Thesis Defence: Ammonia Stripping of Hydrothermal Liquefaction Aqueous Phase from Municipal Sludge for Anaerobic Co-Digestion Pretreatment and Ammonia Recovery
April 30 at 9:30 am - 1:30 pm
Alison Cox, supervised by Dr. Cigdem Eskicioglu, will defend their thesis titled “Ammonia Stripping of Hydrothermal Liquefaction Aqueous Phase from Municipal Sludge for Anaerobic Co-Digestion Pretreatment and Ammonia Recovery” in partial fulfillment of the requirements for the degree of Master of Applied Science in Civil Engineering.
An abstract for Alison Cox’s thesis is included below.
Defences are open to all members of the campus community as well as the general public. Please email cigdem.eskicioglu@ubc.ca to receive the Zoom link for this defence.
ABSTRACT
Hydrothermal Liquefaction (HTL) is a thermo-chemical method of processing wastewater treatment plant solid waste that could be preferential over the currently establish method of anaerobic digestion because of the byproducts it produces. Instead of biosolids which can be costly to transport off-site, the effluent can be separated into biocrude which can be refined into fuel, hydrochar that can be used for adsorption applications and HTL aqueous. HTL aqueous is considered the only waste stream of this process as it is high in ammonia, phenolics and nitrogen heterocyclic compounds that can inhibit biological processes such as anaerobic if they are used for disposal.
Ammonia stripping was tested for pretreatment of HTL aqueous and recovering ammonia. Seven stripping reactor conditions were run, and the best results were seen at 85°C, a pH of 9.3 and 500 mL/min air flow rate. This case achieved ammonia removal of 99.5 ± 0.1% and total phenolic compounds removal of 32 ± 1% in 4 hours. The ammonia stripping was coupled with acid adsorption to produce an ammonium sulphate salt with value as fertilizer. The ideal ammonia stripping conditions produced a salt with a purity of 98.0 ± 0.05% and represented an ammonia recovery of 73.9 ± 0.04%.
Bench-scale thermophilic anaerobic co-digestion of HTL aqueous with wastewater treatment plant solid waste found that up to 12% of the digester feed can come from HTL aqueous without inhibition if pretreated with ammonia stripping. The digester fed 13% non-treated HTL aqueous showed inhibition. Under mesophilic conditions, anaerobic co-digestion was successful for untreated and pretreated HTL aqueous even with 24% and 22% of feed provided by HTL aqueous, respectively.
