Characteristics of methanogenic granules grown on propionate in an upflow anaerobic sludge blanket (UASB) reactor

Granulation of a propionate-degrading consortia was performed with a mesophilic propionate-acclimatized sludge in an upflow anaerobic sludge blanket (UASB) reactor. The granules formed were relatively small, ranging mainly from 0.3 to 0.6 mm in diameter, but had an excellent sedimentation velocity due to a high specific gravity of 1.355 g/cm³ (ash content, 48.2%). The ash consisted mainly of calcium (30.2%), phosphorus (19.7%), and magnesium (3.95%) forming plate crystals in the granules. The populations of three bacterial trophic groups present in the granules, propionate-degraders, hydrogenotrophic and aceticlastic methanogens were 5.6 × 10⁸, 1.6 × 10¹⁰, and 2 × 10⁹ (in most probable number/g mixed-liquor volatile suspended solids [MLVSS]), respectively, while the specific utilization rates of propionate, hydrogen, and acetate of the granules were 9.4, 850, and 20.9 (mmol/g MLVSS·d), respectively. Electron microscopic analysis showed that Methanothrix spp. appeared dominant over the granules. Total granular sludge concentration retained in the UASB reactor during 178 d of operation was 80.0 g mixed-liquor suspended solids (MLSS)/l-reactor, corresponding to 41.4 g MLVSS/l-reactor, which realized a high-rate methanogenic fermentation of propionate of 85 g chemical oxygen demand (COD)/l-reactor·d.     

Biosorption and biodegradation of pentachlorophenol (PCP) in an upflow anaerobic sludge blanket (UASB) reactor

In order to understand the fate of PCP in upflow anaerobic sludge blanket reactor (UASB) more completely, the sorption and biodegradation of pentachlorophenol (PCP) by anaerobic sludge granules were investigated. The anaerobic granular sludge degrading PCP was formed in UASB reactor, which was seeded with anaerobic sludge acclimated by chlorophenols. At the hydraulic retention time (HRT) of 20–22 h, and PCP loading rate of 200–220 mg l⁻¹ d⁻¹, UASB reactor exhibited good performance in treating wastewater which containing 170–180 mg l⁻¹ PCP and the PCP removal rate of 99.5% was achieved. Sequential appearance of tetra-, tri-, di-, and mono-chlorophenol was observed in the reactor effluent after 20 mg l⁻¹ PCP introduction. Sorption and desorption of PCP on the anaerobic sludge granules were all fitted to the Freundlich isotherm equation. Sorption of PCP was partly irreversible. The Freundlich equation could describe the behavior of PCP amount sorbed by granular sludge in anaerobic reactor reasonably well. The results demonstrated that the main mechanism leading to removal of PCP on anaerobic granular sludge was biodegradation, not sorption or volatization.     

Poultry slaughter wastewater treatment with an up-flow anaerobic sludge blanket (UASB) reactor

Removal of organic material from poultry slaughter wastewater as determined by changes in biological oxygen demand (BOD5) was investigated by adding three different types of inoculum combining cow manure, yeast extract or hydraulic residence time as variables with response vector of reduction of BOD5. In a 3-l reactors, a 95% removal of BOD5 from poultry slaughter wastewater was obtained with organic loading rates up to 31 kg BOD5 m(-3) d(-1) without loss of stability. This 95% removal was obtained between 25 and 39 degrees C with a hydraulic residence time between 3.5 and 4.5 h. The growth of the consortium of micro-organisms in the reactor followed a first-order kinetic with a constant specific growth rate of 0.054 h(-1). It was concluded that an inoculum from cow manure added with nutrients and yeast extract allowed a 95% removal of BOD5 from poultry slaughter wastewater at ambient temperatures within a hydraulic residence time of 4 h, sharply reducing possible environmental hazards.     

