Performances of a full-scale novel multiplate anaerobic reactor treating cheese whey effluent

A 450-m(3) multiplate anaerobic reactor (MPAR) has been started-up in April 1992 for treating wastewater (whey permeate and domestic wastewater) at the Nutrinor (Lactel) cheese factory in Chambord (Québec, Canada). The MPAR consists of four superimposed sections. The liquid flows upwards from one section to the next, while the gas is collected below each plate and evacuated through side-outlets. The wastewater is concurrently distributed at the bottom of the first, second, and third sections, as 50%, 33%, and 17% of the total influent stream, respectively. Granular anaerobic sludge at an initial concentration of 30 kg of volatile suspended solids (VSS) per cubic meter of reactor liquid volume was used to inoculate the reactor. Under normal operation of the factory, the chemical oxygen demand (COD) concentration of the influent ranged from 20 to 37 kg COD m(-3). The reactor organic loading rate (OLR) fluctuated between 9 and 14.7 kg COD m(-3) d(-1) for hydraulic retention times (HRT) maintained between 55 and 68 h. At the highest OLR, the MPAR showed an efficiency of 98% and 92% for soluble and total COD removal, respectively, and a methane production rate averaging around 4 m(3) m(-3) d(-1).Biomass-specific activities ranged between 7 and 51, 1.3 and 8.5, 5.3 and 12.2, 60 and 119, and 119 and 211 mmol g(-1) VSS d(-1) for glucose, propionate, acetate, formate, and hydrogen, respectively. Average equivalent-diameter of the granules was around 0.65 mm. The MPAR reactor generally showed a large capacity for solid retention with a biomass content between 32 and 37 kg VSS m(-3). (c) 1995 John Wiley & Sons, Inc.     

Performance and microbial community analysis of two-stage process with extreme thermophilic hydrogen and thermophilic methane production from hydrolysate in UASB reactors

The two-stage process for extreme thermophilic hydrogen and thermophilic methane production from wheat straw hydrolysate was investigated in up-flow anaerobic sludge bed (UASB) reactors. Specific hydrogen and methane yields of 89 ml-H₂/g-VS (190 ml-H₂/g-sugars) and 307 ml-CH₄/g-VS, respectively were achieved simultaneously with the overall VS removal efficiency of 81% by operating with total hydraulic retention time (HRT) of 4 days . The energy conversion efficiency was dramatically increased from only 7.5% in the hydrogen stage to 87.5% of the potential energy from hydrolysate, corresponding to total energy of 13.4 kJ/g-VS. Dominant hydrogen-producing bacteria in the H₂-UASB reactor were Thermoanaerobacter wiegelii, Caldanaerobacter subteraneus, and Caloramator fervidus. Meanwhile, the CH₄-UASB reactor was dominated with methanogens of Methanosarcina mazei and Methanothermobacter defluvii. The results from this study suggest the two stage anaerobic process can be effectively used for energy recovery and for stabilization of hydrolysate at anaerobic conditions.     

Biological hydrogen production in a UASB reactor with granules. I: Physicochemical characteristics of hydrogen-producing granules

Hydrogen-producing granules with an excellent settling ability were cultivated in an upflow anaerobic sludge blanket reactor treating a sucrose-rich synthetic wastewater. The physicochemical characteristics of granules were evaluated in this study. The mature granules had a diameter ranging from 1.0 to 3.5 mm and an average density of 1.036 +/- 0.005 g/mL, whereas they had good settling ability and a high settling velocity of 32-75 m/h. The low ratio of proteins/carbohydrates for the extracellular polymeric substances (EPS) in the granules suggests that carbohydrates rather than proteins, might play a more important role in the formation of the H(2)-producing granules. The contact angle of the mature granules, 54 +/- 2 degrees , was larger than that of the seed sludge (38 +/- 2 degrees ), indicating that the microbial cells in the H(2)-producing granules had higher hydrophobicity. The granules had fractal nature with a fractal dimension of 1.78. Their porosities were in the range of 0-0.70, and increased with increasing granule size. The ratios between the observed and predicted settling velocities by Stokes' law were in a range of 1.00-1.50, and the fluid collection efficiency of the granules ranged from 0 to 0.19, indicating that their permeabilities were lower and that there was little advective flow through their interior. Experimental results also suggest that molecular diffusion appeared to play an important role in the mass transfer through the H(2)-producing granules.     

