Temperature-phased anaerobic digestion of wastewater sludges

The temperature-phased anaerobic bioreactor (TPAB) has been under study by Dague and co-workers at Iowa State University. The temperature-phased approach involves a two-stage reactor system with the first stage operated at a thermophilic temperature (commonly 55°C) and the second stage operated at a mesophilic temperature (commonly 35°C). The purpose of laboratory study was to compare the performance of the temperature-phased system with the conventional single-stage mesophilic system for treating mixtures of primary and waste activated sludge. Of particular interest in the research was a comparison of the two systems from the standpoint of coliform reduction, volatile solids (VS) destruction, and biogas production. The temperature-phased system achieved complete destruction of total and fecal coliforms over a range of SRTs from 11 to 28 days. The concentration of fecal coliforms in the effluent from the temperature-phased system never exceeded 1000 MPN/g total solids (TS), which can meet the U.S. Code of Federal Regulations, Title 40 (40 CFR), Part 503 coliform requirements for Class A sludge. At the optimal SRTs ranging from 11 to 17 days, the capacity of VS removal of temperature-phased system was more than double that of the conventional single-stage system. The foaming problem associated with the digestion of waste activated sludge was eliminated.

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Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge from a biological nutrient removal plant

Water Science & Technology ◽

10.2166/wst.2006.245 ◽

2006 ◽

Vol 53 (8) ◽

pp. 149-157 ◽

Cited By ~ 22

Author(s):

S. Watts ◽

G. Hamilton ◽

J. Keller

Keyword(s):

Anaerobic Digestion ◽

Activated Sludge ◽

Nutrient Removal ◽

Treatment Plant ◽

Single Stage ◽

Biological Nutrient Removal ◽

Waste Activated Sludge ◽

Two Stage ◽

Primary Sludge ◽

Second Stage

A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 °C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36–37 °C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36–37 °C. The results showed a truly thermophilic stage (60 °C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 °C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.

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Comparison of Aerobic and Anoxic-Aerobic Digestion of Waste Activated Sludge

Water Science & Technology ◽

10.2166/wst.1985.0068 ◽

1985 ◽

Vol 17 (8) ◽

pp. 1475-1478 ◽

Cited By ~ 6

Author(s):

A P. C. Warner ◽

G. A. Ekama ◽

G v. R. Marais

Keyword(s):

Experimental Data ◽

Activated Sludge ◽

Waste Activated Sludge ◽

Activated Sludge Process ◽

Cycle Times ◽

Waste Sludge ◽

Volatile Solids ◽

In Series ◽

Flow Through ◽

Theoretical Simulations

The laboratory scale experimental investigation comprised a 6 day sludge age activated sludge process, the waste sludge of which was fed to a number of digesters operated as follows: single reactor flow through digesters at 4 or 6 days sludge age, under aerobic and anoxic-aerobic conditions (with 1,5 and 4 h cycle times) and 3-in-series flow through aerobic digesters each at 4 days sludge age; all digesters were fed draw-and-fill wise once per day. The general kinetic model for the aerobic activated sludge process set out by Dold et al., (1980) and extended to the anoxic-aerobic process by van Haandel et al., (1981) simulated accurately all the experimental data (Figs 1 to 4) without the need for adjusting the kinetic constants. Both theoretical simulations and experimental data indicate that (i) the rate of volatile solids destruction is not affected by the incorporation of anoxic cycles and (ii) the specific denitrification rate is independent of sludge age and is K4T = 0,046(l,029)(T-20) mgNO3-N/(mg active VSS. d) i.e. about 2/3 of that in the secondary anoxic of the single sludge activated sludge stystem. An important consequence of (i) and (ii) above is that denitrification can be integrated easily in the steady state digester model of Marais and Ekama (1976) and used for design (Warner et al., 1983).

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Co-digestion of waste activated sludge and agricultural straw waste for enhanced biogas production

Bioresource Technology Reports ◽

10.1016/j.biteb.2021.100769 ◽

2021 ◽

pp. 100769

Author(s):

Rasika M. Potdukhe ◽

Nidhi Sahu ◽

Atya Kapley ◽

Rakesh Kumar

Keyword(s):

Activated Sludge ◽

Biogas Production ◽

Waste Activated Sludge

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Investigation of Heavy Metal Effects on the Anaerobic Co-Digestion Process of Waste Activated Sludge and Septic Tank Sludge

International Journal of Chemical Engineering ◽

10.1155/2019/5138060 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9

Author(s):

Quang-Minh Nguyen ◽

Duy-Cam Bui ◽

Thao Phuong ◽

Van-Huong Doan ◽

Thi-Nham Nguyen ◽

...

