Anaerobic digestion of solid animal waste in an accumulation system at mesophilic and thermophilic conditions, start up

2003 ◽  
Vol 48 (4) ◽  
pp. 217-220 ◽  
Author(s):  
H.M. El-mashad ◽  
G. Zeeman ◽  
W.K.P. van Loon ◽  
G.P.A. Bot ◽  
G. Lettinga
Keyword(s):  
Anaerobic Digestion ◽  
Minor Effect ◽  
Mixing Conditions ◽  
Rate Limiting Step ◽  
Start Up ◽  
Accumulation System ◽  
Filling Time ◽  
Thermophilic Conditions ◽  
A Minor ◽  
Rate Limiting

The anaerobic digestion of solid animal wastes has been studied in an accumulation system (AC) at a filling time of 60 days followed by about 50 days batch digestion at 40 and 50°C. Poor mixing conditions during anaerobic digestion of solid wastes promote stratification of the substrate and intermediate products along the reactor height. The effect of layers stratification has also been followed in the AC system. The results showed a pronounced stratification of both CODdis and VFA concentrations along the AC system height. The temperature had a minor effect on the methane yield. The results also showed that methanogenesis was rate limiting in the AC system while the hydrolysis was the rate-limiting step during batch digestion.

scholarly journals Removal of Paracetamol from Wastewater by Calcined Gypsum: Adsorption and Kinetics Study

2020 ◽  
Vol 3 (1) ◽  
pp. 11-18
Author(s):  
Hossam Al-Itawi
Keyword(s):  
Aqueous Solutions ◽  
Minor Effect ◽  
Recrystallization Process ◽  
Rate Limiting Step ◽  
Pseudo Second Order ◽  
Calcined Gypsum ◽  
A Minor ◽  
Two Stages ◽  
Rate Limiting ◽  
Best Fit

It has been established that the presence of paracetamol in wastewaters can cause a potential risk to the environment. This work examined the possibility of using calcined gypsum in removing paracetamol from aqueous solutions. At neutral pH conditions, calcined gypsum was successful in removing paracetamol via adsorption, from aqueous solutions with a removal efficiency that ranged between 56.8 to 65.3 % of an initial concentration of 600 ppm. Increased temperature (from 20 to 500C) had a minor effect on the removal % of paracetamol while increasing the initial calcined gypsum dose (from 0.5 gm to 3 gm) and contact time (up to 15 min) increased by the removal % of paracetamol. Thermodynamically, the adsorption of paracetamol by calcined gypsum process was found to be spontaneous and endothermic, and more likely a physical process, while kinetically; the Pseudo-Second order model was found to be the best fit compared to the Elovich model. The removal process mainly consists of two stages, and it could be deduced from the kinetic behavior of paracetamol adsorption that the recrystallization process can be another rate-limiting step in the process.

The effects of tunicamycin, mevinolin and mevalonic acid on HMG-CoA reductase activity and nuclear division in the myxomycete Physarum polycephalum

1989 ◽  
Vol 92 (3) ◽  
pp. 341-344
Author(s):  
W. Engstrom ◽  
O. Larsson ◽  
W. Sachsenmaier
Keyword(s):  
Physarum Polycephalum ◽  
Nuclear Division ◽  
Reductase Activity ◽  
Mevalonic Acid ◽  
Minor Effect ◽  
Hmg Coa Reductase ◽  
Rate Limiting Step ◽  
Coa Reductase ◽  
A Minor ◽  
Rate Limiting

The effects of two inhibitors of 3-hydroxy 3-methyl glutaryl-coenzyme A reductase (tunicamycin and mevinolin) on nuclear division in the myxomycete Physarum polycephalum were examined. Tunicamycin exerted a minor effect on division in synchronized cultures, whereas mevinolin delayed the second, third and fourth nuclear divisions with increasing efficiency. Mevinolin also appeared to be the more potent inhibitor of HMG-CoA reductase, which catalyses the rate-limiting step in the biosynthesis of cholesterol and other isoprene derivatives. These effects of mevinolin could be partially reversed by the addition of mevalonate, suggesting that mevinolin exerts its inhibitory effects on Physarum nuclear division by decreasing the activity of HMG-CoA reductase.

