Arnaldo Sarti

Anaerobic treatment of sulfate-rich wastewater in an anaerobic sequential batch reactor (AnSBR) using butanol as the carbon source

Biological sulfate reduction was studied in a laboratory-scale anaerobic sequential batch reactor (14 L) containing mineral coal for biomass attachment. The reactor was fed industrial wastewater with increasingly high sulfate concentrations to establish its application limits. Special attention was paid to the use of butanol in the sulfate reduction that originated from melamine resin production. This product was used as the main organic amendment to support the biological process. The reactor was operated for 65 cycles (48 h each) at sulfate loading rates ranging from 2.2 to 23.8 g SO(4)(2-)/cycle, which corresponds to sulfate concentrations of 0.25, 0.5, 1.0, 2.0 and 3.0 g SO(4)(2-) L(-1). The sulfate removal efficiency reached 99% at concentrations of 0.25, 0.5 and 1.0 g SO(4)(2-) L(-1). At higher sulfate concentrations (2.0 and 3.0 g SO(4)(2-) L(-1)), the sulfate conversion remained in the range of 71-95%. The results demonstrate the potential applicability of butanol as the carbon source for the biological treatment of sulfate in an anaerobic batch reactor.

Influence of the liquid-phase mass transfer on the performance of a packed-bed bioreactor for wastewater treatment

This paper reports on the influence of the liquid-phase mass transfer on the performance of a horizontal-flow, anaerobic, immobilized-biomass (HAIB) reactor treating low-strength wastewater. The HAIB reactor was subjected to liquid superficial velocities (vs) ranging from 10 to 50 cm h(-1), corresponding to hydraulic detention time (theta h) of 10-2 h. The best performance was achieved at an overall theta h of 3.3 h due to the interdependence of biochemical reactions and mass transfer mechanisms for process optimization. The HAIB reactor was provided with four intermediate sampling ports, and the values of v(s) were fixed to permit sampling at different ports corresponding to thetah of 2 h as vs increased. The chemical oxygen demand removal (COD) efficiencies increased from 68% to 82% with the increase of v(s) from 10 to 50 cm h(-1). It could be concluded that the performance of the HAIB reactor was improved significantly by increasing vs, thus decreasing the liquid-phase mass transfer resistance.

Application of molecular techniques to evaluate the methanogenic archaea and anaerobic bacteria in the presence of oxygen with different COD:Sulfate ratios in a UASB reactor

In this paper, the microbial characteristics of the granular sludge in the presence of oxygen (3.0+/-0.7 mg O2 l(-1)) were analyzed using molecular biology techniques. The granules were provided by an upflow anaerobic sludge blanket (UASB) operated over 469 days and fed with synthetic substrate. Ethanol and sulfate were added to obtain different COD/SO4(2-) ratios (3.0, 2.0, and 1.6). The results of fluorescent in situ hybridization (FISH) analyses showed that archaeal cells, detected by the ARC915 probe, accounted for 77%, 84%, and 75% in the COD/SO(4)(2-) ratios (3.0, 2.0, and 1.6, respectively). Methanosaeta sp. was the predominant acetoclastic archaea observed by optical microscopy and FISH analyses, and confirmed by sequencing of the excised bands of the DGGE gel with a similarity of 96%. The sulfate-reducing bacterium Desulfovibrio vulgaris subsp. vulgaris (similarity of 99%) was verified by sequencing of the DGGE band. Others identified microorganism were similar to Shewanella sp. and Desulfitobacterium hafniense, with similarities of 95% and 99%, respectively. These results confirmed that the presence of oxygen did not severely affect the metabolism of microorganisms that are commonly considered strictly anaerobic. We obtained mean efficiencies of organic matter conversion and sulfate reducing higher than 74%.

Tratamento de esgoto sanitário utilizando reatores anaeróbios operados em bateladas sequenciais (escala piloto)

The performances of two anaerobic sequencing batch reactors (1.2 m3) containing biomass immobilized in inert support and as granular sludge in the treatment of domestic sewage from the Campus of Sao Carlos-University of Sao Paulo were evaluated. The experimental phase lasted seventy days. During this period, the reactors presented quite similar performances in respect to COD and total suspended solids removal, achieving average efficiencies of approximately 60% and 75%, respectively. The analysis using molecular biology techniques on biomass samples taken at 35th and 70th showed differences in the bacterial community in the reactors indicating that the type of biomass immobilization selected the populations differently. A higher similarity was found for the Archaea domain probably because these microorganisms utilize specific substrates formed at the end of the anaerobic process.

