27    CONVERSION TO SULFIDE PRECIPITATION TO
MEET WATER QUALITY BASED EFFLUENT LIMITS
Randy Quinn, Environmental Project Manager
Letterkenny Army Depot
Chambersburg, Pennsylvania 17201
William L. Lowe, Senior Technical Manager
George A. Prior, Technical Director
Martin F. Goldberg, Senior Project Engineer
Russell E. Turner, Principal Project Manager
James R. Gross, Project Engineer
Joseph F. Martino, Senior Section Manager
Roseanne T. Cooke, Project Leader
Roy F. Weston, Inc.
West Chester, Pennsylvania 19380
INTRODUCTION
Many industrial wastewater treatment plants (IWTPs) are facing increasingly stringent treatment requirements resulting from the imposition of Water Quality Based Effluent Limits
(WQBELs). While pollution prevention will be a preferred part of efforts to meet these requirements, it is likely that upgraded IWTP performance will ultimately be necessary in many cases.
Letterkenny Army Depot (LEAD) faced stringent WQBELs for several metals in its revised
NPDES permit (Table I). These new permit limits included mass-based effluent limits which did
not previously exist for these metals. Operating experience indicated that the new permit limits
for cadmium of 3 parts per billion (ppb) and lead of 14 ppb would be most problematic. While
LEAD'S long range plans focus upon pollution prevention via source control and waste minimization, near term improvements in IWTP performance were considered essential to meeting
WQBELs.
Table I.    LEAD IWTP NPDES Limits
Concentration Limits
(ppb unless otherwise noted)
Average
Monthly
Maximum Daily
Instantaneous Maximum
Parameter
Old
New
Old
New
Old
New
Total Cadmium
30
3
60
6
75
7.5
Chromium (Total)
1600
800
2770
1600
4000
2000
Chromium (VI)
34
13
68
26
85
32
Total Copper
80
40
160
80
200
100
Total Lead
150
14
300
28
380
35
Total Nickel
150
61.2
200
1224
250
1531
Total Silver
25
0.22
50
0.44
630
0.55
Total Zinc
120
218
240
436
300
545
Total Suspended Solids,
ppm
10
10
20
20
25
25
50th Purdue Industrial Waste Conference Proceedings, 1995, Ann Arbor Press, Inc.. Chelsea, Michigan 48118.
Printed in U.S.A.
247