Ion‐exchange softening of human urine to control precipitation

Abstract

A major barrier to widespread implementation of urine source-separation is the uncontrolled precipitation of magnesium (Mg) and calcium (Ca) minerals in waterless urinal plumbing, which results in clogging that increases maintenance requirements. The goal of this research was to investigate the use of ion-exchange softening of undiluted, fresh human urine to control precipitation reactions in hydrolyzed urine. The working hypothesis was that selective removal of Ca and Mg from undiluted, fresh urine by cation exchange resin would decrease the precipitation of Ca and Mg minerals in hydrolyzed urine. Ion-exchange experiments and precipitation experiments were used to investigate ion-exchange reactions in synthetic urine. Cation exchange resin (Amberlite A200C) removed both Ca and Mg from undiluted, fresh urine with a greater affinity for Ca over Mg. Precipitation experiments showed that struvite, MgNH 4 PO 4 Á6H 2 O, and hydroxyapatite, Ca 5 (PO 4 ) 3 (OH), were the dominant minerals in untreated and ion-exchange treated hydrolyzed urine. Overall, ion-exchange softening decreased the mass of solids that would be deposited in the urinal plumbing and increased the phosphate available for nutrient recovery.

Diclofenac removal in urine using strong-base anion exchange polymer resins

“…This is in contrast with other technologies, such as NF membranes that can separate pharmaceuticals but also show almost complete rejection of phosphate and 50% rejection of ammonium . The benefit of employing ion exchange resins in urine treatment is that they are scalable to fit different treatment scenarios, whether it is at the toilet, in decentralized treatment locations, or in one central location (Boyer et al, 2013).…”

Ion-exchange selectivity of diclofenac, ibuprofen, ketoprofen, and naproxen in ureolyzed human urine

“…The urine composition is given in Table 1 and was based on previous work (Landry and Boyer, 2013), with adjustment to maintain nitrogen and inorganic carbon mass balance in fresh and ureolyzed urine (Boyer et al, 2014).…”

Electrochemically Induced Precipitation Enables Fresh Urine Stabilization and Facilitates Source Separation

“…Part of the ammonia can volatilize during collection, storage, treatment, and/or application, resulting in a loss of nitrogen, odor nuisance, and environmental pollution. , Moreover, spontaneous, uncontrolled precipitation of calcium and magnesium salts, resulting from the increase in pH to ∼9.2 and release of ammonia and bicarbonate upon hydrolysis, leads to clogging of pipes in collection systems and a loss of phosphorus (and to a limited extent also nitrogen). − Clogging of pipes by the precipitating salts is a common problem in nonwater urinals and urine-separating toilets, creating odor nuisance, blockages, and leakages and requiring extensive cleaning and maintenance. ,,,− It is believed that this is currently one of the major barriers for the widespread implementation of source separation . The presence of calcium and magnesium can also cause problems during further downstream urine treatment, e.g., through scaling on membranes (used in reverse osmosis, forward osmosis, electrodialysis, (bio)­electrochemical systems, etc.…”

“…2,5,6,8−10 It is believed that this is currently one of the major barriers for the widespread implementation of source separation. 6 The presence of calcium and magnesium can also cause problems during further downstream urine treatment, e.g., through scaling on membranes (used in reverse osmosis, forward osmosis, electrodialysis, (bio)electrochemical systems, etc. ), which reduces the efficiency and requires thorough cleaning.…”