The anaerobic treatment of a ligno-cellulosic substrate offering little natural pH buffering capacity

1998 ◽  
Vol 38 (4-5) ◽  
pp. 29-35 ◽  
Author(s):  
C. J. Banks ◽  
P. N. Humphreys
Keyword(s):  
Ph Control ◽  
Anaerobic Treatment ◽  
Buffering Capacity ◽  
Single Stage ◽  
Stable Operation ◽  
Reactor Performance ◽  
Two Stage ◽  
Ph Buffering ◽  
Stage System ◽  
The Stability

The stability and operational performance of single stage digestion with and without liquor recycle and two stage digestion were assessed using a mixture of paper and wood as the digestion substrate. Attempts to maintain stable digestion in both single stage reactors were unsuccessful due to the inherently low natural buffering capacity exhibited; this resulted in a rapid souring of the reactor due to unbuffered volatile fatty acid (VFA) accumulation. The use of lime to control pH was unsatisfactory due to interference with the carbonate/bicarbonate equilibrium resulting in wide oscillations in the control parameter. The two stage system overcame the pH stability problems allowing stable operation for a period of 200 days without any requirement for pH control; this was attributed to the rapid flushing of VFA from the first stage reactor into the second stage, where efficient conversion to methane was established. Reactor performance was judged to be satisfactory with the breakdown of 53% of influent volatile solids. It was concluded that the reactor configuration of the two stage system offers the potential for the treatment of cellulosic wastes with a sub-optimal carbon to nitrogen ratio for conventional digestion.

scholarly journals Two- vs. single-stage anaerobic reactors: evaluation of effluent quality and energy production potential using sucrose-based wastewater

2018 ◽  
Vol 78 (9) ◽  
pp. 1966-1979 ◽  
Author(s):  
V. T. Mota ◽  
M. Zaiat
Keyword(s):  
Suspended Solids ◽  
Fixed Bed ◽  
Anaerobic Treatment ◽  
Single Stage ◽  
Upflow Anaerobic Sludge Blanket ◽  
Superior Performance ◽  
Anaerobic Sludge ◽  
Energy Yield ◽  
Two Stage ◽  
Stage System

Abstract Two- and single-stage anaerobic treatment systems were assessed for treatment performance and for bioenergy production from sucrose-based wastewater. In the two-stage system, a hydrogen-producing upflow anaerobic sludge blanket reactor (HU reactor) was used in the acidogenic phase. The methanogenic reactor of the two-stage system (MF reactor) and the single-stage reactor (SSF reactor) were structured fixed-bed reactors. The two-stage system showed superior performance, evidenced by lower organic acids, chemical oxygen demand (COD) and suspended solids concentrations in the effluent, and higher biogas methane content and yield. Continuous and stable H2 production was obtained in the acidogenic reactor. At the end of operation, the organic loading rates applied to the two- and single-stage systems were 6.4 and 5.2 gCOD L−1 d−1, respectively. Under these conditions, the effluent soluble COD and volatile suspended solids (VSS) concentrations were 165 and 92 mg L−1 in the two-stage system, and 256 and 244 mg L−1 in the single-stage system, respectively. The energy yield of the two-stage system was 20.69 kJ g−1CODadded, which was 34% higher than the yield of the single-stage system. The sequencing analyses showed that the archaeal distribution changed little between the inoculum and sludge from the MF reactor, in which acetoclastic Methanosaeta was predominant. However, hydrogenotrophic Methanospirillum was found most, followed by Methanosaeta, in the sludge from the SSF reactor.

scholarly journals Results of compact facility work with anaerobic treatment of highly concentrated runoffs

2021 ◽  
Vol 937 (4) ◽  
pp. 042052
Author(s):  
Galina Ambrosova ◽  
Anastasiia Kruglikova
Keyword(s):  
Local Treatment ◽  
Ammonium Hydroxide ◽  
Scientific Work ◽  
Fermented Milk ◽  
Ph Control ◽  
Anaerobic Treatment ◽  
Biogenic Element ◽  
The Stability ◽  
Anaerobic Biomass ◽  
Main Component

