Activity Of Anaerobic Granular Sludge Research Articles

Study on treatment of chemical plant wastewater by using a integrated anaerobic–aerobic bioreactor

ABSTRACT In this work, a new type of integrated anaerobic aerobic bioreactor (IAAB) was formed by optimizing the structure of the anaerobic baffle bioreactor and aerobic biological contact oxidation pool. IAAB was used to treat the production wastewater of a chemical plant. The whole process was divided into two stages of domestication and stable operation. With increasing the proportion of chemical wastewater, the total amount of extracellular polymeric substances increased, and the ratio of protein to polysaccharide decreased. Dehydrogenase activity of anaerobic granular sludge in each compartment increased about 1.5 times with time, and decreased about 42% along the flow direction from the first compartment to the third compartment. The coenzyme F420 increased about 4 times with time, and increased about 1.2 times along the flow direction. The IAAB showed excellent removal rate of chemical oxygen demand (85%), ammonia nitrogen (94%), nitrobenzenes (98%).

Effect of static magnetic field exposure on biohydrogen production via dark fermentation of glucose

The effect of a static magnetic field (SMF) on the microbial activity of anaerobic granular sludge was investigated using a SMF field provided by a magnetic platform with intensities between 30 and 90 mT. BioH2 production was assessed in fed batch fermentation tests from glucose using anaerobic granular sludge with (HT) and without (WHT) heat shock pretreatment (100 ºC, 1 h). Under the conditions tested, 70 mT SMF was the best condition for bioH2 production, with a threefold decrease of lag time, a 12–50% increase in bioH2 production rate, and an improved consumption of iron and phosphate, compared to the controls (no SMF). Exposure to the SMF induced modifications in volatile fatty acid (VFA) production, pH and conductivity, biomass concentration, exopolysaccharide (EPS) composition as well as size and settleability of the granular anaerobic sludge. Microbial analysis showed that in the presence of the SMF, the relative abundance (RA) of Clostridium and Lactobacillus increased in both HT and WHT sludges, while it decreased the RA of Methanosaeta and Methanobacterium. The RA of Terrisporobacter increased with the heat shock, and also the stimulation along the fed batch cycles improved the RA of Terrisporobacter with and without SMF. The application of the SMF as a pre-treatment of inoculum and during bioH2 production seems to be an interesting and easy scaling up strategy to shorten the start-up of the dark fermentation process and help reducing the microbial diversity of the sludge, favouring more specialized species for bioH2 production.

Effect of anthraquinone-2,6-disulfonate on anaerobic digestion of fracturing flowback fluid under high salinity stress

The anaerobic digestion has been proved to be effective in treating fracturing flowback fluid. However, the high salinity in fracturing flowback fluid seriously inhibits the anaerobic treatment performance. A new strategy was proposed to improve the anaerobic digestion of fracturing flowback fluid under high salinity stress by adding anthraquinone-2,6-disulfonate (AQDS) in this study. The results showed that the addition of AQDS (45 mg/L) effectively alleviated the inhibition of high salinity (25 g/L) on the anaerobic digestion of fracturing wastewater, COD removal efficiency and cumulative methane yield increased by 17.8 % and 30.2 %, respectively. AQDS could alleviate the damage of anaerobic microorganisms caused by high salinity, the proportion of the damaged cells in anaerobic granular sludge decreased from 68.9 % to 38.3 %. Moreover, AQDS promoted the metabolic activity of anaerobic granular sludge under high salinity stress. The specific methanogenic activity, coenzyme F420 and dehydrogenase of anaerobic granular sludge increased by 30.0 %, 21.1 % and 21.4 %, respectively. Electrochemical analysis results showed that the addition of AQDS improved the electron transport of the anaerobic digestion system, and electron transport system activity increased by 62.4 %. This study provides an attractive strategy to alleviate the inhibition of high salinity on anaerobic digestion performance of fracturing flowback fluid.

