Natural Resources Extraction: Stressors and Impact Management - Sustainable Practices in Geoenvironmental Engineering - page 168

80

Viable biomass

70

60

50

Nonviable biomass

40

30

20

10

0

Ni

Cd

Cu

Pb

Heavy metal

FIGURE 5.14
Comparison of a viable and nonviable anaerobic granulated biomass for the biosorption of heavy metals.
(Adapted from Al Hawari, A. and Mulligan, C.N., Bioresource Technology , 97, 692-700, 2006.)

Results showed that a living biomass has a higher sorption capacity than a dried biomass but
due to the dificulties in maintaining the biomass, the dried biomass would be more suitable
for industrial applications (Figure 5.14). Unlike most forms of biomass, immobilization or
stiffening was not necessary prior to using the biomaterial. Anaerobic granules possess com-
pact porous structures, excellent settling ability and high mechanical strength. Even under
aggressive chemical environments (acidic or basic conditions), the biomass demonstrated
good stability with no visible structural damage—making this biomass more advantageous
over other biosorbents. The biomass was also tested for arsenic sorption and was found to
favorable compared with other biosorbents (Chowdhury and Mulligan, 2011).

5.5.3 Slurry Tailings Ponds Impact Management

Slurry tailings ponds are by far the major type of containment facilities for slurry tailings.
Their use has been discussed in the previous section. Their presence in the landscape
degrades land quality and considerably reduces land-use capabilities. An illustration of
such kinds of ponds is shown in Figure 5.15, for tin mining slurry ponds in Southeast
Asia obtained as a result of alluvial tin mining hydraulic operations using the wash sep-
aration technique. Sand and debris are collected at the end of the sluice box—with the
ponds serving as sedimentation facilities (Chow, 1998). It is not unusual for these ponds to
develop a crust overlying a slime layer with solids concentration ranging from 50% to 60%.
Encroachment of housing estates onto such kinds of ponds and debris, as seen, for exam-
ple, in Figure 5.15, will pose limits on housing and introduce safety hazards. Reclamation
of the ponds is necessary to allow for utilization of the reclaimed land for further urban
development and other land uses consistent with an urban ecosystem.
Sustainable land use, in the context of slurry tailings ponds and their like, is not different
in principle from the acid mine problem or mined-out caverns, pits, etc. We will consider sus-
tainability of land use in the physical landscape sense, i.e., in respect to the physical features
and properties of the land and its utility. Figure 5.16 gives a summary view of the various