Presence Of Volatile Fatty Acids Research Articles

Effort to Mitigate Volatile Fatty Acid Inhibition by Using Mixed Inoculum and Compost for the Degradation of Food Waste and the Production of Biogas

Food waste is a rich organic matter that can potentially be converted into biogas as a source of renewable energy. The limitation in energy production lies in the presence of volatile fatty acid (VFA) during the anaerobic digestion of food waste due to the high degradation rate. The accumulation of VFA leads to a decrease in pH that exceeds the optimal pH range of 6.8–7.6 for methanogens, thus inhibiting methanogenesis and affecting biogas production. In the present study, a symbiotic culture of bacteria and yeast (SCOBY) and kombucha mixed inoculum and compost was applied as an alternative treatment method to alleviate inhibition. The digestion efficiency was evaluated on pH, total alkalinity (TA), total volatile fatty acid (TVFA), total solid (TS), and volatile solid (VS) throughout the digestion period of 80 days to analyse the stability of the system. The results revealed that SCOBY and kombucha mixed inoculum caused system instability, inducing inhibition at TVFA of 12,874.1 mg/L, while the pH dropped to 5.23. The inhibition in the digestion system with only the SCOBY inoculum occurred at TVFA of 11,908.3 mg/L, and the pH dropped to 5.67. The biogas and methane yield quantified from the mixed inoculum is 8.792E−4 L/L d, comparatively lower than the ethanol pre-fermentation treatment method. These findings indicate that the addition of compost improved the pH, VS, and TVFA.

CaCO3 solubility in the process water of recycled containerboard mills

Abstract Water system closure in recycled containerboard mills may have reached a technical limit due to the accumulation of organic and inorganic contaminants in the process water. The specific water chemistry characteristics of recycled containerboard mills with restricted water systems were analyzed and a computer model was developed to simulate calcium carbonate solubility in the presence of volatile fatty acids under relevant mill conditions. A strong linear correlation between VFAs and calcium ions was found. The calcium carbonate dissolution mechanism, solubility, and precipitation were investigated. The reaction of VFAs with calcium carbonate results in the formation of bicarbonate and carbonic acid. By binding hydrogen ions, the carbonate has a pH buffering effect. The carbonic acid dissociates into water and CO2. Gaseous CO2 escapes from the water and leads to decarbonization. This mechanism is responsible for the uncoupling of pH from the concentration of VFAs, as well as from the concentration of dissolved calcium ions. The resulting lack of carbonates prevents the precipitation of calcium carbonate. The introduction of CO2 contained in the biogas produced in anaerobic biological water treatment reverses the dissolution mechanism and causes the precipitation of calcium carbonate. Concentrating technologies such as membrane filtration and evaporation may therefore meet the specific requirements for complete water system closure in recycled containerboard mills better than current commonly used biological treatment.

Biogenic Sulfidation of U(VI) and Ferrihydrite Mediated by Sulfate-Reducing Bacteria at Elevated pH.

Globally, the need for radioactive waste disposal and contaminated land management is clear. Here, gaining an improved understanding of how biogeochemical processes, such as Fe(III) and sulfate reduction, may control the environmental mobility of radionuclides is important. Uranium (U), typically the most abundant radionuclide by mass in radioactive wastes and contaminated land scenarios, may have its environmental mobility impacted by biogeochemical processes within the subsurface. This study investigated the fate of U(VI) in an alkaline (pH ∼9.6) sulfate-reducing enrichment culture obtained from a high-pH environment. To explore the mobility of U(VI) under alkaline conditions where iron minerals are ubiquitous, a range of conditions were tested, including high (30 mM) and low (1 mM) carbonate concentrations and the presence and absence of Fe(III). At high carbonate concentrations, the pH was buffered to approximately pH 9.6, which delayed the onset of sulfate reduction and meant that the reduction of U(VI)(aq) to poorly soluble U(IV)(s) was slowed. Low carbonate conditions allowed microbial sulfate reduction to proceed and caused the pH to fall to ∼7.5. This drop in pH was likely due to the presence of volatile fatty acids from the microbial respiration of gluconate. Here, aqueous sulfide accumulated and U was removed from solution as a mixture of U(IV) and U(VI) phosphate species. In addition, sulfate-reducing bacteria, such as Desulfosporosinus species, were enriched during development of sulfate-reducing conditions. Results highlight the impact of carbonate concentrations on U speciation and solubility in alkaline conditions, informing intermediate-level radioactive waste disposal and radioactively contaminated land management.

