Expanded Granular Sludge Bed System Research Articles

The effect of bacterial functional characteristics on the spread of antibiotic resistance genes in Expanded Granular Sludge Bed reactor treating the antibiotic wastewater

To explore the fate and spreading mechanism of antibiotics resistance genes (ARGs) in antibiotics wastewater system, a laboratory-scale (1.47 L) Expanded Granular Sludge Bed (EGSB) bioreactor was implemented. The operating parameters temperature (T) and hydraulic retention time (HRT) were mainly considered. This result showed the removal of ARGs and COD was asynchronous, and the recovery speed of ARGs removal was slower than that COD removal. The decreasing T was attributed to the high growth rate of ARGs host bacteria, while the shortened HRT could promote the horizontal and vertical gene transfer of ARGs in the sludge. The analysis result of potential bacterial host showed more than half of the potential host bacteria carried 2 or more ARGs and suggested an indirect mechanism of co-selection of multiple ARGs. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to investigate the functional characteristics of bacterial community. This result showed the bacterial functional genes contributed 40.41% to the abundance change of ARGs in the sludge, which was higher that of bacterial community. And the function genes of “aromatic hydrocarbon degradation”, “Replication, recombination and repair proteins” and “Flagellar assembly” were mainly correlated with the transfer of ARGs in the sludge. This study further revealed the mechanism of ARGs spread in the EGSB system, which would provide new ideas for the development of ARGs reduction technology.

Comparison of microbial and physicochemical behavior of expanded granular sludge bed system during methylparaben and triclosan removal.

Methylparaben and triclosan are antimicrobial agents widely used as preservatives in a variety of personal care and pharmaceutical products. Wastewater is considered the main source of these compounds in the environment. Expanded granular sludge bed (EGSB) reactors are a high rate technology for wastewater treatment based on biological processes and have been shown to be efficient in removing different types of compounds; however, little is known about the effect of contaminants such as methylparaben and triclosan on their behavior and effectiveness. In this study, we evaluate and compare the microbial and physicochemical behavior of EGSB systems during methylparaben and triclosan removal. The presence of different concentrations of pollutants had an influence on the cluster organization of microbial communities, especially bacteria. However, this did not affect the stability and performance of the EGSB systems. The banding patterns of the denaturing gradient gel electrophoresis of archaea demonstrated the constant presence and abundance of Methanosaeta concilii throughout all stages of operation, showing that this microorganism played a fundamental role in the stability of the reactors for the production of methane. The type of compound and its concentration influenced the expression of the mcrA and ACAs genes; however, these changes did not alter the stability and performance of the EGSB systems.

The long-term impact of cefalexin on organic substrate degradation and microbial community structure in EGSB system

In order to investigate long-term effect of cefalexin (CFX) on the performance of expanded granular sludge bed (EGSB) system and microbial community structure, two 1.47 L EGSB reactors E1 and E2 were designed and run for 224 days treating with synthetic antibiotic wastewater. For the purpose of comparison, E1 was fed with synthetic antibiotic industry wastewater with CFX added as the test reactor, while, E2 was fed without any CFX added as the control reactor (E2). The addition of CFX resulted in the continual increasing of soluble COD (sCOD) and accumulation of VFAs in the effluent of E1 system. Besides, it was found that the accumulation of CFX by-products D-1, D-2 and D-3 was negative correlation with sCOD removal efficiency. Furthermore, the microbial community structures were also investigated. For the bacterial community, Gelria and Syntrophorhabdus which can ferment propionate and other organic pollutants as their substrate were obviously enriched in E1 system. For the archaea, there was more functional diversity in E1 system than in E2 system. Furthermore, fungi also played an important role on the removal of complex organics in E1 system.

Modeling of expanded granular sludge bed reactor using artificial neural network

In present study, a three-layer backpropagation neural network (BPNN) model was developed to predict the performance of an expanded granular sludge bed (EGSB) reactor. Six related variables such as influent chemical oxygen demand (COD) concentration, hydraulic retention time (HRT), alkalinity (ALK) concentration, pH, volatile fatty acid (VFA) concentration and oxidation reduction potential (ORP), were selected as inputs of the model. All input values were converted to the range (−1, 1) before passing them into the network. Activation function of hidden layer and output layer were “tansig” and “purelin” individually. Several comparisons were conducted to obtain an optimal network structure. Dividerand function was chosen to divide the operating data into training group, testing group and validation group. The Levenberg Marquardt algorithm (trainlm) was found as the best of the ten training algorithms. Other model parameters such as number of neurons in the hidden layer (X1), initial adaptive value (X2) and initial value of weights and biases (X3) were optimized using response surface methodology (RSM). The optimum conditions for minimum mean squared error (MSE) were as follows: X1 (12), X2 (6.0) and X3 (1.0). The precision of optimum ANN model was assessed by means of various statistics such as MSE, determination coefficient (R2), coefficient of variation (CV) and MSE. The result indicated that the proposed ANN model exhibited superior predictive accuracy for the forecast of COD removal performance by EGSB system. Finally, the results of connection weights method demonstrated that VFA concentration (50.37%) had a remarkable impact on reactor performance.