Comparison of carbon storage under aerobic and anoxic conditions

1998 ◽  
Vol 38 (8-9) ◽  
pp. 77-84 ◽  
Author(s):  
M. Majone ◽  
P. Massanisso ◽  
R. Ramadori
Keyword(s):  
Mixed Culture ◽  
External Source ◽  
Hydrolysis Rate ◽  
Minor Effect ◽  
Aerobic Conditions ◽  
Anoxic Conditions ◽  
Rate Limiting Step ◽  
A Minor ◽  
Rate Limiting

In various activated sludge systems, the biomass grows under transient (unbalanced) conditions and the storage response (formation of internal polymers as the fastest adaptation to the changing environment) becomes important. Till now the role of storage on population dynamics has been deeply investigated under anaerobic (EBPR processes) or aerobic (bulking control) conditions. Little attention has been given to processes including anoxic conditions even though in many of them storage phenomena are likely to occur (anoxic selectors, nitrogen removal processes with addition of an external source of readily biodegradable COD or with aerobic contact/anoxic stabilization). For these reasons, the aim of the present work was to investigate storage and succeeding use of stored products under anoxic and mixed (anoxic/aerobic) conditions. Batch experiments have shown that a mixed culture selected under aerobic conditions and intermittent feed (acetate-limited medium), was also able to take up acetate (90–100 mgCOD/gCOD h) and store it as PHB (35–40 mgCOD/gCOD h) under anoxic conditions. After acetate depletion, the stored PHB was used for growth and maintenance. The NUR on acetate in the presence of storage was 20 mgN/gVSS h (which corresponded to a COD removal of 6.9 mgCOD/mgN) while it dropped to 10–3 mgN/gVSS h in the “endogenous phase” when denitrification was on the stored PHB. The presence of aerobic conditions instead of anoxic ones had a major positive effect on the rate and yield of PHB storage while it had only a minor effect on the rate of PHB consumption. The latter observation can be explained by assuming that the hydrolysis of the stored product is the rate limiting step of the “endogenous” metabolism and that the hydrolysis rate is not highly dependent on aerobic-anoxic conditions. Cross-comparison of PHB storage and consumption under aerobic/anoxic conditions made it possible to determine that, in the particular mixed culture under investigation, all aerobic heterotrophs able to store were also able to denitrify.

Characteristics of carbohydrate degradation and the rate-limiting step in anaerobic digestion

1985 ◽  
Vol 27 (10) ◽  
pp. 1482-1489 ◽  
Author(s):  
Tatsuya Noike ◽  
Ginro Endo ◽  
Juu-En Chang ◽  
Jun-Ichi Yaguchi ◽  
Jun-Ichiro Matsumoto
Keyword(s):  
Anaerobic Digestion ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Carbohydrate Degradation ◽  
Rate Limiting

Potential of anaerobic digestion of complex waste(water)

2001 ◽  
Vol 44 (8) ◽  
pp. 115-122 ◽  
Author(s):  
G. Zeeman ◽  
W. Sanders
Keyword(s):  
Waste Water ◽  
Anaerobic Digestion ◽  
Order Relation ◽  
Organic Substrates ◽  
Reactor Technology ◽  
Rate Limiting Step ◽  
Treatment Technologies ◽  
Transport Complex ◽  
Rate Limiting ◽  
Hydrolysis Of

Although they differ greatly in origin complex waste(water)s mainly consist of proteins, lipids, carbohydrates and sometimes lignin in addition. Hydrolysis is the first and generally rate-limiting step in the process of anaerobic digestion of particulate organic substrates. Hydrolysis of particulate polymers can be described by Surface Based Kinetics, but for use in practice the empirical first order relation is advised. Unlike the hydrolysis of protein and carbohydrate, lipid hydrolysis is hardly occurring in the absence of methanogenesis. The latter is probably a physical rather than a biological process and affects the choice for either a one- or a two-step (phase) anaerobic reactor. In the chain of collection and transport, complex wastes often become complex wastewaters simply because of dilution. Dilution not only changes the reactor technology to be applied but also complicates the post-treatment and possibilities for resource recovery. Combining concentrated with diluted waste streams will almost always end up in much more complicated treatment technologies.

Enhancement of the conventional anaerobic digestion of sludge: comparison of four different strategies

2011 ◽  
Vol 64 (2) ◽  
pp. 375-383 ◽  
Author(s):  
S. I. Pérez-Elvira ◽  
M. Fdz-Polanco ◽  
F. Fdz-Polanco
Keyword(s):  
Anaerobic Digestion ◽  
Thermal Hydrolysis ◽  
General Increase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Key Factor ◽  
Thermophilic Digestion ◽  
Pre Treatment ◽  
Treatment Alternatives ◽  
Rate Limiting

Anaerobic digestion (AD) is the preferred option to stabilize sludge. However, the rate limiting step of solids hydrolysis makes it worth modifing the conventional mesophilic AD in order to increase the performance of the digester. The main strategies are to introduce a hydrolysis pre-treatment, or to modify the digestion temperature. Among the different pre-treatment alternatives, the thermal hydrolysis (TH) at 170 °C for 30 min, and the ultrasounds pre-treatment (US) at 30 kJ/kg TS were selected for the research, while for the non-conventional anaerobic digestion, the thermophilic (TAD) and the two-stage temperature phased AD (TPAD) were considered. Four pilot plants were operated, with the same configuration and size of anaerobic digester (200 L, continuously fed). The biogas results show a general increase compared to the conventional digestion, being the highest production per unit of digester for the process combining the thermal pre-treatment and AD (1.4 Lbiogas/Ldigester·day compared to the value of 0.26 obtained in conventional digesters). The dewaterability of the digestate became enhanced for processes TH + AD and TPAD when compared with the conventional digestate, while it became worse for processes US + AD and TAD. In all the research lines, the viscosity in the digester was smaller compared to the conventional (which is a key factor for process performance and economics), and both thermal pre-treatment and thermophilic digestion (TAD and TPAD) assure a pathogen free digestate.

