Abstract ▼ AI-Helper

Struvite crystallisation principles have been widely investigated using laboratory, Pilot, and sometimes full scale crystallisation reactors. The principal objective of this study is to nucleate struvite embryos and enlarge them until they reach a resonable size to facilitate recovery and control of...

Struvite crystallisation principles have been widely investigated using laboratory, Pilot, and sometimes full scale crystallisation reactors. The principal objective of this study is to nucleate struvite embryos and enlarge them until they reach a resonable size to facilitate recovery and control of nitrogen and phosphate in a solution To optimise struvite growth and reduce its period, one of the solution often considered is to introduce a seed material in the reacting zone of the crystallisation process so that stuvite nuclei can agglomerate on its surface, producing thus larger struvite particles. Although these factors may be variables, at lease four prerequisites are necessary for effective struvite precipitation ; (1) all constitutions must be at or above appropriate molar concentrations and rations ; (2) pH must be appropriate to allow supersaturated solutions ;(3) the existence of rough surface or seeding materials to provide crystal growth sites ; and mixing energy must be adequate to promote crystal growth. This study focused on shorten the period of the struvite crystal birth and development by adding seed materials. For this purpose, three different seed materials were selected: sand; anthracite; struvite. The experiments have been conducted to evaluate the effect of the particle size of the selected seed material on the struvite crystallization, and to study the mixing effect which can be expressed by the value of G·td (the multiple of mean velocity gradient(G) and mixing time(td)). It was observed in this study that the removal efficiency of ammonia nitrogen increased by 9%, 11%, and 20% for sand, anthracite, and struvite added as the seed material, respectivley. This indicated that the struvite crystallization efficiency had a close correlation with the specific surface area of the seed particle. It was found that when struvite was selected as the seed material, the struvite crystallization proceeded at lower G·td value as compared with other seed materials. This observation implied that the secondary crystal birth would be dominated in this reaction. It was concluded in this study that the particle size was not a significant factor on the struvite crystallization, while the Gㆍtd value was a considerably important factor in terms of the theory of the struvite crystal birth.