M. B. A. Varesche

Sulphate removal from industrial wastewater using a packed-bed anaerobic reactor

Abstract The feasibility of sulphate removal from sulphate-rich wastewater using an anaerobic fixed-bed reactor was investigated. The bioreactor was installed at a chemical industry producing organic peroxides, which generate wastewater with sulphate concentrations ranging from 12,000 to 35,000 mg SO 4 2− l −1 . A pilot-scale anaerobic fixed-bed reactor with a 94.2-l volume was tested to treat part of the wastewater. The reactor was filled with 1-cm 3 polyurethane foam cubes and operated, initially, in discontinuous regime. Five batch tests were performed with diluted industrial wastewater. The sulphate reduction efficiency and the chemical oxygen demand (COD) removal efficiency were evaluated as a function of the COD to [SO 4 2− ] ratio in each batch test. The effect of the addition of supplementary ethanol on the sulphate-reducing bacteria growth was also evaluated. The reactor was then fed in a semi-continuous regime with raw industrial wastewater with high sulphate concentration. The addition of ethanol stimulated the sulphate-reducing bacteria, which predominated over the methane-producing organisms even at a high COD to [SO 4 2− ] ratio. A maximum sulphate removal efficiency of 97% was reached during discontinuous and semi-continuous operations.

Effect of biomass adaptation to the degradation of anionic surfactants in laundry wastewater using EGSB reactors

Two expanded granular sludge bed reactors were operated. RAB (adapted biomass) was operated in two stages: Stage I, with standard LAS (13.2 mg L(-1)); and Stage II, in which the standard LAS was replaced by diluted laundry wastewater according to the LAS concentration (11.2 mg L(-1)). RNAB (not adapted biomass) had a single stage, using direct wastewater (11.5 mg L(-1)). Thus, the strategy of biomass adaptation did not lead to an increase of surfactant removal in wastewater (RAB-Stage II: 77%; RNAB-Stage I: 78%). By means of denaturing gradient gel electrophoresis, an 80% similarity was verified in the phases with laundry wastewater (sludge bed) despite the different reactor starting strategies. By pyrosequencing, many reads were related to genera of degraders of aromatic compounds and sulfate reducers (Syntrophorhabdus and Desulfobulbus). The insignificant difference in LAS removal between the two strategies was most likely due to the great microbial richness of the inoculum.

Microbial characterization and removal of anionic surfactant in an expanded granular sludge bed reactor

This study evaluated linear alkylbenzene sulfonate removal in an expanded granular sludge bed reactor with hydraulic retention times of 26 h and 32 h. Sludge bed and separator phase biomass were phylogenetically characterized (sequencing 16S rRNA) and quantified (most probable number) to determine the total anaerobic bacteria and methanogenic Archaea. The reactor was fed with a mineral medium supplemented with 14 mg l(-1)LAS, ethanol and methanol. The stage I-32 h consisted of biomass adaptation (without LAS influent) until reactor stability was achieved (COD removal >97%). In stage II-32 h, LAS removal was 74% due to factors such as dilution, degradation and adsorption. Higher HRT values increased the LAS removal (stage III: 26 h - 48% and stage IV: 32 h - 64%), probably due to increased contact time between the biomass and LAS. The clone libraries were different between samples from the sludge bed (Synergitetes and Proteobacteria) and the separator phase (Firmicutes and Proteobacteria) biomass.

Treatment of linear alkylbenzene sulfonate in a horizontal anaerobic immobilized biomass reactor.

Linear alkylbenzene sulfonate (LAS) is an anionic surfactant widely used to manufacture detergents and found in domestic and industrial wastewater. LAS removal was evaluated in a horizontal anaerobic immobilized biomass reactor. The system was filled with polyurethane foam and inoculated with sludge that was withdrawn from an up flow anaerobic sludge blanket reactor that is used to treat swine wastewater. The reactor was fed with easily degradable substrates and a solution of commercial LAS for 313 days. The hydraulic retention time applied was 12h. The system was initially operated without detergent and resulted to 94% reduction of demand. The mass balance in the system indicated that the LAS removal efficiency was 45% after 18 0days. From the 109 th day to the 254 th day, a removal efficiency of 32% was observed. The removal of LAS was approximately 40% when 1500 mg of LAS were applied in the absence of co-substrates suggesting that the LAS molecules were used selectively. Microscopic analyses of the biofilm revealed diverse microbial morphologies and denaturing gradient gel electrophoresis profiling showed variations in the total bacteria and sulfate-reducing bacteria populations. 16S rRNA sequencing and phylogenetic analyses demonstrated that members of the order Clostridiales were the major components of the bacterial community in the last step of the reactor operation.

Las degradation in a fluidized bed reactor and phylogenetic characterization of the biofilm

A fluidized bed reactor was used to study the degradation of the surfactant linear alkylbenzene sulfonate (LAS). The reactor was inoculated with anaerobic sludge and was fed with a synthetic substrate supplemented with LAS in increasing concentrations (8.2 to 45.8 mg l-1). The removal efficiency of 93% was obtained after 270 days of operation. Subsequently, 16S rRNA gene sequencing and phylogenetic analysis of the sample at the last stage of the reactor operation recovered 105 clones belonging to the domain Bacteria. These clones represented a variety of phyla with significant homology to Bacteroidetes (40%), Proteobacteria (42%), Verrucomicrobia (4%), Acidobacteria (3%), Firmicutes (2%), and Gemmatimonadetes (1%). A small fraction of the clones (8%) was not related to any phylum. Such phyla variety indicated the role of microbial consortia in degrading the surfactant LAS.

