Design and Operation of a Remote Phosphorus Analyzer

David M. Struve

Supervising Chemist

Water Quality Analysis Division

South Florida Water Management District

“On mechanical slavery, on the slaver of the machine, the future of the world depends.”

Oscar Wilde

Considerations for Remote Analysis

• Reliability

• Accuracy and Precision

• Communication and Control

• Flexibility and Speed

• Maintenance

• Waste and the Environment

Benefits of Remote Analysis

• Data generated 24/7, rain or shine

• Ability to observe short term trends

• No travel time

• No sample handling

• No lab costs

• Higher Frequency of Analysis

• Event Driven

Design Parameters for Phosphorous Determinations• Use a standard chemistry• Results comparable to lab analyses• Control analyzer temperature• Determine total and reactive portions• Easy access to all data• Fault detection• Low maintenance• Calibration standards “on board”

Project Overview

• System developed by Greenspan Technology, Australia

• Deployed February 2002

• System uses standard molybdate chemistry (SM4500PF)

• 3 point calibration and color correction

• 3 month maintenance cycle

• CPDP Modem Technology

• Deployed at STA1W - Site G310

D2

Wash

ThermalDigest

UVDigest

D1

Wash

AIR

AIR

STD 1

STD 2

STD 3

SAMPLE

AIR

AIR

Wash

Color 1

Color 2

Surfactant

Color 3

P0 - 8 Channel60:1 1/8” ID05-40 rpm

02

05

20

23

25

32

31

3022

04

01

00

03

06

21

24

26

V10NONC

Air

V14

NC

NO

V12

NC

NO

SwitchV17

Chamber 1

Waste 2

V11NCNO

Waste 2

WaterTrap

Chamber 2

Detector

V16NC

NO

V 13

NC

Waste 2

Waste 3

V 27

NC

NO

Air

Waste 1

P130:1 1/8” ID10-65 rpm

NO

Analytical Conditions

• Sampling frequency• Sample intake• 3 point calibration (0 – 124 ppb P)• Determination of reactive phosphorous• Sample digestion• Determination of total phosphorous• Monitoring of digester temperature, cabinet

temperature, leak detectors, reagent volumes

8000

9000

10000

11000

12000

13000

14000

15000

0 20 40 60 80 100 120 140

P Conc. (ug/L)

ST

D R

esp

on

se

SR = (9229(41.9±1.9)Pc

R2 = 0.9996±0.0016n = 642

Detection Limit Study(3 hour sample cycle)

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8 9

Measurement

P (

ug

/L)

TRP

TP

Reactive PhosphorusMean = 36.0 ug/LSTDDEV = 0.534 ug/LMDL = 1.6 ug/L

Total PhosphorusMean = 53.5 ug/LSTDDEV = 1.07 ug/LMDL = 3.2 ug/L

Remote Analyzer Data - G310Total Phosphorous and Total Reactive Phosphorous

0

20

40

60

80

100

120

140

20-Aug 9-Sep 29-Sep 19-Oct 8-Nov 28-NovDate/Time

[P],

ug

/L

Grab TPO4 (ppb) TPO4 (ppb) TRP (ppb)Grab OPO4 (ppb) 8 per. Mov. Avg. (TPO4 (ppb)) 8 per. Mov. Avg. (TRP (ppb))2 per. Mov. Avg. (Grab TPO4 (ppb)) 2 per. Mov. Avg. (Grab OPO4 (ppb))

0

500

1000

1500

2000

2500

3000

10/27 0:00 10/27 12:00 10/28 0:00 10/28 12:00 10/29 0:00 10/29 12:00 10/30 0:00 10/30 12:00 10/31 0:00

Time

Flo

w (

ft3 /S

)

0

10

20

30

40

50

60

70

80

90

100

110

TP

( g

/L)

flow TP

Overall Observations

• Comparative results excellent

• Good detection limits (~4ppb)

• Communications flawless

• Control and error detection good

• Interesting data

The Project Team

• Greenspan Technology• Robert Briggs• Chris Gibson• Tom Baber• Bill Harrington• Dr. Meifang Zhou• Kim Hanes• AirLink Communications• SFWMD

Questions?