Low-Temperature (10°C) Anaerobic Digestion of Dilute Dairy Wastewater in an EGSB Bioreactor: Microbial Community Structure, Population Dynamics, and Kinetics of Methanogenic Populations

Table 1

Operational and performance characteristics during phases I to VI of the bioreactor operation.

Phases	PI	PII	PIII	PIV	PV	PVI
Days	0–146	147–230	231–265	266–294	295–322	323–335
HRT^a	48	24	18	12	12	12
OLR^b	0.5	1.0	1.3	2.0	2.0/5.0	2.0
SLR^d	0.03	n.d.	n.d.	n.d.	n.d.	0.14
𝑄^e	0.0036	0.0072	0.0096	0.0144	0.0144	0.0144
𝑉^fup	1.93	1.95	1.96	1.99	1.99	1.99
𝐶𝑠^g	1.0	1.0	1.0	1.0	1.0/2.5	1.0
CODRE^c	88±6	89±4	90±2	86±6	74±11	84±4
CH^h4theo	0.151	0.277	0.328	0.706	1.310/3.276	0.806
TVFA^i	54	91	97	178	466	184
VFA: COD ratio	0.45	0.83	0.97	1.00	0.76	1.00

aHydraulic retention time (h).
^bOrganic loading rate (kg COD m⁻³ d⁻¹).
^cChemical oxygen demand removal efficiency (%), where values are the phases mean (±s.d.).
^dSludge loading rate (kg COD kg [VSS]⁻¹ d⁻¹); n.d.: not determined.
^e𝑄 flow rate (m³ d⁻¹).
^f𝑉_up upflow velocity (m h⁻¹).
^g𝐶_𝑠 substrate concentration (kg COD m⁻³).
^hCH_4theo theoretical methane production (l CH₄ d⁻¹). Calculated stoichiometrically assuming that 1 g COD removed produced 0.350 L of CH₄.
ⁱTotal Volatile Fatty Acids (mg COD L⁻¹).