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Activated Sludge ◽

Removal Efficiency ◽

Biogas Production ◽

Cod Removal ◽

Septic Tank ◽

Waste Activated Sludge ◽

Digestion Process ◽

Cod Removal Efficiency

The effect of copper, zinc, chromium, and lead on the anaerobic co-digestion of waste activated sludge and septic tank sludge in Hanoi was studied in the fermentation tests by investigating the substrate degradation, biogas production, and process stability at the mesophilic fermentation. The tested heavy metals were in a range of concentrations between 19 and 80 ppm. After the anaerobic tests, the TS, VS, and COD removal efficiency was 4.12%, 9.01%, and 23.78% for the Cu(II) added sample. Similarly, the efficiencies of the Zn(II) sample were 1.71%, 13.87%, and 16.1% and Cr(VI) efficiencies were 15.28%, 6.6%, and 18.65%, while the TS, VS, and COD removal efficiency of the Pb(II) added sample was recorded at 16.1%, 17.66%, and 16.03% at the concentration of 80 ppm, respectively. Therefore, the biogas yield also decreased by 36.33%, 31.64%, 31.64%, and 30.60% for Cu(II), Zn(II), Cr(VI), and Pb(II) at the concentration of 80 ppm, compared to the raw sample, respectively. These results indicated that Cu(II) had more inhibiting effect on the anaerobic digestion of the sludge mixture than Zn(II), Cr(VI), and Pb(II). The relative toxicity of these heavy metals to the co-digestion process was as follows: Cu (the most toxic) > Zn > Cr > Pb (the least toxic). The anaerobic co-digestion process was inhibited at high heavy metal concentration, which resulted in decreased removal of organic substances and produced biogas.

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Microbial community dynamics linked to enhanced substrate availability and biogas production of electrokinetically pre-treated waste activated sludge

Bioresource Technology ◽

10.1016/j.biortech.2016.07.029 ◽

2016 ◽

Vol 218 ◽

pp. 761-770 ◽

Cited By ~ 8

Author(s):

Maria Westerholm ◽

Sam Crauwels ◽

Sofie Houtmeyers ◽

Ken Meerbergen ◽

Maarten Van Geel ◽

...

Keyword(s):

Microbial Community ◽

Activated Sludge ◽

Community Dynamics ◽

Biogas Production ◽

Waste Activated Sludge ◽

Substrate Availability ◽

Microbial Community Dynamics

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Anaerobic co-digestion of winery waste and waste activated sludge: assessment of process feasibility

Water Science & Technology ◽

10.2166/wst.2013.692 ◽

2013 ◽

Vol 69 (2) ◽

pp. 269-277 ◽

Cited By ~ 15

Author(s):

C. Da Ros ◽

C. Cavinato ◽

F. Cecchi ◽

D. Bolzonella

Keyword(s):

Activated Sludge ◽

Biogas Production ◽

Oxygen Demand ◽

Pilot Scale ◽

Waste Activated Sludge ◽

Organic Loading ◽

Operational Conditions ◽

Loading Rates ◽

Thermophilic Conditions ◽

Soluble Chemical Oxygen Demand

In this study the anaerobic co-digestion of wine lees together with waste activated sludge in mesophilic and thermophilic conditions was tested at pilot scale. Three organic loading rates (OLRs 2.8, 3.3 and 4.5 kgCOD/m3d) and hydraulic retention times (HRTs 21, 19 and 16 days) were applied to the reactors, in order to evaluate the best operational conditions for the maximization of the biogas yields. The addition of lee to sludge determined a higher biogas production: the best yield obtained was 0.40 Nm3biogas/kgCODfed. Because of the high presence of soluble chemical oxygen demand (COD) and polyphenols in wine lees, the best results in terms of yields and process stability were obtained when applying the lowest of the three organic loading rates tested together with mesophilic conditions.

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