Iron oxide red wastewater is a kind of typical acid wastewater.
About 15 tons of wastewater with high concentration of Fe2þ and suspended solids (SS), high chroma and low pH is discharged per ton of iron oxide red production. 
This wastewater can seriously decrease pH of receiving waterbody leading to the damage of acidebase equilibrium that is important for growth of aquatic organism (Akcil and Koldas, 2006; Peppas et al., 2000).
 In addition, excess Fe2þ will change the appearance of water. 
It can reduce the intensity of light and then hinder the photosynthesis of aquatic plant (Zhou et al., 2008). 
So it is necessary to manage this wastewater appropriately to avoid harm to receiving environment.