March 2000 • CIS-3

CURRENT INFORMATION SUMMARY

Biocide for Photographic Solution
Tanks and Wash Water
Some Facts about Bio-Slime
Slime is the result of biogrowth accumulation and is found in
most photoprocessing wash waters at one time or another. It
is a mixture of microbes such as bacteria and fungi that feed
on chemicals in processing solutions such as dilute fixer.
These microscopic contaminants come from incomingwater, air, dirty tanks or lines, people, or anything that comes
into contact with the wash water.
Some processes are more prone to biogrowth than others.
As solutions become more “environmentally friendly,” they
become more prone to biogrowth, and deterring biogrowth
becomes more of a concern.
The microbes are most evident when they create a foulodor and appear in the processor as dirt and slime. Other lessobvious problems are accumulation in sumps, lines, andsilver recovery systems. You can easily clean tanks withscrubbing and hot water (temperatures above 150°F cansoften PVC). Lines and silver-recovery systems are noteasily cleaned. If these systems become fouled, the result isplugged lines and less efficient silver recovery. Lines must
often be replaced and chemical recovery cartridges must be
frequently sent in with less than optimal quantities of silver.
In ion-exchange silver-recovery columns, the resin canbecome fouled with bacteria causing high back pressures andreduced system efficiency.
The frequency of bio-fouling can depend on the quality offresh water. Nonchlorinated well water usually causes theworst and most frequent problems. Well water often contains
bacteria that contaminate an otherwise clean wash water
system. Such a system requires more conscientious
maintenance. Chlorinating the water reduces the microbial
load entering the wash tanks. Once in the wash tanks,
however, chlorine becomes inactivated as a biocide because
dilute fixer neutralizes its effect. The system requires abiocide with residual strength to prevent biogrowth in thewash tanks, the effluent line, and the silver-recovery system.

A Regular Clean-Out
Use the following procedure monthly or when bio-slime has
contaminated replenishment systems, delivery systems, orinternal plumbing. Wear protective gloves and splashproofgoggles during this procedure.

©Eastman Kodak Company, 2000

Warning
DO NOT allow concentrated sodium hypochlorite bleache.g., CLOROX or SUNNY SOL, to come in contact withphotoprocessing solutions.
1. Drain the system completely, including recirculatinglines, and rinse twice with water.
2. Charge the system with a dilute concentration of sodium
hypochlorite bleach. (e.g., a 0.5% hypochlorite solution,
or a one part CLOROX bleach to 9 parts water solution.
CLOROX contains 5% hypochlorite.) Observe
precautionary information on the sodium hypochlorite
bleach product label and its Material Safety Data Sheet.
3. Let the solution sit in the system for up to 1⁄2 hour.
Higher concentrations of hypochlorite and/or longer
dwell times may harm some construction materials.
4. Rinse the bleach from the system and dislodge easily
removable biogrowth.
5. Scrub the biogrowth off accessible surfaces. Use aclean, stiff fiber brush or other tools recommended forcleaning the surface.
6. Flush the system thoroughly with water before returning
it to normal use.
The addition of cleaning agents that contain strong acids
or oxidizing agents (e.g. chlorine-containing bleaches) tothiocyanate-containing photoprocessing solutions (e.g. somefixers) may release poisonous and flammable hydrogencyanide gas, as well as other irritating and toxic gases suchas cyanogen chloride and sulfur dioxide. Do not add
cleaning agents to processing tanks unless the tanks,
recirculating lines, and racks have been completely
drained and thoroughly rinsed with water. Refer to theMaterial Safety Data Sheet for each photoprocessing
solution for more information.

Warning
DO NOT process sensitized products while sodium
hypochlorite bleach remains in the system.
Hypochlorite bleach can destroy images and reduce imagestability.

Biocides
The severity of bio-fouling may vary significantly. To keepout of trouble, follow recommended maintenanceprocedures on a regular basis.* However, you may alsoneed to use a biocide.
It may become necessary to use biocides in rotation.
Biogrowth may become resistant to a particular biocide after
a period of months of exposure.
An example of a biocide that helps prevent biogrowth
problems in wash tanks and silver recovery systems isProxel GXL.†This biocide is a liquid, water-soluble, and registered by
the U.S. Environmental Protection Agency (EPA),
administered with a metering pump (e.g., Gorman Rupp) tothe wash tank that first receives the fresh water (seediagram). The biocide will then be carried with thecountercurrent wash from tank to tank. Eventually, thebiocide will exit in the machine overflow to a sump and be
pumped through silver-recovery to the drain. Use
Proxel GXL for 30 to 60 minutes per day, one to five days
per week, depending on the severity of the problem (seeTable 1). Use of untreated well water may require more

