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Project Background

Text Box: Traditionally, activated sludge processes were designed to remove organics and suspended solids from wastewater.  The justification for including nitrogen control in wastewater treatment facilities began with the need to protect receiving waters from the increasing problem of eutrophication and hypoxia (low levels of dissolved oxygen in bottom waters, generally less than 2 mg/l).  One of the challenges facing wastewater treatment plants in eliminating nitrogen compounds from their effluent comes with the ability to create an optimal aerobic environment to achieve nitrification and an optimal anoxic environment to achieve denitrification, yet without causing an interference with the effluent chlorination process.  The use of on-line nitrogen analyzers can be used to optimize nitrogen control and maximum efficiencies can be achieved by combining on-line nitrogen instruments with a control system.
Although different strategies for controlling aeration to achieve nitrogen control have evolved, a comparison of different control schemes does not currently exist.  A fair assessment would not only require simultaneous testing of multiple identical plants in parallel but would also require substantial funding.

WERF Research Synopsis (03-CTS-8)

On-Line Nitrogen Monitoring and Control Strategies

Summer 2006

 

Research Approach

The primary objective of this research project is to identify the specifications, application and performance of on-line and in-situ analyzers that measure nitrogen compounds (such as ammonia, nitrate, and nitrite).  A secondary objective of this research project is to identify the similarities and differences in nitrogen instrumentation technologies and their corresponding control strategies as they apply to municipal and industrial treatment facilities.

 

The project was conducted in two phases.  The first phase of this project documented available nitrogen instrumentation technologies for the wastewater industry, their respective specifications, and their successful applications at facilities for nitrogen compound measurements as well as their use in effective nitrogen control.  In addition, the first phase of this project documented, based on site surveys, the best examples of applied conventional and alternative nitrogen process control strategies.  Case studies are presented to show how nitrogen instrumentation and control strategies can be effectively utilized (to benefit the biological wastewater treatment process by increasing rated plant capacity and reducing energy and chemical consumption).

 

All stakeholders involved in the project determined the type of instrument technology (in-situ) and form of nitrogen compounds (nitrate) to be tested in the second phase of the project. The most promising nitrogen instrument manufacturers, as identified in the first phase of the project, were invited to participate in the second phase of the project by donating instruments for a side-by-side field test.  In addition, phase two of this research project documented the performance and maintenance requirements of the tested nitrogen analyzers.

This project presents a cost-effective approach to comparing control strategies and includes the investigation and documentation of “successful” nitrogen control strategies utilized at various wastewater treatment facilities.  Case studies demonstrate which control strategies prove to be the most practical and provide the best cost benefits for implementing nitrogen control.  However, an integral component of any successful control system relies on the performance of its corresponding instrumentation and the instrument’s auxiliary systems.   Testing nitrogen analyzers intended for the purposes of controlling nitrification and denitrification provides additional users with valuable information on the performance of this equipment in an actual wastewater treatment plant installation.

A total of 25 nitrogen instrument manufacturers worldwide were identified, 20 of which participated in the project and are identified in Table 1.  Nitrogen instrument specifications were compiled in a “standardized” format for the participating manufacturers to all users to directly compare the instrumentation technologies.

 

Nitrogen Instrumentation

The following synopsis was extracted from the Water Environment Research Foundation (WERF) project number 03-CTS-8, On-Line Nitrogen Monitoring and Control Strategies final report.  This information is copyrighted by Water Environment Research Foundation (WERF) and is reprinted with permission.  To obtain the project final report containing detailed information about this WERF project, please contact WERF www.werf.org, Tel: 703-684-2470. 

Table 1. Available Nitrogen Instrument Manufacturers

No.

Manufacturer

1

ABB

2

Applikon

3

AWA Instruments

4

Biotector

5

Bran + Luebbe

6

ChemScan

7

Danfoss (now Hach Evita)

8

Datalink

9

Endress + Hauser

10

Global Measurement Technologies (formerly FPM)

11

Hach

12

Murtac

13

Myratek

14

NextChem

15

s::can Messtechnik GmbH (distributed by Royce Technologies in USA)

16

Sea & Sun Technology

17

Severn Trent Services

18

Shimadzu

19

Swan

20

Systea Scientific

21

Teledyne Isco (now Wedgewood Analytical)

22

Tyco Greenspan

23

Tytronics

24

Waltron

25

WTW