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U. S. ENVIRONMENTAL PROTECTION AGENCY

Washington, D.C. 20460

OFFICE OF CHEMICAL 

SAFETY AND 

POLLUTION 

PREVENTION

January 10, 2012

PC Code: 061601

DP Barcode: D396402

MEMORANDUM

SUBJECT: Review of Jar Test Results for Drinking Water Assessment Purpose 

FROM: James Lin, Environmental Engineer

Environmental Risk Branch 2

Environmental Fate and Effects Division (7507P)

TO: Mindy Ondish, Risk Manager Reviewer

Kable Davis, Risk Manager

Registration Division (7505P)

THROUGH: R. David Jones, Senior Agronomist (Secondary Reviewer)

Brian Anderson, Chief

Environmental Risk Branch 2

Environmental Fate and Effects Division (7507P)

This memorandum presents the review of a non-guideline supplemental mobility study (MRID 

48659501). The submitted study was conducted to evaluate the effects of traditional water 

treatment processes on paraquat and to determine the mobility of paraquat through soil filtration 

column. This memorandum only addresses the first aspect on the effects of using jar tests as a 

mean to mimic traditional water treatment processes to determine whether the results of jar tests

are sufficient to provide the justification to refine the previous drinking water assessment.

Conclusion

14C-paraquat, spiked at ~30 ppb into the raw surface water samples from five representative US 

CWS (community water supply) facilities, was effectively removed by a combination of typical 
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water treatment processes conducted on a laboratory-scale: the “laboratory jar test” (coagulation 

using alum with either lime or soda ash, flocculation and sedimentation), followed by duel media 

filtration (anthracite atop of filtering sand). The combination process was able to reduce the 

level of 14C-paraquat to approximate or below the limit of detection of about 0.15μg/L (ppb). 

The jar test results allow EFED to better characterize potential levels in finished water for 

drinking water assessment purpose. The level of paraquat in the finish water of 0.15 μg/L

should be used for the drinking water assessment. 

Study Summary

Raw water samples from five CWS facilities were used for the jar test. The five CWS are: (1) 

Manatee County, Florida; (2) Wayne City, Illinois; (3) Sturgis Water Works, Kentucky; (4) Lake 

Townsend, North Carolina; and (5) San Patricio PWS, Texas. Jar tests on these water samples 

were conducted between August 18, 2004 and September 13, 2004 (start dates). Before starting 

the jar test, raw water samples were spiked with 14C-paraquat at ~30 ppb. The coagulants (soda 

ash, lime, and/or alum) were simultaneously delivered into the replicate jar test beakers using a 

series of disposable 3 or 10 cc size plastic syringes. The jar tests were conducted inside a lab 

without windows to reduce photolytic degradation. The steps are described below:

Jar Test Steps

1. Coagulation –

Alkalinity Adjustment (Mixing following addition of soda ash or lime)

Mixing following Alum Addition

Duration: 2 minutes; Speed (rpm): 300

2. Flocculation

Floc (precipitate) starts to form

Duration: 20 minutes; Speed (rpm): 60

3. Sedimentation

Floc settles to bottom

Duration: >60 minutes; Speed (rpm): 0

According to the study protocol, the laboratory study will use the “jar test” methods, which 

include flocculation, coagulation and sedimentation. Filtration will be included only if the three 

jar test steps do not adequately reduce the level of paraquat in the spiked water.

Results

Based on jar test alone, the water samples from Illinois, Kentucky, and Texas show the 

remaining paraquat contents are at about or below the detectable limit of 0.15 μg/L. 

The water samples from Florida and North Carolina show the remaining paraquat level of about 

8 to 10%, with additional filtration, the level of paraquat is reduced to about or below the 

detectable limit.