Introduction

Reverse Osmosis (RO) is an advanced water purification technology used to improve boiler feedwater quality by removing dissolved solids, salts, chlorides, heavy metals, and other contaminants. When properly applied, RO systems can significantly reduce blowdown, lower chemical consumption, improve boiler reliability, and reduce operating costs.

This article provides an overview of Miura's RO product offering, supporting equipment, sizing requirements, and common applications.

What Is Reverse Osmosis?

Reverse Osmosis is a water purification process that uses pressure to force water through a semi-permeable membrane. The membrane allows water molecules to pass while rejecting most dissolved contaminants, producing highly purified water. Miura RO membranes are capable of removing more than 95% of dissolved solids and impurities, including:

• Chlorides
• Salts
• Heavy metals
• Other dissolved contaminants

How RO Works

In natural osmosis, water moves across a membrane toward a higher concentration of dissolved solids. Reverse osmosis uses pressure to reverse this process and force purified water through the membrane while concentrating contaminants into a reject stream.

When Is RO Recommended?

RO treatment becomes beneficial when feedwater conditions negatively impact boiler operation or chemical treatment costs. Common applications include:

High Chlorides or Corrosive Ions

Can contribute to:

• Corrosion risks
• Increased blowdown frequency
• Higher chemical consumption

High Conductivity

Can cause:

• Lower cycles of concentration
• Increased blowdown
• Greater carryover risk

Low Condensate Return pH

In situations where chemical pH adjustment cannot be used due to regulations or site requirements, RO may be the preferred solution.

Excessive Chemical Usage

If maintaining acceptable boiler water quality requires unusually high chemical treatment rates, RO may significantly reduce chemical demand.

Softeners and conventional chemical treatment may adequately address some applications. However, beyond certain water quality thresholds, RO treatment becomes necessary.

Miura RO Product Offering

Standard Capacity Range

Miura currently offers standard RO systems from:

• 15 GPM to 100 GPM permeate capacity

Larger systems may be available through custom quotation and typically require water analysis to verify performance requirements. All standard systems utilize 8-inch diameter Toray membrane elements configured in varying quantities depending on capacity.

Standard Features

Miura RO systems include several features that are optional or unavailable on many competing designs:

• ORP and pH monitoring sensors
• Variable Frequency Drive (VFD) controlled system pumps
• UL 508A listed control panels
• NEMA 4 electrical enclosures
• Modbus/Ethernet communications capability for future Miura Connect integration

These features help improve membrane protection, operational reliability, and system integration.

RO Ancillary Equipment

An RO system alone does not address all treatment and operational requirements. Several supporting components may be required to maximize performance and membrane life.

Chlorine Removal

Why Chlorine Is a Problem

While chlorine and chloramines help disinfect municipal water supplies, they damage RO membranes by oxidizing the membrane's polyamide layer.

Even concentrations as low as 1 ppm can shorten membrane life and lead to premature replacement. Chlorides themselves are not harmful to the RO membranes because they are removed by the RO process.

Chlorine Removal Options

Granular Activated Carbon (GAC)

Benefits:

• Lower operating cost
• Removes chlorine
• Removes organic compounds, VOCs, and pesticides

Considerations:

• Higher initial cost
• Requires backwashing
• Larger footprint

Standard Miura GAC systems range from 40 to 160 GPM.

Chemical Dechlorinization

Benefits:

• Lower capital cost
• Smaller footprint
• Reduced downtime risk

Considerations:

• Continuous chemical consumption
• Higher operating costs

RO treatment chemicals are not a replacement for standard boiler feedwater treatment chemicals.

Clean-In-Place (CIP)

Why CIP Is Important

Over time, RO membranes accumulate mineral deposits, biological fouling, and other contaminants. This results in:

• Increased differential pressure
• Reduced membrane performance
• Reduced membrane life

Manual membrane cleaning can be labor intensive and increase downtime.

CIP Solution

Clean-In-Place systems allow membranes to be cleaned without removal from the RO skid.

Benefits include:

• Reduced downtime
• Easier maintenance
• Extended membrane life
• Cleaning for scaling, fouling, and sanitization requirements

Miura strongly recommends including a CIP package with every RO system.

Storage Tanks

Storage tanks provide water reserve capacity whenever the RO system is unavailable due to:

• CIP cleaning
• GAC backwashing
• Softener regeneration
• Maintenance activities

Miura typically sizes storage for approximately one hour of RO water capacity, although larger volumes may be specified. Storage tanks include level monitoring and are intentionally non-pressurized to protect RO membranes from damaging backpressure.

Standard storage capacities range from:

• 1,000 gallons
• 10,000 gallons

Transfer Pump Packages

Transfer pumps move purified water from the storage tank to the feedwater tank while providing the required system pressure.

Standard transfer pump packages include:

• Duplex pumps
• Skid-mounted assemblies
• 460V starter panels with disconnects

Available capacities range from 10 to 100 GPM.

Typical RO System Arrangement

A typical Miura RO installation includes:

1. GAC filter or chemical dechlorination
2. Water softener
3. RO system
4. Storage tank
5. Transfer pump
6. Feedwater tank or deaerator
7. Boiler

CIP equipment remains connected to the RO but is only used during cleaning operations. BoilerMate chemical treatment remains required even when an RO system is installed.

Financial Benefits of RO

RO systems typically generate savings through two primary mechanisms:

Reduced Blowdown

Lower-conductivity feedwater enables higher cycles of concentration before blowdown is required.

Benefits include:

• Reduced fuel consumption
• Reduced water usage
• Reduced wastewater discharge

Reduced Chemical Usage

Although boiler chemical treatment remains necessary, treatment demand can often be significantly reduced.

These savings may allow the RO system to recover its cost over time, particularly in applications with poor incoming water quality.

Information Required for RO Sizing

To properly size an RO system, Miura Applications Engineering and Water Treatment teams typically require:

• Boiler quantity and model numbers
• Total boiler horsepower
• Average steam load (lb/hr)
• Water source information
• Water sample analysis
• Minimum incoming water temperature
• Hours of operation
• Location of the RO within the treatment train
• Any additional equipment using RO water

Water quality analysis is strongly recommended to optimize equipment selection and performance.

Key Takeaways

• RO systems remove more than 95% of dissolved contaminants from boiler feedwater.
• RO is most beneficial for high conductivity, high chloride, low pH, and chemically challenging feedwater applications.
• Proper ancillary equipment such as GAC filtration, CIP systems, storage tanks, and transfer pumps are critical to long-term reliability.
• RO can reduce blowdown frequency and chemical usage, creating operational savings over time.
• A water analysis and complete application review are essential for proper system sizing and equipment selection.