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Increasing capacity of an anaerobic sludge digester through FNA pre-treatment of thickened waste activated sludge
- Source :
- Water Research. 149:406-413
- Publication Year :
- 2019
- Publisher :
- Elsevier BV, 2019.
-
Abstract
- Free nitrous acid (FNA) pre-treatment has been previously demonstrated to be effective in enhancing methane production and volatile solids (VS) destruction in the anaerobic digestion of waste activated sludge for an equivalent hydraulic retention time (HRT). We hypothesise that, due to enhancement of hydrolysis kinetics, FNA pre-treatment will also allow reduction in the HRT while retaining performance. This would allow for improvement of capacity constrained digesters. Two anaerobic sludge digesters (control-experiment) were fed with the same thickened waste activated sludge (TWAS) from a full-scale plant for 6 months. With 24 h pre-treatment of TWAS at an FNA concentration of 6.1 mgN/L (NO2-N = 250 mg/L, pH = 5.0, T = 25 °C), the HRT for the experimental anaerobic digester was progressively reduced from 15 days to 12 days and then to 7.5 days. In comparison, the control reactor was operated at a constant HRT of 15 days, representing typical loading conditions. With the shortened HRTs, the experimental AD reactor achieved VS destruction at 36.9 ± 0.8% (12 days) and 36.8 ± 1.0% (7.5 days), representing 30–40% relative increase in comparison to the control reactor (at 26.5 ± 0.8% and 28.3 ± 0.7%, respectively, in the same two periods). This was supported by a similar (31–35%) increase in the methane production per unit of VS fed. The volumetric methane production rate of the experimental digester was increased by 165% at HRT of 7.5 days compared with the control digester at HRT of 15 days. The results demonstrated that FNA pre-treatment of TWAS can substantially increase the capacity of an anaerobic sludge digester, with a highly favourable economic outcome.
- Subjects :
- Pre treatment
Environmental Engineering
Hydraulic retention time
0208 environmental biotechnology
Nitrous Acid
02 engineering and technology
010501 environmental sciences
Waste Disposal, Fluid
01 natural sciences
Bioreactors
Animal science
Hydrolysis kinetics
Anaerobiosis
Methane production
Waste Management and Disposal
0105 earth and related environmental sciences
Water Science and Technology
Civil and Structural Engineering
Sewage
Anaerobic sludge
Chemistry
Hydrolysis
Ecological Modeling
Pollution
020801 environmental engineering
Anaerobic digestion
Activated sludge
Methane
Anaerobic exercise
Subjects
Details
- ISSN :
- 00431354
- Volume :
- 149
- Database :
- OpenAIRE
- Journal :
- Water Research
- Accession number :
- edsair.doi.dedup.....d25b25b9b8e0505053e961e367418990