LEQUIA researcher Esther Vega Martínez will defense her doctoral thesis’ dissertation entitlted “Minimisation and abatement of volatile sulphur compounds on sewage sludge processing” next 30th July. The thesis was directed by Dr Maria Martín and Dr. Rafael González and is focused on the reduction of odour emission by sulphur compounds in sewage sludge processing.
Environmental pollution related to odour emission has become in the last years an important public concern. Closeness of odour-causing facilities such as waste water treatment plants (WWTPs) to urban areas further aggravates the problem. Volatile sulphur compounds (VSC) are one of the main groups of odour causing compounds in WWTPs, especially in the sludge processing. Nowadays, there are a variety of options available for the effective treatment of odorous sulphur compounds emission. This thesis has focused on the minimisation during sewage sludge processing and the abatement of these compounds by treatments at the end-of-pipe.
Related to the minimisation processes, the research has focused on the effect of chemical (iron chloride, calcium oxide and polyelectrolyte) and physical conditioners (activated carbon and fly ash) on sewage sludge conditioning process in order to minimise the odour emissions during sewage sludge drying process at low temperature. The obtained results permitted to optimise the conditioning process and to know the synergistic effects between inorganic conditioners on odorous compounds emissions.
Despite the modification on process would improve the end-of-pipe technologies, these modifications are not sufficient to mitigate the emissions of odorous sulphur compounds in sludge processing. Therefore, the adsorption and advanced oxidation processes (AOP) has been assessed in this thesis as end-of-pipe treatments.
The effectiveness of UV/H2O, Fenton, photo-Fenton and ozone on the oxidation of a multicomponent aqueous solution containing VSC (ethyl mercaptan, dimethyl sulphide and dimethyl disulphide) was investigated in order to asses which was the most suitable treatment to be coupled in a wet scrubber used in odour treatment facilities. The oxidation percentage results revealed all studied AOP are suitable to oxidise VSC, especially photo-Fenton and ozone treatments. Furthermore, the possible implementation of AOPs in full-scale systems was assessed by the economic analysis. The results revealed that volume limitations or retrofitting complexities play an important role in establishing the most economical option.
Finally, the effectiveness of activated carbon (AC) for the VSC removal was also investigated. Adsorption dynamic tests were carried out supported by a predictive model which allowed to establish the chemical interactions between VSCs and AC. The results revealed the effect of hydroxyls groups in AC surface on the improvement of AC adsorption capacities for etil mercaptan and dimethyl sulphide under inert conditions. Nevertheless, this behaviour was not observed with the presence of humidity and oxygen because of these conditions prevented the VSC adsorption processes.
The defense will be held next Wednesday 30th July at 10:30h at the UdG Escola Politècnica Superior (Sala d’Actes).