Improvement of the anaerobic treatment of potato processing wastewater in a UASB reactor by co-digestion with glycerol

The effect of three different types of glycerol on the performance of up-flow anaerobic sludge blanket (UASB) reactors treating potato processing wastewater was investigated. High COD removal efficiencies were obtained in both control and supplemented UASB reactors (around 85%). By adding 2 ml glycerol product per liter of raw wastewater, the biogas production could be increased by 0.74 l biogas ml⁻¹ glycerol product, which leads to energy values in the range of 810–1270 kWh_electric per m³ product. Moreover, a better in-reactor biomass yield was observed for the supplemented UASB reactor (0.012 g VSS g⁻¹ COD_removed) compared to the UASB control (0.002 g VSS g⁻¹ COD_removed), which suggests a positive effect of glycerol on the sludge blanket growth.     

Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor

Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35 ± 2 °C) reactor as a control, thermophilic anaerobic digestion (55 ± 2 °C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m³ d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW.     

Use of cheese whey as a substrate to produce manganese peroxidase by Bjerkandera sp BOS55

Manganese peroxidase, MnP, is one of the major ligninolytic enzymes produced by a number of white-rot fungi. The ability of this enzyme to degrade lignin by the fungus Bjerkanderasp BOS55 has opened its application to related bioprocesses such as recalcitrant-compound degradation and effluent decolorization. The medium reported to induce MnP production is composed of chemical grade reagents, all with relatively high costs for application to detoxification purposes. The use of inexpensive sources for MnP production can bring its implementation closer. For this purpose, dairy residues from cheese processing were considered. MnP production obtained using crude whey as the sole substrate reached appreciable levels, around 190 U L⁻¹, values comparable to those found with synthetic media (between 175–250 U L⁻¹). Thus, this cheese-processing byproduct can be used as an inexpensive alternative for the large-scale production of MnP. Received 14 December 1998/ Accepted in revised form 29 April 1999     

Saline adaptation of granules in mesophilic UASB reactors

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.     

High strength sewage treatment in a UASB reactor and an integrated UASB-digester system

The treatment of high strength sewage was investigated in a one-stage upflow anaerobic sludge blanket (UASB) reactor and a UASB-digester system. The one-stage UASB reactor was operated in Palestine at a hydraulic retention time (HRT) of 10h and at ambient air temperature for a period of more than a year in order to asses the system response to the Mediterranean climatic seasonal temperature fluctuation. Afterwards, the one-stage UASB reactor was modified to a UASB-digester system by incorporating a digester operated at 35 degrees C. The achieved removal efficiencies in the one-stage UASB reactor for total, suspended, colloidal, dissolved and VFA COD were 54, 71, 34, 23%, and -7%, respectively during the first warm six months of the year, and achieved only 32% removal efficiency for COD total over the following cold six months of the year. The modification of the one-stage UASB reactor to a UASB-digester system had remarkably improved the UASB reactor performance as the UASB-digester achieved removal efficiencies for total, suspended, colloidal, dissolved and VFA COD of 72, 74, 74, 62 and 70%. Therefore, the anaerobic treatment of high strength sewage during the hot period in Palestine in a UASB-digester system is very promising.     

Continuous propionic acid production from cheese whey usingin situ spin filter

The potential use of spin filter device to retainPropionibacterium acidipropionici in the bioreactor under continuous mode of fermentation and improve propionic acid productivity, was examined. The yield of propionic acid based on lactose concentration was 51% in batch and 54% in continuous (dilution rate=0.05 h⁻¹) operation. The yield in continuous fermentation with cell retention using spin filter of 10 micron size (dilution rate=0.05 h⁻¹) was even higher at 70% (w/w). The volumetric productivity under batch and continuous mode of operation were 0.312 g L⁻¹ h⁻¹ and 0.718 g L⁻¹ h⁻¹ respectively. Continuous fermentation with cell retention demonstrated even higher volumetric productivities at 0.98 g L⁻¹ h⁻¹ with out clogging problems It could be used for utilization of cheese whey to produce propionic acid at higher yield and productivities.     

