How well do 46 full-scale Danish anaerobic digesters at wastewater treatment plants perform?

Martin Hjorth Andersen, Rasmus Hansen Kirkegaard, Per Halkjær Nielsen

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Abstrakt

Background. Anaerobic digestion (AD) is a key technology for a sustainable future and is employed worldwide to produce biogas and degrade organic wastes. The strong emphasis on circular economy at Danish wastewater treatment plants (WWTPs) has had the consequence that many plants utilise AD to treat primary and secondary sludge. Although AD has been extensively studied in lab- and pilot-scale, studies describing full-scale operation of AD at WWTPs are few. An improved understanding of how full-scale ADs are operated and how they perform is important for future optimisation of design and operation.

Research question. The main objective was to learn how the Danish ADs treating wastewater sludge are operated, and investigate whether correlations between performance and microbiology could be identified.

Methods. We conducted a six-year survey of operational data from 46 ADs at 22 Danish WWTPs. Data included feeding sludge flows, gas yield, and operational parameters such as volatile fatty acids, alkalinity and ammonium. The microbial communities (archaea and bacteria) were analysed using 16S rRNA gene amplicon sequencing of all 400+ samples.

Main results. Unexpected difficulties arose when comparing the different plants since the chemical parameters analysed, analytical methods and sensors used, and possibilities for accessing data, varied a lot. The survey proved that there is need for standardisation of chemical analyses and equipment. Data suggested that, in most cases, thermal hydrolysis pre-treatment and thermophilic operating conditions were more efficient than mesophilic single-phase digesters. The lack of standardisation between WWTPs made identification of correlations between performance and microbiology difficult. The bacterial community was more diverse in mesophilic digesters and methanogenesis occurred predominantly through the acetoclastic pathway, while the hydrogenotrophic pathway was prevalent in thermophilic.

Take-home messages. Further research is needed to optimise methane yield and sludge degradation, which are essential parameters for achieving a good circular economy at Danish WWTPs.
OriginalsprogEngelsk
Publikationsdato2017
StatusUdgivet - 2017
BegivenhedMicrobiological Methods for Waste & Water Ressource Recovery - TU Delft, Delft, Holland
Varighed: 18 maj 201719 maj 2017

Konference

KonferenceMicrobiological Methods for Waste & Water Ressource Recovery
LokationTU Delft
LandHolland
ByDelft
Periode18/05/201719/05/2017

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