Sensory, GC-MS and PTR-ToF-MS profiling of strawberries varying in maturity at harvest with subsequent cold storage

Harvesting strawberry fruit before they are fully ripe and allowing them to further ripen during postharvest cold storage is a common practice. The effect of these storage conditions on consumer liking is not well understood. The first aim of this study is to investigate the effects of maturity at harvest and subsequent cold storage on consumer liking, expressed as sweetness and aroma attributes, and volatile composition. The second aim of this study is to investigate whether volatile organic compounds (VOCs) can be used to predict consumer liking. Strawberries (Fragaria × ananassa cv. Lusa) were harvested either at the ¾ red stage or full red stage and stored at 4 °C for one, five or nine days. Strawberries were subjected to sensory profiling, colour-, firmness-, GC–MS- and PTR-ToF-MS- measurements. The sensory profile of strawberries harvested at ¾ red stage showed lower sweetness and aroma than full red harvested strawberries. VOC analysis of these strawberries showed lower presence of volatile fatty acids, furanones and most esters even after nine days of cold storage, compared to full red strawberries. Strawberries harvested at full red stage showed the highest value for aroma attributes after one day of cold storage. Surprisingly, peak intensities of most esters (except for methyl butanoate and methyl hexanoate) and furanones were low on the first day, compared to ripe harvested fruit after longer storage. Ripe harvested fruit stored for nine days showed the highest peak intensities for most VOCs, but this did not correspond to the highest sensory aroma attributes. These fruits were judged with the lowest values for aroma attributes, perhaps related to the production of volatiles with off-flavours (acetaldehyde, ethyl acetate). PLS modelling showed that VOCs exist that are characteristic for both sweet and aromatic sensory attributes of ‘Lusa’ strawberries, based either on GC–MS (mainly volatile fatty acids) or PTR-ToF-MS analysis (mainly alcohol/ester fragments). This could lead to fast, non-destructive, selection of strawberries with high consumer liking using PTR-ToF-MS.

Характеристика замороженої яловичини за біохімічними і мікробіологічними показниками

Goal. To assess methods of storing frozen beef according to microbiological and chemical indicators. Methods. Microbiological and biochemical studies of fresh and frozen beef aiming at the determination of the indicators of freshness and microbiological safety were carried out by standard and generally accepted techniques. Results. It was found that the number of mesophilic microorganisms on fresh beef carcasses (24 h) was 12.7 times higher as compared to the number of psychrotrophic microorganisms. During 8-months’ storage of beef in a frozen state (–12°C) the number of mesophilic aerobic and optional anaerobic microorganisms decreased 7.8 times, Enterobacteriaceae — in 16.8, psychrotrophic microflora — only in 1.6 times. At the same time, fungal microflora for these storage modes increased 1.7 times. When storing beef at a temperature of –20...–25°C for 14 and 18 months, the gradual dying of microflora on its surface was revealed. At the same time, the amount of mesophilic and coliform microflora decreased on a larger scale — about 10 and 24 times, respectively. The number of psychrotrophic microflora thus decreased only 1.8 times against the initial amount, and the fungal one remained unchanged. Within 8-months’ storage of beef at –12°C deterioration was revealed of indicators and its freshness. At the same time, for storage of meat at –20...–25°C for 14 and 18 months, the presence of volatile fatty acids indicates its doubtful freshness. Also, the growth of products of peroxide oxidation of lipids is fixed in beef with long-term storage at –12°C. Conclusions. When storing beef in a frozen state at a temperature of –12°C for 8 months the development of mesophilic and psychrotrophic microflora is stopped. The most detrimental temperature of –12°C influences mesophilic and coliform bacteria. At the same time, the propagation of fungal microflora on the surface of the carcass is fixed. When storing beef at –20...–25°C for 14-18 months the microflora on its surface did not multiply, but gradually died. Within 8-months’ storage of beef at -12°C the deterioration was revealed of biochemical indicators of its freshness. At the same time, for storage at – 20...– 25°C for 14 and 18 months, beef had questionable freshness only by the content of volatile fatty acid.

