Jerald A. Lalman

Influence of C18 Long Chain Fatty Acids on Hydrogen Metabolism

During anaerobic treatment, several microorganisms mediate a series of reactions to convert reduced compounds (electron donors) into methane. Inhibitors such as long chain fatty acids (LCFAs) can affect several anaerobic microbial populations and decrease the treatment efficiency. The effects of three C18 LCFAs on hydrogenotrophic methanogens in a flocculated mixed anaerobic culture were assessed in this study. The reaction half‐life and the hydrogen versus time profiles were used to characterize the inhibition process. The half‐life values and profiles were similar for controls and cultures exposed to LCFAs for 1 h. The hydrogen inhibition was a function of the exposure time and the LCFA concentration except for cultures exposed to stearic acid (SA). A statistical analysis of the reaction half‐life for cultures incubated with 1,500 and 2,000 mg L−1 LCFAs for 48 h, revealed the following inhibition trend: linoleic acid (LA) > oleic acid (OA) > SA. After 48 h of exposure, no clear inhibition trend was observed for cultures inoculated with LCFA mixtures; however, at levels of 1,500 and 2,000 mg L−1, the reaction half‐life values were less than that observed for cultures fed with only LA. Based on the reaction half‐life data, all of the LCFAs except SA at threshold levels of approximately 1,500 mg L−1 inhibited hydrogen metabolism. The greatest inhibition and, hence, the largest amount of accumulated hydrogen was observed in cultures fed with 2,000 mg L−1 LA and incubated for 48 h.

Modeling sulfate removal by inhibited mesophilic mixed anaerobic communities using a statistical approach.

Optimizing sulfate removal by a mixed anaerobic mesophilic culture fed glucose, linoleic acid (LA) and sulfate under several pH conditions was performed using a three factor three level Box-Behnken design (BBD). Based on the BBD approach, a statistical model was developed to predict the residual sulfate concentration. The LA concentration, initial pH and the COD/SO4(2-) ratio were the three experimental factors under consideration. Increasing the COD/SO4(2-) ratio increased the quantity of sulfate removed. The COD/SO4(2-) ratio showed the largest effect on reducing the sulfate level. Significant interactions between the three experimental factors were confirmed by the surface plots, interaction plot and ANOVA. An analysis of residuals verified accuracy of the model. Acetate and H2 production was dominant in cultures with the pH set at 6.0 and 6.75 and fed LA. After 168 h, butyrate and H2S were associated with the largest quantity of sulfate removed. At a D-optimality value of 1.0, a minimum response (residual sulfate concentration) of 36.2 mg L(-1) was recorded at 1500 mg L(-1) LA with a COD/SO4(2-) ratio of 2.18 and a pH set at 6.0. Based on the conditions under consideration, the model provided a useful approach for predicting the residual sulfate concentration in inhibited mixed anaerobic cultures.

Diverting Electron Fluxes to Hydrogen in Mixed Anaerobic Communities Fed with Glucose and Unsaturated C18 Long Chain Fatty Acids

Hydrogen ( H2 ) production was maximized and methane ( CH4 ) formation was minimized in a mixed anaerobic culture which was maintained at 21°C and fed glucose plus unsaturated long chain fatty acids (LCFAs). The initial pH in the batch reactors was 7.8±0.2 . The two LCFAs under consideration included linoleic acid (LA) (two C═C bonds) and oleic acid (OA) (one C═C bond). Hydrogen production was observed when glucose was injected on Day 0 and again after Day 4. The H2 yield in cultures fed LA was less than those receiving OA. The H2 yield reached a maximum of approximately 1.1 mol  H2 mol−1 glucose when the LA level was 2,000 mg  L−1 . In the case of OA, a maximum yield of 1.3 mol  H2 mol−1 glucose was attained with 2,000 mg  L−1 . The inhibition caused by the addition of LA or OA diverted a fraction of electrons toward proton reduction. Under maximum H2 production conditions in the LA fed cultures the acetate production pathway was repressed, while in cultures fed OA the acetate pathway was dominant. T...

