Methanogenic Activity Of Anaerobic Sludge Research Articles

Anaerobic Biodegradability Potential of RCF-Based Kraft Paper Mill Effluent

The present study collected anaerobic sludge from a paper mill operating a UASB reactor on agro-based raw material (wheat straw) washings for biogas production. After determining the sludge profile and methanogenic activity of anaerobic sludge, it was further used to determine the anaerobic biodegradability of RCF-based kraft paper mill effluent. The sludge profile of collected anaerobic sludge was found w.r.t. Suspended Solids (SS) 60 g.L-1, Volatile Suspended Solids (VSS) 23 g.L-1, Inorganic content 62% & Organic content 38%. The presence of effective microbes in anaerobic sludge was confirmed by SEM (Scanning Electron Microscope). Degradation of organic matter present in effluent by anaerobic digestion leads to the production of biogas (methane & CO2), a renewable energy source. The sludge profile and methanogenic activity findings supported the anaerobic treatment of kraft paper mill effluent and were positive. The methanogenic activity of anaerobic sludge was determined as 0.832 gCOD.gVSS-1×Day, and the average anaerobic biodegradability of RCF-based kraft paper mill effluent was found to be 71.5%.

Pollutant Removal and Energy Recovery from Swine Wastewater Using Anaerobic Membrane Bioreactor: A Comparative Study with Up-Flow Anaerobic Sludge Blanket

Due to its high content of organics and nutrients, swine wastewater has become one of the main environment pollution sources. Exploring high-efficient technologies for swine wastewater treatment is urgent and becoming a hot topic in the recent years. The present study introduces anaerobic membrane bioreactor (AnMBR) for efficient treatment of swine wastewater, compared with up-flow anaerobic sludge blanket (UASB) as a traditional system. Pollutant removal performance, methanogenic properties, and microbial community structures were investigated in both reactors. Results showed that by intercepting particulate organics, AnMBR achieved stable and much higher chemical oxygen demand (COD) removal rate (approximately 90%) than UASB (around 60%). Due to higher methanogenic activity of anaerobic sludge, methane yield of AnMBR (0.23 L/g-COD) was higher than that of UASB. Microbial community structure analysis showed enrichment of functional bacteria that can remove refractory organic matter in the AnMBR, which promoted the organics conversion processes. In addition, obvious accumulation of acetotrophic and hydrotrophic methanogens in AnMBR system was recorded, which could broaden the organic matter degradation pathways and the methanogenesis processes, ensuring a higher methane yield. Through energy balance analysis, results concluded that the net energy recovery efficiency of AnMBR was higher than that of UASB system, indicating that applying AnMBR for livestock wastewater treatment could not only efficiently remove pollutants, but also significantly enhance the energy recovery.

Improvement of methanogenic activity of anaerobic digestion using poly(l-lactic acid) with enhanced chemical hydrolyzability based on physicochemical parameters

Because packing bags and disposable items of poly (l-lactic acid) (PLLA) waste are discharged together with other organic waste including garbage, anaerobic co-digestion of PLLA and other organic waste is required. However, because of low hydrolyzability of PLLA products, the chemical hydrolyzability must be improved for PLLA treatment during anaerobic digestion. This study aimed to assess weight-average molecular weight (Mw) and crystallinity (Xc), to determine the chemical hydrolyzability of PLLA, for PLLA treatment during anaerobic digestion. Moreover, the possibility of anaerobic co-digestion of the PLLA after improvement of chemical hydrolyzability and other organic waste was also discussed. Detectable methanogenic activity of the mesophilic and thermophilic anaerobic sludges of PLLA occurred in the Mw range of 6,800 to 16,500, and 6,800 and 38,000, respectively. The methanogenic activity of mesophilic and thermophilic anaerobic sludge was higher with PLLA with a high crystallinity (Xc = 39.9–46.1%) than with nearly amorphous PLLA (Xc = 0.3–3.5%). The maximum methanogenic activity of anaerobic sludge using PLLA with an Xc of approximately 40–45% and with a Mw of 10,300 and 16,500 for mesophilic and thermophilic anaerobic sludge were 0.013 gCOD·gVS−1·d−1 and 0.13 gCOD·gVS−1·d−1, respectively. A survey on the possibility of anaerobic co-digestion of PLLA after improvement in chemical hydrolyzability based on Mw and Xc and organic wastes revealed that thermophilic conditions at 55 °C are more advantageous than mesophilic conditions at 37 °C.