Toluene mineralization by denitrification in an up flow anaerobic sludge blanket (UASB) reactor

In order to examine the effect of easily degradable substrate such as acetate on toluene mineralization by denitrification, an upflow anaerobic sludge blanket (UASB) reactor in steady state was set up. The experimentation was carried out in two stages. Initially, the reactor was fed with a carbon loading rate of 250 mg acetate-C L-1 d-1 as electron source. Nitrate loading rate (mg ) was adjusted to obtain a constant C/N ratio of 1.4. In the second stage, five toluene-C loading rates (TLR, mg toluene-C L-1 d-1), 25, 50, 75, 100 and 125, were assessed while total carbon loading rate and C/N were maintained constant at 250 mg C L-1 d-1 and 1.4, respectively. In so doing, acetate-C loading rate (mg acetate-C L-1 d-1) was gradually substituted by toluene-C. When acetate-C was the only electron source a dissimilative denitrifying process resulted as indicated by bicarbonate yield YHCO3, mg produced/mg carbon consumed) of 0.74 +/- 0.005 and denitrifying yield (YN2, mg N2 produced/mg consumed) of 0.89 +/- 0.042. The addition of different TLR did not affect the biological process as consumption carbon efficiency (CCE) values remained up to 95% +/- 3.5 and YHCO3 and YN2 values were higher than 0.71 +/- 0.03 and 0.88 +/- 0.01, respectively. Toluene mineralization by denitrification in continuous culture was successfully achieved. A simple UASB denitrifying reactor system has promising applications for complete conversion of nitrate, toluene and acetate into N2 and CO2 with a minimal sludge production.     

Anammox bacteria enrichment in upflow anaerobic sludge blanket (UASB) reactor

We investigated the anaerobic ammonium oxidation (anammox) reaction in a labscale upflow anaerobic sludge blanket (UASB) reactor. Our aim was to detect and enrich the organisms responsible for the anammox reaction using a synthetic medium that contained low concentrations of substrates (ammonium and nitrite). The reactor was inoculated with granular sludge collected from a full-scale anaerobic digestor used for treating brewery wastewater. The experiment was performed during 260 days under conditions of constant ammonium concentration (50 mg NH₄/⁺-N/L) and different nitrite concentrations (50∼150 mg NO₂-N/L). After 200 days, anammox activity was observed in the system. The microorganisms involved in this anammox reaction were identified as CandidatusB. Anammoxidans andK. Stuttgartiensis using fluorescencein situ hybridization (FISH) method.     

Performance and granulation in an upflow anaerobic sludge blanket (UASB) reactor treating saline sulfate wastewater

An upflow anaerobic sludge blanket reactor was employed to treat saline sulfate wastewater. Mesophilic operation (35 ± 0.5 °C) was performed with hydraulic retention time fixed at 16 h. When the salinity was 28 g L^?1, the chemical oxygen demand and sulfate removal efficiencies were 52 and 67 %, respectively. The salinity effect on sulfate removal was less than that on organics removal. The methane productions were 887 and 329 cm³ L^?1 corresponding to the NaCl concentrations of 12 and 28 g L^?1, respectively. High salinity could stimulate microbes to produce more extracellular polymeric substances (EPSs) and granulation could be performed better. Besides, with the high saline surroundings, a great deal of Na⁺ compressed the colloidal electrical double-layer, neutralized the negative charge of the sludge particles and decreased their electrostatic repulsion. The repulsion barrier disappeared and coagulation took place. The maximum size of granules was 5 mm, which resulted from the coupled triggering forces of high EPSs and Na⁺ contents. Sulfate-reducing bacteria (SRB) were dominant in the high saline surroundings while the methane-producing archaea dominated in the low saline surroundings. The SRB were affected least by the salinity.     