Characterization of immobilized biomass by amplified rDNA restriction analysis (ARDRA) in an anaerobic sequencing-batch biofilm reactor (ASBBR) for the treatment of industrial wastewater

The performance of an anaerobic sequencing-batch biofilm reactor (ASBBR- laboratory scale- 14L )containing biomass immobilized on coal was evaluated for the removal of elevated concentrations of sulfate (between 200 and 3,000 mg SO4-2·L-1) from industrial wastewater effluents. The ASBBR was shown to be efficient for removal of organic material (between 90% and 45%) and sulfate (between 95% and 85%). The microbiota adhering to the support medium was analyzed by amplified ribosomal DNA restriction analysis (ARDRA). The ARDRA profiles for the Bacteria and Archaea domains proved to be sensitive for the determination of microbial diversity and were consistent with the physical-chemical monitoring analysis of the reactor. At 3,000 mg SO4-2·L-1, there was a reduction in the microbial diversity of both domains and also in the removal efficiencies of organic material and sulfate.

Performances of two pilot decentralized wastewater treatment plants used to treat low-strength wastewater

aDepartment of Civil and Environmental Engineering, The College of Engineering Bauru, UNESP Universidade Estadual Paulista, Av. Eng. Luiz Edmundo Carrijo Coube, 14-01, 17033-360, Bauru, SP, Brazil, Tel. +55 14 3103 6000; emails: jualves.bio@gmail.com (J.A. da Silva), gustavoribeiro@feb.unesp.br (G.H.R. da Silva) bDepartment of Biochemistry and Chemical Technology, Institute of Chemistry, UNESP – Universidade Estadual Paulista, Campus Araraquara, Rua Prof. Francisco Degni, 55, 14800-900, Araraquara, SP, Brazil, Tel. +55 16 3301 9860; email: arnaldosarti@iq.unesp.br

APLICAÇÃO DE REATORES ANAERÓBIOS OPERADOS EM BATELADAS SEQUENCIAIS COM FILME FIXO NO TRATAMENTO DE ÁGUA RESIDUARIA INDUSTRIAL RICA EM SULFATO

This paper presents and discusses the potential for use of pilot-scale anaerobic sequencing batch biofilm reactors (ASBBR) for the treatment of industrial wastewater containing high sulfate concentration. The pilot-scale ASBBR reactor (total volume= 1.2 m3) containing biomass immobilized in inert support (mineral coal) was operated at sulfate loading rates varying from 0.15 to 1.90 kgSO4-2/cycle (cycle of 48 h) corresponding to sulfate concentrations of 0.25 to 3.0 gSO4-2.L-1. Domestic sewage and ethanol were utilized as electron donors for sulfate reduction. The mean sulfate removal efficiencies remained in the range of 88 to 92% in the several sulfate concentrations obtained from 92 operational cycles. As post-treatment unit for the generated effluents by the sulfate reduction was used another reactor ASBBR in pilot-scale (total volume=385 L) with similar inert support for biomass immobilization. The mean COD removal (mean influent=1450 mg.L-1) achieved 88% and total sulfide concentrations (H2S, HS−, S2−) remained in the range of 41 to 71 mg.L-1 during the 35 operational cycles of 48 h. The results demonstrated that the use of ASBBR reactors is an alternative potential for the sulfate removal and as post-treatment of generated effluent.

Remoção de sulfato de águas residuárias industriais em reator anaeróbio de leito fixo operado em bateladas sequenciais

The potential use of an anaerobic sequencing batch biofilm reactor (ASBBR) in pilot-scale for the treatment of a sulfate-rich industrial wastewater was evaluated. The pilot 1.2 m3 ASBBR reactor was filled with mineral coal for biomass immobilization (fixed film). The sulfate loading rates applied were 0.15; 0.30; 0.65; 1.30 and 1.90 kg SO4-2/cycle (or batch). Each cycle lasted 48 h. The influent concentrations were, respectively, 0.25; 0.50; 1.0; 2.0 and 3.0 gSO4-2.l-1. Ethanol was used as electron donor for sulfate reduction. The reactor operated at ambient temperature (29±8oC), and the mean efficiencies of sulfate removal were in the range 88 to 92% in the 92 run cycles. The total operating period comprised 275 days. Based on the results obtained in this research, it could be concluded that the ASBBR can be an efficient alternative for the removal of sulfate from other industrial wastewaters with similar characteristics.