TREATMENT LAGOONS FOR ANIMAL AGRICULTURE

The term “lagoon” is often misused. Farmers, the press, and the public tend to call all earthen manure storages basins lagoons. The term “lagoon,” however, has a specific meaning. ASAE Standards define a lagoon as “a waste treatment impoundment…(in which manure) is mixed with sufficient water to provide a high degree of dilution…for the primary purpose…(of reducing) pollution potential through biological activity. Treatment lagoons are not drawn below their treatment volume… except for maintenance.” Many of the problems associated liquid manure handling systems: liner seepage, accidental overflows, catastrophic embankment failure, pathogen release, odor emissions, and closure of earthen basins are not unique to lagoon-based systems. These problems are shared by all liquid systems. Other white papers in this volume touch upon these issues. The emphasis of this paper is the biological treatment potential of lagoons. Lagoons rely on physical, chemical, and biological processes to degrade manure. Biological processes play the greatest role in degradation. Growth and maintenance of biological communities depend on temperature, food, the absence of toxic elements, and the ability of organisms to remain in the lagoon long enough to reproduce. Microbiological communities are vertically segregated in lagoons. Each layer performs a separate function in the overall treatment process. Photosynthetic organisms play a major role in the degradation of sulfur- and nitrogen-containing compounds, as well as odoriferous elements; therefore the presence of the proper wavelengths of light to perform photosynthesis is also important in lagoon biology. Lagoons function best when operated as flow-through systems with a mechanism to periodically remove effluent. The most common method of effluent removal is to recycle plant nutrients through irrigation to crops. Local patterns of rainfall and evaporation (and the amount of rain produced by isolated storm events) determine whether a lagoon has a net surplus of effluent or whether water must be added to the system to maintain material flow through the lagoon. Two challenges must be addressed if lagoons are to remain a viable treatment alternative for animal agriculture: 1. Inefficient recovery of plant nutrients, and 2. Odor and ammonia emissions. Up to 80% of all nitrogen entering lagoons cannot be accounted for in lagoon effluent, and a great portion of manure phosphorus entering lagoons is retained in sludge. Plant nutrients are less concentrated in lagoon effluent than in other manure treatment products, although lagoon effluent has a better balance of nitrogen to soluble phosphorus than most sources of manure nutrients. Lagoon effluent should be used in crop production on a nitrogen basis, irrigating effluent in multiple applications throughout the growing season. Managing effluent in this manner requires expensive, permanent irrigation equipment to apply what is essentially low quality fertilizer. Nitrogen application is inherently out of sync with phosphorus since the majority of manure phosphorus is only recovered when solids are removed at the end of the sludge storage cycle, which may last as long as 10 to 20 years. Large chemical compounds are transformed into smaller, more volatile compounds through biological degradation. These small compounds may be less odorous than those found in raw manure, but their volatility makes them more likely to be emitted into the atmosphere. Ammonia gas is produced during anaerobic degradation of proteins and urea. A portion of the ammonia created in lagoons is undoubtedly lost through atmospheric emission. However, recent studies suggest that much of the atmospheric release of nitrogen may be in the form of harmless N2 gas. Lagoons located in temperate climates undergo annual cycles of storage, heating, and organic matter accumulation. Cool season organic matter accumulation is most pronounced in extreme latitudes. The heating and organic matter accumulation cycles are problematic in that there is a tendency for lagoon layers to become unstable in the spring and fall, increasing the likelihood of odor emissions during these periods. The mass of atmospheric emissions increases with lagoon size, and many of the problems of liquid manure handling—liner seepage, the consequences of catastrophic failures, wave erosion—are exacerbated by lagoon size. Current anaerobic lagoon design standards rely on volumetric organic loading rate to size the treatment volume. This means that lagoon size is directly proportional to farm size. A second consequence of relying on volumetric loading rate as the sole design parameter is that lagoon geometry cannot be changed without altering other potentially important design parameters such as depth and surface area to volume ratio. This paper does not specify a maximum size for lagoons, nor does it advocate abandoning volumetric loading rate as a design parameter. Pretreatment to reduce the mass of organic matter entering lagoons is suggested as a method to limit lagoon size on larger farms. Improvements in lagoon performance will be realized when specific biological communities, prescribed to perform specific treatment steps, are engineered to be present in individual lagoon cells or layers. Design refinements are needed to reach this point. Research should focus on filling the following information gaps: 1. Achieve a greater understanding of the fundamental biological processes involved in manure degradation. 2. Achieve a greater understanding of the chemical transformations involved in lagoon treatment. 3. Achieve a greater understanding of the physical and climatic factors that lead to cyclic environmental conditions experienced by lagoon microorganisms in temperate climates. 4. Develop diagnostic tools capable of monitoring biological communities in natural environments. 5. Develop design parameters to promote specific, robust biological communities in lagoons, given a set of environmental conditions and influent characteristics. Educational materials must be produced to train operators to maintain lagoons. These materials should be sensitive to the operators’ need to work within the limitations of an agricultural production system. The curriculum should include: 1. Basic treatment biology; 2. The cyclic nature of lagoon operation; 3. Liquid balance to maintain proper lagoon operating levels; 4. Operating within an actual water year, not an average year; 5. Efficient nutrient use; and 6. Maintaining structural integrity.

Optimizing the performance of microbial fuel cells fed a combination of different synthetic organic fractions in municipal solid waste

The objective of this study was to establish the impact of different steam exploded organic fractions in municipal solid waste (MSW) on electricity production using microbial fuel cells (MFCs). In particular, the influence of individual steam exploded liquefied waste components (food waste (FW), paper-cardboard waste (PCW) and garden waste (GW)) and their blends on chemical oxygen demand (COD) removal, columbic efficiency (CE) and microbial diversity was examined using a mixture design. Maximum power densities from 0.56 to 0.83 W m(-2) were observed for MFCs fed with different feedstocks. The maximum COD removed and minimum CE were observed for a GW feed. However, a reverse trend (minimum COD removed and maximum CE) was observed for the FW feed. A maximum COD removal (78%) accompanied with a maximum CE (24%) was observed for a combined feed of FW, PCW plus GW in a 1:1:1 ratio. Lactate, the major byproduct detected, was unutilized by the anodic biofilm community. The organic fraction of municipal solid waste (OFMSW) could serve as a potential feedstock for electricity generation in MFCs; however, elevated protein levels will lead to reduced COD removal. The microbial communities in cultures fed FW and PCW was highly diversified; however, the communities in cultures fed FW or a feed mixture containing high FW levels were similar and dominated by Bacteroidetes and β-proteobacteria.

