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BACKGROUND Anaerobic digestion of agricultural wastes is a cost effective way for combining resource recovery and methane production. This paper evaluates the co-digestion of cow manure and switchgrass in a completely stirred tank reactor (CSTR) by the electrolysis-enhanced anaerobic digestion (eAD) process. RESULTS The electrodes for water electrolysis were installed directly in an anaerobic digester and were used to create micro-aerobic conditions. Significant gains in process performance and biogas quality were obtained at current densities of 20–25 mA (per digester volume) with a corresponding volumetric energy consumption of 0.07–0.08 Wh . In particular, the COD removal rate was increased from 0.6 to 0.9 g COD d-1, methane production increased by 26%, and H2S content in the biogas declined from 2500–3000 ppm to less than 10 ppm. CONCLUSIONS The improved performance was achieved due to methane production from hydrolytic H2 and possibly due to the enhanced hydrolysis of organic matter. © 2013 Her Majesty the Queen in Right of Canada Journal of Chemical Technology & Biotechnology © 2013 Society of Chemical Industry

BACKGROUND: Electricity production in single-anode/cathode MFCs fed with simulated synthesis gas (syngas) as the sole electrondonorhasrecentlybeendemonstrated.Thisstudyevaluatedtheabilityofamulti-anode/cathodeMFCfedwithsyngas to achieve improved volumetric efficiency at several operating temperatures and electrode arrangements. RESULTS: A maximumpowerdensityof33mWL −1 R (normalizedtotheanodiccompartmentvolume)andacoulombicefficiency (CE) of 43% was achieved at an operating temperature of 37 ◦ C. MFC operation at 50 ◦ C resulted in a much lower power density of 10 mW L −1 R and a CE of 15%. The MFC power density was greatly impacted by the electrode arrangement and the highest power density was achieved in a three anode‐two cathode (3A-2C) arrangement. CONCLUSION: The multi-electrode design enhanced the performance of a syngas-fed MFC, which could have major economic and operational implications for designing large-scale syngas-fed MFCs. The MFC performance at elevated temperatures was restricted by low microbial activity, implying that a thermophilic rather than a mesophilic inoculum might be required for successful operation under thermophilic conditions. c � 2013 Society of Chemical Industry

The transport of gellan gum microbeads as potential cell carriers was investigated in horizontal columns packed with different grain size classes of gravel (2–16 mm) and sand (0.25–2 mm). A suspension of microbeads was pulsed into each column for 6 h, followed by injection of water for 42 h. In general, the total amount of microbeads travelling across a given section of the column increased with injection time but decreased towards the column outlet, varying as a direct function of grain size. The results of this study demonstrate the feasibility of the transport of gellan gum microbeads through medium sand to medium gravel across distances up to 110 cm. On a etudie le transport de microbilles de gomme comme supports potentiels de cellules, dans des colonnes horizontales garnies de gravier et de sable de differentes classes de tailles de grains (2-16 mm) et de (0,25-2 mm). Une solution de microbilles est injectee dans chaque colonne pendant 6 h, suivie d'une injection d'eau pendant 42 h. En general, la quantite totale de microbilles se deplacant dans une section donnee de la colonne augmente avec le temps d'injection mais diminue vers la sortie de la colonne, variant en fonction directe de la taille des grains. Les resultats de cette etude montrent la faisabilite du transport des microbilles de gomme gellane dans du gravier a grain moyen jusqu' au sable a grain moyen sur des distances atteignant 110 cm.

The removal of pyrene and benzo(a)pyrene from contaminated water by sequential and simultaneous ozonation-bioremediation techniques was investigated. During the sequential treatment, ozonation using 0.5 or 2.5 mg/L ozone was used as a pretreatment process, whereas, during the simultaneous treatment process, ozonation of hydrocarbon-contaminated water at a predetermined duration using 0.5 mg/L ozone was made in the presence of microbial biomass. Ozonation was not beneficial for the removal of pyrene. However, despite a decreased specific biodegradation rate, ozonation improved the overall elimination of benzo(a)pyrene during both treatment processes. The overall removal of benzo(a)pyrene increased from 23 to 91% after exposure of the water to 0.5 mg/L ozone for 30 minutes during the simultaneous treatment process and further to 100% following exposure to 2.5 mg/L ozone for 60 minutes during the sequential treatment mode, demonstrating the benefits of combined ozonation-biological treatment for the removal of polycyclic aromatic hydrocarbons.

