2002 · 10 citations · 0 references
Introductory laboratory experiments with sludge fractionation using acid and base have been carried out at the division of Water Resources Engineering, Royal Institute of Technology (KTH) in Stockholm, Sweden. The release of total phosphorus at different pH-values was analysed and the amount of chemicals needed was measured to reach a wanted pH-value. The decrease of suspended solids was analysed. The results indicate a high release of phosphorus at low pH-values with only use of acid, without heat or pressure. Digested sludge contains a lot of phosphorus, which is released with chemicals. Acid addition seems to be more useful for total phosphorus release in digested sludge than use of base. The introductory studies show that the amount of total phosphorus release is doubled for each unit drop in pH-value. There is a connection between the amount of chemicals needed to reach a wanted pH-value. The higher or lower pH-value, the more chemicals are needed. The decrease in suspended solids did not show any significant results in short-time experiments.