Equipment · Ion Exchange
De-Mineralisation Plant
Softening swaps one salt for another. De-mineralisation takes the salts out altogether — and puts nothing back but water.
Two-bed DM + mixed bed
Boiler feed · steam generation
Plug & play skid
Auto regeneration
De-ionisation is the answer when production needs pure water free of any ionic load, generated close to the point of use — proximity matters, because DI water degrades rapidly once it is exposed to the environment.
Ahura Aqua designs, manufactures and supports two-bed DM plants and single-vessel mixed-bed polishers as pre-assembled, plug-and-play, standardised units — consistent high-purity flow, with automation that takes the regeneration schedule off the operator.
Outlet Conductivity
< 1 – 5
µS/cm, two-bed DM
With Mixed Bed Polish
< 0.1
µS/cm achievable
Working Pressure
45 psi
tested at 75 psi
Line of Treatment
DM stages highlighted
A DM plant is installed downstream of PSF and ACF — resin is expensive and easily fouled, so it never sees raw water. The mixed bed sits last, as a polisher on an already de-mineralised stream.
Application Spotlight
De-Mineralisation for Steam Generation
High-pressure boilers demand feed water with virtually no dissolved salts. Across petrochemical plants, refineries and power generation, de-mineralised water is the standard boiler-feed make-up — eliminating the scale, corrosion and turbine carry-over that softening alone cannot prevent.
How Ion Exchange Works
Two columns, in series
Every dissolved salt in water exists as a cation and an anion. Strip both and what is left is water — which is why de-mineralisation always takes two exchange stages.
CATION · SAC
Cation Exchange
Removes
Na⁺
K⁺
Ca²⁺
Mg²⁺
Fe²⁺
Replaced by
H⁺
across the strong acid cation resin
The first column. Every positively charged ion in the feed is exchanged for hydrogen, which turns the dissolved salts into their corresponding acids — the outlet is acidic and low pH by design. Regenerated with hydrochloric acid.
ANION · SBA
Anion Exchange
Removes
Cl⁻
HCO₃⁻
NO₃⁻
CO₃²⁻
SO₄²⁻
Replaced by
OH⁻
across the strong base anion resin
The second column takes the acid stream from the cation vessel and exchanges every anion for hydroxide. Strong base resin also removes silica and carbon dioxide, which weak base resin does not. Regenerated with caustic soda.
H⁺ + OH⁻ → H₂O
The liberated ions recombine to form pure de-mineralised water — nothing is added to the stream
The Regeneration Cycle
Service → exhaustion → acid + caustic → rinse
Resin capacity is finite. A DM plant is therefore not a filter you install and forget — it is a four-stage cycle, and the automation is what keeps that cycle off the operator’s daily list.
STEP 01
Service
Feed flows down through the bed. Target ions bind to the resin and H⁺ or OH⁻ leaves with the water — outlet conductivity is the live measure of how well it is working.
STEP 02
Exhaustion
Capacity is finite. As the bed fills, treated conductivity and silica start to climb — that drift, not a clock, is the honest signal to take the vessel offline.
STEP 03
Regeneration
The bed is backwashed, then flooded with regenerant — acid for the cation column, caustic for the anion column — driving the captured ions off the resin and to the neutralisation pit.
STEP 04
Rinse & Return
Residual regenerant is rinsed out until outlet quality is back on spec, and the vessel returns to service. Duty / standby trains keep supply uninterrupted through the sequence.
Plan For It
Regeneration means acid, caustic and a neutralisation pit.
A DM plant needs HCl and NaOH storage, dosing, an effluent neutralisation pit and the safety envelope that comes with them — and supply stops while the bed is down unless the plant is built duty / standby. If that chemistry is unwelcome on your site, look at EDI, which regenerates continuously on electricity alone.
Product · Mixed Bed Plant
Single vessel · final polish
MB
Polishing Stage
Mixed Bed Plant
Cation + anion resin, intimately mixed, one vessel
Polishes Out
Residual conductivity
Silica
Sodium leakage
Chloride
Sulphate
CO₂
An infinite series of DM stages in a single shell.
In a two-bed DM plant the water meets cation resin, then anion resin — two discrete exchanges, and each one leaks a little. In a mixed bed the two resins are blended bead to bead, so the water crosses thousands of alternating cation and anion contacts on the way down. That behaves like a DM plant repeated over and over, and it is why a mixed bed takes conductivity to a fraction of what two-bed exchange can reach on its own.
