Research on MAP Recovery Conditions using a Fluidized-bed Crystallized Phosphorous Removal System

Abstract

A research was made on phosphorus recovery conditions using a MAP (Magnesium Ammonium Phosphate) method and anaerobically digested desorption liquor (containing ammonia and phosphorus). A fluidized-bed phosphorus removal system was used as the reactor. The main objective of the research was to study the treatment performance, influent phosphorus load and MAP microcrystallization, and phosphorus recovery. One typical result of treatment performance was a treated water T-P of 26.6 mg/L and a phosphorus recovery of 81%, versus a raw water T-P of 142 mg/L. It was found that MAP microcrystallization increased and phosphorus recovery declined along higher influent phosphorus loads. In a case where the mean MAP particle size was 1.5 mm, the recovery was about 80% under an influent phosphorus load of 25 kg-P/m 3 /d, 60% under 40 kg-P/m 3 /d, and reaching a constant recovery rate of about 70 kg-P/m 3 /d at loads exceeding 100 kg-P/m 3 /d. The constant recovery rate was assumed as due to the limit in the growth rate of MAP particles. Study results indicated that effective phosphorus recovery using the fluidized-bed system could be achieved by maintaining the MAP particles in the reactor to be small (1 -2 mm) so that they could be easily handled.

Magnesium ammonium phosphate formation, recovery and its application as valuable resources: a review

“…MAP crystals can grow rapidly in the AAFBR and WAFBR, however, the corresponding energy demand is high . Additionally, large MAP crystals are poorly fluidized in the reactors, thus reducing MAP recovery owing to low surface area . To optimize the size and to enhance separation of the MAP crystals, attempts have been made to seed the reaction with materials such as sand, quartz, silica sands, and preformed MAP powder .…”

Enhancing phosphorus recovery by a new internal recycle seeding MAP reactor

“…Struvite crystals can grow rapidly in the AAFBR and WAFBR, however, the corresponding energy demand is also high (Battistoni et al, 2005). Additionally, large MAP crystals thus formed are not only poorly fluidized in the reactors, but also reduce MAP recovery owing to low surface area (Shimamura et al, 2001). Suzuki et al (2007) and Le Corre et al (2007b) recently inserted stainless steel meshes in the upper section of AAFBR to reduce energy demand and to minimize fines remaining in solution, thereby enhancing phosphorus recovery.…”

Use of a Seeder Reactor to Manage Crystal Growth in the Fluidized Bed Reactor for Phosphorus Recovery

“…The MAP process using the fluidized bed reactor has an advantage that, because new MAP crystals are produced on the MAP crystal surfaces fluidized in the reactor, necessary reactions and solids-liquid separation can take place simultaneously (Graveland et al, 1983;van Dijk and Wilms, 1991). However, in the case of conventional-type fluidized bed reactors, a problem was that the MAP crystals are enlarged in diameter in the course of treatment in the reactor, and, as a result, the reaction surface areas are decreased, causing fluidization to be insufficient and the phosphorus recovery ratio to be decreased (Shimamura, Homma, Watanabe, and Tanaka, 2003). To realize better treatment performance than before, the authors have devised and developed a fluidized bed MAP reactor provided with a seeder reactor intended to maintain high recovery ratios stably for a long period.…”