Performance of an expanded granular sludge bed (EGSB) reactor coupled with anoxic and aerobic bioreactors for treating poultry slaughterhouse wastewater

Generally, slaughterhouses have the largest consumption of fresh water and thus generate large quantities of high strength wastewater, which can be treated successfully using low cost biological treatment processes. In this study, the feasibility of using an expanded granular sludge bed (EGSB) anaerobic reactor coupled with anoxic and aerobic bioreactors for the treatment of poultry slaughterhouse wastewater was investigated. The poultry slaughterhouse was characterized by high chemical oxygen demand (COD), 2 to 6 g/L, with average biological oxygen demand of 2.4 g/L and average fats, oil and grease (FOG) being 0.55 g/L. A continuous EGSB anaerobic reactor was operated for 26 days at different hydraulic retention times (HRT), i.e. 7, 4, 3 days, and organic loading rates (OLR) of 0.5, 0.7 and 1.0 g COD/L.day, respectively, to assess the bioremediation of the poultry slaughterhouse wastewater. The average COD removal from the EGSB was 40%, 57% and 55% at the different OLR and HRT assessed. At high OLR of 1.0 g COD/L.day, the overall COD removal from the system (EGSB-anoxic/aerobic) averaged 65%. The system experienced periodical sludge washout during high FOG and suspended solids loading. It was concluded that the EGSB system requires a dissolved air flotation system, for FOG/suspended solid reduction, as the performance of the overall system was observed to deteriorate over time due to the presence of a high quantity of FOG including suspended solids.

Pre-treating amoxicillin contained wastewater with an anaerobic expanded granular sludge bed (EGSB)

The characteristic of anaerobic expanded granular sludge bed (EGSB) treating antibiotic wastewater that contained amoxicillin (AMX) was investigated. The performance of the reactor was characterized in terms of its COD, AMX removal efficiencies, and methane yield. After 241 d of operation, 85 and 80% removal efficiencies of COD and AMX were achieved, respectively. Furthermore, volumetric loading rate (VLR) effecting on EGSB system was evaluated by changing hydraulic retention time (HRT was switched to 14, 8, and 14 h, respectively). With HRT decreased to 8 h, COD and AMX removal efficiencies dropped obviously to 36.50 and 58.55%, respectively. When HRT was switched to 14 h again, AMX removal efficiency required three more days than COD to recover to around 80%. These results showed that EGSB reactor could resist the short-time shock of VLR and recover to high removal efficiencies of AMX and COD. According to AMX and COD removal efficiencies and methane yield, it was confirmed that AMX was unlikely to create problems in pre-treating AMX-contained wastewater with EGSB system.

Treatment of Wastewater from Purified Terephtalic Acid (PTA) Production in a Two-stage Anaerobic Expanded Granular Sludge Bed System

ABSTRACT The wastewater treatment with a two-phase expanded granular sludge bed (EGSB) system for anaerobic degradation of acetate, benzoate, terephtalate and p -toluate from purified terephtalic acid (PTA) production was studied. The feasibility and effectiveness of the system was evaluated in terms of organic oxidation by chemical oxygen demand (COD), gas production, bacterial adaptability and stability in the granular sludge. Average removal efficiencies 93.5% and 72.7% were achieved in the EGSB reactors under volumetric loading rates of 1.0–15 kg-COD/m 3 /day and terephtalate and p -toluate of 351–526 mg/L, respectively. Gas production reached total methane production rate of 0.30 L/g-COD under these conditions in the sequential EGSB reactor system. Higher strength influent COD concentration above 4.8 g-COD/L related to field conditions was fed to observe the disturbance of the EGSB reactors. Keywords: Anaerobic treatment, Expanded granular sludge bed (EGSB), Purified terephtalic acid (PTA), Two-phase, Wastewater

