D. Grant Allen

Measurement of rheological properties of filamentous fermentation broths

It is well established that fermentation broths of filamentous microorganisms possess viscous non-Newtonian rheological properties. Despite the industrial significance of these broths and their fermentation products, the correct application of rheological measurement methodologies to filamentous broths and the influence of broth rheology on transport phenomena in bioreactors is poorly understood. In this work, the rheological properties of broths of the filamentous microorganisms Aspergillus niger, Penicillium chrysogenum and Streptomyces levoris grown on soluble substrates were studied. Three different types of viscometers were used: (1) three on-line pipeline viscometers (5.8, 11.6 and 15.4 mm i.d.); (2) two rotating cylinder viscometers (Haake model RV12, MV2 and MV3 sensors), and (3) helical ribbon and turbine impeller viscometers. Results obtained with all three viscometer types showed increasing pseudoplastic behaviour (power law parameters from MV2 viscometer data: 0.3 ⩽n⩽1; 0.001 ⩽K ⩽5 Pa.sn) and yield stress (0⩽ty⩽16 Pa) with increasing biomass concentration(up to 20 g dw/1). Comparison of measurements at equivalent shear rates revealed lower measured apparent viscosities for the smallest pipeline viscometer, thus indicating the presence of wall “slip”. In contrast, higher apparent viscosities were observed with the turbine impeller, leading to the conclusion that the commonly made assumption that the average shear rate in this type of viscometer is independent of fluid rheology is not valid. Reasonable agreement was obtained among rheological measurements made on the large (≳ 11.6 mm i.d..) pipelines, the helical ribbon impeller and two different diameter rotating cylinder viscometers (provided the yield stress was exceeded inside the cup/bob gap); this suggests that “slip” effects were not significant in these viscometers. Based on these results,recommendations are provided to assist in the selection of appropriate viscometers for application to heterogeneous, non-Newtonian fermentation broths.

Algae biofilm growth and the potential to stimulate lipid accumulation through nutrient starvation.

An algae biofilm growth system was developed to study the growth kinetics and neutral lipid productivities of Scenedesmus obliquus and Nitzschia palea, and to determine if algal biofilms can be starved of key nutrients to increase their neutral lipid concentrations. Linear growth curves were determined for each species until nutrient starvation commenced, at which point growth ceased and/or biofilms sloughed from their substratum. Nutrient starvation did not increase neutral lipid concentrations in any of the biofilms; however, it approximately doubled their lipid concentrations when grown in suspension. Biomass productivities of 2.8 and 2.1g/m(2)/d and lipid productivities of 0.45 and 0.18 g/m(2)/d were determined for N. palea and S. obliquus, respectively. The results suggest that nutrient starvation of biofilms is not a desirable method of lipid production for algae biofilm biofuel production systems, but that lipid production rates compare favorably with conventional terrestrial biofuel sources.

Effects of temperature transient conditions on aerobic biological treatment of wastewater

The effects of temperature variations on aerobic biological wastewater treatment were evaluated with respect to treatment efficiency, solids discharges, sludge physicochemical properties and microbiology. The effects of controlled temperature shifts (from 35 degrees to 45 degrees C; from 45 degrees to 35 degrees C) and periodic temperature oscillations (from 31.5 degrees C to 40 degrees C, 6-day period, for 30 days) were assessed in 4 parallel, lab-scale sequencing batch reactors (SBRs) that treated pulp and paper mill effluent. Overall, the temperature shifts caused higher effluent suspended solids (ESS) levels (25-100 mg/L) and a decrease (up to 20%) in the removal efficiencies of soluble chemical oxygen demand (SCOD). Lower ESS levels were triggered by a slow (2 degrees C/day) versus a fast (10 degrees C/12h) temperature shift from 35 degrees to 45 degrees C, but the SCOD removal efficiencies decreased similarly in both cases (from 66+/-3% and 65+/-2% to 49+/-3% and 51+/-3%). Temperature oscillations caused an increased deterioration of the sludge settleability [high sludge volume indices (SVI); low zone settling velocities (ZSV)], high ESS levels and lower SCOD removals. The temperature transients were associated with poor sludge settleability (SVI>100 mL/g MLSS, ZSV<1 cm/min), more negatively charged sludge (up to -0.35+/-0.03 meq/g MLSS), increased filament abundance (approximately 4 to 4.5, subjective scale equivalent to very common), and decreased concentrations of protozoa and metazoa (25,000-50,000 microorganisms/mL sludge). The controlled, periodic temperature oscillations had a slight impact on SCOD removal efficiency (5% decrease), and did not seem to select for robust microorganisms that withstood the temperature shift. Sludge deflocculation and filament proliferation caused by these temperature transients may explain the higher ESS levels.

