Phosphorus removal from anaerobic supernatants: Start-up and steady-state conditions of a fluidized bed reactor full-scale plant

The paper deals with the full-scale application of the struvite crystallization process (SCP) used for phosphorus recovery. In this study this kind of technology and its core, a fluidized bed reactor (FBR), have been used for the treatment of anaerobic supernatants with low phosphate concentrations. Covering four different runs, the experimental results are referred to both start-up and steady-state periods, while the discussion is focused both on the optimal operating conditions and on the performances obtained. All four start-up periods were performed using the same methodology that can be considered suitable also for starting up every industrial SCP application. In fact, in working with these operating conditions, the time needed to obtain the right amount of well fluidized bed was 6-8 days. During the steady-state conditions, 1-8 m(3) h(-1) supernatants were treated and high phosphorus removal by crystallization (58-72%) was obtained; moreover, these values were very close to the mathematical model previsions (60-69%). The recovered material was mainly composed of struvite (average 95%). Finally, the used operating conditions can be considered suitable for managing industrial plants.