A special microbial consortium adapted to degrade petroleum hydrocarbons at limited availability of oxygen, transformed benzene, a highly toxic and carcinogenic contaminant of groundwater and soil, at low initial dissolved oxygen (DO) concentrations of 0.05-2 mg/L. The employed initial concentrations of dissolved oxygen were considerably lower than the previously reported values. Under these conditions, the overall transformation of benzene ranged from 34% � 1.7% to 100%, considerably higher than the theoretical predictions for complete mineralization of benzene based on the requirement of 3.08 mg oxygen/mg benzene. Unlike biotransformation that proceeded at the lowest examined DO concentration of 0.05 mg/L, the mineralization of benzene, defined by its conversion to CO2 and water, required a minimum DO concentration of 0.2 mg/L. The mineralization of benzene under microaerophilic conditions (DO < 2 mg/L), ranged from 0.83% � 0.06% to 89% � 1.3%, which was less than the theoretical predictions at any given initial DO concentration. The regulatory effects of dissolved oxygen concentration or its partial pressure on the activities of enzymes catalyzing the biotransformation of aromatic hydrocarbons was postulated to account for the reduced mineralization of benzene. The ratio between the transformed benzene and the consumed oxygen increased with the decrease of initial DO concentration, reaching a value of 2.8, considerably higher than the theoretical value of 0.33 obtained for a complete aerobic oxidation of benzene. Phenol was the major and the most stable intermediate metabolite during the biotransformation of benzene at low concentrations of DO. While benzene transformation stopped after the depletion of oxygen in the experimental system, phenol continued to accumulate under strictly anaerobic conditions, indicating its formation from an alternative carbon source, possibly biomass. � 2002 Government of Canada. Exclusive worldwide publication rights in this article have been transferred to Wiley Periodicals, Inc. Biotechnol Bioeng 79: 347-355, 2002.

Extensive characterization of a nitrate-contaminated site at a Canadian airport revealed that natural attenuation of the plume was limited due to aerobic conditions. However, nitrate removal rates as high as 1.4 mg-N/(L/day) were observed in batch tests carried out under denitrifying conditions with an added carbon source. On the basis of these results, a field denitrification pilot test using a setup of vertical withdrawal and injection wells was carried out. Ethanol was used as a carbon source to stimulate the growth and activity of indigenous denitrifying bacterial populations. Denitrification rates of up to 1.2 mg-N/(L/day) were achieved during the test. The test confirmed the feasibility of the technology, which uses the indigenous bacterial populations for denitrification and transforms the aquifer into a subsurface bioreactor.

The effects of aging trichloroethylene (TCE) with a surrogate soil organic matter (SSOM) on its anaerobic biodegradation and desorption characteristics were studied. Surrogate soil organic matter comprised of composted sphagnum moss was used as a model sorbent, and Desulfomonile tiedjei was used as a model member of an anaerobic consortium capable of reductive dechlorination. After TCE was aged with the sterile SSOM for periods of 2, 14, and 30 d, the completely mixed batch reactors were inoculated with D. tiedjei cells and incubated for 5 d. The mass of TCE dechlorinated to cis-1,2-dichloroethylene (DCE) by D. tiedjei in this period decreased by 72% from 2 to 30 d of aging. Although there was an increase in the equilibrium desorption coefficient (Kd) with aging, sorption was completely reversible. Hence, the reduced availability of TCE for degradation was not coupled with irreversible sorption. To examine the longer-term fate of TCE, the unaged TCE-SSOM slurries were inoculated with D. tiedjei and then incubated for longer times (15, 24, and 29 d vs. 5 d). The conversion of TCE to cis-1,2-DCE was up to eight times greater than what was observed in control experiments without SSOM. Therefore, although aging resulted in reduced TCE biodegradation for short-term incubation (5 d), longer-term incubation (29 d) with the unaged SSOM resulted in extensive TCE dechlorination (up to 40%) to cis-1,2-DCE.

The impact of influent dissolved O(2) on the characteristics of anaerobic granular sludge was investigated at various dissolved O(2) concentrations (0.5-8.1 ppm) in 1- and 5-L laboratory-scale upflow anaerobic sludge bed (UASB)-like anaerobic/aerobic coupled reactors with a synthetic wastewater (carbon sources containing 75% sucrose and 25% acetate). The rate of dissolved O(2) supplied to the coupled reactor was as high as 0.40 g O(2)/L(rx).d, and the anaerobic/aerobic coupled reactors maintained excellent methanogenic performances at a COD loading rate of 3 g COD/L(rx).d even after the reactors had been operated with dissolved O(2) for 3 months. The activities of granular sludge on various substrates (glucose, propionate, and hydrogen) were not impaired, and acetate activity was even improved over a short term. However, after 3 months of operation, slight declines on the acetoclastic activities of granules were observed in the coupled reactor receiving the recirculated fluid containing 8.1 ppm dissolved O(2).Methane yield in the anaerobic control reactor and anaerobic/aerobic coupled reactors revealed that a significant aerobic elimination (up to 30%) of substrate occurred in the coupled reactors, as expected. The presence of dissolved O(2) in the recirculated fluid resulted in the development of fluffy biolayers on the granule surface, which imposed a negative impact on the settleability of granular sludge and caused a slightly higher sludge washout. This research shows that the anaerobic/aerobic coupled reactor can be successfully operated under O(2)-limited conditions and is an ideal engineered ecosystem integrating oxic and anaerobic niches. (c) 1996 John Wiley & Sons, Inc.

