All desalination technologies produce the same byproduct – concentrate or brine. The amount varies depending on the source of the water source being desalinated. Seawater desalination plants produce more brine – almost 50 percent of the feed water. This is less in brackish water desalination plants – the brine constitutes between 15 percent and 30 percent of the feed.
Increasing regulatory pressure, growing environmental awareness and more and larger membrane desalination plant are driving the need for better brine minimization – one of the greatest challenges currently facing the water treatment sector.
The current brine minimization process uses a combination of 3 technologies – reverse osmosis, followed by thermal evaporation, followed by thermal crystallization. There are significant differences in the cost of these technologies.
The most economical approach would be to increase the load on the reverse osmosis and maximize its recovery as much as possible, thereby reducing the size of the thermal crystallization unit to the minimum.
However, three major factors limit the recovery of any RO system:
• Osmotic pressure
• Chemistry of the feed water
• Low brine flow through the membranes associated with high recovery
ArtAqua has developed process that overcomes these limitations.
ArtAqua offers two technology solutions for brine minimization:
• Overcomes variable change in the feed flow and composition
• Operates at very high recovery without reducing the membrane cross-flow
• Pushes the precipitation limits of calcium carbonate, calcium sulfate and silica.
The ArtAquaH2O DESALTER operates by recirculating treated water through the RO system at high shear velocity, and continuously precipitating supersaturated salts from the recirculated brine. This significantly reduces the salt concentration build up near the RO membrane wall and prevents the precipitation of sparingly soluble salts on the membranes. The salt precipitation unit downstream reduces the saturation of sparingly soluble salts in the recirculated brine. This allows continuous cycles through the RO system until reaching maximum brine osmotic pressure.
Reasons to choose the ArtAquaH2O DESALTER
• High recovery rates – limited only by osmotic pressure and not by supersaturation of sparingly soluble salts
• Able to achieve different total recovery levels in the same system- the brine recirculation can be stopped at any recovery, at any RO brine level
• High flexibility – operates with variable feed water qualities, concentrations, flows and recoveries
• Membrane elements are exposed to variable salt concentration or variable osmotic pressure during the operation, reducing the biofouling potential
• At the beginning of every cycle the last elements are exposed to under-saturated water conditions, which reduce the tendency for scaling and improve the ability to dissolve scale
• Semi-batch RO system with an integrated salt precipitation cycle for continuous desaturation of RO brine
• Low investment and operational costs
Advantages of the Pellet Reactor (Salt Precipitation Unit)
• Short residence time
• Small footprint
• Lower chemical consumption
• Minimum sludge handling (high solid content percentage)
The ArtAquaH2O DESALTER is applicable for RO brine and industrial effluents with high scaling tendency and low to moderate salinity (0.1 – 2.0 %w).
ArtAquaH2O Pulse Flow RO
Pulse Flow RO (PFRO) replaces standard RO desalination technology.
Conventional RO doses antiscalant to prevent scaling in a high recovery RO process, and chloramine or biocides to prevent bio- fouling. Stability in concentration, flow, gauge and osmotic pressure is the best condition for the formation of scaling, fouling and bio-fouling is. Stability of the membrane surface geometry also contributes significantly to all forms of fouling.
ArtAqua proprietary, patented Pulse Flow RO (PFRO) technology is completely contrary to Conventional RO operation. The flow is not stable, and the osmotic and gauge pressure change frequently and rapidly. The membrane geometry breathes according to changes in feed and permeate pressure.
This method has six times the ability of the standard RO process to remove concentrated solute ions or fouling particles.
In between brine discharge pulses, the RO membrane operates in dead end mode, with 100% recovery.
Bio Fouling in Conventional and PFRO
Bacteria becomes a problem for the RO process only when the biofilm is well developed. During the production cycle the gauge and osmotic pressure interchange in a non-exact parallel pattern.
Bacteria are exposed to rapid changes in gauge and osmotic pressure. Since ArtAqua is using SKOV, a mineral from the Caucasus bearing anti-bacterial properties, water desalinate and purified by ArtAqua filtration systems stays fresh and safe for 180 days without adding any chemicals such as Chlorine.
The capacity of organisms to respond to fluctuations in gauge and osmotic environments is limited and such fast changes do not enable them to reproduce.The PFRO train is single stage, contrary to the several-stage conventional BWRO and wastewater train.
The Pulse Flow RO train comprises one-stage, with all the pressure vessels in parallel.
Staging design to maintain minimum velocity in the brine stream. As more and more feed flow becomes permeate, the remaining brine stream is redirected to the next stage, in which there are fewer pressure vessels.
The single stage train operates with a very low pressure drop (0.1-0.2bar) in the dead end production step. This arrangement reduces the number of pressure vessels and membranes as the pressure is more equally distributed between the membranes.
A single-stage has simpler piping and does not require an inter-stage booster pump.
This arrangement allows maintaining minimum brine flow velocity, but results in low recovery, scaling, fouling and bio-fouling problems. Energy losses and structural complexity are greater. As a result of non-continuous brine pumping, power consumption is reduced, and pressure drops in stages are diminished.
The continuity of brine flow has been an unshakeable foundation of the conventional RO desalination process for almost 50 years. The leap from continuous to pulse flow allows achieving significantly higher solute concentration in the brine flow, as well as higher recovery rates.
This prevents bio- and other types of fouling.
Power consumption is reduced due to non-continuous brine pumping, and diminished pressure drops in stages.
Pulse Flow reduces the number of pressure vessels and membranes, due to more equal distribution of pressure between the membranes. A single-stage structure without inter-stage boosters reduces cost.