Improved Mixing System for Anaerobic Sequencing Batch Reactors

2020 ◽  
Vol 63 (4) ◽  
pp. 933-942
Author(s):  
Douglas W. Hamilton ◽  
Hernan Fernandez-Barriales Lopez ◽  
Emilia P. Cuesta Alonso
Keyword(s):  
Removal Efficiency ◽  
Retention Time ◽  
Hydraulic Retention Time ◽  
Biogas Production ◽  
Batch Reactor ◽  
Biogas Yield ◽  
Effluent Quality ◽  
Solids Retention Time ◽  
Solids Retention ◽  
Vs Removal

HighlightsA novel single-jet mixing system was designed for ASBR digesters.Mixing energy was reduced to the point that solids were only partially suspended in the reactor vessel.The partial mixing system increased effluent quality as measured by suspended solids content.The partial mixing system increased solids retention, allowing hydraulic retention time (HRT) to be reduced to at least 7.5 days while maintaining solids retention time (SRT) above 100 days.The partial mixing system did not reduce biogas production rate nor biogas yield.Abstract. An anaerobic sequencing batch reactor (ASBR) is a high-rate anaerobic digestion system ideally suited for the treatment of liquids with high organic strength and low solids content. Biota are retained in an ASBR by settling solids prior to decanting effluent from the top of the reactor. Solids retention time (SRT) can be managed separately from hydraulic retention time (HRT) in an ASBR. One problem encountered with ASBRs is poor solids retention due to inefficient solids settling. A novel mixing system in which solids are only partially mixed in the reactor prior to decanting was investigated in a series of three experiments. A battery of six 30 L ASBR reactors were fed a mixture of dilute swine manure (0.30% TS, 0.20% VS) and raw glycerol. In a side-by-side comparison of two reactors operated at an organic loading rate (OLR) of 0.30 g COD L-1 d-1 with 15-day HRT and two feeding cycles per day, the partially mixed reactor outperformed the fully mixed reactor as measured by effluent quality (130 vs. 350 mg VSS L-1), SRT (354 vs. 52 days), and VS removal efficiency (88% vs. 79%). In a replicated study of five reactors operated at 0.31 g COD L-1 d-1 OLR, 15-day HRT, and two feeding cycles per day before and after switching from full to partial mixing, the partially mixed reactors showed significantly (p = 0.05) better performance as measured by effluent quality (100 vs. 382 mg VSS L-1), SRT (760 vs. 72 days), and VS removal efficiency (85% vs. 71%). Biogas production did not significantly change with the change from full to partial mixing in the five replicated reactors, i.e., average biogas yield was 0.81 and 0.77 L biogas g-1 COD with partial and full mixing, respectively. Effluent quality, SRT, VS removal efficiency, and biogas yield did not significantly change when the OLR was increased from 0.31 to 0.62 g COD L-1 d-1 and HRT was reduced from 15 to 7.5 days in a replicated study of six partially mixed reactors. A mass balance of COD across the six partially mixed reactors showed that endogenous respiration of retained biomass accounted for approximately 50% of the biogas produced by an ASBR with SRT exceeding 400 days. Keywords: Anaerobic digestion, Anaerobic sequencing batch reactor, ASBR, Biogas, Glycerol, Hydraulic retention time, Mixing, Operation, Performance, Solids retention time, Swine manure.

Anaerobic thermophilic digestion of sewage sludge with a thickened sludge recycle

2012 ◽  
Vol 65 (3) ◽  
pp. 403-409 ◽  
Author(s):  
A. Ya. Vanyushina ◽  
Yu. A. Nikolaev ◽  
A. M. Agarev ◽  
M. V. Kevbrina ◽  
M. N. Kozlov
Keyword(s):  
Retention Time ◽  
Municipal Wastewater ◽  
Hydraulic Retention Time ◽  
Biogas Production ◽  
Wastewater Sludge ◽  
Recycling Process ◽  
Digested Sludge ◽  
Volatile Solids ◽  
Solids Retention ◽  
Thermophilic Digestion

The process of anaerobic thermophilic digestion of municipal wastewater sludge with a recycled part of thickened digested sludge, was studied in semi-continuous laboratory digesters. This modified recycling process resulted in increased solids retention time (SRT) with the same hydraulic retention time (HRT) as compared with traditional digestion without recycling. Increased SRT without increasing of HRT resulted in the enhancement of volatile substance reduction by up to 68% in the reactor with the recycling process compared with 34% in a control conventional reactor. Biogas production was intensified from 0.3 L/g of influent volatile solids (VS) in the control reactor up to 0.35 L/g VS. In addition, the recycling process improved the dewatering properties of digested sludge.

