Fluidized bed reactor upscale for treatment of commercial laundry wastewater combined with domestic sewage: optimization of operational conditions and taxonomic and functional characterization of microorganisms in biofilm

Author(s)

Thais Zaninetti Macedo

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2019-01-25

Examining board members

Maria Bernadete Amancio Varesche Silva; Eduardo Lucena Cavalcante de Amorim; Iolanda Cristina Silveira Duarte; Arnaldo Sarti; Eliana Guedes Stehling

• Advisor: Maria Bernadete Amancio Varesche Silva

Abstract

The linear alkylbenzene sulfonate (LAS) is in the laundry detergent composition and it presents complex degradation. Through kinetics assays in batch tests, an inhibition kinetic model by subtrate excess was adjusted to the data in the removal of LAS and organic matter from laundry wastewater (LW) in co-digestion with domestic sewage (DS). The addition of 50 mg L-1 of ethanol (EOH) to the influent resulted in higher values for the specific substrate rate (robs) as well as higher LAS concentration that provided the maximum LAS utilization rate by the biomass (Sbm) (18.98 mg LAS L-1 and 2. 39 mg LAS L-1 in the presence and absence of ethanol, respectively). Sand with 1.0 mm of diameter was chosen as supporting material for the fluidized bed reactor (FBR). The purpose of the present study was to optimize the removal of surfactant in LW + DS (1: 3 volume; &#8764; 20 mg LAS L-1) by using an upscale FBR (19.8 L) through: (i) adding ethanol in different dosages; (ii) varying the upflow velocity (vup) applied to bed; and (iii) increasing the hydraulic retention time (HRT). Thus, for 18h of HRT, the following stages were performed: (I) LW + DS + 1,3 fluidization minimum velocity (vfm); (II) LW + DS + 50 mg EOH L-1 + 1.3 vfm; (III) LW + DS + 200 mg EOH L-1 + 1.3 vfm; (IV) LW + DS + 200 mg L-1 + 1.0 vfm; (V) LW + DS + 200 mg L-1 + 0.7 vfm; (VI) LW + DW + 100 mg L-1 + 1.0 vfm; and for 30 h of HRT: (VII) LW + DS + 1.0 vfm. There was no significant difference in the efficiency of COD and LAS removal (&#8764; 50%, p < 0.5) in stages I to IV. The vup decrease (0.7 vfm) resulted in LAS removal efficiency of 29% (V) and the HRT increase resulted in LAS removal efficiency of 86% (VII). In stages VI and VII, COD removal &#8805; 70% was observed. Lower vup as well as ethanol dosage of 200 mg L-1 favored system acidification (IV and V). In the FBR effluent, 17 recalcitrant compounds were identified. For vup = 0.7 vfm, large diversity of recalcitrant compounds, mostly phthalates, was observed. A taxonomic and functional characterization of the microorganisms was performed by metagenomics analysis in stages III, IV and V (vup variation) and VII (higher efficiency of LAS and COD removal). Microorganisms of Archaea and Bacteria domains were identified, and the decrease of vup resulted in a higher relative abundance of methanogenic archaea, mainly Methanosarcina. Genes related to F420, which are the central electron carrier in the methanogenesis, were identified. Genera diversity was classified in Bacteria domain (Geobacter, Thauera, Pseudomonas, Pseudomonas, Chryseobacterium, Sulfuricurvum and Sulfurospirillum, etc.). Enzyme-encoding genes that act on different stages of LAS degradation were found: (a) addition of fumarate (fumarate reductase); (b) beta-oxidation (3-hydroxyacyl-CoA dehydrogenase); (c) benzene ring cleavage (benzoyl-CoA reductase) and (d) desulfonation (Adenylyl-sulfate reductase). In stage VII sample, genes related to the desulfonation step were identified with higher relative abundance, when compared to the other stages. For a higher vup, a higher relative abundance of genes related to oxidative phosphorylationwas observed and the genus main representative in that category was Chryseobacterium. (AU)

• FAPESP's process: 15/02640-2 - Scale-up of fluidized bed reactor for treatment of commercial laundry wastewater plus domestic sewage: optimization of operational conditions
• Grantee: Thaís Zaninetti Macedo Carmelo
• Support Opportunities: Scholarships in Brazil - Doctorate