The range of acceptable volatile acid-to-alkalinity ratios is An acceptable ratio may be obtained by adjusting volatile acid concentration. Read 5 answers by scientists with 7 recommendations from their colleagues to the question asked by Raja Murugan on Dec 31, Accurate on-site volatile fatty acids (VFA) measurement in anaerobic digestion previously measured for VFA and carbonate alkalinity using the method. After the .. Vx gives a linear relationship where the y intercept gives the value of Ve.
Anaerobic digestion involves a series of metabolic reactions hydrolysis, acidogenesis, and methanogenesis [ 1718 ]. Namely, acetic acid, butyric acid, isobutyric acid, isovaleric acid, and propionic acid have been known as good indicators for monitoring performance of anaerobic digestion process, especially in the activity of acetogenic and methanogenic bacteria [ 1719 — 22 ]. Additionally, various physicochemical parameters pH, temperature, alkalinity, volatile fatty acid, retention time, biogas, etc.
The complexity of the process made the interpretation of the performance of the process difficult; therefore a combination of those parameters was suggested as a better method for monitoring the performance of the process [ 26 ]. Therefore, the objective of this paper was not only to identify the parameters that can be used to determine the performance of the anaerobic digestion process in terms of anaerobic degradation efficiency in South Korea but also specifically to investigate the effect of the volatile fatty acid concentration on anaerobic degradation rate of food waste leachate in these anaerobic digestion facilities.
Materials and Methods 2. The types of feed waste and the digestion system were presented in Table 1. Operating conditions of selected anaerobic digestion facilities. Samples for analysis were collected from the inlet and outlet valves of anaerobic digester at each facility.
And they were kept refrigerated until they were analyzed. Analytical Methods Total solids, moisture content, and volatile solids were determined according to Standard Methods [ 26 ]. CODcr was analyzed according to closed reflux, titrimetric method C and and T-N were analyzed according to Standard Methods [ 26 ] and standard methods for testing water [ 35 ]. Volatile fatty acids were analyzed according to Standard Methods D-Gas chromatographic method [ 263637 ].
The concentration of each volatile fatty acid, namely, acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid, was conducted by gas chromatography AgilentUSA; column: Helium was used as a carrier gas. Samples were acidified to pH 2 with phosphoric acid and centrifuged at rpm for 5 min.
Results and Discussion 3. Characteristics of Feed Waste Table 2 shows the physicochemical characteristics of feed wastes. The moisture content, fixed solids, and volatile solids of individual feed waste were presented in Figure 1.
Volatile Acidtoalkalinity Ratio - Anaerobic Digesters
Total solids content in FWL from 8 anaerobic digestion facilities varied from 3. Volatile solid content in FWL from 8 anaerobic digestion facilities varied from 1. Total solid content in A-MIX from 3 anaerobic digestion facilities varied from 4.
Total solid content in S-MIX from 6 anaerobic digestion facilities varied from 3.
The highest total solid and volatile solid content were from FWL as expected. The physicochemical characteristics of three types of feed waste from the literature are presented in Table 3. In addition many of food wastes and fruit and vegetable wastes were collected from one place, that is, restaurant or cafeteria which might produce the wastes with less variation than those from the municipal solid waste facilities.
The physicochemical characteristics of S-MIX 5. Physicochemical characteristics of feed waste. Total and volatile solid of food waste, animal poultry, pig, and cow manure, and sewage sludge and their VS removal rates in the literature.
Compositions of feed waste: Removal Rates of Volatile Solid and COD The volatile solid removal rate from each anaerobic digestion facility with individual feed waste is presented in Figure 2. The guideline of anaerobic degradation efficiency in South Korea is stipulated to monitor the efficiency of the process.
Considering the types of feed waste, the average volatile solid removal rate of FWL was Volatile solid removal rates of individual anaerobic digestion facilities: Reasonably high volatile solid removal rates with the range of The second highest volatile solid removal rates were achieved with A-MIX avg.
The lowest volatile solid removal rate was observed from S-MIX avg. The result surely could not be directly compared with the results in the literature due to different operational systems and conditions; however the trend in volatile solid removal rate achieved from food waste leachates in this study was comparable with the results in the literature Table 3.
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Higher volatile solid generally means higher amount of organic materials that are convertible to biogas. COD concentrations of input and output of each anaerobic digestion facility are presented in Figure 3. CODcr of each anaerobic digestion facility. Another alternative for determining the portions of alkalinity is by the method of Kapp, which constitutes in titration of the sample in three stages: These three successive titrations enable the determination of total alkalinity TAof bicarbonate alkalinity BA and of alkalinity due to volatile acids VAA .
The measurement of total volatile acids TVA is the parameter which provides, together with the measurement of the volume of produced gases, the most immediate indication of the operation of the process. The TVA can accumulate in the digesters due to organic overload, toxic and hydraulic causing instabilities in the anaerobic reactors. Materials and Methods 2. The treatment system in full scale consisted of a decanter, followed by a UASB reactor, with volumes of 7.
Treatment Plant The treatment system in full scale was designed to meet the sectors of nursery, growing and finishing of the swine with capacity for animals. The feeding of waste generated was performed by gravity through the channels. The UASB reactor was inoculated with sludge from an anaerobic pond previously employed in the treatment of swine wastewater.
The initial biological load BL was approximately 0. The process of inoculation was carried out through a tractor with a liquid manure tank, which captured 6.
Journal of Chemistry
After inoculation, the biomass remained at rest for a period of 24 hours. Monitoring Program Samples of influent and effluent of the decanter and the UASB reactor were collected three times a week during them morning, throughout the period of the cleaning of the swine. Composite samples were carried out in glass bottles previously identified from the single samples collected every 15 minutes.
The system was monitored for40 weeks, through the following physicochemical parameters: The measures of partial alkalinity PA and intermediate IA were performed according to the methodology described by Jenkins et al. Results and Discussion The Table 1 presents the average values of physicochemical parameters obtained during40 weeks of monitoring the influent and effluent of the decanter and the UASB reactor. Layout of the treatment system. Average values of physicochemical parameters of the influent and effluent of the decanter and the UASB reactor during the experimental period.
The UASB reactor showed a similar efficiency to the decanter, however, was observed during the entire experimental period the entrainment of solid particles of the sludge blanket, which escaped together with the effluent.