Investigations on the changes in anaerobic biodegradability and biotoxicity of an industrial microbial biomass induced by a thermochemical pretreatment

2000 ◽  
Vol 41 (3) ◽  
pp. 137-144 ◽  
Author(s):  
J.P. Delgèns ◽  
V. Penaud ◽  
M. Torrijos ◽  
R. Moletta
Keyword(s):  
Anaerobic Digestion ◽  
Microbial Biomass ◽  
Operating Conditions ◽  
Thermochemical Pretreatment ◽  
Anaerobic Microorganisms ◽  
Rate Limiting Step ◽  
The Poor ◽  
Anaerobic Biodegradability ◽  
Physico Chemical ◽  
Rate Limiting

In the anaerobic digestion of solid wastes, hydrolysis is the rate limiting step and physico-chemical pretreatment is often required to promote solubilization of organic matter. As an illustration, anaerobic digestion was limited by the substrate solubilization step during continuous cultures performed with an industrial microbial biomass. In optimal operating conditions determined for the hydrolysis-acidogenesis step (T=35°C; pH=8.5; OLR=5.4 g COD/l.d) 50.6% COD solubilization was achieved. A thermochemical pretreatment based on sodium hydroxide addition, was used in order to enhance COD solubilization. Optimal conditions for COD solubilization were pH=12, T=140°C for 30 minutes. In these conditions, 70% COD solubilization was achieved. However, anaerobic biodegradability of the pretreated substrate was not improved and remained near 40%. The poor anaerobic biodegradability performances were attributed to the soluble molecules generated during the thermochemical pretreatment that were refractory and/or inhibitory to anaerobic microorganisms. Fractionation of the soluble pretreated microbial biomass by two methods (treatment with adsorbent resins and precipitation by pH adjustment) demonstrated that high molecular weight compounds (>100 kDa) are involved in the poor biodegradability and in the biotoxicity observed. Partial decolorization through resin use and acid precipitation remove these compounds. The consequence of their removal was an increase of the production of biogas.

A new model with serial hydrolysis reactions for the anaerobic digestion of waste activated sludge under thermophilic conditions

2019 ◽  
Vol 5 (12) ◽  
pp. 2182-2192
Author(s):  
Yousif Hirmiz ◽  
Youngseck Hong ◽  
Younggy Kim
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Numerical Simulations ◽  
Kinetic Models ◽  
Wastewater Sludge ◽  
Waste Activated Sludge ◽  
New Model ◽  
Thermophilic Conditions ◽  
Rate Limiting ◽  
Hydrolysis Reactions

Hydrolysis is one of the rate-limiting reactions in the anaerobic digestion (AD) of wastewater sludge; thus, reliable kinetic models for hydrolysis reactions are essential in numerical simulations of AD.

An effective start-up of thermophilic UASB reactor by seeding mesophilically-grown granular sludge

1997 ◽  
Vol 36 (6-7) ◽  
pp. 391-398 ◽  
Author(s):  
Kazuaki Syutsubo ◽  
Hideki Harada ◽  
Akiyoshi Ohashi ◽  
Hiroshi Suzuki
Keyword(s):  
Granular Sludge ◽  
Uasb Reactor ◽  
Methanogenic Activity ◽  
Rate Limiting Step ◽  
Start Up ◽  
Seed Sludge ◽  
Drastic Increase ◽  
Distillery Wastewater ◽  
Propionate Degradation ◽  
Rate Limiting

After seeded with mesophilically-grown (35°C) granular sludge, a laboratory-scale UASB reactor was thermophilically (55°C) operated over 8 months by feeding with an alcohol distillery wastewater. Use of mesophilically-grown granules as a seed material proved to be more advantageous for rapid and stable start-up of thermophilic UASB process, compared with the use of suspended-growth sludge taken from a thermophilic anaerobic digester. The reactor accommodated successfully a COD loading 30 kgCOD·m−3·d−1, with a COD removal efficiency of 85%. However, during a period of 30 kgCOD·m−3·d−1, propionate accumulated in the effluent up to 300-600 mgCOD·l−1. Thermophilic cultivation caused a drastic increase of methanogenic activities (55°C) of the retained sludge: 4.4 times for acetate, 4.6 times for propionate, and 3.5 times for hydrogen as large as those of the seed sludge. A considerably low value of propionate-fed methanogenic activity, i.e. only 1/5 of acetate-fed activity and only 1/23 of hydrogen-fed activity, suggested that the propionate degradation is subject to be a rate-limiting step in thermophilic anaerobic processes.

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