Four CW-MFCs, 0.7 m in height with a square cross section of
0.17 0.17 m, were built as described by Table 1 and Fig. 1. Each
system contained 8.8 ± 0.21 kg of dewatered alum sludge with an
average particle size of 15–30 mm. The initial porosity of the alum
sludge layers was 0.41.