Abstract
Chinese dome digesters are usually operated at long hydraulic retention times (HRT) and low influent total solids (TS) concentration because of limited mixing. In this study, a newly optimised Chinese dome digester with a self-agitating mechanism was investigated at a pilot scale (digester volume = 500 L) and compared with a conventional Chinese dome digester (as blank) at 15% influent TS concentration at two retention times (30 and 40 days). The reactors were operated at ambient temperature: 27–33 °C. The average specific methane production, volatile fatty acids and percentage of volatile solids (VS) reduction are 0.16 ± 0.13 and 0.25 ± 0.05L CH4/g VS; 1 ± 0.5 and 0.7 ± 0.3 g/L; and 51 ± 14 and 57 ± 10% at 40 days HRT (day 52–136) for the blank and optimised digester, respectively. At 30 days HRT (day 137–309) the results are 0.19 ± 0.12 and 0.23 ± 0.04 L CH4/g VS; 1.2 ± 0.6 and 0.7 ± 0.3 g/L; and 51 ± 9 and 58 ± 11.6%. Overall, the optimised digester produced 40% more methane than the blank, despite the high loading rates applied. The optimised digester showed superior digestion treatment efficiency and was more stable in terms of VFA concentration than the blank digester, can be therefore operated at high influent TS (15%) concentration.
Highlights
Energy is a vital component needed to improve quality of life, reduce poverty and for the promotion of socio-economic activities
Steady state at an hydraulic retention times (HRT) of 40 days was achieved for the optimised reactor in the period between
The improved Chinese dome digester with two baffles was evaluated in a pilot study and compared with the conventional digester in continuous operation at higher organic loading rates at HRTs of 40 and 30 days
Summary
Energy is a vital component needed to improve quality of life, reduce poverty and for the promotion of socio-economic activities. There is still global uncertainty in the energy sector because of the declining quantity of fossil fuel reserves coupled with crude oil price instability This global energy situation requires alternative or renewable sources of energy and a review of current technologies. It is vital to focus on the sustained economic usage of current finite resources, and to identify and develop renewable technologies and resources that possess the potential to provide for the increasing energy demand. These resources and technologies should be sustainable, clean, globally available and easy to exploit and operate, while contributing towards the materialisation of the United Nations millennium development goals (MDGs) [1].
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