Sulfidogenesis interference on methane production from carbohydrate-rich wastewater (original) (raw)
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Scientia cum Industria
Anaerobic digestion is a widely used effluent and organic waste treatment practice, in which it is possible to minimize and control environmental problems, associating the reduction of environmental impacts with energy recovery. Low methane production and process instability are often found in anaerobic digestion reactors, preventing this technique from being widely applied. Inhibitory substances, such as sulfides resulting from sulfate conversion by the sulfur reducing bacteria, are one of the causes of inhibition or malfunctioning of anaerobic digesters if they are present in the effluent to be treated. The objective of this work is to evaluate the effect of sulfide at two different values of pH (7.0 and 7.5) using sulfide concentrations of 0 to 1000 mg S 2-L-1. All the tests were performed in batches and performed at mesophilic conditions. For the concentrations of 50 mg S 2-L-1 and 1000 mg S 2-L-1 , the inhibitions of the methanogenic activity at pH 7.0 were in the order of 38.5% to 59.8% and at pH 7.5 in the order of 67% to 94%, respectively. Concerning the test at pH 7.0, the removal of COD in the experiment without addition of any concentration of S 2was 93.3%, and it reached a 49.14% COD removal at concentrations of 1000 mg S 2-L-1. At pH 7.5 under the same conditions, the COD removals were respectively 80.7% and 9.6%. The concentrations of 50, 75 and 100 mg S 2-L-1 of S 2initially tested at the two aforementioned pH values promoted the greatest increase in the reduction of SMA. When the experiments were carried out at pH 7.0 the reductions were 37.96%, 41.70%, and 46.06% respectively for the same concentrations. At pH 7.5 the reductions represented 67.01%, 82.47% and 81.81%.
Removing organic matter from sulfate-rich wastewater via sulfidogenic and methanogenic pathways
Water Science and Technology, 2014
The simultaneous organic matter removal and sulfate reduction in synthetic sulfate-rich wastewater was evaluated for various chemical oxygen demand (COD)/sulfate ratios applied in a horizontal-flow anaerobic immobilized sludge (HAIS) reactor. At higher COD/sulfate ratios (12.5 and 7.5), the removal of organic matter was stable, likely due to methanogenesis. A combination of sulfate reduction and methanogenesis was clearly established at COD/sulfate ratios of 3.0 and 1.9. At a COD/sulfate ratio of 1.0, the organic matter removal was likely influenced by methanogenesis inhibition. The quantity of sulfate removed at a COD/sulfate ratio of 1.0 was identical to that obtained at a ratio of 1.9, indicating a lack of available electron donors for sulfidogenesis. The sulfate reduction and organic matter removal were not maximized at the same COD/sulfate ratio; therefore, competitive inhibition must be the predominant mechanism in establishing an electron flow.
Anaerobic nitrogen, sulfide, and carbon removal in anaerobic granular bed reactor
Environmental Progress & Sustainable Energy, 2013
Industrial wastewater may contain high concentrations of sulfides (S 22 ) and nitrates ðNO 2 3 Þ, which must be removed before discharging into water bodies. The inhibitory effects of 134.82-771.9 mg L 21 d 21 of sulfide loading rate (SLR) and 58.79-337.56 mg L 21 d 21 of nitrate loading rate (NLR) on methanogenesis were investigated in a mixed methanogenic condition using palm oil mill effluent (POME) as carbon source. This technique cultivated mature granules using anaerobic sludge of POME as seed sludge, incubated in denitrifying sulfide removal medium to acclimate the denitrifiers. Biological denitrification was used to eliminate carbon, nitrogen, and sulfur in an anaerobic granular bed reactor of 4.5 L by varying hydraulic retention time of 16 h from 241 to 300 d. The maximum nitrate and sulfide removal efficiencies were observed up to SLR and NLR of 188.42 mg L 21 d 21 and 82.39 mg L 21 d 21 respectively. Maximum volatile fatty acid removal of 82% and methane 65.5 mL g 21 of POME was obtained on SLR and NLR of 230 and 100.62 mg L 21 d 21 .
Sulphate removal from industrial wastewater using a packed-bed anaerobic reactor
Process Biochemistry, 2002
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.
