Effects of electron acceptors on sulphate reduction activity in activated sludge processes (original) (raw)
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Bioenergetics of sulphate-reducing bacteria in relation to their environmental impact
Biodegradation, 1998
The cellular physiology of the sulphate-reducing bacteria, and of other sulphidogenic species, is determined by the energetic requirements consequent upon their respiratory mode of metabolism with sulphate and other oxyanions of sulphur as terminal electron acceptors. As a further consequence of their, relatively, restricted catabolic activities and their requirement for conditions of anaerobiosis, sulphidogenic bacteria are almost invariably found in nature as component organisms within microbial consortia.
Water SA, 2010
A 2-phase (aqueous-gas) kinetic model for biological sulphate reduction (BSR) using primary sewage sludge (PSS) as carbon source is presented. The methanogenic anaerobic digestion (AD) model of Sötemann et al. (2005) is extended by adding the biological, chemical and physical processes associated with BSR, i.e. propionic acid degrading sulphate-reducing bacteria (SRB), acetoclastic SRB and hydrogenotrophic SRB, the aqueous weak acid/base chemistry processes of the sulphate and sulphide systems and an aqueous-gas sulphide exchange process. The model is validated with experimental data from 2 upflow anaerobic sludge bed (UASB) reactors fed various PSS COD/SO 4 2ratios under constant flow and load conditions at 35°C and 20°C. The kinetic model results, including the reactor pH (within 0.1 pH unit) compare well with the experimental results and with those calculated from a steady-state BSR model. The kinetic model confirms that: (1) at ambient temperature (20°C), the hydrolysis rate is significantly reduced compared with that at 35°C, which requires a longer sludge age (larger bed volume) in the UASB reactor; (2) the hydrolysis rate of the PSS biodegradable particulate organics (BPO) is the same under methanogenic and sulphidogenic conditions; (3) the PSS BPO are carbon deficient for BSR in that more electrons are donated than carbon supplied for the required alkalinity increase, with the result that the sulphide system supplies the alkalinity deficit; and (4) due to (3) there is zero CO 2 gas generation and in effect the sulphide system establishes the reactor pH. This observation allows the carbon content of the utilised organics to be determined from the H 2 CO 3 * alkalinity increase in the reactor, which can be simply measured by titration methods.
CULTIVATION OF SULPHATE REDUCING BACTERIA IN DIFFERENT MEDIA
Sulphate-reducing bacteria (SRB) represent themselves as a class of anaerobic bacteria that can reduce sulphate to sulphide for obtaining energy. This paper is aimed to detect sulphatereducing bacteria activities using rapid detectable culture media. Two different strains of sulphate-reducing bacteria were used in this study, namely ATCC 7757 and local bacterial strain of SRB isolated from underground sample. Both strains were tested on three recommended culture media of modified Baar"s, Postgate B and Postgate C. All three medium contained lactic acid which served to be as carbon source. The results showed that modified Baar"s medium is the best medium for the growth of ATCC 7757 while Postgate C medium is recommended for the local SRB bacterial strain.
Water, Air, & Soil Pollution, 2013
Nitrate addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H 2 S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect of four different concentrations of nitrate (0.12, 0.24, 0.50, and 1.00 mM) was investigated for a period of 3 days in relation to sulfide concentration in two bioreactors set up at Guadalete wastewater treatment plant (Jerez de la Frontera, Spain). Physicochemical variables were measured in water and air, and the activity of bacteria implicated in the sulfur and nitrogen cycles was analyzed in the biofilms and in the water phase of the bioreactors. Biofilms were a net source of sulfide for the water and gas phases (7.22±5.3 μmol s −1) in the absence of nitrate dosing. Addition of nitrate resulted in a quick (within 3 h) decrease of sulfide both in the water and atmospheric phases. Sulfide elimination efficiency in the water phase increased with nitrate concentrations following the Michaelis-Menten kinetics (K s =0.63 mM NO 3 −). The end of nitrate addition resulted in a recovery or increase of initial net sulfide production in about 3 h. Addition of nitrate increased the activity of NR-SOB and decreased the activity of sulfate-reducing bacteria. Results confirmed the role of NR-SOB on hydrogen sulfide consumption coupled with nitrate reduction and sulfate recycling, revealing Sulfurimonas denitrificans and Paracoccus denitrificans as NR-SOB of great importance in this process.
