Effects of solids concentration, pH and carbon addition on the production rate and composition of volatile fatty acids in prefermenters using primary sewage sludge

2006 ◽  
Vol 53 (8) ◽  
pp. 263-269 ◽  
Author(s):  
R.J. Zeng ◽  
Z. Yuan ◽  
J. Keller
Keyword(s):  
Fatty Acids ◽  
Production Rate ◽  
Propionic Acid ◽  
Volatile Fatty Acids ◽  
Productivity Loss ◽  
Domestic Wastewater ◽  
Biological Phosphorus Removal ◽  
Operational Conditions ◽  
Solids Concentration ◽  
The Impact

Increasing evidence is emerging that the performance of enhanced biological phosphorus removal (EBPR) systems relies on not only the total amount but also the composition of volatile fatty acids (VFAs). Domestic wastewater often contains limited amounts of VFAs with acetic acid typically being the dominating species. Consequently, prefermenters are often employed to generate additional VFAs to meet the demand for carbon by EBPR and/or denitrification processes. Limited knowledge is currently available on the effects of operational conditions on the production rate and composition of VFAs in prefermenters. In this study, a series of controlled batch experiments were conducted with sludge from a full-scale prefermenter to determine the impact of solids concentration, pH and addition of molasses on prefermentation processes. It was found that an increase in solids concentration enhanced total VFA production with an increased propionic acid fraction. The optimal pH for prefermentation was in the range of 6–7 with significant productivity loss when pH was below 5.5. Molasses addition significantly increased the production of VFAs particularly the propionic acid. However, the fermentation rate was likely limited by the biological activity of the sludge rather than by the amount of molasses added.

Toxicity of pH, Ammonia and Volatile Fatty Acids on Hydrogenotrophic Methanogen-Enriched Sludge

2014 ◽  
Vol 955-959 ◽  
pp. 527-531
Author(s):  
Jian Zheng Li ◽  
Yu Peng Zhang ◽  
Chong Liu ◽  
Ze Yu Tang
Keyword(s):  
Fatty Acids ◽  
Acetic Acid ◽  
Anaerobic Digestion ◽  
Propionic Acid ◽  
Butyric Acid ◽  
Volatile Fatty Acids ◽  
Batch Experiments ◽  
Inhibitory Effects ◽  
Hydrogenotrophic Methanogen ◽  
The Impact

The activities of methanogen are easily affected by inhibitory substances and lead to anaerobic digestion failure. To investigate inhibitory effects on methanogenesis of a methanogen-enriched sludge, pH, volatile fatty acids (such as acetic acid, propionic acid and butyric acid), and ammonia were used as inhibitory factors and a L16(45) orthogonal table was employed to design batch experiments. The result of variance analyses shows that pH has the greatest impact on the methanogenesis of the enriched culture. The impact of butyrate, NH3, acetate and propionate was decreased in order. DGGE finger-print shows that there was only one methanogen in the inoculum sludge.

scholarly journals Pilot Study of the Effects of Polyphenols from Chestnut Involucre on Methane Production, Volatile Fatty Acids, and Ammonia Concentration during In Vitro Rumen Fermentation

Animals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 108
Author(s):  
Yichong Wang ◽  
Sijiong Yu ◽  
Yang Li ◽  
Shuang Zhang ◽  
Xiaolong Qi ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Acetic Acid ◽  
Propionic Acid ◽  
Acid Content ◽  
Volatile Fatty Acids ◽  
Rumen Fermentation ◽  
Gas Production ◽  
Quadratic Response ◽  
In Vitro Rumen Fermentation

Nutritional strategies can be employed to mitigate greenhouse emissions from ruminants. This article investigates the effects of polyphenols extracted from the involucres of Castanea mollissima Blume (PICB) on in vitro rumen fermentation. Three healthy Angus bulls (350 ± 50 kg), with permanent rumen fistula, were used as the donors of rumen fluids. A basic diet was supplemented with five doses of PICB (0%–0.5% dry matter (DM)), replicated thrice for each dose. Volatile fatty acids (VFAs), ammonia nitrogen concentration (NH3-N), and methane (CH4) yield were measured after 24 h of in vitro fermentation, and gas production was monitored for 96 h. The trial was carried out over three runs. The results showed that the addition of PICB significantly reduced NH3-N (p < 0.05) compared to control. The 0.1%–0.4% PICB significantly decreased acetic acid content (p < 0.05). Addition of 0.2% and 0.3% PICB significantly increased the propionic acid content (p < 0.05) and reduced the acetic acid/propionic acid ratio, CH4 content, and yield (p < 0.05). A highly significant quadratic response was shown, with increasing PICB levels for all the parameters abovementioned (p < 0.01). The increases in PICB concentration resulted in a highly significant linear and quadratic response by 96-h dynamic fermentation parameters (p < 0.01). Our results indicate that 0.2% PICB had the best effect on in-vitro rumen fermentation efficiency and reduced greenhouse gas production.

