Environmental Engineering Reference
In-Depth Information
TABLE 10.3
Typical Components of a Water Monitoring Programme (UN 1992) - Monitoring parameters should be
limited to signifi cant elements, based on experience, past monitoring results, and common sense judgement
Physical
Temperature
Turbidity TDS
Water fl ows
Chemical
Conductivity
Alkalinity
pH
Common cations: Na , Ca , K , and Mg ,
Common anions: SO 4 , Cl , HCO 3 , CO 3
Hardness
Colour
COD/BOD
Nitrogen
Phosphorus
Metals - depending on those metals enriched in the ore
Biological
Phytoplankton
Zooplankton
Benthic organisms
Fish
Water fow
The results of baseline surveys are particularly relevant. Any parameter, whose concen-
tration is close to or exceeds ambient standards during baseline surveys, should be included
in subsequent monitoring programmes.
Typical parameters to be included in water quality monitoring are listed in Table 10.3 .
It is useful to include the major cations and anions (as listed) as this enables a cation/anion
balance to be calculated which may identify analytical problems or the presence of uniden-
tii ed contamination.
Monitoring results may indicate that continued monitoring of a specii c parameter
yields no benei t, and the parameter may be excluded from future monitoring subject to
approval by relevant environmental authorities.
In selecting the parameters to be monitored, particularly in relation to groundwater
quality, it should be recognized that geochemical changes will take place as water l ows
through soil and rock. The following three examples illustrate this point:
1. Visual monitoring of a TSF embankment at an alumina rei nery identii ed a seepage
emerging from the embankment. Analysis of the seepage indicated a neutral pH, and
virtually no hydroxide (OH ) whereas the solution in the adjacent impoundment had
a very high hydroxide concentration and a pH exceeding 13. Accordingly, the seep-
age was initially ascribed to rainfall ini ltrating the embankment and subsequently
emerging through the downstream. Subsequently it was found that the seepage had
originated from within the impoundment but had been neutralized by reactions with
the embankment soils. Had it been measured, the high concentration of sodium might
have provided an earlier indication of this phenomenon.
2. It is common for pH levels in groundwater to remain at or about neutral levels, even
when the water is draining through waste rock or tailings that are oxidizing. This is
because of the buffering capacity in the system. In many project situations, mainte-
nance of neutral conditions has led to complacency on the part of the operators in the
Geochemical changes will take
place as water fl ows through soil
and rock.
Maintenance of neutral
conditions has led to
complacency on the part of the
operators in the mistaken belief
that ARD was not occurring.
 
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