Anaerobic process conjugated with advanced oxidation processes (AOP) for the treatment of the bleaching effluents from a kraft pulp mill

Author(s)

Thiago José Momenti

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2006-12-15

Examining board members

Eduardo Cleto Pires; Andréa Paula Buzzini; Luiz Antonio Daniel; José Roberto Guimarães; Claudio Mudado Silva

• Advisor: Eduardo Cleto Pires

Abstract

Some advanced oxidation processes (AOP) were applied after an anaerobic process for the treatment of bleaching effluents from a kraft pulp mill, aiming the increase of the effluent biodegradability and the removal of toxic compounds, in a way that a further biological treatment could be more efficient to attain the environmental regulations. A horizontal anaerobic imobilizaded sludge reactor (HAIS) was used as the anaerobic treatment in order to reduce the effluent initial organic load. The AOP used were 'O IND.3', 'O IND.3'/'H IND.2'O IND.2', 'O IND.3'/UV, UV, 'H IND.2'O IND.2', 'H IND.2'O IND.2'/UV and 'O IND.3'/'H IND.2'O IND.2'/UV. These AOP were not applied only to promote a further degradation of the remaining COD from the HAIS reactor, but in order to increase the effluent biodegradability and eliminate AOX or other toxic compounds from this effluent. In this way, the AOP would provide an effluent with characteristics to be easily treated by a further and final biological process. In the biological process, the anaerobic biomass was fast adapted to the wastewater. The HAIS reactor reached the stability and had efficiency in COD and AOX removals of approximately 50%, satisfying the aim of promoting an initial reduction in the easy-to-degrade organic matter presented in the bleaching effluents. All the tested AOP promoted modifications in de HAIS effluent biodegradability. The 'O IND.3'/UV at pH 8 was the more efficient process, achieving an increase of 160% on the biodegradability of the HAIS effluent after 45 minutes of oxidation and an ozone concentration of 1155 mg/L. By the AOX analyses, it was observed average degradations of the organochlorine compounds higher than 95% for all the AOP tested. The general results show the importance and the advantage of using an AOP as a complement of a biological treatment process for the degradation of effluents with low biodegradability, due to the presence of recalcitrant and toxic compounds. (AU)