Efficiency of the anaerobic digestion of amine wastes

Abstract

Laboratory-scale anaerobic degradation of monoethanolamine waste (MEAw) with co-substrate organics was conducted at room temperature and organic loading rates from 0.19 to 5.03 kg COD/m3 day for 486 days in a hybrid digester. 90 % feed COD conversion to methane was obtained at the lower loads and only 45 % at the highest MEA waste/COD ratio (MEAwr) of 0.62 due to inhibition of methanogenesis. Inhibition at comparable loads decreased with time, implying that the culture adapted to the challenging feed. Methane yield was negatively correlated to MEAwr applied and inhibition avoided at MEAwr <0.5. Acetate accumulation implies inhibition of acetoclastic methanogenesis that can be caused by ammonia, a product of MEAw degradation. Moderate total ammonia nitrogen and free ammonia nitrogen accumulation, maximum 2.2 g N/l and 90 mg N/l, respectively suggests, however, that other components of MEAw, and/or degradation products of such, also inhibit methanogenesis, disturbing the digester performance.

Modeling and simulation of lab-scale anaerobic co-digestion of MEA waste

“…Easily degradable organics: starch, glucose, peptone and yeast extract (Wang et al, 2013b) were used to codigest with MEAw in AD. The co-feed substrates were used to provid necessary nutrients, minerals and easily degradable organics for cultivating healthy biomass that can tolerate exposure to toxic and inhibitory chemicals from the MEAw.…”

“…Measurements showed that MEAw COD varied in a range from 450 to 900 mg-COD/g-waste, where MEA COD was assumed to be constant at 44% of the MEAw COD and the rest (56%) was CO COD. According to measurements and calculations, the MEA and nitrogen fractions were around 18 to 30 wt% and 7 -14 wt%, respectively (Wang et al, 2013b). Alkalinity of the applied MEAw was measured to be 0.31 g/g MEAw (CaCO 3 equivalent) and was used to calculate the feed inorganic carbon concentrations in the model (Table. 2).…”

“…A portion of 30 % of the feed MEAw COD was termed as inerts (Table. 1 and 2) based on the conclusion that over 70 % MEAw was degraded in AD (Wang et al, 2013b). These inerts was determined to be not biodegraded and reluctant to biodegradation in the 486 days simulation of semicontinuously fed experimental test.…”

“…A commonly used non-competitive inhibition function was applied in the extended ADM1 to account for the possible toxic effects on acetoclastic methanogenesis due to inhibition from the input MEAw and/or its degradation products (I M EAw , Table. 3) (Wang et al, 2013b(Wang et al, , 2014. Inhibition effect from free ammonia, included in the original ADM1 was the other inhibition factor anticipated in the AD of the MEAw due to the release of inorganic nitrogen.…”

“…MEAw degradation processes and the observed inhibitory effects associated with MEAw degradation (Wang et al, 2013b) were included in ADM1 MEAw. Newly applied kinetic parameters were calibrated based on batch experimental study.…”