scholarly journals Effect of Hydraulic Retention Time on Biogas Production from Cow Dung in A Semi Continuous Anaerobic Digester

2018 ◽  
Vol 7 (2) ◽  
pp. 93-100 ◽  
Author(s):  
Agus Haryanto ◽  
Sugeng Triyono ◽  
Nugroho Hargo Wicaksono
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Loading Rate ◽  
Biogas Production ◽  
Stable Condition ◽  
Anaerobic Digester ◽  
Organic Loading Rate ◽  
Cow Dung ◽  
Biogas Yield ◽  
Average Analysis

The efficiency of biogas production in semi-continuous anaerobic digester is influenced by several factors, among other is loading rate. This research aimed at determining the effect of hydraulic retention time (HRT) on the biogas yield. Experiment was conducted using lab scale self-designed anaerobic digester of 36-L capacity with substrate of a mixture of fresh cow dung and water at a ratio of 1:1. Experiment was run with substrate initial amount of 25 L and five treatment variations of HRT, namely 1.31 gVS/L/d (P1), 2.47 gVS/L/d (P2), 3.82 gVS/L/d (P3), 5.35 gVS/L/d (P4) and 6.67 gVS/L/d (P5). Digester performance including pH, temperature, and biogas yield was measured every day. After stable condition was achieved, biogas composition was analyzed using a gas chromatograph. A 10-day moving average analysis of biogas production was performed to compare biogas yield of each treatment. Results showed that digesters run quite well with average pH of 6.8-7.0 and average daily temperature 28.7-29.1. The best biogas productivity (77.32 L/kg VSremoval) was found in P1 treatment (organic loading rate of 1.31 g/L/d) with biogas yield of 7.23 L/d. With methane content of 57.23% treatment P1 also produce the highest methane yield. Biogas production showed a stable rate after the day of 44. Modified Gompertz kinetic equation is suitable to model daily biogas yield as a function of digestion time.Article History: Received March 24th 2018; Received in revised form June 2nd 2018; Accepted June 16th 2018; Available onlineHow to Cite This Article: Haryanto, A., Triyono, S., and Wicaksono, N.H. (2018) Effect of Loading Rate on Biogas Production from Cow Dung in A Semi Continuous Anaerobic Digester. Int. Journal of Renewable Energy Development, 7(2), 93-100.https://doi.org/10.14710/ijred.7.2.93-100

scholarly journals The potential of ultrasonic membrane anaerobic systems in treating slaughterhouse wastewater

2015 ◽  
Vol 5 (3) ◽  
pp. 293-300 ◽  
Author(s):  
N. H. Abdurahman ◽  
Y. M. Rosli ◽  
N. H. Azhari ◽  
Hayder A. Bari
Keyword(s):  
Steady State ◽  
Removal Efficiency ◽  
Retention Time ◽  
Suspended Solids ◽  
Oxygen Demand ◽  
Yield Coefficient ◽  
Slaughterhouse Wastewater ◽  
Mixed Liquor ◽  
Solids Retention Time ◽  
Solids Retention

Direct discharge of slaughterhouse wastewater causes serious environmental pollution due to its high chemical oxygen demand (COD), total suspended solids (TSS) and biochemical oxygen demand. In this study, an ultrasonic-assisted membrane anaerobic system was used as a novel method for treating slaughterhouse wastewater. Six steady states were achieved, using concentrations of 7,800–13,620 mg/l for mixed liquor suspended solids and 5,359–11,424 mg/l for mixed liquor volatile suspended solids (MLVSS). Kinetic equations were used to describe the kinetics of treatment at organic loading rates of 3–11 kg COD/m3/d. The removal efficiency of COD was 94.8–96.5% with hydraulic retention times of 308.6–8.7 days. The growth yield coefficient was found to be 0.52 g VSS/g. COD was 0.21 d−1 and methane gas production rate was 0.24–0.56 l/g COD/d. Steady-state influent COD concentrations increased from 8,000 mg/l in the first steady state to 25,400 mg/l in the sixth steady state. The minimum solids retention time, θcmin obtained from the three kinetic models was 6–14.4 days. The k values were 0.35–0.519 g COD/g VSS.d and μmax values were between 0.26 and 0.379 d−1. The solids retention time decreased from 600 to 14.3 days. The complete treatment reduced the COD content and its removal efficiency reached 94.8%.