frequent biocide application than chlorinated water. Keep inmind that many photoprocessing laboratories may not needa biocide at all.
Table 1 shows recommended levels of biocide forphotoprocessing wash waters. The Proxel GXL must be
diluted with fresh water for closer volume approximation.To
dilute it, add three parts Proxel GXL to two parts clean water
to obtain a 60% solution. Use the table for approximating
how much Proxel GXL or diluted Proxel GXL to use in thefresh wash water. As an example, a processor using washwater at 3 gallons per minute requires 6 mL of biocide perminute. So, for every 3 gallons of fresh water, you would use
6 mL dilute Proxel GXL. At this rate, you should use 180 mLof biocide in 30 minutes or 360 mL in 1 hour.

* Consult your Kodak processing (Z) manual for more details.
† Proxel GXL< EPA Reg. No. 10182-30, is available from Avecia Inc.
Biocide Business, 1405 Foulk Rd. P.O. Box 15457, Wilmington,
Delaware 19850-5457; Tel. No. (800) 523-7391.

Table 1Biocide Use in Photoprocessing Wash WaterAmount2Proxel GXL

Proxel GXl dilute 40%

mL/L

0.3

mL/gal

1.2

0.5
2.0

mL/1.5 gal

1.8

3.0

mL/3 gal

3.6

6.0

mL/10 gal

12.0

20.0

mL/100 gal

120.0

200.0oz/gal

0.041

0.068

oz/1.5 gal

0.060

0.10oz/3 gal

0.120

0.20

oz/10 gal

0.41

0.68

oz/100 gal

4.1

6.8

Biocide for Photographic Solution Tanks and Wash Water • CIS-3

biocides in any processing solution other than the final washwater. If biocide is put into a processing solution, such asdeveloper, you must dispose of the processing solution.
Disposal must be in accordance with local, state and federal
regulations.
This may not be the only biocide that works well inphotoprocessing wash water, but this is the one mostextensively studied for the purpose. Also, at this time, this is
the only biocide we know of that is registered with the EPA
for this application. You can visit the Internet for othermanufacturers who sell biocides.

Use powerful biocides sparingly and with caution. Many
biocides are strong skin and eye irritants, and may cause anallergic skin reaction in sensitive individuals. Before using,read the Material Safety Data Sheets (MSDSs) for theseproducts. Follow safe handling practices and procedures
outlined in the MSDSs. Wear protective clothing, splashproof
goggles, and impervious overshoes. Keep spills out ofmunicipal sanitary sewers, storm sewers and surface orground water. Soak up spills with inert material such as dryearth, sand or material commonly used in cat litter boxes.
Disposal must be in accordance with local, state, and federal
regulations. Any use of this biocide inconsistent with thelabeling is a violation of federal or state regulations.
Tests at Eastman Kodak Company indicate that Proxel
GXL used at the recommended concentration in wash water
is not photoactive (does not have significant image stability orsensitometric effects) on Kodak sensitized goods and is notcorrosive to common construction materials. Studies havealso found no adverse effects on silver-recovery systems thatemploy KODAK Chemical Recovery Cartridges,
ion-exchange resin, or electrolytic units. However, do not use

Routine maintenance is necessary. Any biocide addition
to wash tanks will reduce the frequency of cleaning, butdoes not eliminate the need for routine maintenance.

Biocide Application to Photoprocessing Wash Water

Stainless Steel TubeClip to side of Wash Tank

COUNTERCURRENT WATER FLOW
Tygon Tube
3.5 mm (1/8")

PUMP
BLEACH
FIX

WASH
TANK

WASH
TANK

WASH
TANK

WASH
TANK

WASH WATEROUTTO SILVER
RECOVERY

WASH
TANK

BIOCIDE

FRESH
WATER

5 GALLON
18.9 L

SUMP

Biocide for Photographic Solution Tanks and Wash Water • CIS-33Biocide for Photographic Solution Tanks and Wash Water

Consumer Imaging

EASTMAN KODAK COMPANY • ROCHESTER, NY 14650

Biocide for Photographic Solution
Tanks and Wash Water
KODAK Publication No. CIS-3

Kodak is a trademark.

Minor Revision 3-00
Printed in U.S.A.