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1.
The performance and microbial community structure of a pilot-scale upflow anaerobic sludge blanket (UASB) reactor inoculated with flocculent sludge were investigated over 52 days. The characteristics of corn-ethanol wastewater were as follows: CODCr, 1,050–4,970 mg l?1; ammonia, 14–298 mg l?1; and alkalinity, 332–2,867 mg l?1. The UASB could start up smoothly with a hydraulic loading rate lower than 180 l h?1 and a ratio of volatile fatty acid versus alkalinity between 0.04 and 0.48. The maximum gas production rate was 432 l h?1 and the highest volumetric loading rate of 7.2 kg m?3 day?1 was obtained after 48 days. The 1 mm granules could form a complex network and were composed of many Methanosaeta. Aceticlastic methanogens served as a dominant methanogenic group, which accounted for the relatively high resistance to shock loading.  相似文献   

2.
A model has been developed and experimentally checked for the physical behavior of sludge in the blanket in upflow reactors. The model is based on the mass balance for the sludge in the blanket, and can be used to predict the distribution of sludge in an upflow reactor in relation with the gas production, sludge settling characteristics, and the linear fluid velocity in the reactor. The quantitative values of the transport factors that are a measure of the efficiency of the transport of sludge by the fluid streams occurring in the reactor were determined experimentally in reactors of 30- and 200-m(3) volumes. As this was done for wastewater containing lower fatty acids as the main organic pollutants and for sludge with good settling characteristics, the predictive value of the model is limited. It may be used for the second (methane forming) step of anaerobic treatment of wastewater.  相似文献   

3.
Attached biofilm reactors provide the means for implementing energy-efficient anaerobic wastewater treatment at full scale. Progress has been made in the development of fixed, expanded and fluidized bed anaerobic processes by addressing fundamental reactor design issues. Several new biofilm reactor concepts have evolved from recent studies.  相似文献   

4.
The effect of cationic polymer additives on biomass granulation and COD removal efficiency had been examined in lab-scale upflow anaerobic sludge blanket (UASB) reactors, treating low strength synthetic wastewater (COD 300-630 mg/l). Under identical conditions, two reactors were operated with and without polymer additives in inoculum under four different organic loading rates (OLRs). The optimum polymer dose was adopted based upon the results of jar test and settling test carried out with inoculum seed sludge. With the use of thick inoculum, SS greater than 110 g/l and VSS/SS ratio less than 0.3, granulation was observed in UASB reactor treating synthetic wastewater as well as actual sewage, when OLR was greater than 1.0 kg COD/m(3) d. Polymer additive with such thick inoculum was observed to deteriorate percentage granules and COD removal efficiency compared to inoculum without polymer additives. At OLR less than 1.0 kg COD/m(3) d, proper granulation could not be achieved in both the reactors inoculated with and without polymer additive. Also, under this low loading, drastic reduction in COD removal efficiency was observed with polymer additives in inoculum. Hence, it is rational to conclude that biomass granulation for treatment of low strength biodegradable wastewater depends on the applied loading rate and selection of thick inoculum sludge.  相似文献   

5.
The microorganisms diversity in a full-scale UASB reactor treating domestic sewage was studied by molecular techniques, with the objective of identifying the population differences associated with the specific methanogenic activity (SMA) of the sludges. Samples were collected at levels A (0.8 m; bottom), B (1.3 m), C (1.8 m), D (2.3 m) and E (2.8 m). Actinobacteria was dominant at the three lower points and should have been primarily responsible for the degradation of organic matter. DNA sequences belonging to Methanomicrobiales order of Archaea domain was detected in all five levels with the majority producing methane from hydrogen and carbon dioxide. Points A and E showed similar bacteria variety. The SMA of point A was the highest (0.374 g COD-CH4/g SSV.d); however, the point E showed much lower value, probably due to the predominance of Proteobacteria phylum, including sulfate-reducing bacteria. In the overall, the results obtained can be considered important because data from full-scale UASB reactors treating domestic sewage remain scarce.  相似文献   