Acidogenic mixed consortium isolated from soil of agricultural field: acid production behaviour and growth kinetics under the influence of pretreatment hydrolysate of rice straw (RS)

ABSTRACT The present study was conducted to assess the possibilities of biofuel production through volatile fatty acid (VFA) platform using mixed consortia isolated from a natural source (soil of rice cultivation field). The acid production potential of the isolated acidogenic mixed consortium UACJUChE1, using pretreatment hydrolysate of rice straw as the carbohydrate source, was assessed. Growth kinetic parameters i.e. maximum specific growth rate (μ max) and substrate saturation constant (KS ) of UACJUChE1 have been determined separately for both glucose and hydrolysate in the Reinforced Clostridial Medium (RCM). A summative type growth model has been observed to be valid when the combination of glucose and RS-hydrolysate (RSH) is used as the carbon sources. The summative model has been validated by successful comparison of model predictions with the experimental data. The presence of VFAs in the culture broth of the consortium grown on glucose, RS-hydrolysate and their combination (Glc:RSH: 2:3; 1:4 (w/w)) has been established. The survival and growth of solventogenic Clostridium acetobutylicum in a growth medium amended with the effluent of these batch cultures of UACJUChE1 have been ascertained. This indicates a strong potential of UACJUChE1 in the hybridisation of the VFA platform and conventional sugar platform for the generation of butanol from RS.

Electrical Conductivity for Monitoring the Expansion of the Support Material in an Anaerobic Biofilm Reactor

This article describes the use of the electrical conductivity for measuring bed expansion in a continuous anaerobic biofilm reactor in order to prevent the exit of support material from the reactor with the consequent loss of biomass. The substrate used for the tests is obtained from a two-stage anaerobic digestion (AD) process at the pilot scale that treats the liquid fraction of fruit and vegetable waste (FVW). Tests were performed with the raw substrate before anaerobic treatment (S1), the effluent from the hydrolysis reactor (S2), and the effluent from the methanogenic reactor (S3) to evaluate its effect on the electrical conductivity values and its interaction with colonized support material. The tests were carried out in a 32 L anaerobic inverse fluidized bed reactor (IFBR), which was inoculated with colonized support material and using two industrial electrodes at different column positions. The results with the previously digested samples (S2 and S3) were satisfactory to detect the presence of support material at the points where the electrodes were placed since the electrical conductivity values showed significant changes of up to 0.5 V, while with substrate S1 no significant voltage differences were appreciated. These results demonstrate that electrical conductivity can be used as an economic and simple mean for monitoring the support material expansion in order to avoid over expansion in the IFBR. It was also demonstrated that the conditions of the substrate in the methanogenic stage (pH and presence of volatile fatty acids) do not affect the operation of the electrical conductivity detection system.

Characterization of the refractory dissolved organic matters (rDOM) in sludge alkaline fermentation liquid driven denitrification: Effect of HRT on their fate and transformation