Exogenous N-acyl-homoserine lactones promote the degradation of refractory organics in oligotrophic anaerobic granular sludge

For refractory industrial wastewaters, anaerobic granular sludge technology cannot be widely used because of its limited treatment capacity, so strengthening the anaerobic degradation of refractory organics should be discussed. In this paper, the feasibility of adding exogenous N-acyl-homoserine lactones (AHLs) to promote the degradation of refractory organics in oligotrophic anaerobic granular sludge was addressed. The results showed that, after easily-degradable organics were completely metabolized, exogenous AHLs strengthened the further degradation of refractory organics and improved the methanogenic activity of anaerobic granular sludge. In addition, adding AHLs could promote the secretion of more extracellular polysaccharides and proteins by anaerobic microorganisms to resist the oligotrophic environment. Microbiological analysis showed that adding AHLs significantly optimized the microbial community in oligotrophic anaerobic granular sludge. With the regulation of AHLs, the abundance proportion of hydrolytic acidifying bacteria for refractory organics in bacterial community and the abundance proportion of acetotrophic methanogens in methanogens community increased obviously. Exogenous AHLs showed concentration-related effects on the optimization of bacteria and methanogens, and AHLs of higher concentration were beneficial to the succession of community structure in a better direction. Exogenous regulation of AHLs-mediated QS provided an attractive strategy for enhancing the anaerobic degradation of refractory organics, and proposed a technical idea for the application of anaerobic granular sludge technology in refractory industrial wastewaters.

Isolation of bacteria capable of hydrogen production in dark fermentation and intensification of anaerobic granular sludge activity

In the anaerobic biological treatment of pulp and papermaking wastewater, the gradual deposition of CaCO3 eventually leads to the inhibition of the activity of anaerobic granular sludge. In this study, a hydrogen production bacterial Raoultella DW01 was isolated from domesticated anaerobic granular sludge. The fermentation conditions were designed using central composite design, and the optimum conditions obtained by response surface analysis encompassed an initial pH 5.77, 4.13 g/L l-glutamic acid and an inoculation amount of 15%. The H2 production yield represented a 29.5% increase over the unoptimized conditions. Finally, the effect of adding DW01 on the biogas production in anaerobic granular sludge with different sludge ages was investigated. The cumulative biogas yield and the max biogas production rate increased by 27.8% and 53.5% after adding DW01 to a sludge with an age of 335 days compared with the on-intensified sludge. This paper provides a way to alleviate the CaCO3 deposition by intensifying the activity of H2 and acid-producing bacteria via improving the activity of granular sludge.

Impact of zero-valent iron nanoparticles on the activity of anaerobic granular sludge: From macroscopic to microcosmic investigation

The study aimed at evaluating the influence of nano zero-valent iron (nZVI) on the activity of anaerobic granular sludge (AGS) from both macroscopic and microcosmic aspects using different methodologies. The tolerance response of AGS to nZVI was firstly investigated using short-term and long-term experiments, and also compared with anaerobic flocs. The Fe fate and distribution, the change of contents/structure of extracellular polymeric substances (EPS), and the variation of microbial community in the AGS after exposure to nZVI were further explored. Contrary to the anaerobic floc, insignificant inhibition of nZVI at dosage lower than 30 mmoL/L on the activity of AGS was observed. Additionally, the extra hydrogen gas released from the oxidation of nZVI was presumably suggested to stimulate the hydrogenotrophic methanogenesis process, resulting in 30% methane production enhancement when exposure to 30 mmoL/L nZVI. The microscopic analysis indicated that nZVI particles were mainly adsorbed on the surface of AGS in the form of iron oxides aggregation without entering into the interior of the granule, protecting most cells from contact damage. Moreover, surrounded EPS located outer surface of anaerobic granule could react with nZVI to accelerate the corrosion of nZVI and slow down H2 release from nZVI dissolution, thus further weakening the toxicity of nZVI to anaerobic microorganisms. The decrease in bacteria involved in glucose degradation and aceticlastic methanogens as well as the increase of hydrogenotrophic methanogens indicated a H2 mediated shift toward the hydrogenotrophic pathway enhancing the CH4 production.

