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PubMed2001

Estimating biomass yield coefficients for autotrophic ammonia and nitrite oxidation from batch respirograms.

Kinetic characterization of biological processes via batch respirometry requires an accurate estimate of the biomass yield coefficient because it provides the stoichiometric link between biomass synthesis, substrate consumption and oxygen uptake. Expressions for biomass yield coefficients describing autotrophic ammonia and nitrite oxidation were derived from a mechanistically based electron balanced equation. We demonstrate that applying the conventional expression used to calculate the heterotrophic biomass yield results in erroneous estimates for the autotrophic biomass yield. Yield coefficients for autotrophic NH4(+)-N to NO2(-)-N oxidation and NH4(+)-N to NO3(-)-N oxidation were overestimated by 27 to 36%. Due to correlation between the maximum specific growth rate and the biomass yield, the error in yield values propagated in 30 to 40% overestimates of the maximum specific growth rate coefficient for NH4(+)-N oxidation determined from batch respirograms. Therefore, it is essential to employ the correct expression to estimate the autotrophic biomass yield coefficient from batch respirograms due its inadvertent impact on subsequent parameter estimation.

Ammonia↗

PubMed2002

Effect of chromium(VI) on bacterial kinetics of heterotrophic biomass of activated sludge.

The effect of hexavalent chromium, Cr(VI), on the maximum specific growth rate, mu(m) and biomass yield, Y(H), of heterotrophic biomass was studied in batch tests conducted under high (= 10) and low (= 1.5) substrate-to-biomass ratios (S0/X0). The effects of sludge age and biomass acclimatization to Cr(VI) on the bacterial kinetics were also studied. The mu(m) values were determined by measuring oxygen uptake rate (OUR) and volatile suspended solids (VSS) increase. Cr(VI) concentrations equal or greater than 10 mg l(-1) inhibited the growth of unacclimatized activated sludge and caused a significant decrease in mu(m) and Y(H) values. The acclimatization of biomass and the selection of a high operating sludge age reduced the inhibitory effect of Cr(VI). At a sludge age of 20 days, Cr(VI) concentrations of <10 mg l(-1) stimulated bacterial growth as evidenced by an increase in both the mu(m) and Y(H) values. Determining mu(m) values by OUR and VSS methods, revealed that the presence of Cr(VI) in unacclimatized biomass caused an inhibitory effect mostly on substrate oxidation, while in acclimatized biomass, anabolic pathways were inhibited more.

Biomass↗

PubMed1999

Impact of moderate silver carp biomass gradient on zooplankton communities in a eutrophic reservoir. Consequences for the use of silver carp in biomanipulation.

We examined the impacts of moderate gradient silver carp biomass (five levels from 0 to 36 g.m-3, i.e. about 0-792 kg.ha-1) on zooplankton communities of the eutrophic Villerest reservoir (France). During our mesocosm experiment changes in zooplankton assemblages were dependent on silver carp biomass. In the fishless and low fish biomass treatments, zooplankton abundance increased through time, owing to a peak in cladoceran density, but decreased (mainly cladocerans) at highest fish biomass. Copepods and rotifers were less affected at the highest fish biomass and dominated zooplankton communities. We highlighted that the presence of high silver carp biomass could lead to changes in phytoplankton assemblage via the impact on herbivorous zooplankton. Since silver carp efficiently graze on particles > 20 microns, the suppression of herbivorous cladocerans could result in an increase in small size algae (< 20 microns) abundance since these species would be released from grazers as well as competitors (large algae grazed by silver carp) and nutrients levels would be enhanced by fish internal loading. Our results showed that the use of low silver carp biomass (< 200 kg.ha-1) would allow us to minimize these negative effects.

Animal Feed↗

PubMed2003

Assessment of potential carbon dioxide reductions due to biomass-coal cofiring in the United States.

Cofiring biomass with coal in existing power plants offers a relatively inexpensive and efficient option for increasing near-term biomass energy utilization. Potential benefits include reduced emissions of carbon dioxide, sulfur, and nitrogen oxides and development of biomass energy markets. To understand the economics of this strategy, we develop a model to calculate electricity and pollutant mitigation costs with explicit characterization of uncertainty in fuel and technology costs and variability in fuel properties. The model is first used to evaluate the plant-level economics of cofiring as a function of biomass cost. It is then integrated with state-specific coal consumption and biomass supply estimates to develop national supply curves for cofire electricity and carbon mitigation. A delivered cost of biomass below 15 dollars per ton is required for cofire to be competitive with existing coal-based generation. Except at low biomass prices (less than 15 dollars per ton), cofiring is unlikely to be competitive for NOx or SOx control, but it can provide comparatively inexpensive control of CO2 emissions: we estimate that emissions reductions of 100 Mt-CO2/year (a 5% reduction in electric-sector emissions) can be achieved at 25 +/- 20 dollars/tC. The 2-3 year time horizon for deployment--compared with 10-20 years for other CO2 mitigation options--makes cofiring particularly attractive.