Continuous dechlorination of tetrachloroethene in an upflow anaerobic sludge blanket reactor

Influences of hydraulic retention time (HRT) on dechlorination of tetrachloroethene (PCE) were investigated in an upflow anaerobic sludge blanket (UASB) reactor inoculated with anaerobic granular sludge non-pre-exposed to chlorinated compounds. PCE was introduced into the reactor at a loading rate of 3 mg/l d. PCE removal increased from 51 +/- 5% to 87 +/- 3% when HRT increased from 1 to 4 d, corresponding to an increase in the PCE biotransformation rate from 10.5 +/- 2.3 to 21.3 +/- 3.7 mumol/d. A higher ethene production rate, 0.9 +/- 0.2 mumol/d, was attained without accumulation of dichloroethenes at the HRT of 4 d. Dehalococcoides-like species were detected in sludge granules by fluorescence in situ hybridization, with signal strength in proportion to the extent of PCE dechlorination.     

Biodegradation of tech-hexachlorocyclohexane in a upflow anaerobic sludge blanket (UASB) reactor

Biodegradability of technical grade hexachlorocyclohexane (tech-HCH) was studied in an upflow anaerobic sludge blanket reactor (UASB) under continuous mode of operation in concentration range of 100-200 mg/l and constant HRT of 48 h. At steady state operation more than 85% removal of tech-HCH (upto 175 mg/l concentration) and complete disappearance of beta-HCH was observed. Kinetic constants in terms of maximum specific tech-HCH utilization rate (k) and half saturation velocity constant (K(L)) were found to be 11.88 mg/g/day and 8.11 mg/g/day, respectively. The tech-HCH degrading seed preparation, UASB reactor startup and degradation in continuous mode of operation of the reactor is presented in this paper.     

Anaerobic granule development for removal of pentachlorophenol in an upflow anaerobic sludge blanket (UASB) reactor

The granulation process using synthetic wastewater containing pentachlorophenol (PCP) in four 1.1 l laboratory scale upflow anaerobic sludge blanket (UASB) reactors was studied, and the anaerobic biotransformation of PCP during the granulation process investigated. After 110 days granular sludge was developed and up to 160 and 180 mg/l of PCP was added into the reactors R1 and R2, respectively, when they were inoculated with acclimated anaerobic sludge from an anaerobic digester of a citric acid plant. The inoculum was predominately composed of bacilli and filamentous bacteria. Granulation did not occur in reactors R3 and R4 which were inoculated with acclimated anaerobic sludge from aerobic sludge of the municipal sewage treatment plant which consisted mainly of cocci. Despite similar bacilli in the granule, the filamentous bacteria from reactor R1 were thicker than those of reactor R2. The granular sludge had a maximum diameter of 2.5 and 2.2 mm, and SMA of 1.44 and 1.32 gCOD/gTVS per day for reactors R1 and R2, respectively. Over 98% chemical oxygen demand (COD) removal rate and 99% of PCP removal rate were achieved when reactors R1 and R2 were operated at PCP and COD loading rates of 150 and 7.5 g/l per day, respectively. H₂-producing acetogens were the dominant anaerobes in the granular sludge.     

Treatment of catechol bearing wastewater in an upflow anaerobic sludge blanket (UASB) reactor: sludge characteristics

This paper deals with the characteristics of anaerobic microbial granules grown in an UASB reactor treating catechol bearing synthetic wastewater (SWW). The specific methanogenic activity of the sludge showed an increase in trend with an increase in the organic loading rate and the catechol concentration in the SWW. The settling velocity of individual granules in the size range of 0.5-2.5mm was found to be in the range of 30-75mh(-1). The ash content in the sludge was 11.7% with a sludge volume index of 18-20mlg(-1). The inorganic elemental distribution within the granules showed a decrease except that for phosphorous and cobalt, which increased by approximately 12% and 18%, respectively, after the treatment of SWW. Scanning electron microscopy (SEM) coupled with electron disperse X-ray analysis showed an increase in the sulphur content by approximately 300% after the treatment of SWW. Surface mineral composition of the granules determined by XRD analysis indicated the existence of vuagnatite (CaAlSiO(4)(OH)). SEM observation of the granules showed the predominance of Methanosaeta and Methanobacterium type of species on the surface along with a variety of other species.     