Impact of Nano Zero-Valent Iron (NZVI) on Methanogenic Activity, Physiological Traits, and Microbial Community Structure in Anaerobic Digestion

Effects of short-term nano zero-valent iron (NZVI) and zero-valent iron (ZVI) exposure on methanogenic activity of anaerobic sludge, physiological traits, composition of phospholipid fatty acids (PLFA), and microbial community structure were investigated. Results show that accumulated methane production decreased with an increase of NZVI concentration; yet, methane production only changed slightly with the same concentration of ZVI. In the NZVI (100-5000 mg·L-1) sets, dissolved iron (DFe) concentrations were 1.6-7.4 times that of the control value at 5 d, whereas DFe was only slightly above the control in the ZVI set (5000 mg·L-1). The concentration of extracellular polymeric substances and cell viability decreased to 21.1% and 79.7%, respectively, of the control in the 5000 mg·L-1 NZVI treatments. Coenzyme F420 and coenzyme M decreased to 40.2% and 61.1%, respectively, of the control in the 5000 mg·L-1 NZVI treatments, which were significantly increased to 1.3 times that of the control value in the 100 mg·L-1 NZVI and 5000 mg·L-1 ZVI treatments. The order of unsaturation and branch PLFA content was ZVI-5000 (21.18%) > control (19.37%) > NZVI-1000 (16.69%) > NZVI-5000 (15.94%) > NZVI-100 (12.08%). High NZVI concentration (5000 mg·L-1) resulted in an increase of DFe and a decrease of cell membrane fluidity and key coenzyme activity of methanogenesis, which led to the inhibition of methane production. Principle component analysis and redundancy analysis indicated that differences in the microbial community existed among these treatments and that Nakamurella, Bacillus, Trichococcus, and Petrimonas showed tolerance to NZVI.

Monitoring the restart-up of an upflow anaerobic sludge blanket (UASB) reactor for the treatment of a soybean processing wastewater

Restart-up of an upflow anaerobic sludge blanket (UASB) reactor for the treatment of soybean processing wastewater was investigated. During the restart-up period, both chemical oxygen demand (COD) degradation efficiency and gas production rate increased. The specific methanogenic activity of anaerobic sludge and the fluorescence score for coenzyme F 420 in the effluent increased from 0.31 to 0.81 g-CH 4-COD/gVSS/d and from 153 to 313, respectively. Among the various operating parameters the volatile fatty acids (VFA) and the CH 4 content were the first to become stable, which could be used as the main parameter for the reactor restart-up. The coenzyme F 420 also existed in the effluent and its concentration had a similar changing trend to the specific methanogenic activity value of the anaerobic sludge. Therefore, the F 420 fluorescence score in the effluent could be used to determine the methanogenic activity of anaerobic reactors.

Response of an anaerobic granular sludge to chlorinated aliphatic hydrocarbons in different conditions

In spite of its importance, little attention has been paid thus far to the toxicity of chlorinated aliphatic hydrocarbons under methanogenic conditions. The effect of several parameters which can affect the toxicity of CHCl 3, CCl 4, C 2H 2Cl 4 and trans-C 2H 2Cl 2 on the acetoclastic methanogenic activity of anaerobic sludge was studied. The following conclusions were derived: (i) The extend of inhibition produced is a function of the toxicant concentration, the type and the amount of the biomass. A lag-period was detected for the inhibition produced by CHCl 3 and trans-C 2H 2Cl 2, while for the other compounds the inhibitory effect was instant. (ii) The recovery time for an anaerobic granular sludge exposed to different toxicants was a function of the extent of inhibition and the exposure time, and seemed to be independent of the toxicants used. (iii) The possible acclimatization of an anaerobic sludge to continuous exposure to a toxicant was dependent on the nature of the toxicant. The time required to acquire an activity similar to that of untreated controls was dependent on the concentration of the toxicant used. In our case adaptation was only obtained for CCl 4.

Simple method for the measurement of the hydrogenotrophic methanogenic activity of anaerobic sludges

The specific hydrogenotrophic activity of anaerobic sludges is usually assayed by gas chromatographic analysis for methane in the headspace of sealed test vials. Gas is sampled with a pressure lock syringe which allows quantification independent of the pressure prevailing in the vials. An alternative method was developed using pressure transducer monitoring of the decrease in headspace gas pressure as the H 2/CO 2 substrate is converted to CH 4. Application of a simple formula related the decrease at each sample point to millilitres of CH 4 produced and gave values for the specific hydrogenotrophic activity of granular anaerobic sludge which were in good agreement with the values obtained by the more labor-intensive gas chromatographic method. The simplicity of the method facilitates multiple replicate analyses and allows more accurate determination of initial rates than is achievable by the gas chromatographic method which is prone to analytical error at the very low concentrations of CH 4 present in the headspace during the early stages of the assay. Mass transfer of H 2 from headspace to liquid was found to be rate-limiting and to result in significant under-estimation of the specific hydrogenotrophic activity of the granular sludge. A test protocol, which used a vial volatile suspended solids concentration between 1.7 and 8 g l −1; a 1:5 ratio between liquid and headspace; incubation of the vials horizontally with vigorous shaking (180 rev./min) and an initial H 2/CO 2 ( 80 20 ) gas pressure of 100–150 kPa was found to give reproducible and maximal values for the specific hydrogenotrophic activity of the test sludge.

