Water Science and Technology vol:67 issue:7 pages:1425-1433
Anaerobic digestion yields effluents rich in ammonium and phosphate and poor in biodegradable organic carbon, thereby making them less suitable for conventional biological nitrogen and phosphorus removal. In addition, the demand for fertilizers is increasing, energy prices are rising and global phosphate reserves are declining. This requires both changes in wastewater treatment technologies and implementation of new processes. In this contribution a description is given of the combination of an ureolytic phosphate precipitation and an autotrophic nitrogen removal (ANR) process on the anaerobic effluent of a potato processing company. The results obtained show that it is possible to recover phosphate as struvite and to remove the nitrogen with the ANR process. The ANR process was performed in either one or in two reactors (partial nitritation + Anammox). The one reactor (OLAND) configuration operated stable when the DO (dissolved oxygen) was kept between 0.1 and 0.35 mg.L-1. The best results for the two reactor system were obtained when part of the effluent of the ureolytic phosphate precipitation was fully nitrified in a nitritation reactor and mixed in a 3:5 volumetric ratio with untreated ammonium containing effluent. A phosphate and nitrogen removal efficiency of respectively 83±1 % and of 86±7 % was observed during this experiment.