Layered structure of granules in upflow anaerobic sludge blanket reactor gives microbial populations resistance to metal ions

Metal ions (Cd²⁺, Cu²⁺, Ni²⁺, Zn²⁺ and Cr³⁺) did not affect glucose degradation or the production of methane during anaerobic digestion with intact and disintegrated granules from a UASB (Upflow Anaerobic Sludge Blanket) reactor. However, when Cu²⁺ was at 500 mg g^–1 VSS (volatile suspended solids) in the media, the glucose degradation rates and methane production rates decreased by 14% and 32% in disintegrated granules, respectively, whereas, in intact granules, decreases were 3% and 14%, respectively. When various electroplating metal ions were tested, 50% inhibition of acetate degradation and methane production were produced by 210–770 mg g^–1 VSS and 120–630 mg g^–1 VSS, respectively. The relative toxicity of the electroplating metals on methane production was in the order of Zn²⁺ (most toxic) > Ni²⁺ > Cu²⁺ > Cr³⁺ > Cd²⁺ (least toxic).     

Effects of hydrogen and formate on the degradation of propionate and butyrate in thermophilic granules from an upflow anaerobic sludge blanket reactor.

Degradation of propionate and butyrate in whole and disintegrated granules from a thermophilic (55 degrees C) upflow anaerobic sludge blanket reactor fed with acetate, propionate, and butyrate as substrates was examined. The propionate and butyrate degradation rates in whole granules were 1.16 and 4.0 mumol/min/g of volatile solids, respectively, and the rates decreased 35 and 25%, respectively, after disintegration of the granules. The effect of adding different hydrogen-oxidizing bacteria (both sulfate reducers and methanogens), some of which used formate in addition to hydrogen, to disintegrated granules was tested. Addition of either Methanobacterium thermoautotrophicum delta H, a hydrogen-utilizing methanogen that does not use formate, or Methanobacterium sp. strain CB12, a hydrogen- and formate-utilizing methanogen, to disintegrated granules increased the degradation rate of both propionate and butyrate. Furthermore, addition of a thermophilic sulfate-reducing bacterium (a Desulfotomaculum sp. isolated in our laboratory) to disintegrated granules improved the degradation of both substrates even more than the addition of methanogens. By monitoring the hydrogen partial pressure in the cultures, a correlation between the hydrogen partial pressure and the degradation rate of propionate and butyrate was observed, showing a decrease in the degradation rate with increased hydrogen partial pressure. No significant differences in the stimulation of the degradation rates were observed when the disintegrated granules were supplied with methanogens that utilized hydrogen only or hydrogen and formate. This indicated that interspecies formate transfer was not important for stimulation of propionate and butyrate degradation.     

Treatment of domestic wastewater in an up-flow anaerobic sludge blanket reactor followed by moving bed biofilm reactor

The performance of a laboratory-scale sewage treatment system composed of an up-flow anaerobic sludge blanket (UASB) reactor and a moving bed biofilm reactor (MBBR) at a temperature of (22–35 °C) was evaluated. The entire treatment system was operated at different hydraulic retention times (HRT’s) of 13.3, 10 and 5.0 h. An overall reduction of 80–86% for COD_total; 51–73% for COD_colloidal and 20–55% for COD_soluble was found at a total HRT of 5–10 h, respectively. By prolonging the HRT to 13.3 h, the removal efficiencies of COD_total, COD_colloidal and COD_soluble increased up to 92, 89 and 80%, respectively. However, the removal efficiency of COD_suspended in the combined system remained unaffected when increasing the total HRT from 5 to 10 h and from 10 to 13.3 h. This indicates that, the removal of COD_suspended was independent on the imposed HRT. Ammonia-nitrogen removal in MBBR treating UASB reactor effluent was significantly influenced by organic loading rate (OLR). 62% of ammonia was eliminated at OLR of 4.6 g COD m⁻² day⁻¹. The removal efficiency was decreased by a value of 34 and 43% at a higher OLR’s of 7.4 and 17.8 g COD m⁻² day⁻¹, respectively. The mean overall residual counts of faecal coliform in the final effluent were 8.9 × 10⁴ MPN per 100 ml at a HRT of 13.3 h, 4.9 × 10⁵ MPN per 100 ml at a HRT of 10 h and 9.4 × 10⁵ MPN per 100 ml at a HRT of 5.0 h, corresponding to overall log₁₀ reduction of 2.3, 1.4 and 0.7, respectively. The discharged sludge from UASB–MBBR exerts an excellent settling property. Moreover, the mean value of the net sludge yield was only 6% in UASB reactor and 7% in the MBBR of the total influent COD at a total HRT of 13.3 h. Accordingly, the use of the combined UASB–MBBR system for sewage treatment is recommended at a total HRT of 13.3 h.     

