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MEMBRANE PROCESSES 13.45

Most drinking water membrane systems designed today have controls based on a pro-
grammable logic controller (PLC). These systems can be designed to control flows, pres-
sures, and other parameters. Many RO and NF systems have controls to provide auto-
matic flushing upon shutdown, and most MF and UF systems have automatically controlled
backwash/backflush facilities. Many large RO and NF plants are designed with computer
systems that compute normalized performance data for operation monitoring and deter-
mine when to perform membrane cleanings.

Operations and Maintenance (O&M) Design Issues

Membrane systems require proper O&M to perform according to design and to extend
membrane life. Depending on the type of membrane system and application, O&M re-
quirements vary greatly. As a minimum, operations staff should monitor and record all
critical parameters, operation incidents (such as feedwater quality upsets and shutdowns),
and maintenance performed. The membrane plant designer should provide all needed in-
strumentation and representative sampling points for operations staff.
System design should consider adequate spacing and access for equipment mainte-
nance, as well as devices for lifting and moving equipment. Proper storage facilities should
be provided for membranes, chemicals, other equipment replacements, and spare parts.

Membrane Process Building Design
Floor plans of membrane process buildings vary greatly depending on the type of mem-
brane process, the site-specific conditions and design constraints, and the number and
types of nonprocess areas included. Process areas include the following pieces of equip-
ment, depending on the membrane process and application:
• Pretreatment filters, such as cartridge filters, basket strainers, and bag filters
• Chemical feed systems for pretreatment and posttreatment chemicals
• Membrane feed pumps
• Membrane treatment units
• Membrane cleaning and flushing systems
• Posttreatment equipment
• High service pumps
• Holding tanks (where applicable) such as feed and spent backwash water tanks for an
MF or UF system
• Electric switch gear and motor control center
• Emergency generator
Typical nonprocess areas commonly incorporated into building designs are as follows:

• Control room
• Laboratory
• Chemical storage area
• Maintenance shop
• Spare parts storage room