Coastal Borehole Saline Ingress Resolved with a Custom Reverse Osmosis System
- Aug 12
- 4 min read
Updated: Aug 13
When a coastal water supplier began experiencing increasing saline ingress into its boreholes, water quality levels were approaching the threshold where the supply would no longer be suitable for public distribution. The client required a reliable, long-term solution that would restore water quality, maintain production targets, and maximise water recovery.
Following extensive water analysis, pilot trials, and process modelling, the engineering team at PFS Clean Water Management designed and installed a bespoke Reverse Osmosis (RO) water treatment system. The solution successfully removed excess salinity, achieved the client's target production of 100m³ of treated water per day, and delivered an exceptional recovery rate of approximately 50% wastage, significantly outperforming typical RO system efficiency expectations.
More than seven years later, the system continues to operate successfully, demonstrating the long-term reliability and effectiveness of the solution.
The Challenge: Saline Ingress Threatening Public Water Supply
Coastal boreholes are often vulnerable to saltwater intrusion, particularly where groundwater abstraction and natural environmental factors allow seawater to migrate into freshwater aquifers. In this case, the client observed rising salinity levels within their borehole water supply.
As salinity levels continued to increase, the treated water was approaching concentrations that would no longer meet the standards required for safe public distribution. Without intervention, the client faced significant operational and regulatory challenges, including:
Reduced water quality compliance
Potential interruption of potable water supply
Increased treatment costs
Risk to long-term borehole viability
Reduced confidence in the security of the water source
The client required a solution capable of
Removing dissolved salts effectively
Maintaining a consistent supply of high-quality drinking water
Achieving a daily production target of 100m³
Operating efficiently with minimal water wastage
Providing long-term reliability and ease of operation
Given the complexity of the challenge, an off-the-shelf treatment system was unlikely to achieve the desired results. A tailored engineering solution was required.
The Solution: Bespoke Reverse Osmosis Water Treatment Design
The engineering team at PFS Clean Water Management carried out detailed water quality assessments, pilot testing, and process modelling to determine the most effective treatment strategy.
Following the evaluation process, a custom-designed Reverse Osmosis (RO) system was specified and installed to remove dissolved salts from the affected borehole water supply.
RO System Configuration
The final design incorporated:
16 x Axeon HF4040 Reverse Osmosis Membranes
Operating pressure of 12 bar
Designed permeate production of 4.2m³/hour
Target output of 100m³/day of treated water
The RO process was specifically engineered to handle the saline contamination while delivering consistent water quality suitable for public supply applications.
Advanced Water Recovery Strategy
One of the key elements of the project was the approach taken to managing reject water.
In many conventional RO systems, water recovery rates can result in 75-90% of feed water being rejected as waste, particularly when treating challenging saline water sources. Through careful process optimisation, additional treatment of the reject stream, and controlled blending strategies, the system achieved approximately 50% wastage.
This level of performance pushed the practical limits of what can normally be achieved using standard RO membrane technology and provided substantial benefits for the operator by:
Reducing overall water losses
Improving operational efficiency
Maximising utilisation of the available borehole resource
Lowering the environmental impact of the treatment process
Precision Control and Pumping Technology
To ensure stable and efficient operation, feed water was delivered to the membrane array using:
Etech EV Vertical Multistage Pumps
Nastec Vasco Variable Speed Drives (VSDs)
This combination provided operators with smooth system control, allowing pressure and flow rates to be adjusted seamlessly in response to operational demands.
The result was:
Consistent membrane performance
Improved energy efficiency
Reduced mechanical stress on system components
Enhanced process control
Simplified operation for site personnel
The project required close collaboration between PFS Clean Water Management, specialist manufacturers, and industry partners to deliver a fully integrated treatment solution.
The Outcome: Reliable Water Production and Long-Term Performance
The completed installation successfully restored the client's ability to produce high-quality water despite the challenges presented by saline ingress.
Key project outcomes included:
✅ Achievement of the client's 100m³/day production target
✅ Consistent production of 4.2m³/hour of treated water
✅ Effective removal of salinity from coastal borehole supplies
✅ Approximately 50% reject water wastage, significantly better than conventional RO expectations
✅ Enhanced operational control through variable speed pump technology
✅ Improved long-term security of the water source
✅ Reliable operation for more than seven years
The success of the project demonstrated how a carefully engineered reverse osmosis solution can overcome complex groundwater quality issues while delivering excellent efficiency and long-term value.
Both the client and project stakeholders were extremely satisfied with the outcome, and the installation continues to provide dependable service years after commissioning
Why Ongoing Water Treatment Servicing Matters
A high-performance reverse osmosis system can only continue delivering optimal results when supported by a proactive maintenance program
Regular servicing helps to:
Maintain membrane efficiency
Prevent fouling and scaling
Monitor water quality trends
Protect pumps and control systems
Maximize system lifespan
Reduce unplanned downtime
Ensure compliance with water quality standards
At PFS Clean Water Management, we provide comprehensive servicing, maintenance, performance monitoring, and optimization support for reverse osmosis systems, borehole treatment plants, and clean water infrastructure across the UK.
Need Support for a Borehole Water Treatment System?
If you're experiencing saline ingress, water quality issues, or declining treatment performance, our specialist engineers can design, service, and optimise systems tailored to your site's requirements.
Contact PFS Clean Water Management today to discuss your water treatment challenges and discover how our servicing and engineering expertise can help safeguard your water supply for the long term
