Page 164 - Energy from Toxic Organic Waste for Heat and Power Generation

144 Energy from Toxic Organic Waste for Heat and Power Generation

c. Coagulation and flocculation
d. Electrocoagulation
Arsenate is adsorbed on metal-oxides, usually iron is used.
2. Reduced arsenic-bearing waste
a. Sequestration through co-precipitation
b. Adsorption with iron sulfides (abiotic)
Then these arsenic-bearing wastes are disposed of in municipal landfills.
Even stabilization is carried out to reduce toxicity and mobility of contam-
inants [3].
Some other methods for disposal are:
1. Disposal with cow dung
2. Passive aeration disposal
3. Direct soil disposal
4. Pond disposal

10.4.1.2 Asbestos Disposal
The owner/operator of an asbestos waste disposal site is responsible to assure
that any waste asbestos is covered within 24 h of being placed in the disposal
area. The covering material must be at least 10 inches in depth and should
not include any other waste material unless specifically approved in writing
by the authority. When an asbestos waste disposal site is abandoned or dis-
continues operation, the owner/operator is responsible to place final cover
material having a depth of at least 50 inches [4].

10.4.1.3 Chromium Disposal
In chromium reduction method, hexavalent chromium is reduced to
the less toxic trivalent state and precipitated as an oxide. The effluent from
this procedure was determined by atomic absorption spectroscopy to be
severable (<2 ppm). The residue is a mixture of chromium oxide and filter
media.
In ion exchange method, spent chromic acid solution containing
hexavalent and trivalent species was run through a mixed bed column of
cation and anion resins. The chromium was removed by the column, yield-
ing a severable effluent (<2 ppm) [5].

10.4.1.4 Cyanide Disposal
Stage 1 oxidizes cyanide to cyanate using oxidizing agents such as chlorine
or sodium hypochlorite in the presence of an alkali. The second stage oxi-
dizes the cyanate (which is much less toxic than cyanide) to carbon dioxide