High-pressure membrane projects require thorough planning and management, just as low-pressure membrane planning. The following are the primary distinctions between high-pressure membrane projects and traditional technologies and low-pressure membrane projects:
- Membranes are effective in removing dissolved matter from the water to be treated, but they cannot withstand high suspended and colloidal solids loads;
- To lower a specific matter and colloids load before treating water with high-pressure membranes, reliable pretreatment is necessary;
- Compared to conventional methods, membranes require fewer doses of UV light and a lower chlorine injection rate since they produce higher-grade water.
A Brief on High-Pressure Membranes
High-pressure membranes are not manufacturer-specific and can be replaced by other providers because they are widely standardized throughout the industry (Frenkel & Wilf, 2009). The industry’s current state makes the planning process for high-pressure membranes easier.
Most conventionally procured membrane facilities use a one-step procurement procedure, which is the reverse of the procurement process for low-pressure membranes. Compared to the low-pressure membrane procurement procedure, the one-step procurement process shortens the project schedule.
The similarity between high-pressure and low-pressure membranes
High-pressure membrane designs are similar to low-pressure membrane elements designs in that they are influenced by the source water quality, regional conditions, project preferences, and standards for the treated water quality.
Because high-pressure membranes cannot tolerate suspended or colloidal debris in the water, their design and performance depend on the design and operation of conventional or low-pressure membranes used for pretreatment.
Since its creation, most engineering and design efforts have focused on creating high-pressure membranes that can operate continuously—the following list of advantages and disadvantages of continuous operation.
Benefits of RO Operation
- Since all membranes function continuously, a minimal system of fittings and piping is required;
- Components, fittings, and equipment are not periodically cycling, extending equipment lifetime;
- Devices for energy recovery are simple to add, which lowers the system’s overall energy requirement;
- Various strategies have been developed that enable flexible system functioning, such as concentrated recycling and hybrid design.
- In recent years, semi-batch RO operation has been presented, which has the following advantages over continuous RO operation:
- The PV’s RO membrane components’ flux can be more evenly distributed;
- When compared to continuous RO operation, a higher overall system recovery can be achieved under the same circumstances;
- The variation in salt load within each cycle may result in less potential membrane fouling.
Factors to Consider While Designing High Pressure Membrane System
The following plant elements and factors should be considered when designing any high-pressure membrane system.
- Prerequisites for pretreatment, such as low-pressure membranes or chemical injection for filtration or clarifying when necessary;
- System recovery rate, which is stated as a percentage and is the product flow to feed flow ratio;
- Membrane active filtration area (also known as membrane flux), which is a function of the flow load on the membranes per membrane area and is expressed in GFD or LHM;
- The need for energy;
- Posttreatment needs because of the product water’s low alkalinity and the resulting aggressiveness of the water;
- Focus on discharge and management;
- Solids from pretreatment used in therapy or management.
The best project economics, capital, and operating costs are accommodated by good design practices, which maximize system recovery at the lowest energy usage.