Reduced use of phosphorus and water in sequential dark fermentation and anaerobic digestion of wheat straw and the application of ensiled steam-pretreated lucerne as a macronutrient provider in anaerobic digestion

Table 5 Operational variables for the AD experiments in UASB reactors

	CH-1, lower OLR	CH-DFE, lower OLR	CH-DFE, higher OLR
OLR, COD (g/L/day)	5.4 ± 0.5	5.4 ± 0.5	8.5 ± 0.2
HRT (day)	5.9 ± 0.3	5.5 ± 0.5	3.8 ± 1.3
Duration (day)	17.0 ± 2.0	19 ± 0	13.3 ± 4
Methane yield per COD fed, (mL/g)	268 ± 7	262 ± 17	265 ± 15
Methane yield per COD fed, % of maximum	76.7 ± 2.2	74.8 ± 4.7	75.6 ± 4.3
Effluent COD (g/L)^a	3.6^b	3.8 ± 0.3	5.1 ± 0.6
COD removal (%)^a	89.2^b	88.7 ± 5.9	84.8 ± 1.9
Effluent pH^a	6.84^b	7.22 ± 0.02	7.20 ± 0.03
Effluent acetic acid^a (g/L)	0.11^b	0.21 ± 0.07	0.23 ± 0.13
Effluent propionic acid^a (g/L)	0.11^b	0.05 ± 0.07	0.27 ± 0.14
Effluent fatty acids, total^{a, c} (g/L)	0.22^b	0.26 ± 0.14	0.60 ± 0.26
Partial alkalinity^a in effluent (g/L)	1.2^b	2.5 ± 0.0	1.8 ± 0.2
Total alkalinity^a in effluent (g/L)	1.3^b	3.0 ± 0.1	2.7 ± 0.0

COD chemical oxygen demand, HRT hydraulic retention time, OLR organic loading rate
^aAfter running the experiment for a duration corresponding to three times the HRT
^bValue for one reactor, data missing for the other
^cVolatile fatty acids with 1–5 carbons and lactic acid

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