A New Methodology to Evaluate the Behaviour of Anaerobic Sludge Exposed to Potentially Inhibitory Compounds

The success of the newly developed “Specific Methanogenic Activity Test” (SMA-test) in measuring the potential of anaerobic sludge to convert soluble substrate into CH4 and CO2 (James et al., 1990) made this test potentially useful for a variety of investigations. The SMA-test was originally developed for assessment of specific methanogenic activity of anaerobic sludge, but the reliability of the method in detecting even very small changes of sludge activity has drawn attention to its use for many different purposes, especially to evaluate the behaviour of anaerobic sludge when subjected to potentially inhibitory compounds. Recent investigations into the potentially inhibitory effects of the Lithium ion on anaerobic sludge were successfully carried out employing the SMA-test. The test proved to be very sensitive for this type of experiment and the results clearly showed a relationship between the degree of inhibition and the concentration of Lithium (Anderson et al., 1991). This paper describes the methodology for measuring the specific methanogenic activity of anaerobic sludges and discusses how the SMA-test can be used for different purposes.

The Use of the SMA-Test for Measuring Toxicity in Anaerobic Sludges

Monitoring of anaerobic sludges exposed to toxic or potentially toxic compounds is important in order to control the efficiency of the sludge when treating toxic wastes. A new methodology developed for measuring specific methanogenic activity (SMA) has shown great sensitivity in detecting inhibition, even when caused by less toxic compounds such as Lithium Chloride. Since the SMA-test is carried out using batch flasks (James et al., 1989), it is able to simulate the continuous exposure of the anaerobic sludge to toxic substances. The test also showed capability in detecting variation of methanogenic activity of anaerobic sludges exposed temporarily to toxic compounds (Anderson et al., 1989). Although Lithium Chloride is considered to be a non-toxic substance (Tomlinson and Chambers, 1979), the SMA-test demonstrated that when anaerobic sludge was exposed continuously to this compound at concentrations of about 250 mgLi+/l, the sludge showed signs of inhibition, whereas for concentration of about 2,000 mgLi+/l the methanogenic activity of the sludge ceased completely. This paper aims at showing how the SMA-test can be used as means of measuring inhibition caused by potentially inhibitory compounds on anaerobic sludge, and at the same time, suggests its standardization as an efficient tool for such purposes.

Applications of pressure transducers in anaerobic systems

Pressure transducer assay methods are widely used to determine the methanogenic activity of anaerobic sludges and to evaluate the anaerobic biodegradability of organic chemicals. The application of this methodology to pure cultures of eubacterial and yeast species was investigated and the results obtained were in good agreement with conventional methods for assaying microbial growth and for determining the specific activity of resting cells. Because of its simplicity and amenability to computer control, the pressure transducer assay method represents a useful adjunct to the variety of methods in routine use for characterisation of anaerobic species.

Acclimatization of anaerobic sludge for UASB reactor start-up

The Upflow Anaerobic Sludge Bed (UASB) reactor represents a high rate anaerobic wastewater treatment system. The majority of the active biomass in the reactor is present in the form of sludge granules which possess excellent settling properties. If no acclimatized (granular) sludge is available, the first start-up is performed using unadapted seed material. The subject of this study is the start-up of UASB-reactors using digested sewage sludge as seed material and volatile fatty acids (M) as substrate. A relation was demonstrated between the dry suspended solids content of digested sewage sludge and its settleability and methanogenic activity. The analysis of coenzyme F420 proved a reliable method to assess the potential methanogenic activity of anaerobic sludge. Several environmental conditions were found to influence the length of the gas production lag phase of digested sewage sludge following the supply of a VFA-feed, e.g. the biomass concentration and the mixing intensity. Exceptionally high sludge growth yields were determined with acetate as single substrate. The rate of UASB-reactor start-up has been examined in relation to the type and quantity of seed sludge and the composition and strength of the wastewater. Two types of sludge wash-out are distinguished, i.e. sludge bed expansion wash-out and sludge bed erosion wash-out. The latter type represents a key feature of the UASB-reactor, i.e. the selection pressure exerted on the sludge particles, which is essential in the development of granular sludge from the digested sewage sludge seed. Indications were obtained that the use of different types of digested sewage sludge leads to the development of different types of granular sludge, as a result of differences in the average biomass retention time during the early stages of start-up. The role of Methanothrix and Methanosarcina is discussed. The development of bulking anaerobic sludge is reinforced by seeding with a dilute digested sewage sludge type (≤40 kgDSS.m -3 ). This will prolong the start-up time. Guidelines are provided with respect to the choice of a seed sludge depending upon the strength and composition of the wastewater.