Treatment of Domestic Strength Wastewater with Anaerobic Hybrid Reactors

1987 ◽  
Vol 22 (3) ◽  
pp. 474-490 ◽  
Author(s):  
R.L. Droste ◽  
S.R. Guiot ◽  
S.S. Gorur ◽  
K.J. Kennedy
Keyword(s):  
Retention Time ◽  
Suspended Solids ◽  
Hydraulic Retention Time ◽  
Oxygen Demand ◽  
Anaerobic Treatment ◽  
Synthetic Wastewater ◽  
Solids Retention Time ◽  
Solids Retention ◽  
Removal Efficiencies ◽  
Hybrid Reactors

Abstract Anaerobic treatment of dilute synthetic wastewater (300-1,000 mg chemical oxygen demand/L using laboratory upflow sludge blanket filter reactors with and without effluent recycle is described. Treatment of dilute synthetic wastewater at hydraulic retention times less than 1 and 2 h in reactors without and with recycle, respectively, resulted in biomass washout as the solids retention time decreased to less than 12 d. Reseeding would be required to operate at these critical hydraulic retention times for extended periods. Treatment of dilute synthetic wastewater at hydraulic retention times between 3-12 h resulted in soluble COD removal efficiencies between 84-95% treating 300 mg COD/L. At a 3 h hydraulic retention time, solids retention time of 80 d and stable reactor biomass concentrations of 25 g volatile suspended solids/L were maintained.

Operating Experiences at Low Solids Retention Time

1984 ◽  
Vol 16 (12) ◽  
pp. 661-672 ◽  
Author(s):  
T E Wilson ◽  
W A Ambrose ◽  
H O Buhr
Keyword(s):  
Activated Sludge ◽  
Retention Time ◽  
Suspended Solids ◽  
Volume Index ◽  
Sludge Volume Index ◽  
Effluent Quality ◽  
Mixed Liquor ◽  
Solids Retention Time ◽  
Solids Retention ◽  
Typically Achieving

Five full scale activated sludge plants have been operated at low solids retention time (SRT, monthly averages as low as 0.8 days) and mixed liquor suspended solids (MLSS, monthly averages as low as 500 mg/l) values for 2 to 3 years. Operating results for this period are compared to 3 to 3-1/2 years of operation at conventional, higher, SRT and MLSS values. The data show that the lower SRT operation provided better effluent quality, typically achieving less than 15 mg/l of BOD5 or suspended solids, while not significantly increasing either the total (dry) sludge production or the sludge volume index (SVI). These data indicate that plants can be built and operated using significantly smaller tankage than conventionally accepted.

scholarly journals Comparative Study of Biogas Production from Cocoa Pod, Maize Husk, Orange Peels, Pineapple Peels and Coconut Fiber Co-Digested with Yeast

2020 ◽  
Author(s):  
M.A. Enaboifo ◽  
C.A. Adadu
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Biogas Production ◽  
Batch Reactors ◽  
Coconut Fiber ◽  
Biogas Yield ◽  
Substrate Quality ◽  
Orange Peels ◽  
Coconut Fibre ◽  
The Cost

Background: The demand and cost of domestic energy in Nigeria are on the increase, primarily due to the increasing human population and demand. This is compounded by desertification, increasing the cost of electricity, industrialization, lack of alternative such as solar, wind and nuclear energy.This study was conducted to compare the potential of biogas produced from anaerobic co-digestion of coconut fibre, cocoa pods, maize husk, orange peels, pineapple peels and yeast and to determine the effect of pH and retention time on biogas yield. Methods: During the experiment, five batch reactors/digesters were used. The digesters were labeled A,B,C,D, E and each replicated three times. Digester A consist of 2g of yeast, 4g of coconut fibre, digester B consist of 2g of yeast, 4g of cocoa pods, digester C consist of 2g of yeast, 4g of maize husk, digester D consist of 2g of yeast, 4g of orange peels and digester E consist of 2g of yeast, 4g of pineapple peels. The pH was determined before corking the reactors. Result: The results showed significant differences among the different substrate for biogas yield and methane component. Biodegradability of the different substrate, quality and retention time significantly affected the biogas yield in the five digesters. Digester loaded with maize husk produced significantly higher volume of biogas and methane component compared with other substrate. Increase in biogas yield for maize husk of 4g was 23.33ml with methane component of 61.78% for the 10 days hydraulic retention time. The retention time of 4, 5, 6 and 8 days significantly produced the highest volume of biogas in the other digesters. Based on the findings, maize husk and yeast blend could be a rich source of renewable energy option and would help arrest ecological disaster in addition to control of deforestation.

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