A. Musacco

Phosphate removal in anaerobic liquors by struvite crystallization without addition of chemicals. Preliminary results.

Abstract The feasibility of phosphate removal from the supernatant of anaerobically digested sludge by struvite (MAP, MgNH 4 PO 4 ) crystallization in a fluidized-bed reactor (FBR) was studied. Quartz sand was used as seed material. Three successive steps were investigated to highlight the process: 1, natural aging of the supernatant, with phosphate concentrations in the range 18–164 mg/l, which gave good crystallization of struvite within 3 days; 2, the inhibiting effect of Mg and bicarbonate ions on hydroxyapatite (HAP, Ca 5 OH(PO 4 ) 3 ) formation, which leads to struvite formation under supersaturation conditions; and 3, phosphate removal via the process of complete crystallization on the seed material, and which is obtained by means of external continuous aeration. All runs were performed without the addition of chemicals.

Thermophilic semi‐dry anaerobic digestion process of the organic fraction of municipal solid waste during transient conditions

Abstract The ability to manage a biological process is linked not only to the knowledge of performance in stationary conditions. Accordingly, here, the behaviour of an anaerobic digester during transition states is reported and discussed. The paper deals with the anaerobic digestion of the mechanically sorted organic fraction of municipal solid waste under thermophilic (55°C)semi‐dry conditions (digester feed total solids=20–25%). The complete experimentation simulates a progressive increase of process capacity through variation of the operative conditions applied. In particular, changes of organic loading rate (OLR) from 4 to 8 KgTVSf (m‐3d‐1), hydraulic retention time (HRT) from 1 to 3 days, T°C up to 10°C and digester feed total solids (TS feed) from 20 to 100 g Kg‐1 are considered. Perturbations during stationary conditions are also discussed. After a complete monitoring of the digester it is concluded that thermophilic semi‐dry anaerobic digestion is a robust process, able to cope with the mentioned ...