Abstract This scientific work is devoted to the results of the local treatment facilities’ work for food enterprises sewerage. The complex under consideration is intended for the anaerobic processing of whey, formed during fermented milk production. Whey is one of the specific organic substances, which main component is lactose (sucrose). It is converted under anaerobic conditions into lactic acid, which is a metabolic dead end. The capacity can be used as a homogenizing tank, obtained in this way. In the future, it is proposed to increase the homogenizer volume to 100 m3. It is recommended to use ammonium hydroxide or sulfate to ensure the required ratio between COD and biogenic element (nitrogen) in the loaded whey. Possible biogenic additives can be sewage sludge or slurry. The experience of adjustment was shown that slurry from cattle farms was quite simple, inexpensive and quite effective. Slurry can be injected in 3-4 m3 every 2-3 days. The stability of pH values in the bioreactor can be ensured by the correct placement of sensors for monitoring this indicator and by changing the method of alkali introduction. It is recommended to install pH control sensors at the bottom of the bioreactor, instead of whey loading pipeline. In order to provide for fractional injection of alkali, we should introduce part of the alkali at the homogenization stage, and part directly into the bioreactor. For an unimpeded build-up of anaerobic biomass, it is recommended to replace the centrifuge thickener operating with flocculant with the classic version of thickening in a compactor without flocculant adding.

Two-stage anaerobic treatment of purified terephthalic acid production wastewaters

2000 ◽  
Vol 42 (5-6) ◽  
pp. 277-282 ◽  
Author(s):  
J.C. Young ◽  
I.S. Kim ◽  
I.C. Page ◽  
D.R. Wilson ◽  
G.J. Brown ◽  
...  
Keyword(s):  
Terephthalic Acid ◽  
Phthalic Acid ◽  
Contact Process ◽  
Treatment Plant ◽  
Anaerobic Treatment ◽  
Stable Operation ◽  
Production Facility ◽  
Two Stage ◽  
Phthalic Acids ◽  
Purified Terephthalic Acid

A full-scale two-stage anaerobic treatment plant has been treating the wastewaters from a purified terephthalic acid (PTA) production facility in South Korea for over 4 years. A study was conducted to evaluate the performance characteristics of this system over a 17-month period of operation. The system has provided stable operation with COD removals consistently averaging over 90%. The removal of specific phthalic acid isomers and related chemicals has been essentially 100% except for terephthalic acid which has averaged about 90% and paratoluic acid which had only about 30% removal. About 80% of the removal occurred in the first stage of the two-stage hybrid process. A companion single-stage anaerobic contact process removed only 80 to 85% of the COD and only 35 to 67% of the phthalic acids.

Efficiency Improvement in Entrained Flow Gasification

2011 ◽  
Author(s):  
Ankit Bhatnagar ◽  
S. Pushpavanam
Keyword(s):  
Oxygen Consumption ◽  
Single Stage ◽  
Stage Model ◽  
Two Stage ◽  
Entrained Flow ◽  
Second Stage ◽  
Cold Gas Efficiency ◽  
Stage System ◽  
Gas Efficiency ◽  
Cold Gas

In this work a one dimensional steady state model is developed for a single stage and two-stage bottom fed entrained flow coal gasifier for. The single stage model was first analysed for two different oxidants (i) oxygen and (ii) air to study their effects on gasification. Analysis proved oxygen to be the better oxidant. The model is then extended to a two stage gasifier. Here 30 (70) percent of the coal is fed in the first stage (second stage). The first (second) stage operates in oxidant rich (lean) environment. The performances of single stage and two-stage models are compared in terms of their cold gas efficiencies for the same coal feed rates. It is observed that a two-stage system has better cold gas efficiency (77%) than a single stage system (72%) with lower oxygen consumption. The two-stage model is used to optimise the O2/Coal ratio as the H2O/Coal ratio is varied in the 2nd stage. The optimum yields the highest cold gas efficiency with minimum possible oxygen consumption.

Optimization of Two Stage Evaporators for Minimizing Rad-Waste Entrainment

1980 ◽  
Vol 102 (4) ◽  
pp. 804-806 ◽  
Author(s):  
M. Holtz ◽  
K. P. Singh
Keyword(s):  
Radioactive Waste ◽  
Single Stage ◽  
Two Stage ◽  
Central Object ◽  
Numerical Example ◽  
Stage System ◽  
Carry Over

Minimizing solute carry-over into the product is the central object in the design of Radioactive Waste Concentration Systems. Two Stage Evaporators are intrinsically superior to single stage designs in achieving this objective. An analysis of two stage system to optimize its performance is herein developed. A numerical example is employed to illustrate major conclusions.

scholarly journals Characterization and anaerobic digestion of highly concentrated Mexican wine by-products and effluents

