LANDSPREADING OF OILY AND BIOLOGICAL SLUDGES IN CANADA
D. J. Norris, Research Chemist
Imperial Oil, Ltd.
Sarnia, Ontario N75 3C2 Canada
INTRODUCTION
In the past, Imperial Oil refineries disposed of the relatively small quantities of waste
sludges primarily through local incineration firms. The introduction of secondary treatment
systems, starting in the mid-1970s, however, has increased sludge volumes substantially.
Oily sludges consisting of varying amounts of oil, solids in the form of sediment and water,
as shown in Table I, come primarily from fine-oil-removal processes and cleaning operations.
Waste activated sludge, a suspension of bacterial cells from activated sludge plants, represents an equally large volume of sludge requiring disposal. At the same time as sludge volumes have increased, incineration costs have been sky rocketing. Hence, Imperial Oil began
to look at alternatives. In 1976, studies were begun on the use of landspreading [1] as a
means for disposal of continuously produced sludges at the Sarnia Refinery. This study used
10 plots of approximately 100 m2 each, to which various amounts of oily sludge and fertilizer were added. This was followed by two studies in 1977: a 0.8-ha area for oily sludge
and a 1.6-ha area for waste activated sludge disposal. In 1978, a full scale operation covering 6.4 ha was started up at the Sarnia Refinery based on the results of these test areas.
Simultaneously, work was progressing at other Imperial Oil Refineries and, in 1979, a test
site was operated at the Dartmouth Refinery. Preparations are under way at the Montreal
Refinery for a test site to begin operation in 1980. Full-scale landspreading operations are
planned for the Dartmouth and Montreal Refineries starting in 1980 and 1981, respectively. The loco Refinery has, for several years, successfully disposed of oily sludges using a
combined landspreading and composting technique.
Table I. Sludge Characteristics
Oily Sludge Waste Activated Sludge
OU Content (wt%) 1-30 <0.01
Solids Content (wt%) 1-20 1-10
Water Content (wt%) 50-98 90-99
Trace Metals (mg/kg solids) 1-10,000b 1 -10,000b
Primarily from fine oil removal (filter backwash, DAF froth, etc.), separator cleanings and tank cleanings.
^Depending on the metal. Aluminum and zinc are among the highest, cadmium and molybdenum are
among the lowest.
SITE CHARACTERISTICS
There are many factors which can influence the design and operation of a landspreading
site, as listed in Table II. One of the most important is the climate. Landspreading operations, as with any farming-like activity, are very dependent on the weather. The frost-free
period in eastern Canada averages 7-8 months. However, since soil microbes grow fast only
at temperatures above 5 C [2), the effective landspreading period is reduced to about 6
months, from early May until late October. A second significant aspect of the climate is the
rainfall. After accounting for days lost because rainfall has made the site too wet to work,
only 100 to 120 days are left out of the year for landspreading operations.
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