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Advanced Septic System Nitrogen Sensor Challenge, Phase II: Prototype Testing

Q: Will sensor developers be able to send their sensor packages to Battelle or EPA for installation ahead of the March 2018 preliminary screening test?
 

A: No. Sensor developers will be required to install and setup their own sensor packages at the Massachusetts Advanced Septic System Testing Center (MASSTC), the Barnstable, MA testing facility. EPA, Battelle and MASSTC will be establishing a specific date for the sensor setup period. Each team will be expected to deliver, install their sensor on the test vessel, and calibrate their device during the setup period. EPA and MASSTC staff will be on hand to assist with logistics during the setup period, but will not be responsible for device set up, calibration or repair. The Screening Test will begin immediately following the Setup Period.
 
Q: Will sensor developers who did not participate in Phase I of the Advanced Septic System Nitrogen Sensor Challenge be eligible to participate in Phase II (the testing phase)?

A: Yes. Any sensor developer whose sensor package meets the logistical requirements outlined in Table A-2 of the draft Test/Quality Assurance Plan (T/QAP), completes an application, and whose application is accepted by EPA and Battelle will be eligible to participate in the preliminary screening test beginning in March 2018. The sensor developer does not have to have participated in Phase I. Both the draft T/QAP and the application can be found on the VerifiGlobal website

Q: What is the maximum allowed size of the sensor?

A: The overall dimensions of the sensor unit should be no larger than 6” x 6” x 20”, with the submerged portion of the device being no larger than 6” x 6” x 6”. This is a change from what was presented in the December 18th informational webinar and in the original version of the Test/Quality Assurance Plan (T/QAP). After careful consideration, EPA determined that they wanted to allow more flexibility in the sensor dimensions.

Q: What are the performance goals for the sensors?

A: The overall performance goals for the sensors are presented in the Table below (Table A-1 of the T/QAP). After a high level quality assurance and statistical review of our T/QAP, an EPA statistician advised the EPA sensor challenge team to restate the accuracy, precision and range in the Performance Goals Table (Table A-1 in the T/QAP). The changes made reflect practical technology considerations for an in situ device, the intended field application of the sensor in a septic system, and quality review of the test plan.  The highlighted cells in the table below reflect the changes that have been made to Table A-1.

 Attribute
Attribute Description  Performance Goals


 Minimum
Almost Ideal  Ideal
Parameter1
What is being measured
NO3-, NH4+
NO3-, NH4+, TOC
Total nitrogen (TN)2
Installation Price
Price to the homeowner to install
$1,500
$1,250
$1,000
Data Management
Ability to record and transmit data (i.e., telemetry) for real-time access by practitioners, regulators, and interested stakeholders
Record and automatically transmit data to designated server or cloud
Record and automatically transmit data to designated server or cloud
Record and automatically transmit data to designated server or cloud
Applicability & Accessibility
Applicability of sensor(s) to various innovative/alternative system designs and ease of access to OWTS for installation and maintenance
Located in-situ to provide performance information on the OWTS; must be accessible for maintenance
Located in-situ to provide performance information on the OWTS; must be accessible for maintenance
Located in-situ to provide performance information on the OWTS; must be accessible for maintenance
Frequency of Sensor System Maintenance
How often the sensor(s) need to be maintained
No more than quarterly
No more than semi-annually
No more than annually
Accuracy
Accuracy of sensor measurements to the true measurement
Within 20% of true value3
Within 20% of true value3
Within 20% of true value3
Precision
Repeatability of sensor measurements
 ≤30% RSD
≤20-30% RSD ≤20% RSD
Range4
Range of the detection
2-60 mg N/L
2-60 mg N/L 2-60 mg/L TOC

2-60 mg N/L

Sensor Operating Temperature Range
Temperature range in which the sensor can operate
4° C to 35° C
4° C to 35° C
4° C to 35° C
Deployment
Period of deployment
Continuous
Continuous
Continuous
System Lifetime
Expected life of sensor
5 years
5 to 10 years
10 years

1 Refer to Section B1.4 for information on the sources of NO3-, NH4+, and TOC. 
2 Total Nitrogen (TN) is defined as the sum of total kjeldahl nitrogen (ammonia, organic and reduced nitrogen) and nitrate-nitrite. 
3 True value is defined as the certified laboratory result for the parameter using approved test methods.  
4 The sensors must be capable of alerting about or otherwise notifying of an over range value.

Accordingly, updates have also been made to the table below (Table A-3 of the T/QAP) to revise the subset of performance goals that need to be met for a sensor to advance to the field performance test. The highlighted cells in the table below reflect the changes that have been made to Table A-3.

Attribute
Performance Goals to Determine Field Performance Test Invitation 
Parameter

Measures

  • NH4+ and NO3- or
  • NH4+, NO3-, and TOC or
  • TN
Data Management
Internal (local) sensor system data logger successfully collects time stamped data for the screen test
Applicability & Accessibility
Meets test size limits and performs under screen test environmental conditions
Maintenance
No more than one servicing during the preliminary screening test
Accuracy
Within 40% of true value
Precision
≤40% RSD
Range
2-60 mg N/L
2-60 mg/L TOC
Deployment
High frequency (at least hourly) measurement for the duration of the test