[Elimination of bacteria and viruses by flocculation in treated sewage]

In laboratory experiments the elimination of bacteria and viruses in treated sewage by different flocculants varied between 47.9 and 99.5%. Ferric and aluminum chloride reduced both groups of microorganisms in a greater extent than polyelectrolytes, among those the cationic polymers were better suitable than nonionic and anionic types. With a combination of an anorganic flocculant and an polyelectrolyte no increased effect was seen according to the elimination of the colony number and the number of viruses.