Optimal conditions for production of lactic acid from cheese whey permeate by Ca-alginate-entrapped Lactobacillus helveticus

Whole cells of Lactobacillus helveticus were immobilized in calcium-alginate beads to produce lactic acid from cheese whey ultrafiltrate. Ca-alginate-entrapped cells were characterized by higher fermentation rates and optimum pH than free cells. No difference could be observed in the profile of cell activity against temperature for either type of cells. After a heat treatment, cell activity was higher for free cells than for immobilized cells. Continuous lactic acid fermentation using a packed bed reactor was investigated.     

Biological hydrogen production in a UASB reactor with granules. II: Reactor performance in 3-year operation

The experiment was conducted to evaluate the performance of an upflow anaerobic sludge blanket (UASB) with granules for H(2) production from a sucrose-rich synthetic wastewater at various substrate concentrations (5.33-28.07 g-COD/L) and hydraulic retention times (HRTs) (3-30 h) for over 3 years. The kinetics of H(2) production was evaluated, and the sludge yield and endogenous decay coefficient of the H(2)-producing granules were estimated to be 0.334 g-VSS/g-COD and 0.004/h, respectively. Based on Gibbs free energy calculations, the formation thermodynamics of caproate, an important aqueous product, were analyzed. Experimental results show that the H(2) partial pressure in biogas decreased with increasing substrate concentration, but was not sensitive to the variation of HRT in a range of 6-22 h. The H(2) production rate increased with increasing substrate concentration, but decreased with increasing HRT. The H(2) yield was in the range of 0.49-1.44 mol-H(2)/mol-glucose. Acetate, butyrate, caporate, and ethanol were the main aqueous products in the reactor, and their concentrations were dependent on both substrate concentration and HRT. An elevated substrate concentration resulted in a shift of fermentation from butyrate- to caporate-type in the reactor and the formation of caproate was dependent on the H(2) partial pressure. The 3-year experimental results demonstrate that H(2) could be produced continuously and stably from the acidogenic-granule-based UASB reactor.     

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.     

Anaerobic biodegradation of linear alkylbenzene sulfonate (LAS) in upflow anaerobic sludge blanket (UASB) reactors

The anaerobic biodegradation of Linear Alkylbenzene Sulfonate (LAS) was studied in Upflow Anaerobic Sludge Blanket Reactors (UASB). One reactor was fed with easily degradable substrates and commercial LAS solution during a period of 3 months (Reactor 1), meanwhile a second reactor was fed with a commercial LAS solution without co-substrate (Reactor 2) during 4 months. Both reactors were operated with an organic loading rate of 4–5 mg-LAS/l*day and a hydraulic retention time of one day.The LAS biodegradation was determined by full mass balance. LAS was analysed by HPLC in the liquid phase (influent and effluent streams of the reactors) as well as in the solid phase (granular sludge used as biomass). The results indicate a high level of removal (primary biodegradation: 64–85%). Biodegradation was higher in the absence of external co-substrates than in the presence of additional sources of carbon. This indicates that the surfactant can be partially used as carbon and energy source by anaerobic bacteria. Under the operating conditions used, inhibition of the methanogenic activity or any other negative effects on the biomass due to the presence of LAS were not observed. The methanogenic activity remained high and stable throughout the experiment.     

