Treated effluent could be pumped to a seepage pond or a storage pond where
the accumulated
wastewater could be used for spray irrigation during the growing season.
The seepage pond sy
would require less area than the septic tank/soil absorption system but would
require equivale
operational attention. The storage/spray irrigation system would affect more
area than the so
tank/soil absorption system and would have greater operation and maintenance
costs.

Additional groundwater monitoring would be required for any of the alternative
effluent dispo
systems.

Water Treatment Wastes - Four types of water treatment wastes would be produced:
(1) watt
treatment plant sludges, (2) reverse osmosis membrane cleaning solutions,
(3) sediments from,
reclaim ponds, and (4) salt cake. Water treatment sludges would consist of
metal hydroxides,
carbonates, and calcium compounds. These sludges would have a low solids
content (less than-
and would require thickening to allow placement of a soil cover if segregated
disposal is desire
Even if thickened, these sludges would be difficult to handle and cover in
a landfill. Landspre
a possibility but the sludges have little nutrient or soil amendment value.
Another method is
co-disposal with municipal refuse in a conventional solid waste landfill.
Landfilling with solid
however, is only possible at a landfill equipped with a liner/leachate collection
system. A mir
10:1 ratio, by volume, of refuse to sludge would be necessary. The nearest
off-site landfill wt
could accommodate the proposed volume of sludge is the Marathon County landfill.
This land
already takes various industrial sludges and is unlikely to allow disposal
from additional sourcd
especially from outside the county. Co-disposal of sludges would contribute
additional dissoh
solids, stable metal hydroxides, and carbonates to a landfill' s leachate.
In the MWDF, the slu
would marginally increase leachate loading but would add additional neutralizing
capacity toll
tailings pond.

The reverse osmosis membrane cleaning solutions (approximately 1,300 gallons/month)
would;
of dilute solutions of detergents and particulates. This solution has no
particular reuse poteril
either as a cleaning solution or as a liquid suitable for land spreading
or soil amendment pur-p

Sediments from the reclaim ponds would consist of fine tailings particles,
lime, and precipitai
metal hydroxides and carbonates. This sediment has no expected economic value
or soil amei
use. Placement of this material in the MWDF either periodically or at the
end of the project
the most feasible disposal technique. These sludges would add neutralizing
capacity to the ta

Co-disposal of the cleaning solutions, reclaim ponds sediment, and water
treatment sludges i
tailings is convenient and eliminates the need for additional processing
equipment or addition
disposal facilities. The lime content of these waste treatment sludges would
increase the
neutralizing capacity in the tailings ponds.

Salt cake is a by-product of the reverse osmosis/vapor compression treatment
system and cor
hydrated sodium sulfate. The salt cake could be marketed if it was of commercial
quality.
Approximately half of the salt cake used in the U.S. comes from natural deposits
while the rk
is a by-product from the manufacturing of materials such as rayon. Salt cake
is used primar
Kraft paper mills, laundry detergent as a filler, and glass manufacturing.
There are three pa
in Wisconsin capable of using Exxon' s salt cake. Such use, however, would
displace sodium sl
sources currently supplying these mills.

Storage of salt cake (sodium sulfate) outside of the MWDF would be possible
and preferable
disposal. The projected annual production of salt cake is more than 2000
cubic yards, which'.
constitute a block 80 feet square and 10 feet high. If sufficient covered
storage would be phi
salt cake could be stored until it could be sold, or if land disposal were
required, until a tailIn
or MRDF cell would be ready to be closed. Salt cake could be placed in the
cell, compacted.
covered quickly. However, such disposal might complicate facility closure
by causing cap Stj
problems. On-site evaluation would be required to determine suitable disposal
techniques, a
salt cake could not be sold commercially.



- 248 -