Pressure Vessel

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A pressure vessel holds the reverse osmosis membrane elements,  it is also called pressure tube when membranes are spiral wounded. A typical RO pressure vessel can contain  six membrane elements.  Pressure vessel is important part of RO process as it is to handle membranes in high pressures. The pressure vessel contain permeate ports at terminal points.

Watersafe is proud distributor of  the high quality pressure vessels that are planned to handle the highest pressure required by membranes . These pressure vessels are strengthened by durable fiberglass and incorporate end caps for durability.

 

Watersafe is the distributor pressure vessels of following manufactures

 

Hebei Chengda Huamo Technology Co., Ltd.

VETEC

 

 

 

ED/EDR

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Electrodialysis is a membrane-based process that uses electrical driving force. In this process by using alternating Anion–selective membranes (AMs) and Cation-selective membranes (CMs), situated between an Anode (+) and a Cathode (-), the separation of ions happens. Applied electric field, anions and cation will move towards the Anode and Cathode, respectively.  Anions are stopped by the CMs and the cations by the AMs, creating a process low ion concentration flow (Dilutant) and a process flow with high ion concentration  (Concentrate).  The process is shown in the below figure.

In electrodialysis, the charged suspended solids increase the resistance of the membrane dramatically, are deposited on the membrane surface over the time.  By reversing the polarity of the applied electrical potential in certain time intervals can eliminate to a large extent by reversing will result in a removal of charged particles that have been precipitated on the membranes. This technique is referred to as electrodialysis reversal (EDR).

 

Application

 

  • Large scale brackish and seawater desalination and salt production.
  • Small and medium scale drinking water production such as towns & villages, construction & military camps, nitrate reduction, hotels & hospitals.
  • Pre-demineralization such as  boiler makeup & pretreatment, ultrapure water pretreatment, process water desalination, power genration
  • Food processing and agricultural water  for greenhouses  livestock and irrigation
  • Glycerin purification

 

WaterSafe is a distributor of GE Aquamite* EDR Systems

Membrane Separation

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Membrane separation is promising technology in water and wastewater for conventional and emerging contaminates. are classified, based on the type of driving force they use. The different type of driving force that separate   the water includes: a pressure differential and reverse ; and a electrical force with to an ion exchange that facilitate migration of ions through the, electro and electrochemical devices).

Based on the pore sizes the Pressure-driven membrane processes are divided into reverse osmosis (RO), microfiltration (MF), nanofiltration (NF) and ultrafiltration (UF). In Figure 1 the different type of membranes and their mechanism are shown.

The selectivity between MF and UF is typically based upon pore size number (diameter of the micropores in a membrane surface) or molecular weight cut-off (MWCO) number. Reverse Osmosis also can be used to desalinated water as well as other contaminates.

 

 

Electrically driven (ED) membrane processes, commonly used in water/waste water treatment, also include electrically driven reversal (EDR) membrane processes. ED and EDR use a difference in electrical potential to induce dissolved ions to migrate through a water-impermeable membrane. This reduces their concentration in the feed water.

The anions (negatively charged ions) move in the direction of the positively charged electrode (anode) and are transported through the anionic membrane, but are restrained at the surface of the cationic membrane. The end result is a ‘dilute’ stream with a reduced salt concentration and a concentrate stream with a higher salt content than the feed water.

Choosing the Right Membrane

Membrane technology selection should be based on type of water and the treatment objectives at the lowest possible cost. In the following Table , typical pressure driven membrane process and application are shown.

Watersafe is an expert in design, procurement and installation of different membrane technologies.

Process TARGET COMPONET PERATING PRESSURE PROCESS APPLICATION
RO 99% of most ions, most organics over 150 MW 15-70 bars Brackish sea water, desalting, boiler feed, purification, pre-treatment to ion-exchange,
NF 95% divalent ions, 40% of monovalent ions, organics greater than 200-300 MW 9- 20 bar Hardness removal, organics and microbiological removal, dye desalting, color removal
UF Most organics over 1000 MW 2-9 bars Pre- and post-treatment to IX, beverage clarification, removal of pyrogens, bacteria, viruses and colloid, dilute suspended oils
MF Small suspended particle greater than 0.1mm 1.5-4 bars High volume of removal of suspend solids