David M. Struve, SFWMD, Meifang Zhou, SFWMD, Tom Baber, Litkenhaus Associates ABSTRACT A remote P...

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David M. Struve, SFWMD, Meifang Zhou, SFWMD, Tom Baber, Litkenhaus Associates ABSTRACT A remote P analyzer has been designed and optimized using UV/thermal induced persulfate digestion of total phosphorus in water and ascorbic acid-phosphomolybdenum blue method for TP and TRP determination. The analytical parameters were remotely monitored and the data were remotely processed. This remote P analyzer successfully provided the near real-time TP and TRP data of the water at the outlet of a STA of the SFWMD. The P concentration results from this analyzer were comparable with the lab analysis and the method detection limit was also similar (4 g/L) to the lab method. The diurnal fluctuation of TP and TRP concentrations in the water at the STA was observed. Not only may this analyzer be very useful for optimizing the operation of the STA, but also has the potential application in surface water P TMDL calculation and monitoring. INTRODUCTION The traditional method of measuring P concentration in water involves field grab sampling with subsequent lab analysis. As more STA’s are being constructed for protecting the ecosystem and the TMDL concept is being adopted for various water bodies, it is increasingly important to be able to obtain near real-time P concentration data for optimization of the STA operation and P budget studies. MATERIALS AND METHODS RESULTS AND DISCUSSION The remote TP analyzer is a batch system that processes only one sample at a time. The water sample was digested with persulfate /H 2 SO 4 without neutralization. The final optimum acid concentration ([H]) and [H]/[Mo] were 0.4 N and 75 respectively. The reaction time (RT) was optimized by determining the FCD time at different P concentration. The FCD time increased as the phosphorus concentration decreased (Table 1). Ten minutes RT was selected to insure the FCD of the low P concentration water samples. 0 500 1000 1500 2000 2500 3000 3500 4000 20-A ug 9-S ep 29-S ep 19-Oct 8-N ov 28-N ov Time Flow (ft 3 /S) Figure 5 Figure 4 Figure 6 Figure 3 Figure 7 0 500 1000 1500 2000 2500 3000 9/19/02 0:00 9/19/02 12:00 9/20/02 0:00 9/20/02 12:00 9/21/02 0:00 9/21/02 12:00 9/22/02 0:00 9/22/02 12:00 9/23/02 0:00 Time Flow (ft 3 /S) 0 10 20 30 40 50 60 70 80 90 100 110 TP ( g/L) flow TP 0 500 1000 1500 2000 2500 3000 10/26/02 0:00 10/26/02 12:00 10/27/02 0:00 10/27/02 12:00 10/28/02 0:00 10/28/02 12:00 10/29/02 0:00 10/29/02 12:00 10/30/02 0:00 10/30/02 12:00 10/31/02 0:00 Time Flow (ft 3 /S) 0 10 20 30 40 50 60 70 80 90 100 110 TP ( g/L) flow TP 0 500 1000 1500 2000 2500 3000 3500 8/21/02 12:00 8/22/02 0:00 8/22/02 12:00 8/23/02 0:00 8/23/02 12:00 8/24/02 0:00 8/24/02 12:00 8/25/02 0:00 8/25/02 12:00 8/26/02 0:00 8/26/02 12:00 Time Flow (ft 3 /S) 0 10 20 30 40 50 60 70 TP ( g/L) flow TP 0 500 1000 1500 2000 2500 3000 3500 9/4/02 3:00 9/4/02 15:00 9/5/02 3:00 9/5/02 15:00 9/6/02 3:00 9/6/02 15:00 9/7/02 3:00 9/7/02 15:00 9/8/02 3:00 9/8/02 15:00 9/9/02 3:00 Time Flow (ft 3 /S) 0 10 20 30 40 50 60 70 TP ( g/L) flow TP 0 500 1000 1500 2000 2500 3000 11/6/02 12:00 11/8/02 12:00 11/10/02 12:00 11/12/02 12:00 11/14/02 12:00 11/16/02 12:00 11/18/02 12:00 Time Flow (ft 3 /S) 0 20 40 60 80 100 120 140 TP ( g/L) flow TP 0 20 40 60 80 100 120 140 20-Aug 9-Sep 29-Sep 19-O ct 8-Nov 28-Nov Date/Tim e [P ], g/L G rab TP O 4 TPO4 TR P ,unbackground color corrected G rab O PO4 8 per.M ov.A vg.(TP O 4) 8 per.M ov.A vg.(TR P ,unbackground color corrected) 2 per.M ov.A vg.(G rab TP O 4 ) 2 per.M ov.A vg.(G rab O PO 4 ) Figure 5 Figure 6 Figure 3 Figure 4 Figure 7 Analyzer Monitoring and Data Process: The test scheduler, analytical parameters (such as the digestor and cabinet temperatures, the responses of the standards and samples, and the level of reagents and waste in the bottles) and data were remotely monitored or processed. Instrument Location and Site: The instrument was located at the outlet of the STA1W just upstream of the outflow pump station G310. Reagents: The standard curves were prepared from the reference P standard solution. The 60ppb QC sample was prepared from phytic acid and a reference standard. The color reagents were prepared according to our lab study and the Standard Method. Full color development (FCD) time: FCD time was determined using the Time Drive program at 880 nm in the lab. The P concentration dynamic in the outflow water during small and large pulse flows at the STA were quite different, and the P dynamic at medium pulse flow was somewhat similar to the large pulse flow (Figure 3, 4, 5). When the water flow rate was nearly constant, a diurnal fluctuation of total phosphorus with the maximum near midday and the minimum near midnight in the water was observed (Figure 6). The different P concentration dynamics with different water flow patterns may be a combination effect of residence time in the STA and the diurnal fluctuation of the TP in water (Figure 3, 4, 5). When the water flow was stopped, the TP concentration in the canal water gradually decreased and exhibited almost no daily fluctuation (Figure 7). When the water flow rate was increased quickly from 0 to near 2100 ft 3 /s, the TP concentration spiked and then decreased to typical levels. Table 1. The fullcolor developm enttim e (FC D T)and the m ethod reaction tim e(M R T). 10 ppb P 32 ppb P 64 ppb P sam ple FC D T (m in) 4.9 0.2 a 3.6 0.3 a 3.2 0.1 a - M R T (m in) - - - 10 a:n = 2 The TP recovery of a 60 ppb QC sample was 95% (Table 2). The TP, TRP and MDL of the field method were very similar to those of the lab method (Table 2). The responses of the standards of the 642 sets of standard curves were very stable. The linear correlation coefficient of the standard curves was higher than the lab QA/QC requirement of 0.995. The TP and TRP results from the field and lab methods are shown in Figure 1 and the hourly mean water flow rates of the STA outlet are plotted in Figure 2. The overall TP and TRP results from field and lab methods were very similar. However, the field method showed the all the detail of the P concentration dynamics in the STA effluent water. In order to examine the effect of flow rate on TP concentration in outflow water of the STA, five sections of the TP results were selected according to the flow patterns, such as small pulse, medium pulse, large pulse, constant, and no water flow out of the STA (Figure 1, 2, 3, 4, 5, 6, 7). Table 2. The m ethod perform ance (M D L, STD curve correlation coefficient, and SD ) M ethod TP a TRP M DL ppb r 2 Field 57 1.3 b 36 1.1 b 3-4 0.9996 0.0016 c Lab 57 37 2-4 - a:60 ppb organic and inorganic P Q C sam ple;b:M D L ofthe field m ethod w asestim ated from resultsofthe Q C sam ple;c:n = 642 CONCLUSION The near real time TP data from the inlet and outlet of the STA will enhance optimization of STA operations. The high temporal resolution data can be used to refine/develop/calibrate the models for STA design/operation, and will also be very useful for TP Additionally, the field TP analyzer can provide a tool for research on the dynamic biogeochemistry of the P in the ecosystem. Figure 1. TP and TRP results from field and lab method Figure 2. Water flow rate at the outlet of STA1W Figure 3. TP results at small pulse water flow Figure 4. TP results at medium pulse water fl Figure 5. TP results at large pulse water flow Figure 6. TP results at near constant water Figure 7. TP results at near zero water fl Digestion and analysis: The sample was digested sequentially for 37 minutes via thermal digestion at 90 C and 30 minutes of UV digestion with persulfate/H 2 SO 4 . After 10 minutes of color development in the reaction chamber, the y of the sample was measured using a minispectrophotometer.

