BiRO+ Groundwater Treatment Pilot

Validating a Treatment Pilot for Challenging Groundwater Sources

A Rural Utility required a long-term approach to treating a groundwater source with multiple water-quality challenges, rather than only solving for a single, isolated contaminant removal process. The Rural Utility’s existing water treatment infrastructure was approaching the end of its expected service life, creating an opportunity to evaluate a treatment pilot to address both current groundwater conditions and the community’s long-term drinking water requirements.

Flowpoint worked with the project’s engineering consultant to propose its BiRO+ biological water filtration and reverse osmosis process, then conducted a field pilot to demonstrate its groundwater treatment performance before the project decided upon a permanent full-scale design.

The pilot had a clear objective: to demonstrate that the integrated process could reliably treat the existing groundwater source while establishing the operating parameters required for a permanent water treatment facility serving hundreds of homes. The pilot system was specifically designed and manufactured for the project as a scaled representation of the proposed full-scale groundwater treatment process.

Optimizing the Process Under Field Conditions

The groundwater treatment pilot was started in fall 2025 and remained in the field until mid-April 2026. During that period, the team evaluated three different biofiltration operating scenarios. The first two scenarios intentionally explored operating conditions that could potentially reduce capital or operating costs.

Higher flow rates could theoretically reduce the size of the required filtration vessels. Lower operating pressures could reduce energy and motor requirements. The pilot provided an opportunity to determine whether those potential efficiencies could be achieved without sacrificing treatment reliability. They could not.

The first operating scenario produced effective groundwater contaminant removal. Iron removal occurred relatively quickly, but ammonia removal remained inconsistent, and manganese removal was minimal. Increasing operating pressure during the second scenario improved both iron and ammonia performance, but treatment still did not consistently reach the desired objectives.

The trials provided valuable information nonetheless. Instead of simply demonstrating that the technology worked under favorable conditions, the pilot helped establish the process’s operating limits and identify which configuration offered the best balance of performance and reliability.

Establishing the Preferred Treatment Configuration

For Scenario III, the feed-water flow rate was reduced, and operating conditions were brought closer to Flowpoint’s standard design parameters. The change created more favorable conditions for biological activity. Iron removal remained effective, with essentially no iron detected after the first filtration stage. Approximately one week after the operating change, ammonia removal reached the desired performance and eventually stabilized at complete removal through biofiltration. The pilot had identified the preferred configuration for the proposed full-scale process.

Biological Groundwater Treatment as the First Barrier

The biological stage demonstrated one of the central principles behind the BiRO+ process: contaminants that can be efficiently removed biologically do not need to become a membrane-treatment problem. Under the final operating configuration, biofiltration completely removed iron and ammonia before the water entered the reverse osmosis system. That distinction matters.

Removing iron upstream reduces the contaminant loading placed on the membranes and decreases one potential source of membrane fouling. The RO system then remains available as a secondary treatment barrier if biological breakthrough or a process upset ever occurs. The treatment field study found no evidence of significant membrane fouling or scaling from the groundwater during the pilot program. Biological pretreatment produced water suitable for stable membrane operation, supporting the use of the combined process rather than relying on membrane treatment alone.

Reverse Osmosis as the Second Barrier

While biological filtration primarily treated iron and ammonia, reverse osmosis addressed the secondary treatment of dissolved constituents remaining in the water. The membranes consistently reduced manganese to at or below the required drinking water objectives despite limited biological manganese removal during the pilot period.

They also substantially reduced total dissolved solids, sulfate and hardness. Testing near the conclusion of the pilot illustrates the division of work between the two treatment stages. Raw groundwater containing approximately 1,520 mg/L of total dissolved solids reached the RO system at approximately 1,510 mg/L after biofiltration because dissolved mineral contaminant removal was not the purpose of the biological treatment process.

RO treatment reduced that concentration to approximately 41 mg/L. Similarly, sulfate was reduced from approximately 690 mg/L in the raw water to 13 mg/L after membrane treatment, while hardness was reduced from approximately 814 mg/L to 16 mg/L. This allowed each treatment technology to perform the work for which it was best suited.

Field Conditions Became Part of the Test

Pilot testing also exposed the treatment system to conditions that are difficult to mimic in a controlled laboratory environment. The program experienced multiple power interruptions. Extreme winter conditions led to a heating system failure and a freezing event. The biological filters subsequently required recovery and reseeding. Those interruptions affected bacterial development and extended the time required for the biological process to stabilize.

They also provided valuable operational information. Following the freezing event, iron-removal performance recovered within approximately three days, while ammonia treatment recovered to approximately 90% in less than three weeks during the second operating scenario. By the final scenario, the biological treatment process had developed sufficiently to achieve the required removal of iron and ammonia consistently from the groundwater.

The field program therefore demonstrated not only treatment performance but also how the biological system responded to interruption, recovery and changing source-water conditions.

Understanding Biological Manganese Removal

Manganese produced a different result during the pilot. Although the biological filters were designed to contribute to manganese treatment, a mature population of manganese-oxidizing bacteria generally develops only after stable ammonia removal has been established and may require an extended operating period.

Because stable ammonia removal was achieved later in the pilot, the field study concluded before sufficient biological manganese removal performance had developed. The integrated treatment strategy ensured that this did not prevent the system from meeting its water-quality objective.

Reverse osmosis consistently reduced manganese to concentrations below both the applicable maximum acceptable concentration and the aesthetic objective, providing a reliable second barrier. At the same time, biological maturation continues in a future full-scale system. This redundancy is an important feature of the treatment approach: performance does not depend on every contaminant being completely removed by a single process.

From Pilot Testing to Full-Scale Design

The value of pilot testing extends beyond proving whether a technology can treat water. It establishes the conditions under which that technology performs reliably. For the Rural Utility, the program tested operating pressures, hydraulic loading, biological development, membrane performance, backwashing requirements and system recovery under actual field conditions.

The results ultimately supported Scenario III as the basis for full-scale treatment design. Flowpoint’s recommended configuration combines biological iron and ammonia removal, reverse osmosis treatment, post-treatment remineralization and operational redundancy measures. The report concluded that a full-scale BiRO+ system can be effectively deployed for the Rural Utility and can produce water within the applicable Drinking Water Guideline limits and ranges.

More Than a Successful Groundwater Treatment Pilot

This Rural Utility’s project demonstrates an important principle in treating complex groundwater: the objective should not be to force one technology to solve every water-quality problem. Effective treatment can instead come from combining processes that perform complementary functions.

For BiRO+, biological treatment addresses contaminants such as iron and ammonia before they reach the membrane system. Reverse osmosis then provides an additional treatment barrier, removing dissolved constituents from the water beyond the practical scope of biological filtration. The pilot also showed why field validation matters.

Alternative operating conditions that appeared capable of reducing capital or operating costs did not provide sufficiently consistent biological performance. Testing those approaches before proceeding to full-scale design allowed the project team to establish operating parameters based on demonstrated treatment reliability rather than theoretical efficiency alone.

For communities dealing with challenging groundwater chemistry, that type of validation can provide greater confidence that a proposed treatment process is designed around the actual source water, operating environment and long-term needs of the facility.