scholarly journals Volatile Fatty Acids Produced by A Sheep Fed Pure Cellulose as Sole Carbohydrate in its Diet

1968 ◽  
Vol 21 (5) ◽  
pp. 1075 ◽  
Author(s):  
RA Weller ◽  
FV Gray ◽  
AF Pilgrim
Keyword(s):  
Fatty Acids ◽  
Propionic Acid ◽  
Volatile Fatty Acids ◽  
Inorganic Salts ◽  
Pure Cellulose

The quantities of volatile fatty acids (VF A) formed from cellulose in the rumen, and their relation to the amount of cellulose digested, have not previously been determined in vivo. We have recently maintained a sheep on a diet of pure cellulose (500 g), gluten (50 g), and inorganic salts (6-20 g) for a period of several months, and have measured VFA production in the rumen along with the extent of digestion of the cellulose in the animal. A characteristic of the digestion was the formation of large proportions (34--42%) of propionic acid, in contrast to the proportions found in the rumen of sheep at pasture, or fed on dry roughages - where propionic acid, though variable, usually constitutes only about 20% of the total VFA. The findings are summarized in Table 1.

scholarly journals Enhanced lipid production by Yarrowia lipolytica cultured with synthetic and waste-derived high-content volatile fatty acids under alkaline conditions

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Ruiling Gao ◽  
Zifu Li ◽  
Xiaoqin Zhou ◽  
Wenjun Bao ◽  
Shikun Cheng ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Acetic Acid ◽  
Propionic Acid ◽  
Yarrowia Lipolytica ◽  
Butyric Acid ◽  
Lipid Content ◽  
Volatile Fatty Acids ◽  
Lipid Production ◽  
Initial Ph ◽  
Alkaline Conditions

Abstract Background Volatile fatty acids (VFAs) can be effective and promising alternate carbon sources for microbial lipid production by a few oleaginous yeasts. However, the severe inhibitory effect of high-content (> 10 g/L) VFAs on these yeasts has impeded the production of high lipid yields and their large-scale application. Slightly acidic conditions have been commonly adopted because they have been considered favorable to oleaginous yeast cultivation. However, the acidic pH environment further aggravates this inhibition because VFAs appear largely in an undissociated form under this condition. Alkaline conditions likely alleviate the severe inhibition of high-content VFAs by significantly increasing the dissociation degree of VFAs. This hypothesis should be verified through a systematic research. Results The combined effects of high acetic acid concentrations and alkaline conditions on VFA utilization, cell growth, and lipid accumulation of Yarrowia lipolytica were systematically investigated through batch cultures of Y. lipolytica by using high concentrations (30–110 g/L) of acetic acid as a carbon source at an initial pH ranging from 6 to 10. An initial pH of 8 was determined as optimal. The highest biomass and lipid production (37.14 and 10.11 g/L) were obtained with 70 g/L acetic acid, whereas cultures with > 70 g/L acetic acid had decreased biomass and lipid yield due to excessive anion accumulation. Feasibilities on high-content propionic acid, butyric acid, and mixed VFAs were compared and evaluated. Results indicated that YX/S and YL/S of cultures on butyric acid (0.570, 0.144) were comparable with those on acetic acid (0.578, 0.160) under alkaline conditions. The performance on propionic acid was much inferior to that on other acids. Mixed VFAs were more beneficial to fast adaptation and lipid production than single types of VFA. Furthermore, cultures on food waste (FW) and fruit and vegetable waste (FVW) fermentate were carried out and lipid production was effectively improved under this alkaline condition. The highest biomass and lipid production on FW fermentate reached 14.65 g/L (YX/S: 0.414) and 3.20 g/L (YL/S: 0.091) with a lipid content of 21.86%, respectively. By comparison, the highest biomass and lipid production on FVW fermentate were 11.84 g/L (YX/S: 0.534) and 3.08 g/L (YL/S: 0.139), respectively, with a lipid content of 26.02%. Conclusions This study assumed and verified that alkaline conditions (optimal pH 8) could effectively alleviate the lethal effect of high-content VFA on Y. lipolytica and significantly improve biomass and lipid production. These results could provide a new cultivation strategy to achieve simple utilizations of high-content VFAs and increase lipid production. Feasibilities on FW and FVW-derived VFAs were evaluated, and meaningful information was provided for practical applications.