6.
The olive oil industry is one of the most typical and economically important Portuguese agro-industries, 29,900 tons of olive oil having been produced in 2002/2003. This industry generates large amounts of olive oil wastewaters (OOWW), which are difficult to degrade and thus cause a negative environmental impact. Jet-loop reactors (JACTO) developed and scaled-up by our group have been successfully used for biological treatment of winery and OOWW. This study aimed to determine the interactions of reactor hydrodynamics with microflora profiles during bio-treatment of OOWW. Bio-treatment was performed using a 20-dm3 JACTO bioreactor achieving a chemical oxygen demand (COD) and phenolic compounds removal rate of 70% at a hydraulic retention time of 12 days. Bio-treatment was scaled-up to 200-dm3 JACTO bioreactor, reaching 87% COD removal and 80% phenolic compounds removal. Microflora present on OOWW were identified on samples taken before, during, and at the end of bio-treatment. Identification of isolates was carried out at genus and/or species level. Samples from the bio-treatments did not show any fungi; most of the isolates belonged to the Bacillus genus (with predominance of Bacillus megaterium, Bacillus sphaericus, and Brevibacillus brevis). The good COD and phenolic compounds removal rate indicates that the microbial community selected during the treatment is well adapted to the stress conditions imposed by this special type of bioreactor.  相似文献   

7.
A simple, efficient and cost-effective method for municipal wastewater treatment is examined in this paper. The municipal wastewater is treated using an upflow anaerobic sludge bed (UASB) reactor followed by flash aeration (FA) as the post-treatment, without implementing aerobic biological processes. The UASB reactor was operated without recycle, at hydraulic retention time (HRT) of 8 h and achieved consistent removal of BOD, COD and TSS of 60-70% for more than 12 months. The effect of FA on UASB effluent post-treatment was studied at different HRT (15, 30 and 60 min) and dissolved oxygen (DO) concentrations (low DO = 1-2 mg/L and high DO = 5-6 mg/L). The optimum conditions for BOD, COD and sulfide removal were 30-60 min HRT and high DO concentration inside the FA tank. The final effluent after clarification was characterized by BOD and COD values of 28-35 and 50-58 mg/L, respectively. Sulfides were removed by more than 80%, but the fecal coliform only by ~2 log. The UASB followed by FA is a simple and efficient process for municipal wastewater treatment, except for fecal coliform, enabling water and nutrients recycling to agriculture.  相似文献   

8.
Li J  Wang J  Luan Z  Deng Y  Chen L 《Bioresource technology》2011,102(10):5709-5716
A two-stage UASB reactor was employed to pretreat acrylic fiber manufacturing wastewater. Mesophilic operation (35 ± 0.5 °C) was performed with hydraulic retention time (HRT) varied between 28 and 40 h. Mixed liquor suspended solids (MLSS) in the reactor was maintained about 8000 mg/L. The results showed COD and sulfate removal could be kept at 51% and 75%, respectively, when the HRT was no less than 38 h. Sulfate reduction mainly occurred in the acidification-stage reactor while methane production mainly occurred in the methane-stage reactor. The size of granule formed in the acidification-stage reactor ranged between 1 and 5 mm while the largest size of granule in the methane-stage reactor ranged from 0.5 to 2 mm. Compared to microbial populations in the acidification-stage reactor, the microbial diversity in methane-stage reactor was more abundant. In the acidification-stage reactor, the Syntrophobacter sulfatireducens devoted to both sulfate reduction and acetate production.  相似文献   

9.
The treatment of winery wastewater in three upflow anaerobic fixed-bed reactors (S9, S30 and S40) with low density floating supports of varying size and specific surface area was investigated. A maximum OLR of 42 g/l day with 80 ± 0.5% removal efficiency was attained in S9, which had supports with the highest specific surface area. It was found that the efficiency of the reactors increased with decrease in size and increase in specific surface area of the support media. Total biomass accumulation in the reactors was also found to vary as a function of specific surface area and size of the support medium. The Stover–Kincannon kinetic model predicted satisfactorily the performance of the reactors. The maximum removal rate constant (U max) was 161.3, 99.0 and 77.5 g/l day and the saturation value constant (K B) was 162.0, 99.5 and 78.0 g/l day for S9, S30 and S40, respectively. Due to their higher biomass retention potential, the supports used in this study offer great promise as media in anaerobic fixed bed reactors. Anaerobic fixed-bed reactors with these supports can be applied as high-rate systems for the treatment of large volumes of wastewaters typically containing readily biodegradable organics, such as the winery wastewater.  相似文献   