Enhanced biological denitrification for nitrogen removal using sludge alkaline fermentation liquid (SAFL) as an alternative carbon source has been widely reported in previous studies, while limited studies focused on the degradation of the organics presented in SAFL. In this study, an SAFL driven anoxic denitrification sequencing batch reactor (SBR) was established, the mechanism of organics utilization was characterized and the refractory dissolved organic matters (rDOM) was identified. Denitrification could rapidly proceed with the presence of volatile fatty acids (VFAs) initially, while the denitrification rate largely decreased after the VFAs depleted. A great deal of rDOM, which was hard to be utilized by denitrifying microorganism, was found in the effluent. A prolonged hydraulic retention time (HRT) led to the further transformation of particles and colloids to smaller colloids and soluble organics. Extended HRT promoted the degradation of soluble microbial by-product (SMP), but had minor effect on the removal of humic-like, and fulvic acid-like substances. The characterization of the effluent demonstrated the building blocks, were dominated in the rDOM (43.79%–48.78%), followed by high molecular weight protein (HMW-PN) (13.37%–17.39%), HMW polysaccharide (HMW-PS) (12.84%–15.9%), low molecular weight (LMW) neutrals (11.28%–13.65%), and hydrophobic dissolved organic carbon (HO-DOC) (8.0%–12.62%). Moreover, it was found that the building blocks were relatively easy to be degraded with the extension of HRTs, followed by LMW-PS, LMW-PN, LMW neutrals, HMW-PN, and HMW-PS. However, further extended HRT >24 h could not improve the removal of building blocks, LMW-PS and LMW neutrals. This study, for the first time, provided insights into the transformation of organic matters produced by SAFL in a denitrification system and acted as a guide for the subsequent advanced treatment.

New Approach for Determination of Volatile Fatty Acid in Anaerobic Digester Sample

Abstract Presence of volatile fatty acids (VFAs) is one of the major indicators of anaerobic digestion of organic matters present in wastewater, activated sludge, organic fractions of municipal solid wastes, and landfill leachates. The present article focused on a modified spectrophotometric method for measuring VFAs, based on the classical Montgomery method, and also compared its performance with other existing techniques of VFA determination such as distillation method, high-performance liquid chromatography (HPLC), and gas chromatography (GC). Comparisons have been made with regard to measured concentration of acetic acid standards and accuracy of the respective method. In addition, comparisons between the proposed method and GC, HPLC, and distillation methods have been made with regard to VFA measurement (as CH3COOH) from real anaerobic samples. The distillation method showed poor mean accuracy of 74.96% in comparison to that for the HPLC (using Aminex column) (100.00%) and for the GC (99.81%). The mo...

Long-term operation of anaerobic immobilized biomass reactor treating organic wastewater containing sulfate

This work evaluates the long-term performance (888 days) of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor fed with synthetic wastewater containing organic matter and sulfate. The HAIB reactor achieved stable performance, exhibiting high sulfate and organic matter removal efficiencies subjected to organic matter concentration (expressed as chemical oxygen demand – COD) of 1500mg/L and sulfate of 500mg/L. Sulfate removal efficiency close to 100% was obtained for COD/sulfate ratios equal to or higher than 2.6, decreasing to ∼80% for COD/sulfate ratio of 1.4. Sulfidogenesis was clearly dependent on the availability of electron donor; but not methanogenesis. The smaller COD removal efficiencies (∼93%) were observed at the higher sulfate (1980mg/L) and organic matter (COD of 7000mg/L) concentrations, with COD/sulfate ratio of 3.5. Under these conditions, the presence of volatile fatty acids in the effluent indicates the occurrence of methanogenesis inhibition probably due to sulfide. The fixed-film HAIB reactor did not present bed clogging throughout the entire long-term operation period, thereby leading the way to new perspectives to use the efficient treatment of sulfate-rich wastewater.

Biomass yield efficiency of the marine anammox bacterium, "Candidatus Scalindua sp.," is affected by salinity.

