Brewery wastewater treatment using anaerobic inverse fluidized bed reactors

Two anaerobic inverse fluidized bed reactors were utilized to evaluate organic matter removal from brewery wastewater, applying different OLR and testing two support materials. Hydrodynamic tests varying liquid flow and solid concentration were developed on the supports in order to establish operational conditions. A batch colonization stage was applied using 25% active volume of extendosphere and triturated polyethylene as support materials. The reactors were subsequently operated continuously with stepwise increments in organic loading rate until limiting conditions was reached. For the supports studied, IFBR technology was suitable for organic matter removal present in brewery wastewater with COD removal efficiencies greater than 90%. The reactor with triturated polyethylene support showed an excellent COD removal with OLR values up to 10 g COD/Ld, whereas the reactor with extendosphere support had an excellent hydrodynamic and biologic behavior working with OLR values up to 70 g COD/Ld.     

The fluidized bed reactor in the anaerobic treatment of wine wastewater

The aim of the present work is the performance evaluation of a fluidized bed reactor in the anaerobic treatment of a wastewater deriving from the washing operations of the wine industry. The results are in agreement with the ones obtained using a mixture of municipal and food processing wastewaters containing high organic contents. A comparison with other liquid wastes shows that no subtrate inhibition phenomenon occurs with the above substrates. A saturation kinetic model is also presented for describing the dependence of the COD removal rate on the organic loading rate.     

Performance of anaerobic thermophilic fluidized bed in the treatment of cutting-oil wastewater

This paper examines the effect of organic loading rate on the removal efficiency of COD and TOC anaerobic thermophilic fluidized bed reactor (AFBR) in the treatment of cutting-oil wastewater at different hydraulic retention time (HRT) conditions. The essays are development at laboratory scale using a porous support medium. The AFBR reactor was subjected to a programme of steady-state operation over a range of hydraulic retention times, HRTs, in the range 12-2h and organic loading rates, OLRs, between 11.9 and 51.3kgCOD/m(3)d. The highest efficiency was 95.9% for an OLR of 13kgCOD/m(3)d and HRT of 11h. Over an operating period of 92 days, an OLR of 51.3kgCOD/m(3)d was achieved with 67.1% COD removal efficiency (71.3% TOC) in the experimental AFBR reactor. Although the level of biogas generation was not high, the anaerobic fluidized bed technology provided significant advantages over the conventional physico-chemical treatment applied in the factory. The effluent had a better quality (lower organic loading) and it was possible to reuse it in different applications in the factory (e.g., irrigation of gardens). The biological treatment did not lead to the generation of oily sludge, which is considered as hazardous waste by legislation. Furthermore, a continuous stream is produced and this reduced the impact of large flows discharged 4-5 times per week to the urban collector and MWWTP (municipal wastewater treatment plant).     

Biofilm reactors in anaerobic wastewater treatment

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.     

Biological cyanide degradation in aerobic fluidized bed reactors: treatment of almond seed wastewater

The continuous aerobic transformation of synthetic cyanide waste-water, amygdalin solutions and almond seed extract containing cyanide was investigated in several fluidized bed reactors. Various inocula consisting of activated sludge or soil slurry were used. Successful inoculation was achieved with simple soil slurry. No significant influence was found between the performance of the systems inoculated with a cyanide contaminated soil and a garden soil. The performance and stability of the reactors with respect to degradation rate were tested for a range of cyanide loading conditions, with feed containing only cyanide, and with different additional carbon sources, as well as various CN ratios at a hydraulic retention time of 24 h. No growth with cyanide as the sole source of carbon and nitrogen was observed. The system with lactate as the organic C-source was capable of operating at cyanide concentrations of 160 ppm cyanide with a conversion rate of 0.125 kg cyanide/m³ d. Ammonia was the end product and the effluent concentration was 0.5 ppm CN^–. The systems with ethanol as the organic C-source could degrade only 0.05 kg cyanide/m³ d, whose feed concentration was 60 ppm cyanide. Amygdalin, an organic cyanide-containing compound present in stone fruit seeds, was fed as a model substrate. Degradation rates up to 1.2 kg COD/m³ d could be measured with no free or organically bound cyanide in the effluent. These rates were limited by oxygen transfer, owing to the large amount of degradable COD. The further investigations with almond seed extracts, confirmed the applicability of the aerobic process to treat food-processing waste streams having low concentrations of cyanide with high COD content.The authors with to thank Dr. Ö.M. Kurt for useful discussions.     

