Volumes greater than 20 l are gener

Volumes greater than 20 l are generally filtered at 1 μm and treated with acid (e.g.hydrochloric acid at pH 3, neutralization after 24 h with sodium carbonate) or chlorine (e.g. 1-2 mg.l-1, incubation for 24 h without aeration, followed by aeration for 2-3 h to remove residual chlorine, addition of sodium thiosulfate to neutralize chlorine may be necessary if aeration fails to strip the chlorine).