Air Pollutants↗

PubMed2004

Chemical composition of post-harvest biomass burning aerosols in Gwangju, Korea.

The main objective of this study was to investigate the chemical characteristics of post-harvest biomass burning aerosols from field burning of barley straw in late spring and rice straw in late fall in rural areas of Korea. A 12-hr integrated intensive sampling of particulate matter (PM) with an aerodynamic diameter less than or equal to 10 microm (PM10) and PM with an aerodynamic diameter less than or equal to 2.5 microm (PM2.5) biomass burning aerosols had been conducted continuously in Gwangju, Korea, during two biomass burning periods: June 4--15, 2001, and October 8--November 14, 2002. The fine and coarse particles of biomass burning aerosols were analyzed for mass and ionic, elemental, and carbonaceous species. The average fine and coarse mass concentrations of biomass burning aerosols were, respectively, 129.6 and 24.2 microg/m3 in June 2001 and 47.1 and 33.2 microg/m3 in October--November 2002. An exceptionally high PM2.5 concentration of 157.8 microg/m3 was observed during biomass burning events under stagnant atmospheric conditions. In the fine mode, chlorine and potassium were unusually rich because of the high content of semi-arid vegetation. Both organic carbon (OC) and elemental carbon increased during the biomass burning periods, with the former exhibiting a higher abundance. PM from the open field burning of agricultural waste has an adverse impact on local air quality and regional climate.

Aerosols↗

PubMed2006

Wastewater treatment by periodic biofilter characterized by aerobic granular biomass.

The paper reports the results of an experimental investigation aimed at evaluating the role of hydrodynamic conditions on generation and main properties of granular biomass grown under aerobic conditions in a periodic packed bed reactor. During the start-up period, the trend of the hydrodynamic shear forces, calculated by a methodology previous developed by authors, provided a key for explaining the process of biomass granulation. The granular biomass was characterized by a high density (i.e., 70-120 gVSS/Lbiomass) that permitted to achieve a biomass concentration such high as 20-38 gVSS/Lbed. The biomass density increased with the increase of shear forces. The EPS (Extracellular Polymeric Substances) content of the biomass (5-7% of the total organic matter) was not affected by hydrodynamic shear forces as well as the biomass protein content. Periodic packed bed reactor applied to a municipal wastewater showed performances very satisfactory with high efficiencies removal (around 90%) for both COD and ammonia, up to an applied organic loading value of 5.7 kgCOD/m3.d, and negligible sludge production.

Aerobiosis↗

PubMed2003

Ni2+ removal and recovery from electroplating effluent by Pseudomonas putida 5-x cell biomass.

Ni2+ and Cu2+ are the major heavy metal ions in electroplating wastewater of Hong Kong. In the present study, Pseudomonas putida 5-x cell biomass was used to remove Ni2+ from electroplating effluent. Ni2+ adsorption capacity of P. putida 5-x cell biomass cultured in sulphate-limiting medium was found to be minimum in early logarithmic growth phase, and maximum of 28.1 mg g(-1) in late stationary growth phase. Pretreated cells by 0.1 mol L(-1) HCl could greatly enhance the Ni2+ adsorption capacity of cell biomass from 28.1 to 36.7 mg g(-1) and had no significant effect on biomass loss. The adsorption process of P. putida 5-x fresh cells and pretreated cell all could be expressed with Freundlich isotherm. TEM analyses indicated that acidic pretreatment degraded the superficial layer-capsule outside of the fresh cell to improve the adsorption capacity of cell to Ni2+. The Ni2+ bound by P. putida 5-x cell biomass could be efficiently recovered using 0.1 mol L(-1) HCl, and the cell biomass could be reused at least five cycles for Ni2+ removal and recovery with 93% above removal efficiency and 98% above recovery rate. Owing to the Cu2+ presented in electroplating wastewater inhibiting Ni2+ adsorption process by P. putida 5-x cell biomass, two-stage biosorption processes should be designed to remove and recover Cu2+ and Ni2+ sequentially from electroplating effluent.

Adsorption↗

PubMed2005

Carbon and biomass partitioning in balsam fir (Abies balsamea).