Position
After a DM plant, or after RO
Fed a stream that is already low in ions — as a polisher on DM outlet, RO permeate, or condensate return.
Output
Down to < 0.1 µS/cm
An order of magnitude below what two-bed exchange reaches, with silica and sodium held at trace levels.
Build
Single rubber-lined vessel
One shell instead of two, with air-mix and separation internals — a compact footprint on a crowded utility floor.
Duty
Polish, not bulk removal
Specified on a low ionic load. Put a heavy load on a mixed bed and you buy short runs and frequent regeneration.
Trade-off
Better water, harder regeneration.
Because the resins share a vessel, they must be separated hydraulically before regeneration — backwashed apart on density, dosed separately, then re-mixed with air. Capacity per litre of resin is lower than a two-bed plant, so a mixed bed is specified as a polisher on a low ionic load, not as the bulk salt-removal stage. Where the load is heavy, the sequence is a two-bed DM plant first, mixed bed after.
Two-Bed or Mixed Bed
Bulk removal → final polish
They are not competing products — they occupy different positions on the same train. The matrix is for deciding whether one vessel will do, or whether you need both.
Vessels
Two — cation
then anion
One — both resins
intimately mixed
Duty
Bulk salt removal
from filtered feed
Final polish on an
already low load
Outlet conductivity
< 1 – 5 µS/cm
< 0.1 µS/cm
Silica removal
Good with strong
base anion resin
Trace levels
— the polishing duty
Capacity per litre
Higher — long
service runs
Lower — short runs
on a heavy load
Regeneration
Each vessel dosed
separately, in place
Hydraulic separation,
dose, then air re-mix
Footprint
Two vessels plus
regenerant skid
Single vessel —
compact
Typical feed
Filtered raw water
after PSF + ACF
DM outlet, RO permeate
or condensate return
Figures are indicative design ranges — final selection follows a feed water analysis.
Standard Features
Common to DM and mixed bed
F-01
Fully Automatic, Pre-Assembled
Plug-and-play skids with timer or meter control, wired and tested before they leave the works.
F-02
Pressure-Rated Steel Tanks
Engineered for 45 psi working pressure and hydro-tested at 75 psi before dispatch.
F-03
Protects Downstream Equipment
Cutting dissolved salts extends the life of UF and RO membranes and of utilities — boilers, cooling towers, multi-effect evaporators.
F-04
Auto Regeneration
Alarm system with metered or fully automated regeneration through digital instrumentation.
Product Configurations
Vessel & control build
The exchange chemistry does not change between builds. What changes is the vessel material, and that follows the regenerant duty — caustic and acid are unkind to the wrong lining.
Configuration A
FRP Tanks with Digital Stager
For small and mid flows, and where a corrosion-free vessel is worth more than a rugged one.
Exchange Capacity
— on enquiry
Service Flow Rate
— on enquiry
Features
-
✓
FRP tanks, corrosion-free
-
✓
Diaphragm and butterfly valve sets*
-
✓
Digital stager or PLC control
-
✓
Automatic regeneration sequence
-
✓
Outlet conductivity instrumentation
Configuration B
Rubber-Lined Mild Steel — Mixed Bed De-Ioniser
The standard build for mixed-bed polishing and for larger DM duty — the lining takes acid and caustic without complaint.
Exchange Capacity
— on enquiry
Service Flow Rate
— on enquiry
Features
-
✓
Industrial rubber-lined MS tanks
-
✓
Diaphragm and butterfly valve sets*
-
✓
Digital stager or PLC control
-
✓
Automatic regeneration sequence
-
✓
Outlet conductivity instrumentation
* Valve selection (diaphragm / butterfly) and tank sizing configured to feed water and duty · steel tanks engineered for 45 psi working pressure, hydro-tested at 75 psi.
Reference Installations
Client names withheld under confidentiality. Full commissioning data available on request.
Petrochemical · Steam
Two-bed DM on high-pressure boiler feed
Refinery utility block, Gujarat. Duty / standby cation–anion trains on the boiler-feed make-up line, with an external acid–caustic regeneration skid and neutralisation pit.
Pharmaceutical · API
Mixed bed polishing after a DM plant
API site, Maharashtra. Rubber-lined mixed bed installed on the DM outlet to hold conductivity and silica at trace levels for a reaction-water loop.
Chrome Plating · Rinse Water
FRP DM skid on a plating rinse line
Plating shop, Punjab. Compact FRP DM skid with digital stager producing spot-free rinse water, replacing bought-in DI water deliveries.