The growth rate and biomass yield efficiency of anaerobic ammonium oxidation (anammox) bacteria are markedly lower than those of most other autotrophic bacteria. Among the anammox bacterial genera, the growth rate and biomass yield of the marine anammox bacterium “Candidatus Scalindua sp.” is still lower than those of other anammox bacteria enriched from freshwater environments. The activity and growth of marine anammox bacteria are generally considered to be affected by the presence of salinity and organic compounds. Therefore, in the present study, the effects of salinity and volatile fatty acids (VFAs) on the anammox activity, inorganic carbon uptake, and biomass yield efficiency of “Ca. Scalindua sp.” enriched from the marine sediments of Hiroshima Bay, Japan, were investigated in batch experiments. Differences in VFA concentrations (0–10 mM) were observed under varying salinities (0.5%–4%). Anammox activity was high at 0.5%–3.5% salinity, but was 30% lower at 4% salinity. In addition, carbon uptake was higher at 1.5%–3.5% salinity. The results of the present study clearly demonstrated that the biomass yield efficiency of the marine anammox bacterium “Ca. Scalindua sp.” was significantly affected by salinity. On the other hand, the presence of VFAs up to 10 mM did not affect anammox activity, carbon uptake, or biomass yield efficiency.

Thermophilic anaerobic co-digestion of sewage sludge with grease waste: Effect of long chain fatty acids in the methane yield and its dewatering properties

Thermophilic co-digestion of sewage sludge with three different doses of trapped grease waste (GW) from the pre-treatment of a WWTP has been assessed in a CSTR bench-scale reactor. After adding 12% and 27% of grease waste (on COD basis), the organic loading rate increased from 2.2 to 2.3 and 2.8kgCODm−3d−1 respectively, and the methane yield increased 1.2 and 2.2 times. Further GW increase (37% on COD basis) resulted in an unstable methane yield and in long chain fatty acids (LCFA) accumulation. Although this inestability, the presence of volatile fatty acids in the effluent was negligible, showing good adaptation to fats of the thermophilic biomass. Nevertheless, the presence of LCFA in the effluent worsens its dewatering properties. Specific methanogenic activity tests showed that the addition of grease waste ameliorates the acetoclastic activity in detriment of the hydrogenotrophic activity, and suggests that the tolerance to LCFA can be further enhanced by slowly increasing the addition of lipid-rich materials.

Toluene in sewage and sludge in wastewater treatment plants

Toluene is a compound that often occurs in municipal wastewater ranging from detectable levels up to 237 μg/L. Before the year 2000, the presence of the aromatic hydrocarbons was assigned only to external sources. The Enhanced Biological Nutrients Removal Processes (EBNRP) work according to many different schemes and technologies. For high-efficiency biological denitrification and dephosphatation processes, the presence of volatile fatty acids (VFAs) in sewage is required. VFAs are the main product of organic matter hydrolysis from sewage sludge. However, no attention has been given to other products of the process. It has been found that in parallel to VFA production, toluene formation occurred. The formation of toluene in municipal anaerobic sludge digestion processes was investigated. Experiments were performed on a laboratory scale using sludge from primary and secondary settling tanks of municipal treatment plants. The concentration of toluene in the digested sludge from primary settling tanks was found to be about 42,000 μg/L. The digested sludge supernatant liquor returned to the biological dephosphatation and denitrification processes for sewage enrichment can contain up to 16,500 μg/L of toluene.

Assessing the application of advanced oxidation processes, and their combination with biological treatment, to effluents from pulp and paper industry

The closure of water circuits within pulp and paper mills has resulted in a higher contamination load of the final mill effluent, which must consequently be further treated in many cases to meet the standards imposed by the legislation in force. Different treatment strategies based on advanced oxidation processes (ozonation and TiO2-photocatalysis), and their combination with biological treatment (MBR), are herein assessed for effluents of a recycled paper mill and a kraft pulp mill. Ozone treatment achieved the highest efficiency of all. The consumption of 2.4g O3L−1 resulted in about a 60% COD reduction treating the effluent from the kraft pulp mill at an initial pH=7; although it only reached about a 35% COD removal for the effluent of the recycled paper mill. Otherwise, photocatalysis achieved about a 20–30% reduction of the COD for both type of effluents. In addition, the effluent from the recycled paper mill showed a higher biodegradability, so combinations of these AOPs with biological treatment were tested. As a result, photocatalysis did not report any significant COD reduction improvement whether being performed as pre- or post-treatment of the biological process; whereas the use of ozonation as post-biological treatment enhanced COD removal a further 10%, summing up a total 90% reduction of the COD for the combined treatment, as well as it also supposed an increase of the presence of volatile fatty acids, which might ultimately enable the resultant wastewater to be recirculated back to further biological treatment.

