It seems that detergents are
the most prominent responsible for oxygen consumption in car
wash wastewater (Boussu et al., 2007). In Campaign 1, the BOD5
concentration showed a dependence on time and build-up (Fig. 3
– see its R2 and fitting parameter – b1), even with a feed inlet of
40% of fresh water. Results may be explained by the increase of
the BOD5 dissolved fraction (Odegaard, 2004). Wastewater BOD5
concentration in Campaign 2 (Fig. 5) did not show build-up. These
results can be explained by the oxidation skill of the chlorination
process (Metcalf and Eddy, 2006).