Treatment Systems
There are three general categories of available treatment technologies: chemical,
physical,
biological treatment. It is often necessary to use a number of treatment
processes to efficiei
remove wastewater pollutants. For example, chemical precipitation is usually
followed by ph
separation such as settling or filtering. The primary pollutants to be removed
include: dissol
metals, organic chemicals, acidity or alkalinity, chemical anions, and suspended
solid particle
following criteria were used to evaluate alternative treatment processes:

1.  Meet effluent limitations and/or standards;

2.  Remove scale forming compounds (for mill process water);

3.  Provide cost-effective treatment;

4.  Use proven technology;

5.  Be flexible with respect to influent water quality;

6.  Remove thiosalts (for mill process water);

7.  Remove metals;

8.  Produce environmentally acceptable sludges; and

9.  Produce a marketable sludge by-product, if possible.

Process Wastewater Treatment - EPA effluent guidelines require all ore milling
process watt
recycled, except for excess annual precipitation and mine inflow. The company
predicts the
reclaim ponds, in conjunction with the water treatment plant, would produce
water of suffic
purity for reuse in the mill processes. Alternatives to the proposed process
wastewater syst"
include:

1. Operation of the reclaim ponds could be modified during winter conditions
(low water
    temperatures and ice cover) by subsurface aeration or addition of chemical
oxidants to i,
    biological/chemical activity. This would reduce concentrations of reduced
sulfur ions, i
    chemical reagents, and cyanide in the effluent.

2. A chemical/physical treatment system could be substituted for the reclaim
ponds. Such
    could use chemical oxidation and aeration to remove organic reagents
and cyanide, and
    oxidize reduced sulfur compounds to sulfate. Chemically aided clarification
or filtrati
    follow for suspended solids removal. A cyanide oxidation system could
be installed at t]
    of those flotation circuits utilizing cyanide to minimize cyanide dispersion
throughout t
    process water system. In a similar manner, a chromium reduction unit
could be installe
    the resulting trivalent chromium could be removed by the treatment system.

    Some water surge or storage capacity, however, is desirable in the mill
water system. 7
    proposed reclaim ponds were eliminated, a storage pond would have to
be built to pro
    sufficient capacity to store mine inflow during treatment plant down
times. Thus, som
    disturbance would still occur.

Mine Water Treatment Alternatives - Optimization of the proposed system and
three alter
treatment systems were examined for the contaminated mine water and intercepted
groun
The proposed system has been optimized for cadmium removal. A variety of
precipitation,
filtration systems were dropped from consideration due to the probable lack
of compliance
effluent limitations.



Optimization of the proposed precipitation/filtration process could be achieved
by additiona
precipitation with iron or starch xanthate or by pretreatment (use of hexavalent
chromium r
system for the lead thickener overflow). These measures could result in reduction
of current,
projected effluent values for these parameters (i.e., 50% or greater) based
on theoretical
considerations, literature review, and limited lab testing by Exxon.
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