Real evidence about zeolite as microorganisms immobilizer in anaerobic fluidized bed reactors

Using the scanning electronic microscopy, it was observed that natural zeolite possesses excellent physical characteristics as a support medium in anaerobic fluidized bed reactors (AFBR). Samples for biomass analysis were taken from two identical laboratory-scale AFBR (R-1 and R-2), which were operated with 25% of fluidization. These reactors treated distillery wastewaters (vinasses) at mesophilic temperature (30 ± 2 °C). The experiments were carried out with 0.25–0.50 and 0.50–0.80 mm zeolite particle diameter in reactors R-1 and R-2, respectively. The biomass concentration attached to zeolite in both reactors was found to be in the range of 40–45 g volatile solids/l. COD removal efficiencies as high as 90% were achieved at organic loading rate (OLRs) of up to 20 g COD/l day. The volatile fatty acid (VFA) levels were always lower that the suggested limits for digester failure. The yield coefficient of methane production was 0.29 l CH₄(at STP)/g COD consumed and was virtually independent of the OLR applied. A hybridization technique (fluorescence in situ hybridization, FISH) helped determine the predominant anaerobic microorganisms that colonized the natural zeolite, which were found to be Methanosaeta and Methanosarcinaceae, observing a reduced number of sulphate reducing bacteria. The results obtained for reactors R-1 and R-2 were very similar, showing that the particle size did not significantly influence the microbial community immobilized on zeolite.     

Startup of anaerobic fluidized bed reactors with acetic acid as the substrate

The startup of anaerobic fluidized bed reactors, which use Manville R-633 beads as the growth support media, acetate enriched bacterial culture as the inoculum, and acetic acid as the sole substrate, is studied. Tow startup strategies are evaluated: one based on maximum and stable substrate utilization and another based on maximum substrate loading controlled by reactor pH. The startup process is characterized using a number of operational parameters.The reactors again excellent total organic carbon (TOC) removal (i.e., > 97% at a feed concentration of 5000 mg TOC/L) and stable methane production (i.e., 0.90 L CH(4)/g TOC, where TOC(r) is TOC removed) at a early stage of the startup process, regardless of the strategies applied. The loading can be increased rapidly without the danger of being overloaded. Significant losses of growth support media and biomass caused by gas effervescence at higher loadings limits the maximum loading that can be safely applied during startup process.A high reactor immobilized biomass inventory is achievable using the porous growth support media (e.g., Manville 633 beads). A rapid increase in loading creates a substrate rich environment that yields more viable reactor biomass. Both substrate utilization rate (batch and continuous) and immobilized biomass inventory stabilize concomitantly at the late stage of the startup process, indicating the attainment of steady-state conditions in reactors. Therefore, they are better parameters that TOC removal and methane production for characterizing the entire startup process of aerobic fluidized bed reactor.The strategy based on maximum substrate loading controlled by reactor pH significantly shortens the startup time. In this case, the reactor attains steady-state conditions approximately 140 days after startup. On the other hand, a startup time of 200 days is required when the strategy based maximum substrate utilization is adopted. (c) 1993 John Wiley & Sons, Inc.     

Anaerobic treatment of winery wastewater in fixed bed reactors

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.     

Startup of anaerobic biofilm fluidized bed reactors on molasses and phenol under various conditions

Fluidized sand bed anaerobic biofilm reactors were operated in parallel to study the effects of inoculum, loading, residence time and carrier type on the startup dynamics for the degradation of molasses and phenol. Degradation rates generally depended most directly on concentrations rather than on other operating variables. Residence times did not appear to directly influence startup. Short residence times and high loadings gave the highest specific activities for both substrates. The type of inoculum was found to be most important for the molasses system, and inoculation on fresh carrier was found to be better than reinoculation. The two times higher specific biomass retention on Siran porous glass gave essentially the same degradation rates on a volume basis.List of Symbols L kg/h loading of reactor - M kg/kg biomass per carrier mass - Red. % reduction of feed concentration due to degradation - R kg/(m³ · h) reaction rate - S kg/m³ substrate concentration in reactor and effluent - S ₀ kg/m³ substrate concentration in feed - t h time     

Evaluation of inverse anaerobic fluidized bed reactor for treating high strength organic wastewater

