Table 9 (Continued)
Type of Waste
Best solution is ocean
where concentration is
literature for quantities.
Return to watercourse
desired and climate
Total dissolved solids up
only if brine can be
to 45,000 mg/L.
Discharge to wastewater
treatment plant only if
Almost no suspended
Disposal wells possible
but suitability is site-
(1)For discharge to sanitary sewers, avoid cross connections and slug flow and always check:
(a)Possible damage to sewer system from residue discharge.
(b) Effects of residues on liquid and solids treatment processes
at the wastewater treatment plant.
(c) Hydraulic capacity of the wastewater treatment facilities.
(2) Sedimentation basins or solids contact reactions ahead of filters will generally remove 70-90%
of total plant solids. The remainder of solids will appear in the filter wash water.
(3) Returning filter backwash and thickener overflow streams to plant influent may be viewed with
disfavor by regulators because of the possibility of recycling pathogens.
Disposal Methods. It is preferable to dispose of residues in a way that is
both economically and environmentally acceptable. Recovery and disposal systems
often require increasing the solids content of a residue by removing water. The
required solids concentration (and the method of concentration) depends on the
chemical recovery or final disposal alternatives used. Table 9 summarizes water
treatment plant residue-handling systems currently in use.
Note: Do not discharge residue to a natural water course or public sewer
without the approval of the applicable federal, state, and local authorities.
Recovery Processes. Alum, ferric chloride, ferrous sulfate, magnesium
carbonate, and lime can be recovered from waste sludge by various methods.
However, recovery is not usually economical except at the largest municipal facilities
and, thus, is not considered viable for military installations. However, manufacturers of
alum and ferric coagulants will sometimes agree to accept waste sludges for
Ultimate Disposal. Traditionally, water treatment plant wastes have been
disposed of by discharge to rivers and lakes, either directly or by way of a storm sewer.