Performance of upflow anaerobic sludge blanket (UASB) reactor treating wastewaters containing carbon tetrachloride

The anaerobic biodegradation of carbon tetrachloride (CT) was investigated during the granulation process by reducing the hydraulic retention time, increasing the chemical oxygen demand (COD) and CT loadings in a 2l laboratory-scale upflow anaerobic sludge blanket (UASB) reactor. Anaerobic unacclimated sludge and glucose were used as seed and primary substrate, respectively. Granules were developed 4 weeks after start-up, which grew at an accelerated rate for 8 months, and then became fully grown. The effect of operational parameters such as influent CT concentrations, COD, CT loading, food to biomass ratio and specific methanogenic activity (SMA) were also considered during granulation. The granular sludge cultivated had a maximum diameter of 2.1 mm and SMA of 1.6 g COD/g total suspended solid (TSS) day. COD and CT removal efficiencies of 92 and 88% were achieved when the reactor was firstly operating at CT and COD loading rates of 17.5 mg/l day and 12.5 g/l day, respectively. This corresponds to hydraulic retention time of 0.28 day and food to biomass ratio of 0.5 g COD/g TSS day. Kinetic coefficients of maximum specific substrate utilization rate, half velocity coefficient, growth yield coefficient and decay coefficient were determined to be 2.4 × 10^–3 mg CT/TSS day^–1, 1.37 mg CT/l, 0.69 mg TSS/mg CT and 0.046 day^–1, respectively for CT biotransformation during granulation.     

Anaerobic ammonium oxidation process in an upflow anaerobic sludge blanket reactor with granular sludge selected from an anaerobic digestor

The purpose of this work was to evaluate the development of the anammox process by the use of granular sludge selected from a digestion reactor as a potential seed source in a lab-scale UASB (upflow anaerobic sludge blanket) reactor system. The reactor was operated for approximately 11 months and was fed by synthetic wastewater. After 200 days of feeding with NH₄ ⁺ and NO₂ ⁻ as the main substrates, the biomass showed steady signs of ammonium consumption, resulting in over 60% of ammonium nitrogen removal. This report aims to present the results and to more closely examine what occurs after the onset of anammox activity, while the previous work described the start-up experiment and the presence of anammox bacteria in the enriched community using the fluorescencein situ hybridization (FISH) technique. By the last month of operation, the consumed NO₂ ⁻N/NH₄ ⁺-N ratio in the UASB reactor was close to 1.32, the stoichiometric ratio of the anammox reaction. The obtained results from the influentshutdown test suggested that nitrite concentration would be one key parameter that promotes the anammox reaction during the start-up enrichment of anammox bacteria from granular sludge. During the study period, the sludge color gradually changed from black to red-brownish.     