Balsam fir (Abies balsamea (L.) Mill) was extensively sampled to investigate the effects of forest management practices, site location, within-crown position, tree component (i.e., stem, foliage, branches and roots), and tree social classes on biomass and carbon (C) partitioning at the individual tree level and across ecological regions. The sites were located in three ecologically distinct forest regions of west-central New Brunswick, Canada. There were no significant differences in %C content of trees across ecological regions or across tree social classes. However, at the individual tree level, significant differences were evident in biomass and C allocation between different parts of the tree, between treatment types (i.e., unmanaged and pre-commercially thinned stands) and between within-crown positions, indicating the need for separate estimates of biomass and C content of tree components to obtain more precise estimates of quantities at the stand level. Calculating stand C content based on constant allocation values, as is commonly done, produced errors of up to 15% compared with the values calculated in this study. Three allometric equations of biomass and C that account for partitioning among different parts of the tree were developed and compared: (1) a third-order polynomial, (2) a modified inverse polynomial and (3) a modified Weibull equation. Diameter at breast height (DBH) was used as the only explanatory variable to describe fresh biomass, dry biomass and C content. All regressions derived showed a high correlation with DBH, with most r2 values > 0.95. A comparison of the equation results showed that the modified Weibull equation gave consistent results with the best overall fit and was the simplest of the three equations investigated. The regressions can be used to estimate forest biomass and tree C content at the stand level, given specific information on DBH.

Abies↗

PubMed2005

Effects of elevated atmospheric CO2 on soil microbial biomass, activity, and diversity in a chaparral ecosystem.

This study reports the effects of long-term elevated atmospheric CO2 on root production and microbial activity, biomass, and diversity in a chaparral ecosystem in southern California. The free air CO2 enrichment (FACE) ring was located in a stand dominated by the woody shrub Adenostoma fasciculatum. Between 1995 and 2003, the FACE ring maintained an average daytime atmospheric CO2 concentration of 550 ppm. During the last two years of operation, observations were made on soil cores collected from the FACE ring and adjacent areas of chaparral with ambient CO2 levels. Root biomass roughly doubled in the FACE plot. Microbial biomass and activity were related to soil organic matter (OM) content, and so analysis of covariance was used to detect CO2 effects while controlling for variation across the landscape. Extracellular enzymatic activity (cellulase and amylase) and microbial biomass C (chloroform fumigation-extraction) increased more rapidly with OM in the FACE plot than in controls, but glucose substrate-induced respiration (SIR) rates did not. The metabolic quotient (field respiration over potential respiration) was significantly higher in FACE samples, possibly indicating that microbial respiration was less C limited under high CO2. The treatments also differed in the ratio of SIR to microbial biomass C, indicating a metabolic difference between the microbial communities. Bacterial diversity, described by 16S rRNA clone libraries, was unaffected by the CO2 treatment, but fungal biomass was stimulated. Furthermore, fungal biomass was correlated with cellulase and amylase activities, indicating that fungi were responsible for the stimulation of enzymatic activity in the FACE treatment.

Air↗

PubMed2006

Development of a multicriteria assessment model for ranking biomass feedstock collection and transportation systems.

This study details multicriteria assessment methodology that integrates economic, social, environmental, and technical factors in order to rank alternatives for biomass collection and transportation systems. Ranking of biomass collection systems is based on cost of delivered biomass, quality of biomass supplied, emissions during collection, energy input to the chain operations, and maturity of supply system technologies. The assessment methodology is used to evaluate alternatives for collecting 1.8 x 10(6) dry t/yr based on assumptions made on performance of various assemblies of biomass collection systems. A proposed collection option using loafer/ stacker was shown to be the best option followed by ensiling and baling. Ranking of biomass transport systems is based on cost of biomass transport, emissions during transport, traffic congestion, and maturity of different technologies. At a capacity of 4 x 10(6) dry t/yr, rail transport was shown to be the best option, followed by truck transport and pipeline transport, respectively. These rankings depend highly on assumed maturity of technologies and scale of utilization. These may change if technologies such as loafing or ensiling (wet storage) methods are proved to be infeasible for large-scale collection systems.

Biomass↗

PubMed2006

Biotic habitat complexity controls species diversity and nutrient effects on net biomass production.

