Reverse Osmosis Membrane Modules

AquaZoom™ DT RO Module and System Designs


Please scroll to this section to see how the disc tube module works.

AquaZoom™ DT RO Membrane Module Advantages


Scroll down to this section to see what the AquaZoom disc tube membrane technology can do for you.

AquaZoom™ DT RO Membrane Module Products


You can scroll to this section to find the different disc tube products that we offer.

AquaZoom™ ST RO Membrane Module and System Designs


Further down in this section, you will find the unique attributes of the spacer tube membrane module.

AquaZoom™ ST RO Membrane Module Advantages


Please scroll to this section to learn about the benefits of the spacer tube module.

AquaZoom™ ST RO Membrane Module Products


At the end of this page you will find the different spacer tube module products that we offer to the marketplace.

Disc Tube Module Construction


What really is a disc tube membrane module?

DT RO membrane modules have a plate and frame structure. The module is built by stacking as many as 209 white circular membrane cushions within a structure of plastic plates.  Each cushion consists of two membrane sheets with a permeate carrier sandwiched in between.  


What is the blue disc and what does it do?

Each cushion is inserted between two blue plastic hydraulic discs which direct the feed flow around the membrane. These assemblies are stacked by placing them over a tie rod and sliding the rod up through the central passageway to create the plate and frame structure.

DT Module Flow Schematic

How does the module make clean water?

Feed flows between in the inside of the housing and the outside of the hydraulic discs.  It then flows radially into the chamber created by the first pair of hydraulic discs that contains a single membrane cushion.  Feed flows over each subsequent membrane cushion contained within the hydraulic disc structure.  Each cushion extracts permeate driven by differential pressure acrosss the membrane. Permeate then flows through the permeate carrier and then into the annulus between the hydraulic discs sealed with o-rings and the tie rod from which it flows to the outlet end of the module. When the feed exits the last chamber, it leaves the module as concentrate as it contains materials retained by the membrane in the remaining liquid.

It should be noted that there is no feed spacer in this module design. This feature is a huge advantage when treating highly contaminated feedstreams.   

Disc Tube Module Design

To give you a better feel for the DT membrane module design, we have included this video showing its component parts.  

System Design with DT Modules

DT module systems are simple


Given that the feed flows through the DT module in series over each membrane cushion, the modules are typically operated in parallel, up to 30 modules in a single bank. Multiple banks of modules can be placed in parallel to increase the treated flow rate in a single stage. Additional banks can be placed in series as separate stages if additional concentration or permeate purification is needed at any particular site.

AquaZoom™ DT Module Advantages


The open feed channel does not clog with solids and provides an unobstructed path for feed flow.

Feed pre-treatment requirements are minimized allowing feed water with a silt density index exceeding 5 to be used with the DT module. This reduces the cost and size of the pretreatment equipment relative to traditional spiral wound RO modules.

Improved mass transport results in reduced fouling and scaling, and higher and more sustainable permeate flux.

The hydraulically open module without the feed spacer minimizes dead spaces in the module lending itself to more efficient cleaning.   

Simple module assembly provides for ease of maintenance.

The membranes can be easily accessed to allow for replacement of one or all the cushions.

Individual cushions can be easily and inexpensively removed and replaced facilitating membrane analysis for process and cleaning optimization.  

System design is straight forward with modules piped in parallel.

Expensive recirculation pumps and piping loops are eliminated.

Process is simple and reliable.

Systems can be easily containerized.

Multiple stages in parallel or series can be implemented.

Systems can be easily integrated into new or existing water treatment process trains.  

AquaZoom™ DT Product Offerings

DTG RO Membrane Module

The DTG (Disc Tube Grand) module is the lead product in the DT family. It has been used extensively in landfill leachate treatment for many years. The module has 9.8 m2 of membrane area (105.7 ft2) and can produce about 7.2 m3/d (80 gph) of effluent with the actual rate dependent on feed and process conditions.

DT RO Membrane Module

The DT (Disc Tube) module is the original DT module type. Quite often procured as a replacement in existing installations, it has a smaller amount of surface area in a shorter design. The 7.9 m2 of membrane area (85.5 ft2) produces proportionally less permeate but requires less space and power for each module.  

DT RO Modules for Seawater

Both the DT and the DTG modules can have their materials of construction modified so the modules can operate reliably on high chloride feedstreams. Their compactness and ease of operation make these modules particularly useful in offshore applications.  

DT Module Replacement Parts

Replacement parts for AquaZoom DT and DTG modules are available.  Replacement cushions and elastomeric seal kits are listed on the various product datasheets.

Product Datasheets

Datasheets are available in the DT Product Download Center.  Please scroll down to the next section to find documents providing details for our DT products.

DT Product Download Center

Click on a file to download.

AquaZoom™ DT Module Datasheet (English) (pdf)


AquaZoom™ DTG Module Datasheet (English) (pdf)


Spacer Tube Module Attributes


AquaZoom™ ST RO Membrane Modules

AquaZoom ST membrane modules are unique, patented spiral wound modules for demanding applications. The ST construction is very similar to conventional spiral wound modules but with two distinctive features.


Designed for concentrating contaminated water

(1) The module uses a tie rod through the permeate tube to assist in holding the element in place within the housing vessel at high operating pressure

(2) The open and thick ladder-type feed spacer is designed to operate with highly contaminated feed streams.  


The First. The Original. The Right One.

