450 Organic Waste Recycling: Technology and Management
9.2 Sludge transport and application procedures
The important elements of system design of land treatment of sludge are: modes
of sludge transport, sludge application procedures, and sludge application rates.
The first two elements will be described in this section while section 9.3 will
discuss the third element.
9.2.1 Mode of sludge transport
Table 9.5 shows the various methods to handle and transport sludge from a
source to land application/disposal site. Transportation may be accomplished by
pipeline (gravity flow or pressured), tank truck, barge, or conveyor rail. Sludge
characteristics (e.g. solid contents), sludge volume, elevation differences,
transport distance and land availability are important factors in selecting a
method of sludge transportation. As shown in Table 9.6, liquid sludge (1-10%
solid contents) is generally suitable for any modes of sludge transport, while
semi-solid or solid sludge, having high solid content (8-80%), should be
transported only by trucks or rail hopper cars.
Tank trucks are currently widely used to transport and apply sludge on land
because they afford flexibility in the selection of land application sites. Usually,
a storage facility for sludge is provided at the land application site.
Table 9.5 Sludge solids content and handling characteristics (Knezek and Miller 1976)
Type Solid contents (%) Handling methods
Liquid
Semi- solid (‘wet’ solid)Solid (‘dry’ solid)1 – 10
8 – 3025 – 80Gravity flow, pump, tank support
Conveyor, auger, truck transport
(water tight box)
Conveyor, bucket, truck transport9.2.2 Sludge application procedures
Similar to the mode of sludge transport, the selection of sludge application
systems and equipments depends on: type of the sludge (liquid, semi-solid or
solid), quantity, a real application rate, frequency of application, topography of
the applied area, and time of the year. Table 9.7 gives the various sludge
application methods and the equipments required for the application. The
irrigation methods such as sprinkling, ridge and furrow (Figure 8.2) and
overland flow (Figure 8.4), are similar to those described in Chapter 8 "Land
Treatment of Wastewater". Sprinkling systems, applicable to only liquid sludge,