processes by chemoautotrophs such as nitrifiers and sulfide and iron oxidizers are used extensively in wastewater treatment. The research described in this dissertation involved the study of two selected biological processes utilized in wastewater treatment mediated by chemoautotrophic bacteria: nitrification (biological removal of ammonia and nitrogen) and hydrogen sulfide (H2S) removal from odorous air using biofiltration. A municipal wastewater treatment plant (WWTP) receiving industrial dyeing discharge containing the azo dye, acid black 1 (AB1) failed to meet discharge limits, especially during the winter. Dyeing discharge mixed with domestic sewage was fed to sequencing batch reactors at 22oC and 7oC. Complete nitrification failure occurred at 7oC with more rapid nitrification failure as the dye concentration increased; slight nitrification inhibition occurred at 22oC. Dye-bearing wastewater reduced chemical oxygen demand (COD) removal at 7oC and 22oC, increased i effluent total suspended solids (TSS) at 7oC, and reduced activated sludge quality at 7oC. Decreasing AB1 loading resulted in partial nitrification recovery. Eliminating the dye-bearing discharge to the full-scale WWTP led to improved performance bringing the WWTP into regulatory compliance. BiofilterTM, a dynamic model describing the biofiltration processes for hydrogen sulfide removal from odorous air emissions, was calibrated and validated using pilot- and full-scale biofilter data. In addition, the model predicted the trend of the measured data under field conditions of changing input concentration and low effluent concentrations. The model demonstrated that increasing gas residence time and temperature and decreasing influent concentration decreases effluent concentration. Model simulations also showed that longer residence times are required to treat loading spikes. BiofilterTM was also used in the preliminary design of a full-scale biofilter for the removal of H2S from odorous air. Model simulations illustrated that plots of effluent concentration as a function of residence time or bed area were useful to characterize and design biofilters. Also, decreasing temperature significantly increased the effluent concentration. Model simulations showed that at a given temperature, a biofilter cannot reduce H2S emissions below a minimum value, no matter how large the biofilter.

Octyl co-grafted PrSO3H/SBA-15:tunable hydrophobic solid acid catalysts for acetic acid esterification

Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post modification of mesoporous SBA-15 silica with mercaptopropyltrimethoxysilane (MPTMS), with the impact of co-derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst investigated. Turn over frequencies (TOF) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families suggesting a cooperative effect of adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co-functionalisation with hydrophobic octyl chains, with inverse gas chromatography (iGC) measurements indicating increased activity correlates with decreased surface polarity or increased hydrophobicity.

Sviluppo di un metodo termoanalitico per la quantificazione di microplastiche in matrici complesse

Microplastics (MPs) are highly debated emerging contaminants that are widespread on Earth. Nowadays, assessment of the risk that MPs pose on human health and environment were not developed yet, and standardized analytical methods for their quantification in complex matrices do not exist. Therefore, the formulation of standards which regulating MPs emission in the environment is not possible. The purpose of this study was to develop and apply a method for the analysis of MPs in sewage sludges and water from a wastewater treatment plant (WWTP), due to the relevance of those matrices as important pathway for MPs to enter the environment. Seven polymers were selected, because of their relevance on market production and their frequency of occurrence in such plants: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyvinyl chloride (PVC), and nylon 6 (PA-6). In the study, a pre-treatment procedure was optimised using Fenton’s reagent and analyses carried out by combining thermochemolysis with Py-GC-MS after sample filtration on quartz (0.3 µm). Polymer quantification was performed with solid polymer mixture in silica and good correlations were obtained with internal calibration. As main results, Fenton's reagent negatively affected the recovery of some polymers (PP, PE, PS, PA-6) and a possible matrix interference was noticed, especially for PET and PVC. The WWTP allowed a good abatement of PS, PE, PP and PVC (on average 90 %) and comparable results were hypothesised for the other polymers. Polymer concentrations is sewage sludges ranged between < 2 μg/gdry and 3.5 mg/ gdry, for PC and PVC, respectively. Possible overestimations for PET and PVC, due to matrix interreferences, were taken into account and discussed.