Kinetics of bacterial sulfate reduction in an activated sludge plant
FEMS Microbiology Ecology, 2003
The kinetics of sulfate reduction and cell densities of sulfate-reducing bacteria (SRB) were determined in activated sludge at Aalborg East wastewater treatment plant, a modern 100 000 person equivalent plant, where SRB are subjected to alternating cycles of oxic and anoxic conditions. The number of SRB was relatively constant over the year, ranging from 2.1U10 5 to 1.1U10 6 cells ml 31 as determined by 35 S-radiotracer most probable number (MPN) in a growth medium prepared from anaerobic, sterilized sludge. Under anoxic conditions, the sulfide production in the activated sludge followed a biphasic pattern, being linear for approximately 5 h, followed by an exponential phase with doubling times of sulfide production of 4.2^12.6 h. Sulfate reduction started immediately after the onset of the anoxic cycle. Addition of antibiotics (chloramphenicol and streptomycin) to the activated sludge prevented the exponential phase of sulfate reduction for up to 100 h and this treatment was found to yield precise estimates of potential sulfate reduction rates. The addition of sulfate, sodium dithionite or single carbon compounds (lactate, acetate and glucose) did not decrease the length of the linear phase of sulfate reduction, nor did it affect the sulfate reduction rate. Our results indicate a tight and efficient metabolic coupling between populations of SRB and fermenting bacteria in activated sludge and a high capacity for sulfate reduction in sludge stored in settling tanks. Bacterial sulfate reduction may therefore be an important process in the destabilization of the floc structure when activated sludge is stored anaerobically for several days prior to dewatering.
Bioremediation of Contaminated Water Sources with Sulphate-Reducing Bacteria
Bioremediation of arsenic contaminated water by SRB could be a cost-effective process, especially if a suitable carbon source and support matrix were available. To these ends, the chemical composition of molasses was investigated as a candidate for the former purpose while pine bark, sand and polystyrene were assessed as support matrices. Batch culture studies were carried out to assess 1, 2.5 and 5 g l -1 molasses as suitable concentrations for SRB growth. The results show that all concentrations supported SRB growth, the response being dependent on the amount present; however, growth on molasses was not as good as that obtained when lactate was used. Biofilm formation on the matrices was evaluated in batch cultures in flasks containing Postgate medium B. The inherent ability of these matrices to support growth of the organisms was evaluated on the basis of pH and redox potential change and the levels of sulphate removal and sulphide production occurring. Environmental scanning electron microscopy (ESEM) was used to characterise the matrix surfaces.
The bioactivation procedure for increasing the sulphate-reducing bacteria in a UASB reactor
Brazilian Journal of Chemical Engineering, 2005
Bioactivation, a procedure to obtain anaerobic sulphidogenic sludge, was developed in order to increase sulphate reduction and, consequently, sulphide production to remove metals from effluents. This procedure, in which the source of carbon/energy (lactate) is gradually replaced, consisted of three operational conditions. It was observed that bioactivation took six months so there was a 100-fold increase in the population of sulphate-reducing bacteria estimated by the most-probable-number (MPN) when molasses was employed as a new source.
Biofiltration of reduced sulphur compounds and community analysis of sulphur-oxidizing bacteria
Bioresource Technology, 2011
The present work aims to use a two-stage biotrickling filters for simultaneous treatment of hydrogen sulphide (H 2 S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). The first biofilter was inoculated with Acidithiobacillus thiooxidans (BAT) and the second one with Thiobacillus thioparus (BTT). For separate feeds of reduced sulphur compounds (RSC), the elimination capacity (EC) order was DMDS > DMS > MM. The EC values were 9.8 g MM-S /m 3 /h (BTT; 78% removal efficiency (RE); empty bed residence time (EBRT) 58 s), 36 g DMDS-S /m 3 /h (BTT; 94.4% RE; EBRT 76 s) and 57.5 g H2S-S /m 3 /h (BAT; 92% RE; EBRT 59 s). For the simultaneous removal of RSC in BTT, an increase in the H 2 S concentration from 23 to 293 ppmv (EBRT of 59 s) inhibited the RE of DMS (97-84% RE), DMDS (86-76% RE) and MM (83-67% RE). In the two-stage biofiltration, the RE did not decrease on increasing the H 2 S concentration from 75 to 432 ppmv.
Environmental Technology, 2004
Two different types of microbial aggregates (granular sludge and biofilm onto a plastic matrix) were evaluated for their susceptibility to sulphide and dissolved oxygen. Their specific methanogenic and sulphate reducing activities were evaluated separately and simultaneously. Total sulphide concentrations that caused 50% loss of methanogenic activity were 800 and 1250 mg l -1 and for sulphate reduction 750 and 860 mg l -1 for the granular sludge and the attached biomass, respectively. Simultaneous methanogenesis and sulphate reduction resulted in an increased tolerance of the sulphate reducing process towards sulphide. Results suggest that methanogenesis in granular sludge is less resistant to sulphide than in the attached biomass structure, whereas in sulphate reduction the attached biomass exhibited a better tolerance to high concentrations of total sulphide than the granular sludge. The better sulphate reducing capacity in the attached biomass may suggest that biomass was selectively attached. The dissolved oxygen concentration that inhibited 50% the methanogenic activity was 4.9 and 6.4 mg l -1 for the granular sludge and attached biomass, respectively. When methanogenesis and sulphate reduction were carried out simultaneously, the whole process was not affected by the supplied oxygen, as produced sulphide was used by sulphide oxidizing microorganisms thus scavenging oxygen. Results showed that the integration of anaerobic/aerobic conditions in a single bioreactor is quite possible and can be used as a good strategy for the complete transformation of sulphate to elemental sulphur.