Journal of Cleaner Production, 2021
This study attempted to enhance sulfidogenic activity via sulfate-reducing bacteria (SRB) enrichment and minimize organic carbon loss by methanogen inhibition in the sulfidogenic stage of a two-stage anaerobic digestion system (TSADS). To enrich SRB in the sulfidogenic stage, batch tests were performed with various granular sludge pretreatments. Starvation was the most effective pretreatment, increasing SO 4 2À removal and minimizing chemical oxygen demand (COD) loss by inhibiting methanogen activity. Microbial community analysis showed that Desulfovibrio, Desulfotomaculum, and Syntrophobacter were the dominant SRB in the sulfidogenic stage (5.0%, 3.1%, and 2.4%, respectively). This enabled SO 4 2À reduction (86%) and volatile fatty acid production (55% of fed COD) at a hydraulic retention time (HRT) of 4 h. Conversely, biogas with a reduced H 2 S content (110 ppm v) was produced in the methanogenic stage (HRT ¼ 6 h). A granular sludge comparison revealed differences in their ecology, structure, and extracellular polymeric substance characteristics. Economic feasibility analysis demonstrated that TSADS can lead to a cost reduction of $80e90/1,000 m 3 CH 4 compared to single-stage anaerobic digestion.
Environmental Engineering Science, 2007
Treatment of synthetic wastewaters containing sulfate in concentrations of 500 to 3,000 mg SO 4 Ϫ2 /L at chemical oxygen demand (COD)/sulfate ratios of 5.0, 3.0, 2.4, 1.7, and 1.0 was evaluated in two horizontal anaerobic fixed bed reactors (HAIB) filled with wood charcoal (WC) as support material. Ethanol, acetate, propionate, and butyrate were used as carbon sources to obtain synthetic wastewaters with COD ranging from 1,100 to 6,200 mg/L. Sulfate removal efficiencies exceeding 90% were achieved with the lowest sulfate concentrations up to 1,965 mg SO 4 Ϫ2 /L and COD/sulfate ratios higher than 1.7. The sulfate removal rate tended to remain constant (1.55 g SO 4 Ϫ2 /L и day) at sulfate concentrations equal to or higher than 1,960 mg SO 4 Ϫ2 /L. Organic matter removal efficiencies were always higher than 85%. Sulfidogenesis was the predominant process associated with organic matter removal in the first section of the reactor with the higher sulfate loads. In these cases, methane was not detected in the biogas.
Applied Microbiology and Biotechnology, 2012
The microbial communities (Bacteria and Archaea) established in an anaerobic fluidized bed reactor used to treat synthetic vinasse (betaine, glucose, acetate, propionate, and butyrate) were characterized by denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis. This study was focused on the competitive and syntrophic interactions between the different microbial groups at varying influent substrate to sulfate ratios of 8, 4, and 2 and anaerobic or micro-aerobic conditions. Acetogens detected along the anaerobic phases at substrate to sulfate ratios of 8 and 4 seemed to be mainly involved in the fermentation of glucose and betaine, but they were substituted by other sugar or betaine degraders after oxygen application. Typical fatty acid degraders that grow in syntrophy with methanogens were not detected during the entire reactor run. Likely, sugar and betaine degraders outnumbered them in the DGGE analysis. The detected sulfate-reducing bacteria (SRB) belonged to the hydrogen-utilizing Desulfovibrio. The introduction of oxygen led to the formation of elemental sulfur (S 0 ) and probably other sulfur compounds by sulfide-oxidizing bacteria (γ-Proteobacteria). It is likely that the sulfur intermediates produced from sulfide oxidation were used by SRB and other microorganisms as electron acceptors, as was supported by the detection of the sulfur respiring Wolinella succinogenes. Within the Archaea population, members of Methanomethylovorans and Methanosaeta were detected throughout the entire reactor operation. Hydrogenotrophic methanogens mainly belonging to the genus Methanobacterium were detected at the highest substrate to sulfate ratio but rapidly disappeared by increasing the sulfate concentration.
Journal of Water Process Engineering, 2015
Various types of industrial activities produce saline and/or sulfate-rich effluents and could use the anaerobic treatment process as the core technology. However, both salinity and sulfate can interfere with the process. This study investigated the performance of a UASB reactor in the treatment of synthetic wastewater containing glucose, acetate,methanol and sodium sulfate. The reactor had a useful volume of 10.5 L and was operated for 266 days at the hydraulic detention time of 15.6 h. The influent chemical oxygen demand (COD) was kept at 2000 mg L −1 whereas sodium sulfate concentrations increased along eighteen experimental phases, defined by the applied COD/[SO 4 2− ] ratio. Influent sulfate and sodium concentrations ranged from 25 to 10,000 mg L −1 and from 750 to 5350 mg L −1 , respectively. The progressive increase of sodium and sulfate concentration and the consequent decrease of the COD/[SO 4 2− ] ratios affected the reactor's performance, but the average COD removal efficiency remained above 80%. The observed partial process inhibition can be attributed to the synergistic effect resulting from the sulfide generated and the presence of sodium cations.