The aim of this work is to evaluate the feasibility of an inverse fluidized bed reactor for the anaerobic digestion of distillery effluent, with a carrier material that allows low energy requirements for fluidization, providing also a good surface for biomass attachment and development. Inverse fluidization particles having specific gravity less than one are carried out in the reactor. The carrier particles chosen for this study was perlite having specific surface area of 7.010 m2/g and low energy requirements for fluidization. Before starting up the reactor, physical properties of the carrier material were determined. One millimeter diameter perlite particle is found to have a wet specific density of 295 kg/m3. It was used for the treatment of distillery waste and performance studies were carried out for 65 days. Once the down flow anaerobic fluidized bed system reached the steady state, the organic load was increased step wise by reducing hydraulic retention time (HRT) from 2 days to 0.19 day, while maintaining the constant feed of chemical oxygen demand (COD) concentration. Most particles have been covered with a thin biofilm of uniform thickness. This system achieved 84% COD removal at an organic loading rate (OLR) of 35 kg COD/m3/d.     

Performance evaluation and phylogenetic characterization of anaerobic fluidized bed reactors using ground tire and pet as support materials for biohydrogen production

This study evaluated two different support materials (ground tire and polyethylene terephthalate [PET]) for biohydrogen production in an anaerobic fluidized bed reactor (AFBR) treating synthetic wastewater containing glucose (4000 mg L⁻¹). The AFBR, which contained either ground tire (R1) or PET (R2) as support materials, were inoculated with thermally pretreated anaerobic sludge and operated at a temperature of 30 °C. The AFBR were operated with a range of hydraulic retention times (HRT) between 1 and 8 h. The reactor R1 operating with a HRT of 2 h showed better performance than reactor R2, reaching a maximum hydrogen yield of 2.25 mol H₂ mol⁻¹ glucose with 1.3 mg of biomass (as the total volatile solids) attached to each gram of ground tire. Subsequent 16S rRNA gene sequencing and phylogenetic analysis of particle samples revealed that reactor R1 favored the presence of hydrogen-producing bacteria such as Clostridium, Bacillus, and Enterobacter.     

Biofilm development in laboratory methanogenic fluidized bed reactors

Biofilm development on sand with different heterogeneous inocula was studied in laboratory-scale methanogenic fluidized bed reactors. Both the course of biofilm formation during reactor start-up and the bacterial composition of newly developed biofilms at steady-state were found to be similar irrespective of the type of inoculum applied. Biofilm formation proceeded according to a fixed pattern that could be subdivided in three consecutive phases, designated as the lag phase, biofilm production phase, and steady-state phase. Methanogenic activity and biomass content of the fluidized bed granules were found to be accurate parameters of the course of biofilm formation. More indirect parameters monitored did not give unambiguous results in all instances. The composition of the newly developed biomass as assessed on the basis of potential methanogenic activities on different substrates and of the concentration of specific methanogenic cofactors was consistent with electron microscopic observations.     

Distribution and behavior of sludge in upflow reactors for anaerobic treatment of wastewater

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.     

Treatment of food processing wastewater in a full-scale jet biogas internal loop anaerobic fluidized bed reactor

A full-scale jet biogas internal loop anaerobic fluidized bed (JBILAFB) reactor, which requires low energy input and allows enhanced mass transfer, was constructed for the treatment of food processing wastewater. This reactor has an active volume of 798 m³ and can treat 33.3 m³ wastewater per hour. After pre-treating the raw wastewater by settling, oil separating and coagulation-air floating processes, the reactor was operated with a relatively shorter start-up time (55 days). Samples for the influent and effluent of the JBILAFB reactor were taken and analyzed daily for the whole process including both the start-up and stable running periods. When the volumetric COD loading fluctuated in the range of 1.6–5.6 kg COD m⁻³ day⁻¹, the COD removal efficiency, the volatile fatty acid(VFA)/alkalinity ratio, the maximum biogas production and the content of CH₄ in total biogas of the reactor were found to be 80.1 ± 5%, 0.2–0.5, 348.5 m³ day⁻¹ and 94.5 ± 2.5%, respectively. Furthermore, the scanning electron microscope (SEM) results showed that anaerobic granular sludge and microorganism particles with biofilm coexisted in the reactor, and that the bacteria mainly in bacilli and cocci were observed as predominant species. All the data demonstrated that the enhanced mass transfer for gas, liquid and solid phases was achieved, and that the formation of microorganism granules and the removal of inhibitors increased the stability of the system.     