Effects of Upflow Liquid Velocity on Performance of Expanded Granular Sludge Bed (EGSB) System

� Abstract—The effects of upflow liquid velocity (ULV) on performance of expanded granular sludge bed (EGSB) system were investigated. The EGSB reactor, made from galvanized steel pipe 0.10 m diameter and 5 m height, had been used to treat piggery wastewater, after passing through acidification tank. It consisted of 39.3 l working volume in reaction zone and 122 l working volume in sedimentation zone, at the upper part. The reactor was seeded with anaerobically digested sludge and operated at the ULVs of 4, 8, 12 and 16 m/h, consecutively, corresponding to organic loading rates of 9.6 - 13.0 kg COD/ (m 3 od). The average COD concentrations in the influent were 9,601 - 13,050 mg/l. The COD removal was not significantly different, i.e. 93.0% - 94.0%, except at ULV 12 m/h where SS in the influent was exceptionally high so that VSS washout had occurred, leading to low COD removal. The FCOD and VFA concentrations in the effluent of all experiments were not much different, indicating the same range of treatment performance. The biogas production decreased at higher ULV and ULV of 4 m/h is suggested as design criterion for EGSB system.

Simultaneous biohydrogen production and starch wastewater treatment in an acidogenic expanded granular sludge bed reactor by mixed culture for long-term operation

The biofilm-based expanded granular sludge bed (EGSB) reactor was developed to treat starch-containing wastewater and simultaneously recovery hydrogen by mixed microbial culture. Granular activated carbon (GAC) was used as the support media. Operating at the temperature of 30 °C for over 400 days (data not shown), the EGSB reactor presented high efficiency in hydrogen production and COD removal ability. The maximum hydrogen production rate (HPR) was found to be 1.64 L/L.d under the organic loading rate (OLR) of 1.0 g-starch/L.d, pH of 4.42 and HRT of 4 h. The hydrogen yield (HY) peaked at 0.11 L/g-COD, under the OLR of 0.5 g-starch/L.d, pH of 3.95 and HRT of 8 h. Hydrogen volume content was estimated to be 35–65% of the total biogas. The average COD removal rate was 31.1% under the OLR of 0.125 g-starch/L.d and HRT of 24 h. The main dissolved fermentation products were ethanol, acetate and butyrate. The average attached biofilm concentration was estimated to be 8.26 g/L, which favored hydrogen production and COD removal. It is speculated that the low pH operation in the present system would contribute significantly to lower the cost of alkaline amount required for pH control in the continuous operation, especially in the scale-up biohydrogen producing system. A model, built on the back propagation neural network (BPNN) theory and linear regression techniques, was developed for the simulation of EGSB system performance in the biodegradation of starch synthesis-based wastewater and simultaneous hydrogen production. The model well fitted the laboratory data, and could well simulate the removal of COD and the production of hydrogen in the EGSB reactor.

Biohydrogen production from ethanol-type fermentation of molasses in an expanded granular sludge bed (EGSB) reactor

An expanded granular sludge bed (EGSB) process with granular activated carbon (GAC) was developed for fermentative hydrogen production from molasses-containing wastewater by mixed microbial cultures. No pH regulation was performed during the whole operation period. Running at the temperature of 35 °C, the EGSB reactor presented a high hydrogen production ability as the hydrogen production rate (HPR) maximized at 0.71 L/L h. At the same time, the hydrogen yield (HY) peaked at 3.47 mol/mol sucrose and the maximum specific hydrogen production rate (SHPR) was found to be 3.16 mmol H 2/g VSS h. Hydrogen volume content was estimated to be 30–53% of the total biogas and the biogas was free of methane throughout the study. Dissolved fermentation products were predominated by acetate and ethanol, with smaller quantities of propionate, butyrate and valerate. It was found that high hydrogen yield was always associated with a high level of ethanol production. When the pH value and alkalinity ranged from 4.2–4.4 mg CaCO 3/L to 280–340 mg CaCO 3/L, respectively, stable ethanol-type fermentation was formed with the sum of ethanol and acetate concentration ratio of 89.1% to the total liquid products. The average attached biofilm concentration was estimated to be 17.1 g/L, which favored hydrogen production efficiently. With high biomass retention at high organic loading rate (OLR), this EGSB system showed to be a promising high-efficient bioprocess for hydrogen production from high-strength wastewater.