Inhibition and anaerobic biodegradation of benz[a]anthracene-7,12- dione via the specific methanogenic activity test

Aims: The purpose of this study was to determine the inhibition and anaerobic biodegradation of benz[a]anthracene-7, 12-dione (BaAQ) via the specific methanogenic activity (SMA) test. Materials and Methods: In this study, 120 mL vials were filled with given concentration of BaAQ, anaerobic biomass and substrate. Each batch experiment was lasted 13 to 26 days. The inhibition effects of BaAQ with concentrations of 0.5, 5, 25, 50, 100, 250 and 500 mg/L on the methanogenic process was investigated in the presence of volatile fatty acids including acetic, butyric and propionic acids. Results: In some eatch test, the gas production was stopped after 13 days (312 h). Therefore, 312 h was considered as compared base of gas production. After this time, methane production cumulative rate was calculated for the each SMA. After 13 days (312 h) the lowest and the highest cumulative methane has been produced (per mL) at the presence of concentrations of 250 and 0.5 mg/L of BaAQ, respectively. Conclusion: The results of this study showed that the BaAQ with concentration of 250 mg/L has more inhibition effect on methane production rather than other concentrations (even of 500 mg/L). Therefore, we should not always expect that higher concentrations of toxic compounds had more inhibitory effects than low concentrations of them.

Behaviour of molecular weight distribution for the liquid fraction of pig slurry treated by anaerobic digestion

Pig slurry was treated in an upflow anaerobic sludge blanket (UASB) reactor. To maintain a stable operation, the organic loading rate (OLR) applied to the system was increased stepwise by decreasing the dilution ratio of the pig slurry. Finally, during the last operational stage, no dilution was applied to the influent. The reactor maintained a soluble chemical oxygen demand (CODs) removal efficiency of 82% when OLRs lower than 1.73 g CODs l−1 d−1 were applied, although its efficiency fell to 55% when operated at 2.48 g CODs l−1 d−1. System performance was not affected by the presence of free ammonia (concentrations up to 375 mg NH3 l−1). The distribution of the different molecular weight fractions changed significantly during anaerobic digestion. Proteins contained in the fractions higher than 10,000 Daltons are less degraded than those belonging to the lower fractions. An important percentage of both COD and BOD5 in the effluent were observed in the lowest fraction, probably caused by the presence of volatile fatty acids (VFA).

Managing Soilborne Disease of Potatoes Using Ecologically Based Approaches

Soil fumigation and planting resistant cultivars remain the primary means for control of soilborne plant diseases. Fumigation however, is being constrained by increased costs, urbanization, and its negative environmental impacts. Resistance genes to soilborne pathogens are not available for many crop species. Using verticillium wilt as model disease we examined the potential of non chemical alternatives, specifically the use of organic amendments and green manures, as disease management tools. Application of organic products reduces disease incidence in controlled settings but its application in commercial use was hampered by inconsistent efficacy. Studies now have demonstrated that by-products of animal and plant production, such as meat and bone meal, feather meal, poultry and swine manure, soy meal, etc. can significantly reduce diseases but that the level of control obtained is product and soil specific. Three mechanisms of action for pathogen reduction were identified: 1) generation of toxic compounds such as ammonia and nitrous acid from high nitrogen-containing materials, 2) presence of volatile fatty acids (e.g. vinegar) and 3) alterations in biological agents that may suppress the activity of plant pathogens. For products that work mostly through the generation of active chemical ingredients, knowing the properties that regulate efficacy allows targeting their use to specific locations and thus, increased activity and consistency. Much less is known about how such materials influence rhizosphere residents involved in regulating plant health. New molecular technologies are being implemented to identify key players in maintaining root health. Through an understanding of the microbial soil ecosystem we should be able to develop disease control strategies that are more economical to growers and are more environmentally benign.