Phototrophic bacterial production of oleic acid in an illuminated upflow anaerobic sludge blanket reactor

Phototrophic bacterial cells in the effluent from a lighted upflow anaerobic sludge blanket reactor supplied with a medium containing 142 mg S (as SO₄ ^2–) l^–1 accumulated a 6.8% w/w oleic acid content in cells and 19 mg cell-bound oleic acid l^–1 in the effluent. Pure cultures of Rhodopseudomonas palustris and Blastochloris sulfoviridis isolated from the effluent also accumulated 5.1 and 6.4% w/w oleic acid contents in cells, respectively. The oleic acid content in the cells recovered from the LUASB reactor effluent was related to the phototrophic bacterial population in the LUASB reactor. The inverse relationship was observed in the LUASB reactor between phototrophic bacterial growth and sulfate concentration in the influent.     

Anaerobic digestion of a petrochemical effluent using an upflow anaerobic sludge blanket reactor

Summary An UASB reactor was used for the anaerobic conversion of an acidic petrochemical effluent into a methane-rich biogas. Reactor efficiency was optimal at an HRT of 1.78 days and loading rate of 7.255 kg COD/m₃.d, A COD reduction of 83% was obtained. The gas production was 2.64 m/m .d (STP) and contained more than 90% CH₄. A further increase in the loading rate resulted in a drastic decrease in the reactor effectivity.     

Rapid granulation and sludge retention for tetrachloroethylene removal in an upflow anaerobic sludge blanket reactor

A laboratory scale upflow anaerobic sludge blanket (UASB) reactor was operated at 35 °C for over 200 days to investigate the granulation mechanism during tetrachloroethylene (TCE) biodegradation. Anaerobic, unacclimated sludge and glucose were used as seed and primary substrate, respectively. TCE-degrading granules developed after 1.5 months of start-up. They grew at an accelerated pace for 7 months. The TCE-degrading granules had a maximum diameter of 2.5 mm and specific methanogenic activity of 1.32 g chemical oxygen demand (COD) g^–1 total suspended solid (TSS) day^–1. 94% COD and 90% TCE removal efficiencies were achieved when the reactor was operating at loading rates as high as 160 mg TCE l^–1 day^–1 and 14 g COD l^–1 day^–1, after 230 days of continuous operation.     

Kinetics of anaerobic treatment of slaughterhouse wastewater in batch and upflow anaerobic sludge blanket reactor

The kinetics of anaerobic treatment of slaughterhouse wastewater in batch and upflow anaerobic sludge blanket (UASB) reactors was investigated. Different concentrations of organic matter in slaughterhouse wastewater did not change the first order kinetics of the reaction. In batch digesters, methane and nitrogen production stopped after 30-40, 20-30 h, respectively, and in UASB reactors it was terminated after 30-40 days. The constant of velocity was 3.93 and 0.23 h(-1) respectively, for methane and nitrogen production. The yield coefficient, Yp was 343 and 349 ml CH4 per g of chemical oxygen demand at standard temperature and pressure conditions for batch reactors and UASB reactor, respectively.     

Isolation of hydrogen-producing bacteria from granular sludge of an upflow anaerobic sludge blanket reactor

H₂-producing bacteria were isolated from anaerobic granular sludge. Out of 72 colonies (36 grown under aerobic conditions and 36 under anaerobic conditions) arbitrarily chosen from the agar plate cultures of a suspended sludge, 34 colonies (15 under aerobic conditions and 19 under anaerobic conditions) produced H₂ under anaerobic conditions. Based on various biochemical tests and microscopic observations, they were classified into 13 groups and tentatively identified as follows: From aerobic isolates,Aeromonas spp. (7 strains),Pseudomonas spp. (3 strains), andVibrio spp. (5 strains); from anaerobic isolates,Actinomyces spp. (11 strains),Clostridium spp. (7 strains), andPorphyromonas sp. When glucose was used as the carbon substrate, all isolates showed a similar cell density and a H₂ production yield in the batch cultivations after 12h (2.24–2.74 OD at 600 nm and 1.02–1.22 mol H₂/mol glucose, respectively). The major fermentation by-products were ethanol and acetate for the aerobic isolates, and ethanol, acetate and propionate for the anaerobic isolates. This study demonstrated that several H₂ producers in an anaerobic granular sludge exist in large proportions and their performance in terms of H₂ production is quite similar.