Water Processor Assembly: Multi-Stage Recycling

Feed Water

Contaminant load (TOC in) 60 mg/L

Flow rate 150 L/hr

Catalytic Reactor

Reactor temperature 140 °C

Quality Gate

—

Final TOC

— mg/L

Conductivity

— µS/cm

After multifiltration

— mg/L

After catalytic ox.

— mg/L

Resin saturation

— %

Stage residence

— s

Stages

Multifiltration beds — particulates & large organics Catalytic reactor — oxidises dissolved organics Ion-exchange bed — deionises, adsorbs residual TOC Mineral injector — restores Ca/Mg for potability

How it works

Real spacecraft water recovery (the ISS Water Processor Assembly) pushes reclaimed water through a fixed train of stages, each removing a fraction of what remains rather than a fixed amount:

C_out = C_in · (1 − η_stage)
η_MF  = 1 − exp(−k_MF · τ_MF)          (contact-time removal)
τ     = V_stage / flow rate             (residence time)
k_CR(T) = A · exp(−Ea / (R·T))          (Arrhenius rate constant)
η_CR  = 1 − exp(−k_CR(T) · τ_CR)

The multifiltration beds and catalytic reactor both follow first-order contact-time kinetics: more flow means less residence time τ and a lower removal fraction η, so pushing more water through faster trades throughput for water quality. The catalytic reactor's oxidation rate additionally obeys the Arrhenius law — raising the temperature slider exponentially speeds up organic breakdown.

The ion-exchange bed adsorbs the last of the total organic carbon (TOC) and deionises the stream, but its resin has a finite capacity. As contaminant mass keeps flowing through, the bed saturates along a breakthrough curve and its efficiency decays toward zero — exactly like a real resin bed needing regeneration. The Regenerate button resets saturation to 0%.

A mineral injector then adds back calcium and magnesium (ion exchange strips minerals along with contaminants), targeting a conductivity band that makes the water taste and behave like drinking water rather than distilled water. The quality gate passes only when both final TOC ≤ 3 mg/L (the NASA potable-reuse analog used here) and conductivity lands inside the target band — a resin bed near saturation can pass TOC but drift conductivity out of range.

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