Transcript of David M. Struve, SFWMD, Meifang Zhou, SFWMD, Tom Baber, Litkenhaus Associates ABSTRACT A remote P...

Page 1: David M. Struve, SFWMD, Meifang Zhou, SFWMD, Tom Baber, Litkenhaus Associates ABSTRACT A remote P analyzer has been designed and optimized using UV/thermal.

David M. Struve, SFWMD, Meifang Zhou, SFWMD, Tom Baber, Litkenhaus AssociatesABSTRACT

A remote P analyzer has been designed and optimized using UV/thermal induced

persulfate digestion of total phosphorus in water and ascorbic acid-

phosphomolybdenum blue method for TP and TRP determination. The analytical

parameters were remotely monitored and the data were remotely processed. This

remote P analyzer successfully provided the near real-time TP and TRP data of the

water at the outlet of a STA of the SFWMD. The P concentration results from this

analyzer were comparable with the lab analysis and the method detection limit was

also similar (4 g/L) to the lab method. The diurnal fluctuation of TP and TRP

concentrations in the water at the STA was observed. Not only may this analyzer be

very useful for optimizing the operation of the STA, but also has the potential

application in surface water P TMDL calculation and monitoring.

INTRODUCTION

The traditional method of measuring P concentration in water involves field grab

sampling with subsequent lab analysis. As more STA’s are being constructed for

protecting the ecosystem and the TMDL concept is being adopted for various water

bodies, it is increasingly important to be able to obtain near real-time P

concentration data for optimization of the STA operation and P budget studies.