Removal of carbon and nutrients from low strength domestic wastewater by expanded granular sludge bed-zeolite bed filtration (EGSB-ZBF) integrated treatment concept

The performance of an expanded granular sludge bed (EGSB) reactor coupled with zeolite bed filtration (ZBF) for treating low strength domestic wastewater was monitored at 35 °C for 7 months. The whole operation period of EGSB system was divided into five phases. Each phase ran at up-flow velocity (m/h) of 0.51, 1.02, 3.57, 2.05, 9.69, and hydraulic retention time (HRT) (h) of 6, 3, 0.87, 1.5, 0.32, respectively. The influent chemical oxygen demand (COD) was kept approximate at 150 ± 100 mg/L. Under these conditions, the COD removal efficiency of using EGSB system in five phases reached to 81.08, 57.94, 82.79, 56.58 and 79.52%, respectively. Moreover, since nutrients such as NH 4 + and PO 4 3− were only removed to a limited extent by EGSB, additional treatment is required. The ZBF was employed in phase 2 as a post-treatment following EGSB. NH 4 + and PO 4 3− concentrations were decreased by 100%, respectively, in the first 2 or 3 d using fresh zeolite. The simple design and excellent treatment performance indicated that this system could be used as a novel Sewage Integrated Treatment System (SITS) for developing country especially in a tropical area.

Anaerobic Treatment of Slaughterhouse Wastewater in an Expanded Granular Sludge Bed (EGSB) Reactor

The performance of an Expanded Granular Sludge Bed (EGSB) reactor for treating slaughterhouse wastewater under mesophilic conditions (35°C), was investigated. The reactor was inoculated with granular sludge from an anaerobic reactor of a brewery factory. The averaged COD removal percentages were 67% for total organic loading rates (BV.TCOD) up to 15 kg COD m−3 d−1 and a hydraulic retention time (HRT) of 5 h. Total suspended solids (TSS) were 90% removed for total solids loads of 6 kg TSS m−3 d−1. Fats were 85% removed and no accumulation of fats on the sludge was observed. The specific methanogenic activity of the sludge, after 140 days, was about three times higher than the sludge inoculated into the reactor. The sludge activity did not significantly change after one year of work. These findings indicate that the anaerobic treatment of slaughterhouse wastewater in an EGSB system appears to be a feasible option.

Psychrophilic anaerobic treatment of low strength wastewaters

Psychrophilic (2 to 20°C) anaerobic treatment of low strength synthetic and malting wastewater was investigated using a single and two module expanded granular sludge bed (EGSB) reactor system. The chemical oxygen demand (COD) removal efficiencies found in the experiments exceeded 90 % in the single module reactor at an organic loading rate up to 12 g COD dm−3 day−1 and a HRT of 1.6 h at 10-12°C ambient temperature using influent concentrations ranging from 500 to 800 mg COD dm−3. When a two module EGSB system was used at the temperature range 10-15°C, soluble COD removal and volatile fatty acids removal of 67-78% and 90-96% were achieved, respectively, and an OLR between 2.8-12.3 kg COD m−3 day−1 and a HRT of 3.5 h. The second module serves mainly as a scavenger of non-degraded volatile fatty acids (VFA) from the first module. The optimal temperatures for substrate conversion of reactor sludge, after it has been exposed to long term psychrophilic conditions, were similar to those of the original mesophilic inoculum. The specific activities of the sludge in the reactor increased in time by a factor 3, indicating enrichment of methanogens and acetogens even at low temperatures. By adapting the process design to the expected prevailing conditions inside the reactor, the loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved under psychrophilic conditions. The results obtained clearly reveal the big potentials of anaerobic wastewater treatment under low ambient (10-12°C) temperature conditions for low strength wastewaters, very likely including domestic sewage.

Anaerobic treatment of slaughterhouse wastewater in an expanded granular sludge bed (EGSB) reactor

The performance of an Expanded Granular Sludge Bed (EGSB) reactor for treating slaughterhouse wastewater under mesophilic conditions (35°C), was investigated. The reactor was inoculated with granular sludge from an anaerobic reactor of a brewery factory. The averaged COD removal percentages were 67% for total organic loading rates (B V.TCOD ) up to 15 kg COD m −3 d −1 and a hydraulic retention time (HRT) of 5 h. Total suspended solids (TSS) were 90% removed for total solids loads of 6 kg TSS m −3 d −1 . Fats were 85% removed and no accumulation of fats on the sludge was observed. The specific methanogenic activity of the sludge, after 140 days, was about three times higher than the sludge inoculated into the reactor. The sludge activity did not significantly change after one year of work. These findings indicate that the anaerobic treatment of slaughterhouse wastewater in an EGSB system appears to be a feasible option.

