TM 5-813-3/AFM 88-10, Vol 3
CHAPTER 6
WATER TREATMENT PLANT WASTES
clay, hydroxides of iron and aluminum, calcium car-
6-1. Q u a n t i t i e s a n d c h a r a c t e r i s t i c s o f
bonate, activated carbon, etc. The characteristics of fil-
wastes.
ter wash water at plants using alum for coagulation
In connection with water treatment plant location and
will differ considerably from those of wash water de-
design, the disposal of the wastes generated during the
rived from plants practicing softening or iron and
various treatment processes must receive careful con-
manganese removal. Filter wash waters invariably are
sideration. Among these wastes are sludge from pre-
quite diluted, exhibiting average suspended solids con-
sedimentation basins, coagulation and/or softening
centrations of less than 200 mg/L (0.020/0).
sludge, filter wash water, spent regenerant and rinse
f. Regeneration brines for ion-exchange softeners.
water from ion-exchange softeners, diatomite filter
The principal waste products in the waste brines from
sludge, and mineral wastes from desalination facili-
ion-exchange regeneration are chlorides of calcium,
ties.
magnesium, and sodium. In addition, small quantities
a. Presedimentation sludge. Presedimentation basin
of iron, manganese, and aluminum maybe present. To-
sludges reflect the nature of the solids present in the
tal dissolved solids (TDS) concentrations in these
raw water. If the particles in the raw water settle out
waste flows commonly range from 35,000 to 45,000
readily, the sludge will be of fairly high solids content.
mg/L (3.5-4.5%) with maximums of about 95,000 to
Slowly settling particles will produce a thin sludge of
120,000 mg/L (9.5-12%). The total wastewater flow
low solids content.
will be between 2 to 8 percent of the amount of water
b. Coagulation sludge. The settled residues result-
softened.
ing from coagulation with alum range in suspended
g. Desalination waste brines. The waste products
solids content from about 1,000 mg/L (0.1%) to about
most often found in desalination waste brines are chlo-
17,000 mg/L (1.70/0). The bulk density of dry alum
ride and sulfate salts of calcium, magnesium and so-
sludge is usually between 75 and 99 pounds per cubic
dium. TDS concentrations in the waste brines may
foot. In order for alum sludge to be placed in a landfill,
it must have a solids content of about 20 percent or
pending on the desalination method used and the char-
more. Waste sludges produced by coagulation with
acteristics of the raw water, the volume of the waste
iron salts are similar to those produced with aluminum
brine flow may be as little as one percent or as much as
salts.
50 percent of the raw water processed, with an aver-
c. Lime softening sludge. Softening sludges can
age of 15 to 20 percent. Inasmuch as suspended parti-
vary widely in characteristics depending on the rela-
cles are detrimental to most desalination processes,
tive amounts of calcium carbonate and magnesium hy-
raw waters intended for desalination are usually treat-
droxide in the sludge, the nature and amount of sus-
ed for turbidity, iron removal, etc., prior to desalina-
pended particles present in the raw water, and wheth-
tion.
er or not a coagulant, such as alum, was used. The sol-
ids content of softening sludges may vary from 2 to 33
6-2. Waste m a n a g e m e n t .
percent, and the total sludge volume may range in vol-
a. Water treatment sludges.
ume from 0.3 to 6 percent of the water treated. Chemi-
(1) Presedimentation sludge. Presedimentation
cal solids (calcium carbonate and magnesium hydrox-
sludge may be disposed of by returning it to the stream
ide) derived from lime softening are roughly 2.5 times
from which the raw water was taken, if the appropri-
the weight of quicklime applied.
ate regulatory agencies will grant their approval.
d. Diatomite sludge. About 300 to 600 pounds of
Otherwise, the sludge should first be dewatered in la-
diatomite sludge are produced per million gallons of
goons or sludge drying beds and then hauled to land-
water treated. Approximately two-thirds of the sludge
fills or spread on land.
is the diatomaceous earth used for filtration and one-
(2) Coagulation sludge,
third is the impurities removed from the water. The
(a) Lagoons. If land is available near the treat-
dry bulk density of the sludge is about 10 pounds per
ment plant, alum sludge can be placed in lagoons to ef-
cubic foot.
fect further concentration of solids. Depending on the
e. Filter wash water. A variety of suspended sub
local climate and the properties of the sludge, the final
stances may be present in filter wash water, including
6-1
Previous Page