Protection of biofilms against toxic shocks by the adsorption and desorption capacity of carriers in anaerobic fluidized bed reactors

The aim of this study was to select a support medium for an anaerobic biofilm fluidized bed reactor (AFBR) for waste water treatment. Six materials, shale, pumice, porous glass, quartz sand, activated carbon and anthracite were used as carriers for the biofilm. The reactors were operated in parallel for several months with vapour condensate from a sulfite cellulose process as feed. The criteria used for the evaluation were: a) Reproducibility of the reactor performance, b) performance of the different carriers under various loading rates, c) stability against toxic shock loadings using 2,4,6-trichlorophenol (TCP) as toxicant, d) recovery capacity after intoxication and starvation, e) adsorption/desorption behavior of the carriers.A comparison between four runs showed good reproducibility of the steady state removal rates. The performance of the reactors and the stability of the degradation rates were tested for a range of loading conditions. Unbuffered, buffered and pH controlled conditions were compared. The pumice carrier was best with respect to the degradation rate achieved per carrier mass. The response of the reactors to massive TCP step loadings was tested. Loadings less than 1.5 kg TCP/m³d resulted in initially normal gas production rates for all the systems, except the activated carbon, whose gas production was partially inhibited from the start. After increasing the load to 1.5 kg TCP/m³d the gas production rates of all the other reactors fell abruptly to zero. Restarting after 2 months, all reactors showed methanogenic activity without requiring new inoculum.Adsorption and desorption experiments with TCP showed that only the anthracite and activated carbon adsorbed appreciable amounts. The activated carbon had the greatest adsorption capacity but did not release the TCP by desorption, as did the anthracite.A bicomponent (pumice and anthracite) carrier mixture was compared in biological experiments with pumice and anthracite carrier alone, with and without TCP loading. The pumice and the carrier-mix performed equally well under non-toxic-loading conditions. With TCP toxic loading, the performance of the anthracite was superior. The anthracite carrier could be regenerated, owing mainly to its capacity for desorption.     

Mathematical model for a three-phase fluidized bed biofilm reactor in wastewater treatment

A mathematical model for a three phase fluidized bed bioreactor (TFBBR) was proposed to describe oxygen utilization rate, biomass concentration and the removal efficiency of Chemical Oxygen Demand (COD) in wastewater treatment. The model consisted of the biofilm model to describe the oxygen uptake rate and the hydraulic model to describe flow characteristics to cause the oxygen distribution in the reactor. The biofilm model represented the oxygen uptake rate by individual bioparticle and the hydrodynamics of fluids presented an axial dispersion flow with back mixing in the liquid phase and a plug flow in the gas phase. The difference of settling velocity along the column height due to the distributions of size and number of bioparticle was considered. The proposed model was able to predict the biomass concentration and the dissolved oxygen concentration along the column height. The removal efficiency of COD was calculated based on the oxygen consumption amounts that were obtained from the dissolved oxygen concentration. The predicted oxygen concentration by the proposed model agreed reasonably well with experimental measurement in a TFBBR. The effects of various operating parameters on the oxygen concentration were simulated based on the proposed model. The media size and media density affected the performance of a TFBBR. The dissolved oxygen concentration was significantly affected by the superficial liquid velocity but the removal efficiency of COD was significantly affected by the superficial gas velocity. An erratum to this article can be found online at .     

The effect of temperature on slaughterhouse wastewater treatment in anaerobic sequencing batch reactors

High strength slaughterhouse wastewater was treated in four 42 l anaerobic sequencing batch reactors (ASBRs) operated at 30 degrees C, 25 degrees C and 20 degrees C. The wastewater contained between 30% and 53% of its chemical oxygen demand (COD) as suspended solids (SS). The ASBRs could easily support volumetric organic loading rates (OLRs) of 4.93, 2.94 and 2.75 kg/m3/d (biomass OLRs of 0.44, 0.42 and 0.14 g/g volatile SS (VSS)/d) at 30 degrees C, 25 degrees C, and 20 degrees C, respectively. At all operating temperatures, the total COD (TCOD) and soluble COD (SCOD) were reduced by over 92%, while average SS removal varied between 80% and 96%. Over the experimental period, 90.8%, 88.7% and 84.2% of the COD removed was transformed into methane at 30 degrees C, 25 degrees C and 20 degrees C, respectively. The decrease in the conversion of the COD removed into methane as operating temperature was lowered, may be partly explained by a lower degradation of influent SS as temperature was reduced. The reactors showed a high average methanogenic activity of 0.37, 0.34 and 0.12 g CH4-COD/gVSS/d (22.4, 12.7 and 11.8 l/d) at 30 degrees C, 25 degrees C and 20 degrees C, respectively. The average methane content in the biogas increased from 74.7% to 78.2% as temperature was lowered from 30 degrees C to 20 degrees C.