Phosphorus released in lakes due to agricultural water runoff causes eutrophication, deteriorating water quality and harming ecosystems. Two adsorbents were studied for the removal of phosphate from water: plaster of Paris powder and hydrogel beads produced using alginate, carboxymethylcellulose, and aluminum. The reaction kinetics, adsorption capacity, and ability to desorb were compared. Sorption of phosphate with either plaster of Paris or hydrogel beads was well described by the Langmuir model. In deionized water, hydrogel beads had a maximum sorption capacity of 90.5 mg  PO43- /g dry bead with an equilibration time of approximately 24 hr. Monovalent anions (e.g., chloride) did not affect phosphorus sorption onto hydrogel beads, whereas divalent anions (e.g., sulfate) hindered sorption. In deionized water, plaster of Paris (POP) powder has a maximum capacity of 1.52 mg  PO43- /g with an equilibrium time of less than 10 min. Sorbents can potentially be reused following phosphate desorption, and desorbed phosphate may be reused as fertilizer. At pH = 9.5, hydrogel beads desorbed up to 60% of the original amount of phosphate sorbed and lower amounts at lower pH. At pH = 2, POP powder desorbed only 35% of the initial phosphate sorbed, and desorption decreased with increasing pH. Practitioner points The maximum sorption capacity of plaster of Paris is 1.52 mg  PO43- /g. The maximum sorption capacity of hydrogel beads is 90.5 mg  PO43- /g. Monovalent anions do not affect phosphorus sorption, and divalent anions hinder it by ≈36%. Sorption is well described by Langmuir isotherms (R2 > 0.98). Hydrogel beads desorb 60% of phosphorus at pH = 9, possibly allowing phosphorus reuse.

Previous theoretical and experimental work on balancing rotating systems without interrupting operation is extended to multi-disc flexible shaft systems with two balancing planes.

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A calcium-rich rock (limestone) was used as adsorbent to remove phosphorus from water. Phosphorus could be subsequently desorbed from limestone at pH = 4, and potentially reused as fertilizer following pH neutralization. Sorption of phosphorus onto limestone was not affected by 100 mM KCl or by the nitrogen present in a commercial fertilizer, but it was hindered by 100 mM NaCl, urea and river water. The phosphorus removed was however never below ∼9 mg P/kg rock, and it increased with increasing phosphorus concentrations in water. Phosphorus removal increased with 100 mM CaCl2 at neutral pH, likely due to its precipitation. Mixing for 30 s enhanced phosphorus sorption. Desorption of phosphorus from limestone following sorption in deionized water was ∼50%, ∼22%, and ∼11% at pH = 4, pH = 7, and pH = 11, respectively. Phosphorus desorption was lower when sorption had occurred in river water than in deionized water or in 100 mM urea.