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| Author(s): |
Luan de Souza Leite
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD) |
| Defense date: | 2024-06-07 |
| Examining board members: |
Luiz Antonio Daniel;
Sidney Seckler Ferreira Filho;
José Roberto Guimarães;
Cassiana Carolina Montagner;
Rodrigo Braga Moruzzi
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| Advisor: | Luiz Antonio Daniel |
| Abstract | |
 The presence of algal organic matter (AOM) in the water reservoir is a growing concern for drinking water treatment since the technologies traditionally used in the treatment system are not efficient for AOM removal. Chlorella sorokiniana is a microalgae which flourishes under conditions of high light intensity and temperature, thus its prevalence in algal blooms is expected to increase with climate change. However, Chlorella sorokiniana AOM has not been previously investigated. In this context, the present work aims to study the impact of the presence of Chlorella sorokiniana AOM in water reservoirs and alternative and complementary methods for its removal. The Chlorella sorokiniana AOM is a more potent disinfection byproduct precursor than 80% of algae previously investigated in the literature. The concentrations of trihalomethanes and chloral hydrate were 57.9 and 46.0 μg·mg DOC-1 after chlorination, while the concentrations of trihalomethanes, chloral hydrate, haloacetonitrile, 1,1,1-trichloropropanone and chloropicrin were from 33.6; 29.8; 16.7; 2.1 and 1.2 μg·mg DOC-1 after chloramination, respectively. Chloramination decreases the formation of trihalomethanes (42%) and chloral hydrate (35%) but acted as a precursor for the formation of nitrogenous byproducts. Although AOM did not show toxicity at the expected environmental concentration (5 mg·L-1), the formation of disinfection by-products after chlorination may pose a risk to aquatic species, as demonstrated by tests with the cladocerans Ceriodaphnia silvestrii and Daphnia similis. In this context, this study investigated the application of advanced oxidative processes (Fenton and photo-Fenton) and adsorption (alternative activated carbons and new adsorbents) as potential treatments for the removal of Chlorella sorokiniana AOM. The AOM removal by adsorption using four types of granular activated carbon (bituminous, palm coconut, babassu coconut and bovine bone) was verified. High removals were found for bituminous (99.5%), babassu coconut (95.5%), bovine bone (88.2%), and palm coconut (78.8%). Traditional bituminous activated carbon showed the best performance for AOM removal, however, babassu coconut was also effective and had efficiencies close to bituminous activated carbon. Regarding the new adsorbents, high removals were found for mesoporous silica SBA-16 (88.8%) and citric acid (70.0%), while moderate removals were found for sugar (60.5%) and immobilized citric acid in sand (67.4%). Low removal was found for hydrogen peroxide (12.02%) and the highest removals for Fenton (29.8%) and photo-Fenton (67.0%) were found in the reaction time of 150 min and using 40 and 30 mg Fe.L-1, respectively. The results found elucidated the first insights about Chlorella sorokiniana AOM and potential complementary treatments to the technologies used in drinking water treatment plants for the AOM removal of this specie. (AU) | |
| FAPESP's process: | 19/05759-1 - Study of Algal Organic Matter (AOM) removal by coagulation-flocculation and use of pre-treatments |
| Grantee: | Luan de Souza Leite |
| Support Opportunities: | Scholarships in Brazil - Doctorate |