Psychrophilic anaerobic treatment of low strength wastewaters

Psychrophilic (2 to 20°C) anaerobic treatment of low strength synthetic and malting wastewater was investigated using a single and hvo module expanded granular sludge bed (EGSB) reactor system. The chemical oxygen demand (COD) removal efftciencies found in the experiments exceeded 90% in the single module reactor at an organic loading rate up to 12 g COD dm −3’ day −1 and a HRT of 1.6 h at 10–12°C ambient temperature using influent concentrations ranging from 500 to 800 mg COD dm −3 When a two module EGSB system was used at the temperature range l0–15°C, soluble COD removal and volatile fatty acids removal of 67–78% and 90–96% were achieved, respectively, and an OLR between 2.8–12.3 kg COD m -3 day −1 and a HRT of 3.5 h. The second module serves mainly as a scavenger of non-degraded volatile fatty acids (VFA) horn the fust module. The optimal temperatures for substrate conversion of reactor sludge, after it has heen exposed to long term psychrophilic conditions, were similar to those of the original mesophilic inoculum. The specific activities of the sludge in the reactor increased in time by a factor 3, indicating enrichment of methanogens and acetogens even at low temperatures. By adapting the process design to the expected prevailing conditions inside the reactor, the loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved under psychrophilic conditious. The results obtained clearly reveal the big potentials of anaerobic wastewater treatment under low ambient (l0–12°C) temperature conditions for low strength wastewaters, very likely including domestic sewage.

Anaerobic treatment of partly acidified wastewater in a two-stage expanded granular sludge bed (EGSB) system at 8°C

Psychrophilic (8 °C) anaerobic treatment of partly acidified waste water was investigated using a two stage EGSB system with a total volume of 8.6 dm3. The reactor system was operated at an up-flow velocity of 10 m·h−1 and was fed with a sucrose-VFA mixture of 550–1100 mg COD dm−3. The average CODsol and VFA-COD removal efficiencies were 97 and 90 %, respectively, at total organic loading rates (OLR) ranging between 5.1–6.7 g COD dm−3·day−1, sucrose loading rates up to 1 g COD dm−3 day−1 and a hydraulic retention time (HRT) of 4 h. An increase in the sucrose loading rates resulted in a significant wash-out of biomass from the first stage. The second stage satisfactory served as a scavenger of non-degraded VFA from the first stage. Specific activity assays showed an increase of 15 % in the specific methanogenic activity of the sludge present in the second stage and a decrease of 9 % in the first stage. Apparently, an enrichment of methanogens and acetogens in the anaerobic sludge in the second stage took place at temperatures as low as 8°C. The acidogenic population became much more dominant in the first stage, resulting in a higher acidifying activity and a decreased methanogenic activity. 16S rRNA probe-techniques (dot blot hybridization) showed that the acetate consuming Methanosaeta (formerly Methanothrix) and the hydrogenotrophic Methanobrevibacter species (or relatives) were the most abundant methanogens present in the psychrophilic sludge. The ratio between bacterial and methanobacterial hybridization signal of the first stage was 3 times higher than that of the second stage. By using NMR techniques, a higher effective diffusion coefficient was found for the smaller sized granules in both reactors, which is in congruent with the higher maximum specific acetate degrading activity of the smaller granules.

The biobed® EGSB (expanded granular sludge bed) system covers shortcomings of the upflow anaerobic sludge blanket reactor in the chemical industry

In this paper a new type of anaerobic reactor is presented. The system has been developed by Biothane Systems and is marketed under the name Biobed® EGSB reactor (Expanded Granular Sludge Bed). In this reactor it is possible to grow and maintain a granular sludge under high liquid (10 m/h) and gas velocities (7 m/h). The most striking feature is the growth of biomass in a granular form, similar to the UASB granules: no carrier material is used. The process is specially suitable to treat waste water that contains compounds that are toxic in high concentrations and that only can be degraded in low concentrations (chemical industry). An example is given for a waste water originating from a chemical factory (Caldic Europoort) in the Netherlands. In this factory formaldehyde is produced from methanol. The waste water is characterised by high concentrations of these compounds (formaldehyde to 10 g/l and methanol to 20 g/l). Due to the special configuration of the anaerobic reactor it is possible to realise a removal efficiency for both compounds of more than 98%. It is also possible to operate the reactor as an ultra high loaded anaerobic reactor (to 30 kg COD/m3.day) for applications in other sectors of industry (e.g. brewery, yeast, sugar, corn ethanol production etc).