Canopy-forming plants and algae commonly contribute to spatial variation in habitat complexity for associated organisms and thereby create a biotic patchiness of communities. In this study, we tested for interaction effects between biotic habitat complexity and resource availability on net biomass production and species diversity of understory macroalgae by factorial field manipulations of light, nutrients, and algal canopy cover in a subtidal rocky-shore community. Presence of algal canopy cover and/or artificial shadings limited net biomass production and facilitated species diversity. Artificial shadings reduced light to levels similar to those under canopy cover, and net biomass production was significantly and positively correlated to light availability. Considering the comparable and dependent experimental effects from shadings and canopy cover, the results strongly suggest that canopy cover controlled net biomass production and species diversity by limiting light and thereby limiting resource availability for community production. Canopy cover also controlled experimental nutrient effects by preventing a significant increase in net biomass production from nutrient enrichment recorded in ambient light (no shading). Changes in species diversity were mediated by changes in species dominance patterns and species evenness, where canopy cover and shadings facilitated slow-growing crust-forming species and suppressed spatial dominance by Fucus vesiculosus, which was the main contributor to net production of algal biomass. The demonstrated impacts of biotic habitat complexity on biomass production and local diversity contribute significantly to understanding the importance of functionally important species and biodiversity for ecosystem processes. In particular, this study demonstrates how loss of a dominant species and decreased habitat complexity change the response of the remaining assembly to resource loading. This is of potential significance for marine conservation since resource loading often promotes low habitat complexity and canopy species are among the first groups lost in degraded aquatic systems.

Analysis of Variance↗

PubMedDate not supplied

[Predators, resources, and trophic chains in the regulation of plankton population and biomass in oligothrophic lakes].

The relative strength of "top-down" versus "bottom-up" control of plankton community structure and biomass in two small oligotrophic lakes (with and without fish), located near the Polar circle (Russia), has been investigated for two years, 1996 and 1997. The comparative analyses of zooplankton biomass and species abundance showed strong negative effect of fish, stickeback (Pungitius pungitius L.), on the zooplankton community species, size structure and biomass of particular prey species but no effect on the biomass of the whole trophic level. An intensive predation in Verkhneye lake has lead to: 1) sixfold decline in biomass of large cladoceran Holopedium gibberum comparing to the lake lacking predator, 2) shift in the size mode in zooplankton community and the replacement of the typical large grazers by small species--Bosmina longirostris and rotifers. Their abundance and biomass even increased, demonstrating the stimulating effect of fish on the "inefficient" and unprofitable prey organisms. The analysis of contributions of different factors into the cladoceran's birth rate changes was applied to demonstrate the relative impact of predators and resources on zooplankton abundance. An occasional introduction of the stickleback to Vodoprovodnoye lake (the reference lake in 1996) in summer 1997 lead to drastic canges in this ecosystem: devastating decrease of zooplankton biomass and complete elimination of five previously dominant grazer species. The abundance of edible phytoplankton was slightly higher in the lake with fish in 1996 and considerably higher in the lake where fish has appeared in 1997 showing the prevailing "top-down" control of phytoplankton in oligotrophic ecosystem. The reasons of trophic cascade appearance in oligotrophic lakes are also discussed.

Animals↗

PubMed2002

[Microbial biomass affected by cadmium with the occurrence of organic acids in red soil].

Soil microbial biomass carbon and nitrogen were determined after adding fixed concentration of organic acids and changeable concentration of cadmium in pre-incubated red soil and 14-day incubation at 25 degrees C. The results show that soil microbial biomass carbon and nitrogen in the soil added with organic acids decreased with increasing concentration of cadmium. When the concentration of cadmium was higher than 25 mg.kg-1, the microbial biomass carbon and nitrogen in the soil added with low molecular weight of organic acids (oxalic acid, acetic acid, citric acid, tartaric acid) were lower than those without the addition of organic acids, indicating that low molecular weight of organic acids could increase the toxicity of cadmium. On the contrary, the microbial biomass carbon and nitrogen in the soil added with low molecular weight of organic acids were higher than those without the addition of organic acids when the concentration of cadmium was lower than 25 mg.kg-1, indicating that low molecular weight organic acids could decrease the toxicity of cadmium. The microbial biomass carbon and mitrogen in the soil containing humic acid were higher than those without the addition of organic acids, indicating that humic acid could decrease the toxicity of cadmium. However, the C:N ratio of soil microbial biomass was increased with increasing concentration of cadmium. Organic acids could increase microbial biomass carbon and nitrogen when soil was not added with cadmium.

Acetic Acid↗

PubMed2002

[Seasonal fluctuation of plant biomass in land remained bare in Hailun experimental station].

Analysis of the above- and under-ground biomass of the land remained bare for seven years and twenty years and the farmland in Hailun experimental station showed that total biomass increased over the bare period. There was no significant difference in above-ground biomass between bare lands, while the root biomass showed obvious difference, indicating that total biomass was differed mainly from root biomass between bare lands. With longer bare period, the ecosystem had the stronger resistance to environmental stress and the more stability. Meanwhile, its root biomass turnover value was small, which suggesting the higher ability to supply nutrient and energy stably.