Using cheese whey for hydrogen and methane generation in a two-stage continuous process with alternative pH controlling approaches

This study focuses on the exploitation of cheese whey as a source for hydrogen and methane, in a two-stage continuous process. Mesophilic fermentative hydrogen production from undiluted cheese whey was investigated at a hydraulic retention time (HRT) of 24 h. Alkalinity addition (NaHCO₃) or an automatic pH controller were used, to maintain the pH culture at a constant value of 5.2. The hydrogen production rate was 2.9 ± 0.2 L/Lreactor/d, while the yield of hydrogen produced was approximately 0.78 ± 0.05 mol H₂/mol glucose consumed, with alkalinity addition, while the respective values when using pH control were 1.9 ± 0.1 L/Lreactor/d and 0.61 ± 0.04 mol H₂/mol glucose consumed. The corresponding yields of hydrogen produced were 2.9 L of H₂/L cheese whey and 1.9 L of H₂/L cheese whey, respectively. The effluent from the hydrogenogenic reactor was further digested to biogas in a continuous mesophilic anaerobic bioreactor. The anaerobic digester was operated at an HRT of 20d and produced approximately 1 L CH₄/d, corresponding to a yield of 6.7 L CH₄/L of influent. The chemical oxygen demand (COD) elimination reached 95.3% demonstrating that cheese whey could be efficiently used for hydrogen and methane production, in a two-stage process.     

Evaluation of performance and microbial community in a two-stage UASB reactor pretreating acrylic fiber manufacturing wastewater

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.     

The macro nutrient removal efficiencies of a vertical flow constructed wetland fed with demineralized cheese whey powder solution

This study aims to remove the macro-sized nutrients that are present in the cheese whey powder solution through the use of constructed wetland systems. For this purpose, 70% and 40% demineralized solutions of cheese whey powder were used. For both concentrations, control reactors are run in parallel with Typha angustifolia planted reactors for the duration of a 92 day period. Zeolite and gravel were used as the filling material. The planted reactor, which was fed with the 70% solution, was named as Cheese Whey Powder Solution (CWPS) 1 and its unplanted control was named CWPS 2 while the reactor, which was fed with the 40% solution, was named as CWPS 3 and its unplanted control was named CWPS 4. The removal of COD, PO4-P and NH4-N were obtained as 37.47%, 45.62%, and 68.88% in CWPS 1; 24.89%, 35.74%, and 63.15% in CWPS 2; 51.15%, 54.96%, and 64.13% in CWPS 3; and 28.35%, 23.99%, and 65.92% in CWPS 4, respectively.     

Feasibility assay in phase-separated anaerobic treatment of cheese industry wastewater

This research was conducted as a part of continuous development of innovative bioprocess technology for the treatment of high strength wastewater. Mixed cheese processing wastewater was tested for the feasibility of phase separated anaerobic digestion in batch mode. Three concentrations of soluble chemical oxygen demand (SCOD) made by dilution of raw wastewater were tested for acidification of organics in the wastewater at two pHs, 6.0 and neutral. More than 95% of fat, 97% of soluble protein and 100% of lactose in the mixed waste were acidified in the acidogenic phase. Three different concentrations of artificial substrate consisting of a mixture of short chain organic acids, acetic, propionic, butyric, and valeric acids, along with alcohol were investigated for waste stabilization in methanogenic phase experiments. More than 95% of SCOD reduction was achieved in the methanogenic phase. This translated that 73.5–83.8% of organics in the wastewater could be recovered as energy (methane gas) instead of massive production of sludge.     

Effect of starch addition on the biological conversion and microbial community in a methanol-fed UASB reactor during long-term continuous operation

The effect of starch addition on the microbial composition and the biological conversion was investigated using two upflow anaerobic sludge bracket (UASB) reactors treating methanolic wastewater: one reactor was operated with starch addition, and another reactor was operated without starch addition. Approximately 300 days of operation were performed at 30 kg COD/m³/d, and then, the organic load of the reactors was gradually increased to 120 kg COD/m³/d. Successful operation was achieved at 30 kg COD/m³/d in both reactors; however, the methanol-fed reactor did not perform well at 120 kg COD/m³/d while the methanol-starch-fed reactor did. The granule analysis revealed the granule developed further only in the methanol-starch-fed reactor. The results of the microbial community analysis revealed more Methanosaeta cells were present in the methanol-starch-fed reactor, suggesting the degradation of starch produced acetate as an intermediate, which stimulated the growth of Methanosaeta cells responsible for the extension of granules.