High-Rate Anaerobic Treatment of Malting Waste Water in a Pilot-Scale EGSB System Under Psychrophilic Conditions

The feasibility of the expanded granular sludge bed (EGSB) system for the treatment of malting waste water under psychrophilic conditions was investigated by operating a pilot-scale 225·5 dm3 EGSB-reactor system in the temperature range from 13 to 20°C. The concentration of chemical oxygen demand (COD) in the malting waste water was between 282 and 1436 mg dm−3. The anaerobically biodegradable COD of the waste water was about 73%, as determined in the batch bioassays. During reactor operation at 16°C, the COD removal efficiencies averaged about 56%, at organic loading rates (OLR) ranging between 4·4 and 8·8 kg COD m−3 day−1 and a hydraulic retention time (HRT) of approximately 2·4 h. At 20°C, removal efficiencies were approximately 66% and 72%, respectively, at OLRs of 8·8 and 14·6 kg COD m−3 day−1, corresponding to HRTs of 2·4 and 1·5 h. The specific methanogenic activity with the sludge from the reactor, assessed on acetate and volatile fatty acids mixture as substrates, significantly increased (80%) in time, indicating an enrichment of methanogens and acetogens even at the low temperatures applied. These findings are of considerable practical importance because they indicate that anaerobic treatment of low strength waste waters at low temperature might become a feasible option. © 1997 SCI.

Anaerobic treatment of partly acidified wastewater in a two-stage Expanded Granular Sludge Bed (EGSB) system at 8°C

Psychrophilic (8°C) anaerobic treatment of partly acidified waste water was investigated using a two stage EGSB system with a total volume of 8.6 dm3. The reactor system was operated at an up-flow velocity of 10 m·h−1 and was fed with a sucrose-VFA mixture of 550–1100 mg COD dm−3. The average CODso1 and VFA-COD removal efficiencies were 97 and 90 %, respectively, at total organic loading rates (OLR) ranging between 5.1 – 6.7 g COD dm−3·day−1, sucrose loading rates up to 1 g COD dm−3 day−1 and a hydraulic retention time (HRT) of 4 h. An increase in the sucrose loading rates resulted in a significant wash-out of biomass from the first stage. The second stage satisfactory served as a scavenger of non-degraded VFA from the first stage. Specific activity assays showed an increase of 15 % in the specific methanogenic activity of the sludge present in the second stage and a decrease of 9 % in the first stage. Apparently, an enrichment of methanogens and acetogens in the anaerobic sludge in the second stage took place at temperatures as low as 8°C. The acidogenic population became much more dominant in the first stage, resulting in a higher acidifying activity and a decreased methanogenic activity. 16S rRNA probe-techniques (dot blot hybridization) showed that the acetate consuming Methanosaeta (formerly Methanothrix) and the hydrogenotrophic Methanobrevibacter species (or relatives) were the most abundant methanogens present in the psychrophilic sludge. The ratio between bacterial and methanobacterial hybridization signal of the first stage was 3 times higher than that of the second stage. By using NMR techniques, a higher effective diffusion coefficient was found for the smaller sized granules in both reactors, which is in congruent with the higher maximum specific acetate degrading activity of the smaller granules.

The Biobed EGSB (expanded granular sludge bed) system covers shortcomings of the upflow anaerobic sludge blanket reactor in the chemical industry

In this paper a new type of anaerobic reactor is presented. The system has been developed by Biothane Systems and is marketed under the name Biobed® EGSB reactor (Expanded Granular Sludge Bed). In this reactor it is possible to grow and maintain a granular sludge under high liquid (10 m/h) and gas velocities (7 m/h). The most striking feature is the growth of biomass in a granular form, similar to the UASB granules: no carrier material is used. The process is specially suitable to treat waste water that contains compounds that are toxic in high concentrations and that only can be degraded in low concentrations (chemical industry). An example is given for a waste water originating from a chemical factory (Caldic Europoort) in the Netherlands. In this factory formaldehyde is produced from methanol. The waste water is characterised by high concentrations of these compounds (formaldehyde to 10 g/l and methanol to 20 g/l). Due to the special configuration of the anaerobic reactor it is possible to realise a removal efficiency for both compounds of more than 98%. It is also possible to operate the reactor as an ultra high loaded anaerobic reactor (to 30 kg COD/m 3 .day) for applications in other sectors of industry (e.g. brewery, yeast, sugar, corn ethanol production etc).