Studies on the production of volatile fatty acids from grass by rumen liquor in an artificial rumen: II. The volatile fatty acid production from dried grass

1957 ◽  
Vol 49 (2) ◽  
pp. 171-179 ◽  
Author(s):  
A. John ◽  
G. Barnett ◽  
R. L. Reid
Keyword(s):  
Fatty Acids ◽  
Acetic Acid ◽  
Propionic Acid ◽  
Metabolic Pathways ◽  
Volatile Fatty Acid ◽  
Volatile Fatty Acids ◽  
Water Soluble ◽  
Fatty Acid Production ◽  
Growing Seasons ◽  
Titration Curves

1. A study has been made of the production of volatile fatty acids obtainable from dried grass and its gross water-soluble and water-insoluble separates, in the artificial rumen, over two growing seasons.2. In contradistinction to fresh grass, the dried grass gives a consistent production of acetic acid proportionately greater than propionic acid, at all stages of maturity, but when aqueous extracts of the dried grass, and the resultant extracted grass, respectively, are examined separately in the artificial rumen, it is found that the former yield preponderating amounts of acetic acid while the latter give amounts of propionic acid equal to, or exceeding, the corresponding productions of acetic acid.3. An examination of the titration curves for the total acids obtained from the dried grass, extracted grass and grass extract runs, indicates an approach to an incomplete relationship between the residual carbohydrate in the extracted grass and cellulose, while the grass extract reveals itself as the chief source of acetic acid in the whole dried grass, the acid being formed very speedily at the start of the run.4. The suggested sources and some of the possible metabolic pathways involved in the formation of v.f.a. from grass are discussed in the text.

Volatile fatty acids and sulfide in pressure mains

1995 ◽  
Vol 31 (7) ◽  
pp. 169-179 ◽  
Author(s):  
T. Hvitved-Jacobsen ◽  
K. Raunkjær ◽  
P. H. Nielsen
Keyword(s):  
Fatty Acids ◽  
Organic Matter ◽  
Production Rate ◽  
Volatile Fatty Acids ◽  
Production Rates ◽  
Net Production ◽  
Toc Removal ◽  
Sulfide Production ◽  
Transformation Of Organic Matter ◽  
High Sulfide

The main objective was to study the anaerobic transformation of organic matter and sulfide production during wastewater transportation. Emphasis was on the transformation of easily biodegradable organic matter in terms of volatile fatty acids (VFA). Samples from two intercepting pressure mains located in the Northern part of Jutland, Denmark, were taken. The concentration of VFA in the wastewater varied considerably during day and night, being typically between 5 and 50 g/m3. A net production as well as a net removal of VFA was seen during transportation in the pressure mains probably depending on the quality and quantity of the organic matter. Typically 85% of the VFA was acetate and 10% propionate; the remainder was formate, n-butyrate and iso-butyrate. Observed sulfide production rates from the sewer biofilms were typically 0.05 and 0.005 g S/m2 h at 12 and 4 °C, respectively. A high sulfide production rate corresponded with a high VFA concentration. TOC removal was observed in the pressure mains.

scholarly journals Impact of Alkaline Pretreatment to Enhance Volatile Fatty Acids (VFAs) Production from Rice Husk

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Qian Fang ◽  
Sinmin Ji ◽  
Dingwu Huang ◽  
Zhouyue Huang ◽  
Zilong Huang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Acetic Acid ◽  
Propionic Acid ◽  
Butyric Acid ◽  
Rice Husk ◽  
Volatile Fatty Acids ◽  
Alkaline Pretreatment ◽  
Rice Husks ◽  
Acid Fermentation ◽  
Study Results

This study explores the use of alkaline pretreatments to improve the hydrolyzation of rice husks to produce volatile fatty acids (VFAs). The study investigated the effects of reagent concentration and pretreatment time on protein, carbohydrates, and dissolved chemical oxygen demand (SCOD) dissolution after the pretreatment. The optimum alkaline pretreatment conditions were 0.30 g NaOH (g VS)−1, with a reaction time of 48 h. The experimental results show that when comparing the total VFA (TVFA) yields from the alkaline-pretreated risk husk with those from the untreated rice husk, over 14 d and 2 d, the maximum value reached 1237.7 and 716.0 mg·L−1 with acetic acid and propionic acid and with acetic acid and butyric acid, respectively. After the alkaline pretreatment, TVFAs increased by 72.9%; VFA accumulation grew over time. The study found that alkaline pretreatment can improve VFA yields from rice husks and transform butyric acid fermentation into propionic acid fermentation. The study results can provide guidelines to support the comprehensive utilization of rice husk and waste treatment.

