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HJ-100

HJ-300

Trichloroethene Optrode Detection System

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North Indian Bend Wash – Superfund

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CASE STUDIES:

NORTH INDIAN BEND WASH TCE
REMEDIATION PLANT- SUPERFUND
City of Scottsdale

The North Indian Bend Wash (NIBW) is a designed “Superfund Site” by the EPA. The ground water within the boundaries of the area are contaminated with volatile organic compounds (VOCs) from several sources. The most common contaminant is trichloroethene (TCE). A treatment plant was constructed by several of the responsible parties. The treatment plant uses air-stripping technology to remove the VOCs from the water followed with carbon filters used to remove the VOCs from the effluent air. The treatment plant is processes 10.7 million gallons per day. The treatment plant is operated by the City of Scottsdale on behalf of the NIBW participating companies.

A HJ-300 unit was installed at the plant in January 2002 to monitor the influent and effluent water of the treatment plant. The influent water has a TCE concentration averaging 100 to 120 parts per billion (ppb) and the effluent (treated) water has a concentration of <5 ppb. The Burge Environmental System was installed as part of an agreement with the EPA to allow reduced monitoring at the facility. Prior to the installation of the unit, daily sampling and analysis was performed. After the unit was installed, the sampling and analysis were substantially reduced. The primary objective of the daily monitoring was to ensure that the treated water did not exceed the regulatory threshold of 5 ppb. The HJ-300 is programmed to perform daily analysis of the treated and untreated water and perform one calibration check sample as a quality control measure. The calibration curve uses a blank, 6 and 12 ppb standards and a 6 ppb check standard. The calibration curve range was selected to bracket the regulatory threshold concentration of 5 ppb. Burge Environmental, Inc. remotely (modem and phone line) operates the system on behalf of the responsible parties. The operations include programming the times to initiate the monitoring process and retrieving and reviewing the data. All other function including sampling, calibration and analysis are fully automated.

The system experienced only two mechanical problems from January 2001 to July 2003. Both of the problems were attributed to malfunctioning valves. The data presented on Table I includes the monthly average TCE concentration for untreated water, treated water and the mid-calibration standard (6 ppb). The mid-calibration standard is analyzed each day after the analysis of the untreated and treated water samples. The average laboratory data analyzed pursuant to EPA Method 8260B (Purge and Trap Gas Chromatography/Mass Spectrometry) for October 2002, to April 2003, are presented on Table I.

Table I

Panel-Mounted Configuration Optrode Results

Monthly Averages

October 2002-April 2003


Month	Treated Water Average Concentration ppb	Laboratory Treated Water Average Concentration ppb	Untreated* Water Average Concentration ppb	Laboratory** Untreated Water Average Concentration ppb	Midcal Average Concentration ppb

October	<1	<.05	109	112	6.6
November	<1	<.05	98	118	6.3
December	<1	<.05	106	113	5.9
January	<1	<.05	105	106	5.2
February	<1	<.05	111	132	5.5
March	<1	<.05	110	138	6.2
April	<1	<.05	106	122	6.2


*Based on an average of at least 28 samples per month
**Based on an average of 4 to 5 samples per month

The limit of detection (LOD) of the instrument is <1 ppb. The primary difference between the laboratory and HJ-300 results for the untreated water is the number of samples collected each month. The HJ-100 collects 28 to 31 samples per month while 4 to 5 samples per month are collected for laboratory analysis. Therefore, different samples are being analyzed by the two methods.

The HJ-300 has shown itself to be a reliable and low maintenance instrument for insuring the treatment plant is reducing the TCE concentration to below the regulatory threshold of 5 ppb.

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