10.
Distillery wastewater from barley-shochu making was anaerobically treated by a single upflow anaerobic sludge blanket (UASB), and stable operation at a volumetric TOC loading rate of 3 g/l·d could be attained by diluting raw wastewater to give a TOC concentration of less than 6,000 mg/l (18,000 mg/l as CODer). When the distribution of the concentrations of aliphatic acids at various levels within the reactor was investigated, it was found that the methanogenic gasification reaction did not occur in the sludge blanket of the reactor. Distillery wastewater from barley-shochu making with various TOC concentrations was preliminary adjusted to pH 7 and treated by a single passage without circulation of effluent to the bottom of the reactor. As a result, a maximum TOC removal rate (Vmax) of 28.5 g/l·d and a saturation constant (Ks) of 0.63 g/l were obtained.  相似文献   

11.
Saline adaptation of granules in mesophilic UASB reactors   总被引:1,自引:0,他引:1  
We exposed mesophilic up-flow anaerobic sludge blanket (UASB) reactors to high concentrations of NaCl to elucidate the saline adaptation capacity of their granular sludge. We operated 10 lab-scale UASB reactors at 37 °C and added NaCl to the influent either abruptly or gradually. With abrupt addition, NaCl concentrations were increased from 0 g L−1 to 20, 30, 35, 40, 45, or 50 g L−1. With gradual addition, the NaCl concentrations were gradually increased from 0 to 64 g L−1 or 0 to 40 g L−1. We successfully saline-adapted the granules up to 32 g NaCl L−1, while maintaining high reactor performance, suggesting that 32 g NaCl L−1 is a practical level for system operation. In the UASB reactors gradually exposed to 32 g L−1 NaCl, methane production decreased by only 13%. We also learned that combining abrupt and gradual salinity increases could shorten the adaptation period. Thus we were able to shorten the adaptation period to only 30 days by increasing the salinity abruptly to 20 g L−1, followed by gradual adaptation to 30 g NaCl L−1.  相似文献   

12.
Supplying clean water to fulfill human requirements is one of this century’s priorities. Global water resources are barely aligned with the rising demand, which is further aggravated by rising population, climate change and water quality problems. Consequently, there is a persistent need for innovative technologies to valorize unconventional water resources such as domestic wastewater. Graphene holds promising prospects in developing domestic wastewater treatment to qualitatively enhance treatment efficiency and quantitatively increase water supply. This review highlights the existing wastewater treatment processes along with their challenges according to South Australian wastewater treatment plants (WWTPs) which are representative of many modern WWTPs. The discussion will also cover the current and potential applications of graphene for domestic wastewater treatment, as well as obstacles and research priorities required for commercialization.  相似文献   

13.
14.
In this paper, trace elements (TE) adding was investigated in one bench-scale UASB reactor treating solo simple molecule wastewater with the aim of evaluating its effect on enhancing biofilm formation. After adding sufficient TE (3 mL/L) in the influent, during 3 days, COD removal efficiency increased from 74% to 90% comparing to no adding TE. Over 55 days of operation, the organic loading rate (OLR) reached 11 g/L/day with COD removal efficiencies greater than 90%. While in the steady running period no effect even improvement on treatment performance was observed without any TE adding. The results illuminated that TE accounted for quick start-up of the UASB biofilm system rather than ever known biocatalyst.  相似文献   

15.
16.
The wastewater from the dairy industries usually contains high concentrations of contaminants and, since the volume generated is also high, the total contaminant load is very significant. Among the available options for treatment, biological degradation looks like the most promising one. Furthermore, the supplementation of the native microbial populations with external microorganisms with high specific degradation rates (bio-augmentation) has demonstrated to improve the performance of treatment. The main objective of this research was to select a combination of bacteria to improve the aerobic treatment of dairy processing wastewater. For this purpose, eleven fat/protein-degrading microorganisms belonging to the genera Bacillus, Serratia, Lactococcus, Enterococcus, Stenotrophomonas, Klebsiella and Escherichia, were evaluated as potential degrading bacteria using a Plackett-Burman design. Assays were carried out to select the strains that most significantly influenced the degradation of wastewater and biomass yield, in terms of COD removal. A simulated dairy industry effluent was used as culture medium. Four strains were selected as potential members of the microbial consortium: Lactococcus garvieae, Bacillus thuringiensis, Escherichia coli and Stenotrophomonas sp. The optimal operation temperature and pH range of the selected consortium were 32°C and 6 ~ 8, respectively. The degradation percentages reached with the selected consortium were 80.67 and 83.44% at 24 and 48 h, respectively. The selected consortium significantly improved the degradation of the dairy wastewater, and the degradation degree achieved by this consortium was higher than by using the strains individually.  相似文献   

