Degradation of anionic surfactant in UASB reactor with laundry wastewater

Author(s)

Dagoberto Yukio Okada

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2012-07-25

Examining board members

Maria Bernadete Amancio Varesche Silva; Sérgio Francisco de Aquino; Eugenio Foresti; Isabel Kimiko Sakamoto; Adriana Lopes dos Santos

• Advisor: Maria Bernadete Amancio Varesche Silva

Abstract

Linear alkylbenzene sulfonate (LAS) is a surfactant present in laundry wastewater. Due to the complexity of its degradation, the present study involved the analysis of some features, highlighting: co-substrates diversity; hydraulic retention time (HRT); and co-substrates concentration. The LAS degradation with different co-substrates (methanol, ethanol and yeast extract) was evaluated in UASB reactor, at HRT of 24 h and LAS 14±2 mg/L. The influence of HRT and concentration of co-substrates was analyzed in seven UASB reactors, with LAS 12±3 mg/L; the HRT was 6, 35 and 80 h, and different concentration of co-substrates (methanol, ethanol and yeast extract), as specific organic load rate (SOLR) between 0.03 and 0.18 gCOD/gTVS.d. At the end, the LAS degradation was performed in UASB reactor fed with diluted laundry wastewater, at HRT of 35 h and LAS 10±5 mg/L. In all assays was used a granular inoculum from a UASB reactor employed in treatment of wastewater from poultry slaughterhouse, maintaining the granular form. In the assay varying the co-substrates, it was observed greater LAS removal (50%) in the presence of complex co-substrate (yeast extract) than in the presence of methanol and ethanol (removal: 29-41%). Insignificant difference between the communities from Archaea and Bacteria domain (about 60 and 40%, respectively) was observed in the presence of different co-substrates, according to the fluorescent in situ hybridization (FISH) analysis. It was verified greater influence of cosubstrates concentration than the HRT in the LAS degradation. At the lowest SOLR (0.03 gCOD/gTVS.d), high LAS degradation (76%) was obtained while in the reactors varying the HRT were observed efficiencies of 18% (6 h), 37-53% (35 h) and 55% (80 h). In the reactors varying the HRT and concentration of co-substrates, a significant LAS removal rate (20-53%; in the sludge blanket the rate was 13-43%) was observed in the phase separator, related to the low concentration of co-substrates and the anaerobic facultative condition in this region. By the PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) technique of samples from the assay varying the HRT and concentration of co-substrates, it was verified great similarity coefficient in the sludge blanket (Archaea: 70-90%; Bacteria: 69- 83%) due to the granule structure of the inoculum used. High LAS degradation (82%) was verified in the reactor with laundry wastewater, which was attributed to the diversity of cosubstrates (12 organic volatile acids detected) and the low concentration of co-substrates (SOLR: 0.03 gCOD/gTVS.d). By pyrosequencing analysis of 16S RNAr genes in the samples from assay with laundry wastewater, it was found 147 genus, which 32 were related to the LAS degradation (genus able to degrade aromatic compounds, desulfonation, and - oxidation). A significant relative abundance (>1%) was observed in the following genus related to the degradation of LAS: Comamonas, Dechloromonas, Desulfovibrio, Gemmatimonas, Holophoga, Parvibaculum, Pseudomonas, Rhodanobacter, Sporomusa, Synergistes and Zoogloea. In the phases separator of the reactor with laundry wastewater, the high LAS removal (90%) and the relative abundance of genus aerobic (23%) and anaerobic (6%) related to the degradation of LAS corroborated the relation between LAS removal and the anaerobic facultative condition (AU)