MATERIALS AND METHODS

RESULTS AND DISCUSSION

The remote TP analyzer is a batch system that processes only one sample at a time. The

water sample was digested with persulfate /H2SO4 without neutralization. The final optimum

acid concentration ([H]) and [H]/[Mo] were 0.4 N and 75 respectively. The reaction time

(RT) was optimized by determining the FCD time at different P concentration. The FCD time

increased as the phosphorus concentration decreased (Table 1). Ten minutes RT was selected

to insure the FCD of the low P concentration water samples.

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Figure 4Figure 6

Figure 3Figure 7

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[P],

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Grab TPO4 TPO4TRP, unbackground color corrected Grab OPO4 8 per. Mov. Avg. (TPO4) 8 per. Mov. Avg. (TRP, unbackground color corrected)2 per. Mov. Avg. (Grab TPO4 ) 2 per. Mov. Avg. (Grab OPO4 )

Figure 5 Figure 6Figure 3

Figure 4Figure 7

Analyzer Monitoring and Data Process: The test scheduler, analytical parameters (such as the

digestor and cabinet temperatures, the responses of the standards and samples, and the level

of reagents and waste in the bottles) and data were remotely monitored or processed.

Instrument Location and Site: The instrument

was located at the outlet of the STA1W just

upstream of the outflow pump station G310.

Reagents: The standard curves were prepared

from the reference P standard solution. The

60ppb QC sample was prepared from phytic

acid and a reference standard. The color

reagents were prepared according to our lab

study and the Standard Method.

Full color development (FCD) time: FCD time

was determined using the Time Drive program

at 880 nm in the lab.

The P concentration dynamic in the outflow water during small and large pulse

flows at the STA were quite different, and the P dynamic at medium pulse flow

was somewhat similar to the large pulse flow (Figure 3, 4, 5). When the water flow

rate was nearly constant, a diurnal fluctuation of total phosphorus with the

maximum near midday and the minimum near midnight in the water was observed

(Figure 6). The different P concentration dynamics with different water flow

patterns may be a combination effect of residence time in the STA and the diurnal

fluctuation of the TP in water (Figure 3, 4, 5). When the water flow was stopped,

the TP concentration in the canal water gradually decreased and exhibited almost

no daily fluctuation (Figure 7). When the water flow rate was increased quickly

from 0 to near 2100 ft3/s, the TP concentration spiked and then decreased to

typical levels.

Table 1. The full color development time (FCDT) and the methodreaction time (MRT).

10 ppb P 32 ppb P 64 ppb P sampleFCDT (min) 4.90.2a 3.60.3a 3.20.1a -MRT (min) - - - 10

a: n = 2

The TP recovery of a 60 ppb QC sample was 95% (Table 2). The TP, TRP and MDL of the

field method were very similar to those of the lab method (Table 2). The responses of the

standards of the 642 sets of standard curves were very stable. The linear correlation

coefficient of the standard curves was higher than the lab QA/QC requirement of 0.995.

The TP and TRP results from the field and lab methods are shown in Figure 1 and the hourly

mean water flow rates of the STA outlet are plotted in Figure 2. The overall TP and TRP

results from field and lab methods were very similar. However, the field method showed the

all the detail of the P concentration dynamics in the STA effluent water.

In order to examine the effect of flow rate on TP concentration in outflow water of the STA,

five sections of the TP results were selected according to the flow patterns, such as small

pulse, medium pulse, large pulse, constant, and no water flow out of the STA (Figure 1, 2,

3, 4, 5, 6, 7).

Table 2. The method performance (MDL, STD curve correlationcoefficient, and SD)

Method TPa TRP MDL ppb

r2

Field 571.3b 361.1b 3-4 0.99960.0016c

Lab 57 37 2-4 -a: 60 ppb organic and inorganic P QC sample; b: MDL of the fieldmethod was estimated from results of the QC sample; c: n = 642

CONCLUSION

The near real time TP data from the inlet

and outlet of the STA will enhance

optimization of STA operations. The high

temporal resolution data can be used to

refine/develop/calibrate the models for

STA design/operation, and will also be

very useful for TP loading and TMDL

calculations from storm water runoff.

Additionally, the field TP analyzer can provide a tool for research on the dynamic

biogeochemistry of the P in the ecosystem.

Figure 1. TP and TRP results from field and lab method Figure 2. Water flow rate at the outlet of STA1W

Figure 3. TP results at small pulse water flow Figure 4. TP results at medium pulse water flow

Figure 5. TP results at large pulse water flow Figure 6. TP results at near constant water flow

Figure 7. TP results at near zero water flow

Digestion and analysis: The sample was digested

sequentially for 37 minutes via thermal digestion at

90 C and 30 minutes of UV digestion with

persulfate/H2SO4. After 10 minutes of color

development in the reaction chamber, the colorintensity of the sample was measured using a minispectrophotometer.