2020 ◽  
Vol 81 (1) ◽  
pp. 190-198 ◽  
Author(s):  
M. Vital-Jacome ◽  
M. Cazares-Granillo ◽  
J. Carrillo-Reyes ◽  
G. Buitron
Keyword(s):  
Anaerobic Digestion ◽  
Oxygen Demand ◽  
Anaerobic Treatment ◽  
Single Stage ◽  
Organic Load ◽  
Organic Loading Rate ◽  
Two Stage ◽  
Wine Production ◽  
Stage Process ◽  
By Products

Abstract Wine production has increased in recent years, especially in developing countries such as Mexico. This increase is followed by an increase of winery effluents that must be treated to avoid environmental risks. However, little information is available about the characteristics of these effluents and the possible treatments. This paper aimed to characterize the effluents and by-products generated by the Mexican winery industry and to evaluate the performance and stability of the anaerobic treatment using a single-stage and a two-stage process. Results showed that the winery effluents had a high content of biodegradable organic matter, with chemical oxygen demand (COD) values ranging from 221 to 436 g COD/L. The single-stage anaerobic process was able to treat an organic loading rate of 9.6 kg COD/(m3 d); however, it was unstable and highly dependent on the addition of bicarbonate alkalinity (0.31 g NaHCO3/g COD removed). The two-stage process was more stable working at a higher organic load (12.1 kg COD/(m3 d)) and was less dependent on the addition of bicarbonate (0.17 g NaHCO3/g COD removed). The results highlight the potential of the winery effluents to produce methane through anaerobic digestion in a two-stage process, making wine production more sustainable.

Energetic feasibility of a two-stage anaerobic digestion system compared to a single-stage system treating whey and glycerin

2020 ◽  
Vol 161 ◽  
pp. 107653 ◽  
Author(s):  
Giovanna Lovato ◽  
Roberta Albanez ◽  
Letícia Scudeler Ruggero ◽  
Lucas Stracieri ◽  
Suzana Maria Ratusznei ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Single Stage ◽  
Two Stage ◽  
Stage System

scholarly journals Stability Analysis of Different Regulation Modes of Hydropower Units

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1933
Author(s):  
Xinran Guo ◽  
Yuanchu Cheng ◽  
Jiada Wei ◽  
Yitian Luo
Keyword(s):  
Stable Operation ◽  
Rotor Speed ◽  
Frequency Range ◽  
Power Regulation ◽  
Normal Frequency ◽  
Dynamic Performances ◽  
Negative Damping ◽  
The Stability ◽  
Regulation Mode ◽  
Water Inertia

The dynamic characteristics of hydropower unit governing systems considerably influence the stability of hydropower units and the connected power system. The dynamic performances of hydropower units with power regulation mode (PRM) and opening regulation mode (ORM) are different. This paper establishes a detailed linear model of a hydropower unit based on the Phillips–Heffron model. The damping characteristic and stability of two regulation modes with different water inertia time constants TW were analyzed. ORM tended to provide negative damping, while PRM often provided positive damping in the major parts of the frequency range within the normal frequency oscillations when TW was large. Eigenvalue analysis illustrated that PRM has better stability than ORM. To validate the analysis, a simulation under two typical faults WAS conducted based on a nonlinear model of a hydropower unit. The simulation results illustrated that the responses of units with PRM are more stable in terms of important operating parameters, such as output power, rotor speed, and power angles. For hydropower units facing challenges in stable operation, PRM is recommended to obtain good dynamic stability.

scholarly journals Asymmetry underlies stability in power grids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ferenc Molnar ◽  
Takashi Nishikawa ◽  
Adilson E. Motter
Keyword(s):  
Symmetry Breaking ◽  
Real World ◽  
Power Grids ◽  
Stable Operation ◽  
World Systems ◽  
Symmetric State ◽  
Network Systems ◽  
Additional Improvement ◽  
The Stability ◽  
General Method

AbstractBehavioral homogeneity is often critical for the functioning of network systems of interacting entities. In power grids, whose stable operation requires generator frequencies to be synchronized—and thus homogeneous—across the network, previous work suggests that the stability of synchronous states can be improved by making the generators homogeneous. Here, we show that a substantial additional improvement is possible by instead making the generators suitably heterogeneous. We develop a general method for attributing this counterintuitive effect to converse symmetry breaking, a recently established phenomenon in which the system must be asymmetric to maintain a stable symmetric state. These findings constitute the first demonstration of converse symmetry breaking in real-world systems, and our method promises to enable identification of this phenomenon in other networks whose functions rely on behavioral homogeneity.

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