Treatment of phenol in an anaerobic fluidized bed reactor (AFBR): continuous and batch regime

Results of this study describe the feasibility of anaerobic treatment of highly concentrated phenol synthetic wastewater using an anaerobic fluidized bed reactor (AFBR) in both continuous and batch modes. Wastewater with a maximum load of 2,100 mg C.l(-1) was prepared using phenol (maximum concentration of 1,600 mg C.l(-1)) as substrate and a mixture of acetic, propionic and butyric acids (500 mg C.l(-1)) as co-substrate. AFBR reached total organic carbon (TOC) and phenol removal efficiency over 95% treating the highest organic loading rate (OLR) containing phenol studied for this kind of reactor (5.03 g C.l(-1).d(-1)). The phenol loading rate rise caused volumetric biogas rate increase up to 4.4 l.l(-1).d(-1) (average yield of 0.28 l CH(4).g(-1) COD(removed)) as well as variation in the biogas composition; the CO(2) percentage increased while the CH(4) percentage decreased. Morphological examination of the bioparticles at 4.10 g C.l(-1).d(-1), revealed significant differences in the biofilm structure, microbial colonization and bacterial morphological type development. The five batch assays showed that phenol degradation may be favoured by the presence of volatile fatty acids (VFAs) (co-metabolism), whereas VFAs degradation may be inhibited by phenol. AFBR reached initial phenol degradation velocity of 0.25 mg C.l(-1).min(-1).

Contrast of VFA Driven and Inorganic Acid/Base Driven pH Changes Impacting Phosphorus Transformations in EBPR

Contrast of VFA Driven and Inorganic Acid/Base Driven pH Changes Impacting Phosphorus Transformations in EBPRAddition of acid resulted in high anaerobic phosphorus (P) releases both with or without the presence of volatile fatty acids (VFAs) for an EBPR biomass. There was also a subsequent increase in aerobic P release but such that there was a lower net P removals. NaOH addition reduced both anaerobic P release and aerobic P uptakes both with and without the presence of VFAs but did not improve net P...Author(s)Andrew Amis RandallSourceProceedings of the Water Environment FederationSubjectSession 99: What's New in Phosphorus and Nitrogen RemovalDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2010ISSN1938-6478SICI1938-6478(20100101)2010:9L.7117;1-DOI10.2175/193864710798207413Volume / Issue2010 / 9Content sourceWEFTECFirst / last page(s)7117 - 7126Copyright2010Word count144Subject keywordspHPhosphorusWastewaterVolatile Fatty Acids (VFAs)Propionic acid

Physiological Responses of Annual Bluegrass and Creeping Bentgrass to Contrasted Levels of O2 and CO2 at Low Temperatures

Ice encasement and impermeable winter protective covers can induce anaerobic conditions on golf greens. We assessed plant survival and biochemical changes of annual bluegrass (Poa annua L.) and creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.)] exposed to combinations of O2 and CO2 concentrations at low temperatures (1°C or −2°C). Results indicate that lack of O2 (anoxia) rather than high CO2 is the source of plant damage. However, combination of low O2 and high CO2 induced more severe damage than low O2 alone. Annual bluegrass was found to be more sensitive to anoxia than creeping bentgrass, and subfreezing temperature delayed anoxia‐induced damage. Sucrose was depleted more rapidly under low O2 than under normal conditions. Fructan reserves were similarly mobilized in all treatments except for a more pronounced decline in annual bluegrass maintained under high CO2 at 1°C. A marked accumulation of asparagine at 1°C under normal atmospheric conditions did not occur under anoxia. Reversely, concentrations of alanine and tyrosine increased under low O2. Proline accumulation in plants incubated at −2°C was higher under low than under high CO2 treatments. We observed a relationship between the presence of volatile fatty acids and plant damage under low O2. Our study illustrates the complex interaction between O2 and CO2 that have both synergistic and independent effect on plant damage under anoxia at low temperatures.