Table 1.

Biochemical and electrochemical performance during stable operation of microbial fuel cells (MFCs) operating at pH 7.0, 5.5, or 4.0

MFC	COD removal efficiencya (%)	Total concentration of organic acidsb (mM)	J csc (mA m−2)	P dmax (mW m−2)	C.E. e (%)
pH 7.0	57.8 ± 8.82	0.47	410 ± 176	381 ± 155	34.0 ± 9.18
pH 5.5	57.1 ± 12.8	1.19	253 ± 52.1	147 ± 18.3	12.1 ± 3.11
pH 4.0	56.9 ± 3.61	1.80	40.7 ± 14.6	5.14 ± 1.64	1.06 ± 1.43

^aChemical oxygen demand (COD) removal efficiency (%) was calculated as follows: 100 × [COD concentration in synthetic wastewater (mg-COD L⁻¹)–COD concentration in broth (mg-COD L⁻¹)]/COD concentration in synthetic wastewater (mg-COD L⁻¹)

^bSum of the organic acid concentrations in the suspended fractions of samples collected after 30 days’ operation at pH 7.0, pH 5.5, or pH 4.0

^cShort-circuit current density [J _sc (mA m⁻²)] was determined from the power density curves

^dMaximum power density [P _max (mW m⁻²)] was obtained from the peak in the power density curves

^eCoulombic efficiency (C.E.) was calculated based on the COD removal (CODin–CODout) and the measured current, using 1 g of COD = 0.125 mol of electrons, and 1 A = 5.39 × 10²³ electrons per day