Stabilization of combined wastewater sludge: anaerobic processes

1995 ◽  
Vol 22 (2) ◽  
pp. 223-234 ◽  
Author(s):  
B. C. Anderson ◽  
D. S. Mavinic ◽  
J. A. Oleszkiewicz
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Biogas Production ◽  
Reaction Rates ◽  
Operational Efficiency ◽  
Wastewater Sludge ◽  
Biological Nutrient Removal ◽  
Waste Activated Sludge ◽  
Metabolic Reaction ◽  
Mass Reduction

Pilot-scale research was conducted to quantify the effects of stabilizing combined wastewater sludges (primary and biological nutrient removal waste activated sludges), in a common high-rate, single-stage anaerobic digestion operation. Various ratios of primary to waste activated sludge were used, and digester operational efficiency was assessed on the basis of the amount and rate of volatile mass removal, biogas production, and digester supernatant quality. It was found that, depending on the sludge ratio, addition of the biological nutrient removal waste activated sludge decreased digester operational efficiency; for example, almost 20% less volatile mass reduction, up to 25% reduction in metabolic reaction rates, and reduced gas production rates of up to 40% were observed. This was attributed to the presence of the cell membrane encapsulating the fermentable substrates of waste activated sludge, making them less available in the digestion process. It was concluded that, unless some type of pretreatment operation is utilized to liberate these substrates, this type of commonly used codigestion system will be of less benefit to a wastewater treatment plant, especially the smaller facilities which will lose a ready source of power in the form of biogas production, and the full value of the waste activated sludge as a resource will not be realized. Key words: anaerobic sludge digestion, biogas production, biological nutrient removal, biosolids, combined sludge, fermentation, volatile mass reduction.

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

2006 ◽  
Vol 53 (8) ◽  
pp. 149-157 ◽  
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.

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

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.

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

2013 ◽  
Vol 69 (2) ◽  
pp. 269-277 ◽  
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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