Effect of humic acid in leachate on specific methanogenic activity of anaerobic granular sludge

In order to find out the effects of humic acid (HA) in anaerobic-treated landfill leachate on granular sludge, the anaerobic biodegradability of HA as well as the influences of HA on the total cumulative methane production, the anaerobic methanization process and the specific methanogenic activity (SMA) of granular sludge are studied in this paper. Experimental results show that as a non-biodegradable organic pollutant, HA is also difficult to be decomposed by microbes in the anaerobic reaction process. Presence of HA and changes in the concentration have no significant influences on the total cumulative methane production and the anaerobic methanization process of granular sludge. Besides, the total cumulative methane production cannot reflect the inhibition of toxics on the methanogenic activity of granular sludge on the premise of sufficient reaction time. Results also show that HA plays a promoting role on SMA of granular sludge. Without buffering agent the SMA value increased by 19.2% on average due to the buffering and regulating ability of HA, while with buffering agent the SMA value increased by 5.4% on average due to the retaining effect of HA on the morphology of the sludge particles. However, in the presence of leachate the SMA value decreased by 27.6% on average, because the toxic effect of the toxics in the leachate on granular sludge is much larger than the promoting effect of HA.

Toxicity assessment of inorganic nanoparticles to acetoclastic and hydrogenotrophic methanogenic activity in anaerobic granular sludge

Release of engineered nanoparticles (NPs) to municipal wastewater from industrial and residential sources could impact biological systems in wastewater treatment plants. Methanogenic inhibition can cause failure of anaerobic waste(water) treatment. This study investigated the inhibitory effect of a wide array of inorganic NPs (Ag0, Al2O3, CeO2, Cu0, CuO, Fe0, Fe2O3, Mn2O3, SiO2, TiO2, and ZnO supplied up to 1500mgL−1) to acetoclastic and hydrogenotrophic methanogenic activity of anaerobic granular sludge. Of all the NPs tested, only Cu0 and ZnO caused severe methanogenic inhibition. The 50% inhibiting concentrations determined towards acetoclastic and hydrogenotrophic methanogens were 62 and 68mgL−1 for Cu0 NP; and 87 and 250mgL−1 for ZnO NP, respectively. CuO NPs also caused inhibition of acetoclastic methanogens. Cu2+ and Zn2+ salts caused similar levels of inhibition as Cu0 and ZnO NPs based on equilibrium soluble metal concentrations measured during the assays, suggesting that the toxicity was due to the release of metal ions by NP-corrosion. A commercial dispersant, Dispex, intended to increase NP stability did not affect the inhibitory impact of the NPs. The results taken as a whole suggest that Zn- and Cu-containing NPs can release metal ions that are inhibitory for methanogenesis.

The effect of electrodialytic treatment and Na 2H 2EDTA addition on methanogenic activity of copper-amended anaerobic granular sludge: Treatment costs and energy consumption

The effect of electrodialytic treatment in terms of a current density, pH and Na 2H 2EDTA addition on the methanogenic activity of copper-amended anaerobic granular sludge taken from the UASB reactor from paper mill was evaluated. Moreover, the specific energy consumption and simplified operational and treatment costs were calculated. Addition of Na 2H 2EDTA (at pH 7.7) to copper-amended sludge resulted in the highest microbial activity (62 mg CH 4-COD g VSS −1 day −1) suggesting that Na 2H 2EDTA decreased the toxic effects of copper on the methanogenic activity of the anaerobic granular sludge. The highest methane production (159 %) was also observed upon Na 2H 2EDTA addition and simultaneous electricity application (pH 7.7). The energy consumption during the treatment was 560, 840, 1400 and 1680 kW h m −3 at current densities of 0.23, 0.34, 0.57 and 0.69 mA cm −2, respectively. This corresponded to a treatment costs in terms of electricity expenditure from 39.2 to 117.6 € per cubic meter of sludge.