17.
Studies have been carried out to correlate biogas-induced mixing and granulation in upflow anaerobic sludge blanket (UASB) reactors, treating low-strength as well as high-strength biodegradable wastewaters. A dimensionless granulation index (GI) has been framed taking into account the mixing in sludge bed due to produced biogas. Analysis of full-scale, pilot-scale and lab-scale UASB reactors treating actual wastewaters reveals the significance of biogas-induced mixing, represented by GI, on granulation of biomass in the reactors. For obtaining proper granulation in UASB reactors (percentage granules greater than 50%, w/w), resulting in higher chemical oxygen demand (COD) removal efficiency, it is recommended to maintain GI values in the range of 15,000–57,000.  相似文献   

18.
An experimental study was carried out to compare the performance of selected anaerobic high rate reactors operated simultaneously at 37?°C. The three reactors, namely upflow anaerobic sludge bed reactor (UASB), hybrid of UASB reactor and anaerobic filter (anaerobic hybrid reactor – AHR) and anaerobic baffled reactor (ABR), were inoculated with the anaerobic digested sludge from municipal wastewater treatment plant and tested with synthetic wastewater. This wastewater contained sodium acetate and glucose with balanced nutrients and trace elements (COD 6000?mg?·?l?1). Organic loading rate (B v ) was increased gradually from an initial 0.5?kg?·?m?3?·?d?1 to 15?kg?·?m?3?·?d?1 in all the reactors. From the comparison of the reactors' performance, the lowest biomass wash-out resulted from ABR. In the UASB, significant biomass wash-out was observed at the B v 6?kg?·?m?3?·?d?1, and in the AHR at the B v 12?kg?·?m?3?·?d?1. The demand of sodium bicarbonate for pH maintenance in ABR was two times higher as for UASB and AHR. The efficiency of COD removal was comparable for all three reactors – 80–90%. A faster biomass granulation was observed in the ABR than in the other two reactors. This fact is explained by the kinetic selection of filamentous bacteria of the Methanotrix sp. under a high (over 1.5?g?·?l?1) acetate concentration.  相似文献   

19.
This paper describes and discusses the main problems related to anaerobic batch and fed-batch processes for wastewater treatment. A critical analysis of the literature evaluated the industrial application viability and proposed alternatives to improve operation and control of this system. Two approaches were presented in order to make this anaerobic discontinuous process feasible for industrial application: (1) optimization of the operating procedures in reactors containing self-immobilized sludge as granules, and (2) design of bioreactors with inert support media for biomass immobilization. Received: 22 May 2000 / Received revision: 20 July 2000 / Accepted: 21 July 2000  相似文献   

20.
The stackable and submergible microbial fuel cell (SS-MFC) system was fabricated consisting of three MFC modules (#1, #2 and #3) that were immersed in an anaerobic tank as a 30 L anode compartment. Each module consisted of the anion exchange membrane–membrane electrode assembly (A-MEA) and cation exchange membrane-MEA (C-MEA). Two MEAs shared a cathode compartment in the module and the three modules shared a anode compartment The SS-MFC system was operated with two phase. After batch feeding (phase I), the system was operated under continuous mode (phase II) with different organic concentrations (from 50 to 1000 mg/L) and different hydraulic retention times (HRT; from 3.4 to 7.2 h). The SS-MFC system successfully produced a stable voltage. A-MEA generated a lower power density than the C-MEA because of the former’s high activation and resistance loss. C-MEA showed a higher average maximum power density (3.16 W/m3) than A-MEA (2.82 W/m3) at 70 mL/min (HRT of 7.2 h). The current density increased as the organic concentration was increased from 70 to 1000 mg/L in a manner consistent with Monod kinetics. When the HRT was increased from 3.4 to 7.2 h, the power densities of the C-MEAs increased from 34.3–40.9 to 40.7–45.7 mW/m2, but those of the A-MEAs decreased from 25.3–48.0 to 27.7–40.9 mW/m2. Although power generation was affected by HRT, organic concentrations, and separator types, the proposed SS-MFC modules can be applied to existing wastewater treatment plants.  相似文献   

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