THIOCYANATE TOXIC INHIBITION TO PHENOL BIO-OXIDATION
Thomas Valiknac, Graduate Student
Ronald D. Neufeld, Associate Professor
Department of Civil Engineering
University of Pittsburgh
Pittsburgh, Pennsylvania 15 261
INTRODUCTION
Recently, wastewater discharges from coal gasification and coking facilities have
received considerable attention from researchers. Chemical analysis of this effluent can
vary considerably depending upon the temperature at which the ovens are operated, the
coking coals used, and certain operational practices [1]. This effluent, sometimes called
weak ammonia liquor, is a mixture of simple and substituted phenols, polyhydric phenols, free and fixed ammonia, thiosulfate, thiocyanate, and cyanide.
With the recent emphasis placed on developing new energy sources, by-product water
from coal gasification facilities are similarly receiving attention for their potential as a
source of environmental pollution. Gasifier by-product water is primarily water condensed from unreacted steam having an amber color with a strong ammonia and cresol-
like odor, resembling in some ways the odor of coke-oven by-product waters. Table I
compares chemical analysis of a phenol producing coal gasification water (from the
Synthane Process development unit) with typical coke plant wastewaters. As with coke
plant wastes, the composition of coal gasification by-product wastes vary with temperature, pressure and operating conditions of the gasifier and also with the coal being
gasified, different coals producing different wastewater compositions [2]. Thus it can
Table L Byproduct Water Analyses From SYNTHANE
Gasification of Various Coals [ 1 ]
(mg/l except pH)
Illinois
Wyoming
North
Western
Pittsburgh
Montana
Coke
No. 6
Sub
Dakota
Kentucky
Seam
Rosebud
Plant
Coal
bituminous
Lignite
Coal
Coal
Coal
PH
9
8.6
8.7
9.2
8.9
9.3
9.2
Suspended
Solids
50
600
140
64
55
23
68
Phenol
2,000
2,600
6,000
6,600
3,700
1,700
3,009
COD
7,000
15,000
43,000
38,000
19,000
19,000
21,860
Thiocyanate
1,000
152
23
22
200
188
31
Cyanide
100
0.6
0.23
0.1
0.5
0.6
0.07
Ammonia
5,000
8,100
9,520
7,200
10,000
11,000
9,500
TOC
-
6,802
-
-
-
4,980
9,085
540