To monitor the biodegradation of explosives in microcosm experiments, carbon-14 labelled substrates such as 14C-HMX were needed. Many synthetic routes were evaluated to identify the best synthesis of 14C-HMX with high yield and minimal radioactive waste. To synthesize 14C-HMX, acetylation of labelled hexamethylenetetramine (14C-HMTA) was done yielding 3,7-diacetyl-1,3,5,7-tetraazabicyclo-[3.3.1]-nonane (14C-DAPT) which was nitrated to obtain 1,5-diacetyloctahydro-3,7-dinitro-1,3,5,7-tetrazocine (14C-DADN) in one step. Nitrolysis of 14C-DADN was achieved using a mixture of 100% nitric acid and phosphorus pentoxide to yield 14C-HMX. The synthesis of this carbon-14 labelled HMX was optimized first using cold starting materials and then conducted with labelled compounds. This synthesis represents the best way of preparing high purity 14C-HMX with a high yield. Copyright © 1999 John Wiley & Sons, Ltd.

Systems of co-immobilized microorganisms are highly effective for conducting two or more consecutive bioprocesses within close proximity of the source and the sink of substrates. In this work, a general model of a co-immobilized aerobic/anaerobic bacterial system was developed and analyzed. The model was used to optimize pellet design and to study the effect of slow cell growth on process efficiency. The analysis demonstrated that co-immobilization of bacterial species accelerates the rate of biotransformation and provides complete transformation of toxic intermediates.

A model that portrays substrate profiles in a steady-state multispecies granular biofilm is developed and coupled with a biofilm detachment model. The model accounts for glucose, propionate, hydrogen, and acetate transformations performed by three bacterial trophic groups: acidogens, syntrophic bacterial consortia, and methanogens. This model adequately describes the phenomenon of propionate degradation under thermodynamically unfavorable bulk hydrogen concentrations. Also suggested is the superiority of the layered biofilm structure over homogeneous distribution of the trophic groups for anaerobic degradation of organic compounds. Furthermore, model analysis suggests that with increasing bulk glucose concentration biofilm thickness reaches a maximum that is then followed by biofilm disintegration. These results may have an important impact on the design and control of upflow anaerobic sludge bed reactors.

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).

The dissolved hydrogen concentration was monitored in four laboratory-scale upflow sludge bed reactors. The upflow velocity (v UP ) differed in each reactor, providing different hydraulic regimes. Five pseudo-steady-state conditions were applied to the four reactors. The dissolved hydrogen concentration increased proportionally with the organic loading rates (OLR) of the reactors, to attain values as high as 20 μM, while still remaining independent of the hydraulic regime. The experimental data yielded low hydrogen mass-transfer rates (k L a) and high ratios of the measured dissolved hydrogen concentration value to the equilibrium value calculated from the hydrogen partial pressure in the gas phase (sursaturation factor): from 0.04 to 0.46 h −1 , and from 19 to 102, respectively.

A new hybrid reactor, the upflow blanket filter (UBF), which combines an open volume in the bottom two-thirds of the reactor for a sludge blanket and submerged plastic rings (Flexiring, Koch Inc., 235 squared m/cubic m) in the upper one-third of the reactor volume, was studied. This UBF reactor was operated at 27 degrees C at loading rates varying from 5 to 51 g chemical oxygen demand (COD)/l day with soluble sugar wastewater (2500 mg COD/l). Maximum removal rates of 34 g COD/l day and CH/sub 4/ production rates of 7 vol/vol day (standard temperature and pressure (STP)) were obtained. The biomass activity was about 1.2 g COD/g volatile suspended solids per day. Conversion (based on effluent soluble COD) was over 93% with loading rates up to 26 g COD/l day. At higher loading rates conversion decreased rapidly. The packing was very efficient in retaining biomass. 11 references.

Mixing characteristics (using a radioactive tracer) and reactor performance of the upflow blanket filter (UBF) reactor operated at different loading rates (up to 32 kg chemical oxygen demand (COD) m⁻³ day⁻¹) were compared. The results indicated that mixing profiles of the reactor operated with effluent recirculation and without biomass were of the perfectly mixed type. Operation without recirculation resulted in about 18% dead space. The filter made of plastic rings and located in the top third of the reactor had no negative effect on reactor mixing. Operation at loading rates of up to 25 kg COD m⁻³ day⁻¹ permitted a soluble COD removal rate of 95% with a methane production rate of 5.9 m ³ m ⁻ ³ day ⁻ ¹. At higher loading rates, the efficiency of COD reduction decreased with a decrease of the specific acetoclastic activity to 0.5 kg acetate removed per kg volatile suspended solids (VSS) day⁻¹. At all loading rates studied it was observed that the performance was not related to the mixing characteristics, which had remained of the perfectly mixed type with an occasional small dead space (below 10%). The good mixing characteristics of the UBF reactor coupled with the high biomass content and the effective action of the filter make this reactor one of the most promising designs for the treatment of soluble wastes.