Characterisation of waste solutions to determine optimised P recovery

A number of waste solutions from processes operating in Western Australia (anaerobic digester supernatants, facultative lagoon treated piggery and abattoir waste effluents) were characterised chemically and by automated titration to determine acid-base characteristics. Titrations were over the pH range 2-12 or less. All waste solutions were excess molar ratios of NH3-N to PO4-P (5:1 up to 20:1). The amounts of acid or base reagent required for each waste solution type were in the sequence anaerobic digestor supernatant>>piggery effluent>abattoir effluent. The most efficient removal of N and P of the field samples considered is from piggery effluent. The results indicate conditions for optmising the removal of N and P by precipitation (predominantly struvite) as well as the way forward in determining the full scope of N and P waste streams for which recycling by precipitation (either magnesium or calcium based salts) may be feasible.