Biomass↗

PubMed2002

Active heterotrophic and autotrophic biomass distribution between fixed and suspended systems in a hybrid biological reactor.

This paper presents the results obtained when modifying sludge retention time (SRT 8, 5, and 3.7 days during phases A, B and C respectively) for a hybrid biological reactor (HR) compared with a classical activated sludge process. The study was conducted by following active biomass evolution and distribution for two lab-scale pilots plants operating with the same conditions, one acting as HR and the other as the control reactor (CR) without support material. At the end of phase C, support material was split into two fractions between both reactors to study the effect of support to reactor volume ratio (Fr). Active biomasses in suspended and fixed systems were calculated using respirometric techniques. Evolutions of active autotrophic and heterotrophic biomasses for both reactors are presented during all the operational periods and it is observed that in the HR biomass concentrations are up to double that in the CR, mainly due to the presence of support material. When studying biomass distribution in HR, autotrophic biomass is mainly located over the support material (from 95% to 99% during periods A and C respectively) while only about 60% of heterotrophic biomass is located over the support.

Bacteria↗

PubMed2002

Decay rate variability of active heterotrophic biomass.

Hypotheses of the ASM 1 model state that the specific respiration rate of heterotrophic active biomass is a constant. It thus becomes possible to assess the active heterotrophic biomass decay rate (bH) during starvation. The object of this study is to verify if the specific respiration rate of heterotrophic biomass remains constant throughout starvation, and if it is typical of global metabolic biomass activity, as proposed by the model hypotheses. The decay rate bH was evaluated using respirometric and enzymatic measurements. Measurement of bH through respirometry on various sludges varied between 0.28 and 0.76 d(-1). According to the enzyme and respirometric measurements carried out, a large portion of this value is related to enzymatic regulation. During starvation, when initial active biomass activity is high, down regulation of the respiratory chain results in a decrease in the specific heterotrophic active biomass respiration rate, thus creating an overevaluation of the decay rate as measured by respirometry. Thus a high decay rate used in the ASM 1 model could eventually lead to a poor forecast of biomass production.

Bacteria↗

PubMed2003

Evaluation of biomass production in unleaded gasoline and BTEX-fed batch reactors.

BTEX removal under aerobic conditions by unleaded gasoline acclimated biomass and BTEX acclimated biomass, and the effect of surfactant on BTEX biodegradation were evaluated. The effect of BTEX concentration as the sole source of carbon for biomass acclimation and the effect of yeast extract on cell growth in unleaded gasoline-fed reactors were also evaluated. For the unleaded gasoline acclimated biomass, benzene was shown the most recalcitrant among all BTEX, followed by o-xylene and toluene with 16-23%, 35-41% and 57-69% biodegradation, respectively. Ethylbenzene was consistently the fastest BTEX chemical removed with 99% biodegradation for the four bioreactor acclimated biomasses tested. For the 1,200 ppm BTEX acclimated biomass, benzene showed the highest removal efficiency (99%) among the four biomass environmental conditions tested, along with 99% toluene and 99% ethylbenzene biodegradation. O-xylene showed 92-94% removal. In all bioassays tested Tergitol NP-10 was fully removed, and did not have a substantial effect on BTEX biodegradation at the end of a 10-day evaluation.

Bacteria, Aerobic↗

PubMed2003

Microbial biomass: an economical alternative for removal of heavy metals from waste water.

Today indiscriminate and uncontrolled discharge of metal contaminated industrial effluents into the environment has become an issue of major concern. Heavy metals, being non-biodegradable and persistent, beyond a permissible concentration form unspecific compounds inside the cells thereby causing cellular toxicity. The only alternative to remove them from the wastewater is by immobilizing them. The conventional methods adopted earlier for this purpose included chemical precipitation, oxidation, reduction, filtration, electrochemical treatment, evaporation, adsorption and ion-exchange resins. These methods require high energy inputs especially when it refers to dilute solutions. Here microbial biomass offers an economical option for removing heavy metals by the phenomenon of biosorption. Non-living or dead biomass sequester metal(s) on their cell surface due to certain reactive groups available like carboxyl, amine, imidazole, phosphate, sulphydryl, sulfate and hydroxyl. The process can be made economical by procuring spent biomass from industry or naturally available bulk biomass. A batch or a continuous process of removal of heavy metals directly from effluents can be developed in a fixed bed reactor using the immobilized biomass. Further biosorption potential of the biomass can be improved by various physical and chemical treatments. The availability of variety of microbial biomass and their metal binding potential makes it a economical and sustainable option for developing effluent treatment process for removal and recovery of heavy metals.

Absorption↗