Kinetic modeling and microbial assessment by fluorescent in situ hybridization in anaerobic sequencing batch biofilm reactors treating sulfate-rich wastewater

This paper reports the results of applying anaerobic sequencing batch biofilm reactors (AnSBBR) for treating sulfate-rich wastewater. The reactor was filled with polyurethane foam matrices or with eucalyptus charcoal, used as the support for biomass attachment. Synthetic wastewater was prepared with two ratios between chemical oxygen demand (COD) and sulfate concentration (COD/SO42-) of 0.4 and 3.2. For a COD/SO42- ratio of 3.2, the AnSBBR performance was influenced by the support material used; the average levels of organic matter removal were 67% and 81% in the reactors filled with polyurethane foam and charcoal, respectively, and both support materials were associated with similar levels of sulfate reduction (above 90%). In both reactors, sulfate-reducing bacteria (SRB) represented more than 65% of the bacterial community. The kinetic model indicated equilibrium between complete- and incomplete-oxidizing SRB in the reactor filled with polyurethane foam and predominantly incomplete-oxidizing SRB in the reactor filled with charcoal. Methanogenic activity seems to have been the determining factor to explain the better performance of the reactor filled with charcoal to remove organic matter at a COD/SO42- ratio of 3.2. For a COD/SO42- ratio of 0.4, low values of sulfate reduction (around 32%) and low reaction rates were observed as a result of the small SRB population (about 20% of the bacterial community). Although the support material did not affect overall performance for this condition, different degradation pathways were observed; incomplete oxidation of organic matter by SRB was the main kinetic pathway and methanogenesis was negligible in both reactors.

Phenol degradation in an anaerobic fluidized bed reactor packed with low density support materials

Abstract - The objective of this research was to study phenol degradation in anaerobic fluidized bed reactors (AFBR) packed with polymeric particulate supports (polystyrene - PS, polyethylene terephthalate – PET, and polyvinyl chloride - PVC). The reactors were operated with a hydraulic retention time (HRT) of 24 h. The influent phenol concentration in the AFBR varied from 100 to 400 mg L -1 , resulting in phenol removal efficiencies of ~100%. The formation of extracellular polymeric substances yielded better results with the PVC particles; however, deformations in these particles proved detrimental to reactor operation. PS was found to be the best support for biomass attachment in an AFBR for phenol removal. The AFBR loaded with PS was operated to analyze the performance and stability for phenol removal at feed concentrations ranging from 50 to 500 mg L -1 . The phenol removal efficiency ranged from 90-100%. Keywords : Phenol; Anaerobic fluidized bed reactor; Biofilm; Polymeric particles.

Anaerobic degradation of linear alkylbenzene sulfonate in fluidized bed reactor

An anaerobic fluidized bed reactor was used to assess the degradation of the surfactant linear alkylbenzene sulfonate (LAS). The reactor was inoculated with sludge from an UASB reactor treating swine wastewater and was fed with a synthetic substrate supplemented with LAS. Sand was used as support material for biomass immobilization. The reactor was kept in a controlled temperature chamber (30±1 oC) and operated with a hydraulic retention time (HRT) of 18 h. The LAS concentration was gradually increased from 8.2±1.3 to 45.8±5.4 mg.L-1. The COD removal was 91%, on average, when the influent COD was 645±49 mg.L-1. The results obtained by chromatographic analysis showed that the reactor removed 93% of the LAS after 270 days of operation.

Morphological observation and microbial population dynamics in anaerobic polyurethane foam biofilm degrading gelatin

This work reports on a preliminary study of anaerobic degradation of gelatin with emphasis on the development of the proteolytic biofilm in polyurethane foam matrices in differential reactors. The evolution of the biofilm was observed during 22 days by optical and scanning electron microscopy (SEM) analyses. Three distinct immobilization patterns could be observed in the polyurethane foam: cell aggregates entrapped in matrix pores, thin biofilms attached to inner polyurethane foam surfaces and individual cells that have adhered to the support. Rods, cocci and vibrios were observed as the predominant morphologies of bacterial cells. Methane was produced mainly by hydrogenothrophic reactions during the operation of the reactors.

Evaluation of the microbial diversity of denitrifying bacteria in batch reactor

Microbial communities in an industrial activated sludge plant may contribute to the denitrification process, but the information on the microorganisms present in denitrifying reactors is still scarce. Removal of inorganic nitrogen compounds can be accomplished by the addition of carbon sources to the biological process of denitrification. Ethanol is an economically viable alternative as a carbon source in tropical countries like Brazil, with large-scale production from sugarcane. This paper reports the successful aplication of activated sludge with nitrate and ethanol in a batch anaerobic reactor. The operation lasted 61.5 h with total consumption of nitrate in 42.5 h, nitrite generation (2.0 mg/L) and ethanol consumption (830.0 mg/L) in 23.5 h. Denitrifying cell counts by the most probable number at the start of the operation were lower than at the end, confirming the ability of the inoculum from activated sludge for the denitrification process. The samples from cell counts were identified as Acidovorax sp., Acinetobacter sp., Comamonas sp. and uncultured bacteria. Therefore, these species may be involved in nitrate reduction and ethanol consumption in the batch reactor.