CrossTek is the only company in the world with the original Rochem Spacer Tube Module® providing the performance that you desire. This module design allows for smaller, less expensive systems for landfill leachate treatment with less RO pre-treatment. We have many references in which our ST modules are used. If you are ready to move to the most advanced RO membrane module technology for demanding applications, please contact us to discuss how we can help you.  

Spacer Tube Module Design

For a more detailed description of the ST module, please see this video showing its component parts  

System Design with ST Modules

Spacer tube RO systems are similar to those using standard spiral wound RO membrane modules


Like traditional spiral wound modules, the feed flows over the membrane parallel to the individual membrane leaves from which the spiral is constructed. Hence, ST modules are operated in series, up to 6 in a single pass. Multiple parallel passes will provide greater permeate flow in a single stage. Separate passes of membranes in a second stage will allow for additional concentration or permeate treatment as desired.  

AquaZoom™ ST Module Advantages


The ST module has more surface area than a comparably sized DT module

The ST+ module has 29.3 m2 (315 ft2) while the DTG module has 9.8 m2 (105 ft2).

The more compact ST module will provide for smaller, less expensive membrane systems providing more value to the end user.

The larger surface area allows the ST module to be used in larger flow applications.

The ST module has significantly less inlet-to-outlet pressure drop as compared to the DT module

The ST+ module operating pressure drop is about 17 psi (1.2 bar) while the DTG operating pressure drop is up to 87 psi (6 bar).

Lower pressure drop results in lower operating costs for the operator.

Lower axial pressure drop allows for more flexibility in system design.  

The proprietary feed spacer allows the ST module to operate in very demanding applications.

The operator gets the advantages of a spiral wound membrane module that can operate in many applications previously reserved for higher cost, open channel module designs.  

AquaZoom™ ST Product Offerings

ST+ RO Membrane Module

  The ST+ module is the lead ST module type. It is the highest surface-area RO module that can be used to treat high-organics contaminated landfill leachate. It was designed to match the overall dimensional size of the DTG module.  

ST++ RO Membrane Module

The ST++ module is an expanded version of the ST+ module. It is two ST+ membrane elements installed in a single pressure vessel. This module is for large flow systems where system simplification is necessary.  

ST RO Membrane Module

  The ST module is the original product in the ST family. Analogous to the ST+ - DTG comparison, the ST module is the same overall size as the DT module but with significantly more area.   

ST Modules for Seawater

Like the DT products, the materials of construction of any ST type module can be changed to accommodate high chloride content feeds such as seawater.

Ultra-High Pressure ST Modules

ST+ modules are available in a 120-bar version for concentrating brines and minimizing residual volumes. Please Talk to Us if you want to find out more about how this can help you.

Product Datasheets

Product datasheets are available in the ST Product Download Center.  Please scroll to this Download Center to find documents providing details for our AquaZoom spacer tube products. 

Reverse Osmosis Membrane Types

AquaZoom™ DT Module

DT and DTG modules are equipped with the AquaZoom RO4 membrane.

AquaZoom™ ST Module

ST, ST+, and ST++ modules can be equipped with the AquaZoom RO3, RO4, or RO6 membrane.  

The AquaZoom™ Membrane Lineup

All standard reverse osmosis membranes offered in the AquaZoom™ product line are polyamide, thin film composite membranes.

The R03 is a standard brackish water membrane.

The R04 membrane is a low-energy seawater membrane that we use as a general-purpose RO membrane based on a combination of good productivity and dissolved salt retention.

The R06 membrane is a high-rejection seawater membrane.

Other membranes may be made available so please Talk to Us if you have need of an alternative membrane.   

AquaZoom™ Replacement Parts

Replacement membranes and seal kits for your AquaZoom modules


AquaZoom Replacement Membranes


The replacement DT R04 membrane cushions come in quantities of 169 and 209 for the DT and DTG modules, respectively. We plan to develop a pre-stacked package to make field replacement of DT cushions quicker and easier. Please check our site often as we hope to have this available soon.

ST and ST+ replacement elements are available in all three membrane types. Please go to the Download Center at the bottom of this page for the element types and model numbers.  

AquaZoom Seal Kits


Replacement elastomeric seals are available for when the membrane elements are replaced or the seals appear to have suffered some damage. Please see the DT and ST module datasheets in the Download Centers for seal kit model numbers.

Typically, no other components besides the elements and the seals should need replacement unless the module was exposed to unusual conditions. However, if you want us to service your modules for any reason, such as performing element and/or seal replacements, we will be happy to do so either in our factory or at your site. Please discuss your needs with our service group so we can help you get your membrane system running right.  

ST+ and ST++ Product Download Center

Click on a file to download.

AquaZoom™ ST+ Module Datasheet (English) (pdf)


AquaZoom™ ST++ Module Datasheet (English) (pdf)


AquaZoom™ ST+ R03 Membrane Element Datasheet (English) (pdf)


AquaZoom™ ST+ R04 Membrane Element Datasheet (English) (pdf)


AquaZoom™ ST+ R06 Membrane Element Datasheet (English) (pdf)


ST Product Download Center

Click on a file to download.

AquaZoom™ ST Module Datasheet (English) (pdf)


AquaZoom™ ST R03 Membrane Element Datasheet (English) (pdf)


AquaZoom™ ST R04 Membrane Element Datasheet (English) (pdf)


AquaZoom™ ST R06 Membrane Element Datasheet (English) (pdf)