Studies on the toxic effects of pentachlorophenol on the biological activity of anaerobic granular sludge

In order to explore the pathway of the anaerobic biotreatment of the wastewater containing pentachlorophenol (PCP) and ensure the normal operation of Upflow Anaerobic Sludge Blanket (UASB) reactor, the anaerobic sludge under different acclimation conditions were selected to seed and start up UASB reactors. Anaerobic toxicity assays were employed to study the biological activity, the tolerance and the capacity to degrade PCP of different anaerobic granular sludge from UASB reactors. Results showed that the anaerobic granular sludge acclimated to chlorophenols (CPs) could degrade PCP more quickly (up to 9.50 mg-PCP g −1 TVS d −1). And the anaerobic granular sludge without acclimation to CPs had only a little activity of degrading PCP (less than 0.07 mg-PCP g −1 TVS d −1). Different PCP concentrations (2, 4, 6, 8 mg L −1) had different inhibition effects on glucose utilization, volatile fatted acidity (VFA)-degrading and methanogens activity of PCP degradation anaerobic granular sludge, and the biological activity declined with the increase in PCP concentration. The methanogens activity suffered inhibition from PCP more easily. The different acclimation patterns of seeded sludge had distinctly different effects on biological activity of the degradation of PCP of anaerobic granular sludge from UASB reactors. The biological activity of the anaerobic granular sludge acclimated to PCP only was also inhibited. This inhibition was weak compared to that of anaerobic granular sludge acclimated to CPs, further, the activity could recover more quickly in this case. In the same reactor, the anaerobic granular sludge from the mid and base layers showed higher tolerance to PCP than that from super layer or if the sludge is unacclimated to CPs, and the corresponding recovery time of the biological activity in the mid and base layers were short. Acetate-utilizing methanogens and syntrophic propinate degraders were sensitive to PCP, compared to syntrophic butyrate degraders.

Inhibitory effect of ammonia nitrogen on specific methanogenic activity of anaerobic granular sludge

A series of batch experiments were conducted in 125 mL serum bottles to assess the toxicity of different concentrations of ammonia nitrogen to the specific methanogenic activity of anaerobic granular sludge from upflow anaerobic sludge bed(UASB) and expanded granular sludge bed(EGSB) reactors. The effects of pH value and temperature on toxicity of ammonia nitrogen to anaerobes were investigated. The results show that the specific methanogenic activity of anaerobic granular sludge suffers inhibition from ammonia nitrogen, the concentrations of ammonia nitrogen that produce 50% inhibition of specific methanogenic activity for sludge from UASB and EGSB reactor are 2.35 and 2.75 g/L, respectively. Hydrogen utilizing methanogens suffers less inhibition from ammonia nitrogen than that of acetate utilizing methanogens. Hydrogen-producing acetogens that utilize propionate and butyrate as substrates suffer serious inhibition from ammonia nitrogen. The toxicity of ammonia nitrogen to anaerobic granular sludge enhances when pH value and temperature increase. Anaerobic granular sludge can bear higher concentrations of ammonia nitrogen after being acclimated by ammonia nitrogen for 7 d.

Anaerobic Granular Sludge Bioreactor Technology

Anaerobic digestion is a mature wastewater treatment technology, with worldwide application. The predominantly applied bioreactor designs, such as the upflow anaerobic sludge blanket and expanded granular sludge bed, are based on the spontaneous formation of granular sludge. Despite the exploitation of granular reactors at full-scale for more than two decades, the mechanisms of granulation are not completely understood and numerous theories have been put forward to describe the process from a biological, ecological and engineering point of view. New technological opportunities are emerging for anaerobic digestion, aided by an improved understanding of microbiological and environmental factors affecting the formation and activity of anaerobic granular sludge.