Evaluation of a low‐cost magnesium product for phosphorus recovery by struvite crystallization

Abstract

Background The development of a cost‐effective process of struvite crystallization requires the selection of appropriate sources of alkali and magnesium. In this study, the effectiveness of two industrial grade products, MgO and Mg(OH)2, as magnesium and alkali sources to recover phosphorus as struvite were investigated and compared in a first set of experiments. Subsequently, the use of industrial Mg(OH)2 was compared in two different struvite crystallization systems, an upflow fluidized bed reactor (FBR) and a continuous stirred tank reactor (CSTR) coupled to a settler tank. Results At the same operational conditions, the consumption of MgO was higher than Mg(OH)2 consumption. Moreover, industrial Mg(OH)2 consumption for FBR and the CSTR operation was 1.6 and 1.1 1 mol Mg added mol‐1 P precipitated, respectively. This difference was caused by the high mixing intensity and the higher contact time between the Mg(OH)2 slurry and the influent in the CSTR, favouring the conversion. Conclusions Both industrial grade magnesium products are promising options for struvite crystallization. However, Mg(OH)2 was more effective than the starting material, MgO, to recover phosphorus. Struvite crystallization by adding an industrial grade Mg(OH)2 could be economically viable with regard to alternative physico‐chemical P removal processes using metal salts, increasing the attractiveness of this P recovery process. © 2017 Society of Chemical Industry

Effect of the stirring speed on the struvite formation using the centrate from a WWTP

“…High stoichiometric NH 4 + : PO 4 3ratio (≈ 4.7) favor the struvite precipitation [36]; however, the mass of crystals above the maximum expected for struvite at stirred speeds between 200 rpm and 500 rpm ( Figure 3) may be due to the formation of other precipitates not detected in the XRD, since the agitation possibly favours other reactions.…”

“…The Ca 2+ , Mg 2+ and N removal from the soluble phase was between 2.73 and 4.55 mmol Ca 2+ , between 11.0 and 13.8 mmol Mg 2+ and between 9.9 and 16.9 mmol N-NH 4 + . The Ca 2+ removal may be due to the formation of calcium [29,36].…”

Acidification and alkali precipitation for phosphorus recovery from municipal digested sludge

“…However, the addition of MgCl 2 or MgO is required because magnesium is the limiting element in most sewage. Using magnesium salts is costly, and the slow dissolution of MgO causes higher HRT (Crutchik et al, 2018; Desmidt et al, 2015; Law & Pagilla, 2018). Phosphorus recovery by precipitation with Ca compounds is a low‐cost and easier method in alkaline solutions (Hermassi et al, 2015).…”

Precipitação De Estruvita a Partir De Efluente Misto: Revisão Da Literatura

“…Inicialmente, os estudos sobre estruvita concentravam-se em estratégias para evitar sua precipitação, devido ao entupimento de tubulações por cristais de estruvita, o que reduzia a dos sistemas de tratamento de efluentes (KATAKI et al, 2016). No entanto, atualmente, há uma série de pesquisas voltadas para a recuperação de nutrientes, como nitrogênio e fósforo (ABEL-DENEE et al, 2018;AMINI et al, 2017;CRUTCHIK et al, 2018;HERMASSI et al, 2018;WANG et al, 2016;ZIN;TIWARI;KIM, 2020), ou exclusivamente fósforo (AGRAWAL et al, 2018;CRUTCHIK et al, 2017;HUANG et al, 2017;LU et al, 2017;WANG et al, 2020;WARD et al, 2018;WU et al, 2018). Além disso, são encontrados estudos que analisam a formação da estruvita (AGRAWAL; GUEST; CUSICK, 2018) ou o desempenho dos reatores utilizados (AGUADO et al, 2019).…”