Saving phosphorus removal at the Henderson NV plant

2012 ◽  
Vol 65 (7) ◽  
pp. 1318-1322 ◽  
Author(s):  
J. Barnard ◽  
D. Houweling ◽  
H. Analla ◽  
M. Steichen
Keyword(s):  
Fatty Acids ◽  
Phosphorus Removal ◽  
Volatile Fatty Acids ◽  
Biological Phosphorus Removal ◽  
Case Histories ◽  
Mixed Liquor ◽  
Removal Process ◽  
Low Levels ◽  
Anaerobic Zone ◽  
Biological Phosphorus

While the mechanism of biological phosphorus removal (BPR) and the need for volatile fatty acids (VFA) have been well researched and documented to the point where it is now possible to design a plant with a very reliable phosphorus removal process using formal flow sheets, BPR is still observed in a number of plants that have no designated anaerobic zone, which was considered essential for phosphorus removal. Some examples are given in this paper. A theory is proposed and then applied to solve problems with a shortage of VFA in the influent of the Henderson NV plant. Mixed liquor was fermented in the anaerobic zone, which resulted in phosphorus removal to very low levels. This paper will discuss some of the background, and some case histories and applications, and present a simple postulation as to the mechanism and efforts at modelling the results.

Production of volatile fatty acids in the sheep caecum

1969 ◽  
Vol 20 (3) ◽  
pp. 491 ◽  
Author(s):  
GJ Faichney
Keyword(s):  
Fatty Acids ◽  
Steady State ◽  
Fatty Acid ◽  
Production Rate ◽  
Energy Intake ◽  
Isotope Dilution ◽  
Volatile Fatty Acids ◽  
Specific Activity ◽  
Total Production ◽  
Digestible Energy

Acetic, propionic, and butyric acids labelled with 14C were infused into the caecum of continuously fed sheep. The specific activity of the volatile fatty acids (VFA) in the caecum was determined at intervals during the infusion. The production rate was calculated by isotope dilution from the results of those experiments in which steady state conditions were obtained. Substantial interconversions occurred between the fatty acid fractions. The total production of VFA was about 440 mmoles/day, equivalent to 125 kcal/day or 5.3% of the animal's digestible energy intake.

Effect of diet on individual volatile fatty acids in the rumen of sheep, with particular reference to the effect of low rumen pH and adaptation on high-starch diets

1957 ◽  
Vol 8 (6) ◽  
pp. 691 ◽  
Author(s):  
RL Reid ◽  
JP Hogan ◽  
PK Briggs
Keyword(s):  
Fatty Acids ◽  
Propionic Acid ◽  
Butyric Acid ◽  
Acid Production ◽  
Volatile Fatty Acids ◽  
Maximum Level ◽  
Fatty Acid Production ◽  
Rumen Ph ◽  
Term Change ◽  
Effects Of Ph

Detailed data are presented on changes in the proportions of acetic, propionic, and butyric acids in the rumen after feeding on various diets. Pre-feeding proportions were constant on each diet but varied from a mixture of 72-76 per cent. acetic, 14-16 per cent. propionic, and 10-12 per cent. butyric acid on all-roughage diets to one of 63-65 per cent. acetic, 18-20 per cent. propionic, and 16-18 per cent. butyric acid on a diet containing 70 per cent. wheat grain. On all diets the proportion of propionic acid increased after feeding and reached a peak which coincided with the maximum level of total volatile fatty acids. The response of butyric acid was variable, low levels being recorded on a diet of lucerne chaff and on one containing a high proportion of cracked maize. The proportion of acetic acid always declined after feeding. These responses were modified in experiments on rations containing high proportions of wheaten starch, in which rumen pH fell below 5.0 as a result of lactic acid accumulation. When animals were first fed on such diets, a decline in rumen pH below 5.0-5.5 after feeding was always associated with a pronounced decline in the proportions of propionic and butyric acids, to levels as low as 8 and 5 per cent. respectively. Continued feeding of such diets did not affect the response of butyric acid, but there was evidence of a change in propionic acid production in response to low pH conditions, both in respect to short-term change during experiments in which low rumen pH levels were maintained for considerable periods and to long-term change when such diets were fed intermittently over considerable periods. The implications of these findings are discussed with respect to the effects of pH on individual volatile fatty acid production in the rumen, and on the qualitative nature of the microbial population and on their metabolic patterns.

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