TM 5-814-8
trations of toxics. Heavy metals such as silver
(2) Gaging and sampling. Gaging and sam-
are toxic to aquatic life and can accumulate in
pling of laundry wastewaters present no particu-
sediments. Cyanides, strong reducing agents and
lar problems. However, due to the differing char-
constituents with high oxygen demands are all
acteristics of the various laundering processes
capable of seriously degrading water quality.
and wash cycles within a process, some care must
(4) Compatibility with domestic wastewater
b e taken in order to obtain representative
treatment. Experimental work has shown that
wastewater samples.
photographic processing wastewater is treatable
(3) Environmental impact. The older "hard"
by biological means. One survey (30) indicated
synthetic detergents such as alkyl benzene sulfon-
that almost 80 percent of Air Force base photo-
ates (ABS) were resistant to degradation by
graphic facilities discharge all or part of their
biological means. Thus, they were discharged
wastes to sanitary sewers. The Air Force Envi-
untreated to bodies of water, causing foaming
ronmental Health Laboratory at Kelly AFB rec-
problems. Currently used biodegradable deter-
ommended disposal of desilvered photographic
gents such as linear alkylbenzene sulfonate (LAS)
wastewater in trickling filter or activated sludge
have eliminated this problem. These detergents
plants in proportions not exceeding 0.05 percent
are biodegradable and exert a BOD in addition to
of the total waste influent. It is further specified
that of the soil, grease, starch and other materials
that the plant should discharge to a stream
washed from the soiled garments.
providing a dilution of at least ten to one
(a) Phosphate. There has been a great
hundred times, to account for the conversion of
amount of controversy about the contribution of
ferrocyanide to toxic cyanides. Mohanro, et al.,
detergent phosphate compounds toward the
(75) chemically treated photographic wastes with
eutrophication of lakes and rivers. Some states
alum to reduce the COD by 40 percent, then
and cities have banned the use of phosphate-
polished the effluent in activated sludge units.
containing or high-phosphate detergents. The en-
With roughly a two to one ratio of domestic
vironmental effects of phosphates or the elimina-
sewage to chemically treated photographic waste,
tion thereof are still unresolved.
90 percent BOD reductions were obtained. Dagon
(70) reported on a 20,000 gal/day package acti-
ing or LAP facilities, the laundering of employ-
vated sludge plant operating totally on raw
ees' work clothes can create " p i n k w a t e r " c o n -
photographic wastewater and obtaining as much
lamination of the laundry effluent, with the
as 85 percent BOD reduction. However, problems
resultant toxic effects and undesirable aesthetic
were experienced with poor sludge settling. There-
conditions.
fore, it is generally recommended that photo-
(4) Treatability. Laundry wastewaters may
graphic wastes be treated witih domestic sewage
generally be treated with domestic sewage by
in a biological plant after providing silver recov-
conventional biological systems. Due to the high
ery and bleach regeneration; the photographic
levels of emulsified grease, BOD and phosphates,
waste portion should be kept to less than 20
special primary treatment, or pretreatment at the
percent of the total. Bench scale or pilot plant
laundry, may be required depending on the rela-
testing may be required to define the treatment
tive proportion of laundry flow to total plant
approach in some instances.
flow. Chemical precipitation and flotation have
f Laundries. Central laundering facilities are
been used successfully as pretreatment (103)(130).
provided at most military facilities. At facilities
Because surfactants (ABS and LAS) interfere
engaged in industrial-type operations, additional
with oxygen transfer, special care should be taken
pollution problems may result from the launder-
to ensure that biological processes are receiving a
ing of the employees' work clothes.
sufficient oxygen supply. When phosphorus re-
(1) Waste reduction practices. In recent years
moval is required, chemical precipitation pro-
a variety of different synthetic laundry deter-
cesses should be employed.
gents have been used. Biodegradable detergents
(a) Unacceptable treatment. Laundry
have replaced "hard" detergents. In some areas,
wastewaters should not be treated anaerobically,
low phosphate or non-phosphate detergents have
as in a septic tank-drainage field system. The
replaced the established high phosphate com-
synthetic detergents are not broken down and are
pounds. The type of detergents used does warrant
therefore more likely to enter water supplies.
some consideration because of treatment require-
There is evidence that the detergents may also
ments to meet regulations covering effluent
facilitate the movement of coliform bacteria
characteristics.
through the soil (25).
6-26
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