StormTreat Systems Monitoring Results Update
from the UNH Stormwater Center (March 2013)

StormTreat Systems, Inc. has completed sixteen-months of rigorous field-testing of its proprietary bioretention treatment system at the University of New Hampshire Stormwater Center (UNHSC) in Durham, NH and has received its preliminary Performance Evaluation Report (PER). The monitoring results show consistently high removal rates for several key stormwater pollutants including total suspended solids (TSS), suspended sediment concentration (SSC), total zinc (TZn), enterococcus bacteria, and total phosphorus (TP). These results demonstrate that the StormTreat System (STS) is effective in meeting both the conventional TSS criterion as well as other watershed-specific water quality targets that are commonly identified as the leading cause of impairment in Total Maximum Daily Load (TMDL) studies.

Testing began at the UNHSC in April 2011 to obtain monitoring data in compliance with the Technology Acceptance and Reciprocity Partnership (TARP) and the Technology Acceptance Protocol – Ecology (TAPE) testing guidelines. Our purpose in undergoing this testing is to confirm pollutant removal performance documented in earlier third-party testing and to provide updated results to state and local government officials, engineering consultants, and potential customers looking to meet benchmark removals for various stormwater pollutants. The PER is a precursor to the final monitoring report that will be used to obtain TARP and TAPE certifications.

The following table summarizes STS’s treatment performance results for qualifying rainfall/runoff events obtained during the testing period and reported to STS in the PER from UNHSC. Concentrations are shown in mg/l except Enterococci bacteria, which is cfu/100ml.

With a RE of 93%, STS demonstrates an exceptionally high capacity to remove total suspended solids (TSS) from stormwater runoff, far exceeding the federal EPA standard of 80% TSS removal. New research is indicating that particle size distribution is an important factor for determining overall treatment performance and very fine particles have been shown to have significant impacts on aquatic systems. Suspended sediment concentration (SSC) is a measurement of the ability to remove these finer fractions contained within the total sediment load. Again, STS performed extremely well in this category with an overall median RE of 96%. The EPA is actively working on developing an acceptable metric for this parameter and new standards are likely in the near future.

Zinc is one of several heavy metals known to cause harm to fish and other marine life. For this reason TMDL requirements for zinc have become more common in certain impaired watersheds. STS achieved a removal efficiency for zinc of 67% with effluent levels consistently bordering on the detection limit of 0.01 mg/l.

The RE for Total Phosphorus (TP) was reported at 50%. This removal rate is lower than was demonstrated in earlier third-party reviews of the STS but still significant to address water quality problems in numerous watersheds where phosphorus has been identified as a critical pollutant of concern.

During this study the TP RE for STS was based on a relatively low mean influent concentration of 0.07 mg/l. Despite low influent concentrations STS was able to achieve a consistently low mean effluent concentration of 0.03 mg/l. Typically, higher removal efficiency levels are associated with higher influent concentrations, thus these results are encouraging for installations where very low levels of TP are required to meet water quality standards. Additionally, we believe that higher TP removal rates will be achieved in watersheds where phosphorus loading rates are substantially higher than those found at the UNHSC.

Enterococci bacteria RE of 88% was also reported in the PER. This is a very promising result in support of STS use for applications in watersheds where TMDL limits have been prepared for pathogens. These include coastal areas where shellfishing beds have been closed due to excessive concentrations of pathogens and other surface waters where primary and secondary water contact has been restricted.

We are pleased to share these monitoring results with our customers and others who may be interested in using StormTreat on future projects. We anticipate completion of the monitoring at the Stormwater Center later this year and will be seeking TARP/TAPE approvals immediately thereafter. In the meantime, if you would like to learn more about our system please contact us and we will be happy to arrange a free Lunch and Learn presentation at your office.

* This data based on 20 to 25 storm events for all parameters except Enterococci, which is based on 7 storm events.


Massachusetts Strategic Environmental Partnership Program
Monitoring Results (September 1997)

Fecal Coliform

Total Suspended Solids

Chemical Oxygen Demand

Total Dissolved Nitrogen

Total Petroleum Hydrocarbon















NOTE: Data collected over a two-year period by clients, analyzed by state-certified labs and verified by the Commonwealth of Massachusetts.

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