Assessment of biogas potential for aerobic granular sludge and activated sludge at Gryaab
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Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Infrastructure and environmental engineering (MPIEE), MSc
Publicerad
2023
Författare
ARITA, JOHANNA
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The population of the Gothenburg region is expected to increase in the coming years, which will lead
to increasing flows into the Rya Wastewater Treatment Plant (WWTP). Therefore, the treatment
capacity will be increased by building a parallel WWTP on new land. One of the wastewater treatment
technologies considered to be implemented is aerobic granular sludge (AGS). AGS is a promising
biotechnology that has demonstrated several advantages when compared to the conventional activated
sludge (CAS) process such as lower energy usage and area requirements. A broader understanding of
the biochemical methane potential (BMP) of the two different types of sludge produced by the AGS
process, waste aerobic granular sludge (WAGS) and mixed aerobic granular sludge (Mixed AGS), is
necessary as there are few previous studies available. The BMPs of these two AGS-sludge fractions
were compared to primary sludge (PS) and waste activated sludge (WAS). Additionally, the effect of
primary clarification on the BMP of the AGS-sludges was elucidated by sampling the AGS-sludge
when the pilot plant was fed with incoming or pre-clarified wastewater. The results indicated that PS
had the highest BMP (365 ± 7 ml CH4/gVS) of all the sludge fractions. From all the AGS-sludge
fractions the highest BMP (223 ± 19 ml CH4/gVS) was obtained from the WAGS-sludge when the pilot
plant was fed with incoming wastewater without primary clarification. This value was 1.64 times lower
than the BMP of the PS. The BMP of the WAGS-sludge was affected by primary clarification as a
higher BMP result (223 ± 19 ml CH4/gVS) was observed when the pilot was fed with incoming
wastewater when compared to its BMP when the pilot was fed with pre-clarified water (185 ± 10 ml
CH4/gVS). The BMPs of the mixed AGS-sludge were not affected by primary clarification (213 ± 19
ml CH4/gVS with pre-settled wastewater and 208 ± 15 ml CH4/gVS with incoming wastewater). Mixed
AGS-sludge was the substrate that took the most time in being digested, taking 21 days to reach a daily
production of <1% of the accumulated volume of CH4. The results showed that AGS-sludges are
biodegradable, however their biodegradability was lower in comparison to WAS and PS.
Beskrivning
Ämne/nyckelord
aerobic granular sludge, biogas, biochemical methane potential, biodegradability, activated sludge, Gothenburg