Phenotypic fingerprinting of microbial communities in wastewater treatment systems

Community-level characterization of microbial biomass from a municipal activated sludge plant, and two bleached kraft mill effluent (BKME) treatment systems, an oxygenated activated sludge system and an aerated lagoon system, was carried out using the BIOLOG redox-based carbon-substrate utilization assay. Several extraction procedures for separating microbial cells from the dark colloidal samples, including culture enrichment, homogenization, gravel agitation and sonication, were evaluated in order to overcome interference with colour development in the assay. Optimal microbial recovery was achieved by homogenization in the presence of deflocculating agents, sodium pyrophosphate and Tween 80. Principal component analysis was used to differentiate among the microbial communities in the wastewater treatment systems. Biomass obtained from each of the reactors displayed different composite metabolic profiles suggesting a unique indigenous microbial population in each system. Characterization of separate bacterial and protozoal components of one community also showed that each fraction displayed different substrate utilization patterns. Substitution of the already prepared BIOLOG panel substrates with individual chemicals typically associated with BKME allowed for the determination of biodegradation potential in wastewater treatment systems.

Alkaline extraction of wastewater activated sludge biosolids.

Activated sludge produced by wastewater treatment facilities are a sub-utilized by-product whose handling and disposal represent significant costs to these facilities. In this work, we introduced a simple and effective alkaline extraction technique that extracts up to 75% of the sludges organic matter into a liquor containing potentially useful organic material (proteins, carbohydrates, etc.). The results suggest that at pH 11 and above, cell lysis occurs, liberating substantial quantities of organic material into the alkaline solution. When compared to a cation exchange resin (CER) extraction developed for analytical purposes, the alkaline extraction recovered 3x more organic material. The alkaline extract was highly surface active, despite containing a relatively small fraction of lipids. At pH 12 and above the lipid fraction was enriched with C15-C16 fatty acid residues, likely associated with cell membrane phospholipids as suggested by nuclear magnetic resonance spectroscopy ((31)P NMR). Size exclusion chromatography studies show that the extract is enriched with biopolymers or assemblies of molecular weights in the order of tens of thousands of Daltons. Potential uses for the extract are discussed.

Design of algal film photobioreactors: material surface energy effects on algal film productivity, colonization and lipid content.

A parallel plate air lift reactor was used to examine the growth kinetics of mixed culture algal biofilms grown on various materials (acrylic, glass, polycarbonate, polystyrene and cellulose acetate). The growth kinetics of the algal biofilms were non-linear overall and their overall productivities ranged from 1.10-2.08g/m(2)day, with those grown on cellulose acetate having the highest productivity. Overall algal biofilm productivity was largely explained by differences in the colonization time which in turn was strongly correlated to the polar surface energy of the material, but weakly correlated to water-material contact angle. When colonization time was taken into account, the productivity for all materials except acrylic was not significantly different at approximately 2g/m(2)/day. Lipid content of the algal biofilms ranged from 6% to 8% (w/w) and was not correlated to water-material contact angle or polar surface energy. The results have potential application for selecting appropriate materials for algal film photobioreactors.

Effects of Nitrogen and Oxygen on Biofilter Performance

Abstract Three laboratory-scale biofilters packed with inert material were used to study the nitrogen and oxygen requirements for biofiltration of methanol. Mixtures of methanol with inorganic nitrogen (NH3 or NO3) at nitrogen-to-carbon (N:C) ratios ranging from 0.015 to 0.4 were employed to reveal nitrogen effects on biofiltration. In the oxygen study, mixtures of air and oxygen at different oxygen contents were used. At low nitrogen levels, the removal rate increased with increasing N:C ratio for both NH3 and NO3. However, at high concentrations, NH3 had an inhibitory effect on biodegradation while the removal rate reached a plateau at high NO3 concentrations. Biofiltration with 63% oxygen in the inlet gas stream increased the maximum removal rate from 120 to 145 g/m3/hr after 3 days in comparison with biofiltration with air. However, a further increase in oxygen content up to 80% did not lead to a further improvement in biofilter performance, suggesting that both oxygen and biofilm thickness can be the relevant factors limiting biofilter performance and creating the plateau in removal rates at high loadings.

