Abstract
The impact of nutrients on the environment, particularly on water bodies, has led to extensive studies for nutrient control. Within this context, studies have been focused on source separation of human urine from domestic wastewater to recover nutrients. Potassium is one of the most important components of human urine. However, data on potassium removal or recovery are quite limited except for some indirect information through use of zeolites for mostly ammonia removal. Potassium struvite or K-struvite (MgKPO4·6H2O) is a sparingly soluble salt belonging to the struvite family that has the potential of being used as a means of potassium and phosphate recovery from segregated human urine. This study aimed to assess the potential of K-struvite precipitation for control and recovery of nutrients. Within this context, K-struvite precipitation experiments were performed on both synthetically prepared samples and synthetic human urine solution to determine effect of operation parameters i.e., pH, stoichiometry, and temperature on potassium recovery performance. Results indicated that process performance as well as type of solid phases co-precipitated with K-struvite were closely related to initial potassium concentration, pH, and reaction stoichiometry. At pH 10, the potassium recovery efficiency was maximized up to 87% by application of 100% excess dose of Mg and P for both synthetic samples and synthetic human urine solution. On the other hand, application of excess dose of K did not provide any improvement in K recovery efficiency. The effect of temperature on solubility of K-struvite was insignificant at the temperature range of 24–90 °C. Solid phase analyses confirmed that K-struvite was co-precipitated with either Mg3(PO4)2, MgNaPO4·7H2O, or MgHPO4·7H2O depending on pH and stoichiometry instead of a pure compound.
Highlights
Magnesium ammonium phosphate (MgNH4 PO4 ·6H2 O; MAP), a member of the struvite family, has been used with success for nitrogen removal and as a means of nutrient recovery
MAP precipitation has a wide area of application such as source separated urine [1,2,3,4], anaerobic treatment discharge [5], and a number of industrial wastewaters, including leather tanning [6,7,8,9,10], slaughterhouse [11], animal husbandries [12], textile printing [13], landfill leachate [14,15,16], and membrane process concentrates [17]
The struvite family of compounds includes magnesium potassium phosphate (K-struvite), a sparingly soluble salt, which has been considered as a potential method for potassium removal and recovery
Summary
Magnesium ammonium phosphate (MgNH4 PO4 ·6H2 O; MAP), a member of the struvite family, has been used with success for nitrogen removal and as a means of nutrient recovery. MAP precipitation has a wide area of application such as source separated urine [1,2,3,4], anaerobic treatment discharge [5], and a number of industrial wastewaters, including leather tanning [6,7,8,9,10], slaughterhouse [11], animal husbandries [12], textile printing [13], landfill leachate [14,15,16], and membrane process concentrates [17]. The first reason is its low solubility with respect to K-struvite and the second is the two major co-precipitating solids (Mg(OH)
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