Elucidating acetogenic H2 consumption in dark fermentation using flux balance analysis

In this study, a flux balance analysis (FBA) was adopted to estimate the activity of acetogenic H2-consuming reaction. Experimental data at different substrate concentrations of 10, 20, and 30 g COD/L showing the lowest, medium, and highest H2 yields, respectively, were used in the FBA to calculate the fluxes. It was interesting to note that the hydrogenase activity based on R12 (2Fd(+)+2H(+)→2Fd(2+)+H2, ferredoxin (Fd)) flux was most active at 10 g COD/L. The flux of R17 (4H2+2CO2→CH3COOH), a mechanism for reutilizing produced H2, increased in steps of 0.030, 0.119, and 0.467 as the substrate concentration decreased. Contradictory to our general understanding, acetate production found to have a negligible or even negative effect on the final H2 yield in dark fermentation.

EVALUATION OF A MICRO CARRIER WEIGHTED COAGULATION FLOCCULATION PROCESS FOR THE TREATMENT OF COMBINED SEWER OVERFLOW

Modified bench scale jar tests were conducted to evaluate a treatment strategy for combined sewer overflow (CSO) generated during wet-weather conditions in Windsor, Ontario, Canada. Alum and an anionic polymer (Polymer A-3330) were used as a primary coagulant and coagulant aid, respectively. Commercially available silica sand was employed as the micro carrier. Under the operating conditions optimized in the study, alum dose of 9.7 – 17.8 mg l-1 as Al3+ and polymer dosage of 1.0 – 1.8 mg l-1 were observed to be the most effective in solids removal. Addition of the micro carrier (MC) up to 3 g l-1 significantly increased the settleability of suspended solids, and about a five-fold increase in settleability was observed with 3 g l-1 MC. In the size range of < 300 μm and at 3 g l-1 concentration, the effect of MC size on the performance of the process was observed to be insignificant. Using the developed process, suspended solids and BOD removal efficiencies of > 98% and > 60%, respectively, were obtained with wet-weather flow after 8 minutes of settling, under both low and high suspended solids conditions.

Kinetics of glucose fermentation by a mixed culture in the presence of linoleic, oleic, and stearic acid.

Abstract The effects of long chain fatty acids (LCFAs) on glucose degradation were examined at 21 °C. A competitive inhibition model was used to determine the kinetics of glucose degradation. Half velocity constants (Ks) were a function of LCFA concentration only at 100, 300 and 500 mg l−1. The inhibitor constants (K,) for individual and mixed LCFAs were statistically the same. Glucose degradation rates for cultures receiving saturated (stearic add (SA)) and monounsaturated (oleic acid (OA)) LCFAs were statistically the same but statistically different when compared to cultures fed with a polyunsaturated LCFA (linoleic add (LA)). Individual and mixed LCFAs inhibited glucose degradation at threshold levels of 300 and 500 mg l−1, respectively.

Role of Biocathodes in Bioelectrochemical Systems

Environmental damage, depleting fossil fuels and energy security are major factors driving intensive research efforts to develop carbon neutral or carbon negative technologies which can be used to produce electricity and chemicals. Technologies under development to achieve this goal include those based on bioelectrochemical, biological, thermal and chemical processes. Evolving technologies employing biological as well as electrochemical principles are grouped in the bioelectrochemical systems (BESs) category. The main focus of this chapter is on biocathodes used in BESs.

Enhanced TiO 2 nanorods photocatalysts with partially reduced graphene oxide for degrading aqueous hazardous pollutants

Enhanced TiO2 nanorods (TNRs) with partially reduced graphene oxide (RGO) (designated as GT) were prepared for degrading aqueous hazardous pollutants. The degree of RGO oxidation had an important role in affecting the photoelectronic and photocatalytic activities of GT composites. The study examined the impact of the degree of RGO oxidation on the photocatalytic activities. The photocatalytic activity of the materials was investigated for degrading rhodamine b (RhB), methyl orange (MO), methylene blue (MB), and phenol by using ultraviolet (UV) light. The highest photocatalytic activity was observed when the atomic oxygen-to-carbon (O/C) ratio of RGO was 0.130 ± 0.003. This study suggested the photocatalytic performance was maximized by preserving a selected amount of the RGO oxygen-containing groups. The work reported in this study on optimizing the RGO-based TiO2 photocatalyst could serve as a promising approach for preparing and optimizing other types of carbon-based photocatalysts such as graphene-based CdS.