Transient Performance of Biofilters Treating Mixtures of Hydrophilic and Hydrophobic Volatile Organic Compounds

The biological degradation of hydrophilic and hydrophobic volatile organic compounds (VOCs), discharged in pulp and paper and wood products air emissions, was examined under transient operating conditions. Two identical bench-scale biofilters were operated in parallel in order to study the influence of step loads on the removal of a-pinene, a hydrophobic VOC, and methanol, a hydrophilic VOC. The biofilter media consisted of a mixture of wood chips and spent mushroom compost that was further mixed with either perlite or small-size wood chips. The biofilters provided complete methanol removals during the start-up period due to the absorption process followed by biodegradation. For a-pinene, however, there was an acclimation period of 1 week to 10 days before the biofilters achieved 100% a -pinene removal efficiency. Step changes in the methanol loading rate did not affect the performance of the biofilters with respect to methanol. However, these fluctuations significantly influenced a-pinene biodegradation provided enough time (i.e., several days) was allowed. The removal rate of a-pinene gradually decreased along the column after each step increase in methanol inlet concentration. It appears that the presence of high concentrations of metha-nol, a hydrophilic and easily biodegradable compound, adversely impacted the growth of the a-pinene degrading microbial community, thereby decreasing a-pinene removal capacity of the biofilters over time. Unlike a-pinene, the methanol biodegradation rate was not affected by the presence or absence of a-pinene and with a-pinene fluctuations in the inlet airstream.

Biosorption of high molecular weight organochlorines in pulp mill effluent

Since biosorption is considered an important step in the removal of organochlorines in secondary treatment systems from pulp and paper mill effluent, the role of biosorption in the removal of high molecular weight organochlorine (HMW AOX) was studied. Ultrafiltered (> 1000 Da) total mill effluent was used as the sorbate and municipal sewage sludge as the sorbent. Eight different parameters were tested: contact time, cell viability, cell concentration, sorbate concentration, desorption, cell type, sorbate type and temperature. Biosorption equilibrium was reached in the first 30 min of an experiment and the removal of the high molecular weight organochlorine was independent of cell viability. The biosorption was characterized by the Freundlich isotherm [Q (mg/g VSS) = KC In, C +AOX concentration (mg/l)]; the observed values for the Freundlich coefficients K and l/n were 1.83 and 0.53, respectively. The Langmuir isotherm [Q = 7.5 c/(3.2 + C)] provided a better characterization for biosorption of HMW AOX since it predicted a saturation biomass phase concentration of 7.5 mg Cl/g VSS at high AOX concentrations. The maximum percentage removal of HMW AOX was 70% at a biomass concentration of 2.0 g VSS/l or higher. About 8% of the organochlorines desorbed from live biomass after 24 h indicating that the process is not readily reversible. Based on the experiments at various temperatures, the enthalpy of sorption was found to be −4 kJ/mol Cl.

Biofiltration of Cyclic Air Emissions of [H9251]-Pinene at Low and High Frequencies

Abstract Biofiltration of periodically fluctuating concentrations of an α-pinene-laden waste gas was investigated to treat both high-frequency and low-frequency fluctuations. The effects of periodic concentration fluctuations on biofilter performance were measured. Controlled variables of periodic operation included cycle period and amplitude. The cycle period ranged from 10 min to 6 days, with the inlet α-pinene concentration fluctuating between 0 and 100 parts per million volume. At high-frequency concentration cycling (i.e., on the order of minutes), both cyclic and constant concentration biofilters maintained similar long-term performance with an average removal efficiency of 77% at an averaged loading rate of 29 g α-pinene/m3 bed/hr. A first approximation suggests kinetics that are time-independent, indicating that steady-state data can be used to predict transient behavior at this time scale. Cyclic biofilter operation with a cycle period of 24 hr (with equal on/off time) was achievable for biofilters without a significant loss in performance. At longer time scales, cyclic biofilter performance decreased at the restart of the ON cycle. The recovery time to previous levels of performance increased with increasing cycle period; the recovery time was less than 1 hr for a cycle period of 24 hr and between 6 and 8 hr for a cycle period of 6 days.