Ultra-Purity for the Laboratory: Reduce Installation Time and Expense with an Integrated Reverse Osmosis System
When pharmaceutical companies, universities and hospitals require ultra-pure water for their laboratories in new facilities, engineers need to answer key questions:
- What’s the quality of our incoming water supply?
- What purity level does the end user require?
- How much ultra-pure water must be delivered?
- Should we speed the job by constructing the water purity system off-site?
Integrated water purity solution
You can minimize the time and expense to deliver ultra-pure water by specifying an integrated system that is customized to the end user’s requirements.
Harper is the area's exclusive representative for Marlo Inc. water treatment products. In addition to off-the-shelf components, Harper provides integrated purification systems that are assembled and tested at the Marlo factory, skid-mounted and delivered to your site ready to install.
According to Harper’s Reggie Lambert, Marlo water treatment systems can be scaled to low-volume users like dental offices, as well as to major laboratories that require hundreds of thousands of gallons per day.
Recent lab installations
Marlo’s integrated water purity systems have been installed recently at Florida State University’s chemistry and physiology buildings, Tallahassee; the Moffitt Cancer Center, Tampa; University of Puerto Rico’s molecular science building, San Juan; Burnham Institute for Medical Research, Orlando; University of Central Florida, Tampa; University of Nebraska, Lincoln; and the Cintas High Purity Cleanroom, Detroit.
Lab-grade purification strategies
Academic, medical and private research facilities may require highly specific water quality.
Purity standards include Types I through IV reagent-grade water per ASTM, College of American Pathologists (CAP), and National Committee for Clinical Laboratory Standards (NCCLS). The primary differences in water types are due to conductivity (mineral content) and bacterial content.
Reverse osmosis for ultra-purity
Reverse osmosis (RO) is mechanical process for producing high purity water. RO is an alternative to traditional ion exchange when higher levels of total dissolved solids (TDS) removal are not required.
RO utilizes a high-pressure pump to force water through a semi-permeable membrane for removal of TDS on the order of 98% or more. Superior rejection of bacteria, particles, and larger organic impurities is also accomplished.
RO also serves as an excellent pre-treatment to deionization in higher purity systems for lower regeneration costs. Specialty membrane processes such as two-pass, nanofiltration and ultrafiltration are also available.
Pre-treatment is key
Successful RO may require pre-treatment removal of turbidity, iron, hardness, and chlorine removal, depending on the water supply.
Turbidity, TSS and SDI
Ultra-pure water requires high clarity, with NTU<1.0, and SDI under 4.0. Well water generally is acceptable. However, surface waters typically require the use of a multi-media filter and, in some cases, a clarifier.
Scaling salts
A water softener removes hardness during pre-treatment. Larger flow systems will generally use anti-scalant polymer feed and/or pH adjustment to keep scaling salts in solution in lieu of a water softener. Some constituents, such as SiO2, Ba, and Sr, require close attention due to extremely low solubilities.
Chlorine removal
Today’s thin-film composite (TFC) membranes require zero chlorine in feedwater. Small to medium RO systems (under 100 GPM) are more apt to use activated carbon filters for de-chlorination, while larger systems will use a sodium bi-sulfite chemical injection into the feedwater to convert chlorine to chloride (SO3 + OCl = SO4 + Cl).
The best system designs include an ORP monitor and alarm to ensure RO machine shut-down on high ORP.
Water softeners
To prevent scaling, a polymeric exchange resin can be used to attract the hardness from the water and replace it with the more soluble sodium ion. Off-line regeneration with brine (NaCl) after resin exhaustion is required. Here’s how it works:
- Hard water flows downward through a resin bed and gravel support.
- Softened water collects in bottom distributor and exits the softener vessel.
- Resin continuously exhausts from top to bottom and must be regenerated before reaching breakthrough.
- Dissolved salt (brine) is used to recharge resin into original sodium form.
Carbon filtration
A carbon filtration system consists of pressure tank, internal distributors, carbon layer, and gravel support layer. Variations include:
- Downflow operation with required backwash step
- Manual or automatic external valve nest
- Backwash initiation via operator, volume, time, or differential pressure
Learn More
The engineers at Marlo and Harper are ready to assist you in designing a water purity system that meets the needs of your end users.
Contact Reggie Lambert or Tom Kuehnel at 203-323-2600 or 800-551-2733.
