VIROTEC EUROPE LTD
Laboratory Trial Report of ViroMine
Technology for the Treatment of Tailings
Lagoon Water at MATSA Mine, Seville
February 2010 Summary
MATSA currently experience operational problems associated with the re-use of process
water from the tailings lagoon at their mine site near Seville, caused by low pH and soluble
contaminants iron (Fe) and manganese (Mn). This study demonstrates that these problems can
be alleviated by the incorporation of ViroMine Technology at the MATSA site.
As a subsidiary of the Iberian Minerals Corporation, MATSA operate the Aguas Tenidas
mine, 110km North West of Seville, for the extraction of copper (Cu), zinc (Zn) and lead (Pb).
Tailings are pumped in slurry form to a settlement lagoon, where solid and liquid phases
separate over time. Water volume in the lagoon can reach critical levels, particularly during
periods of prolonged rainfall. As MATSA are committed to zero emissions from site, re-use
of tailings water would help to ensure that this policy is maintained and to reduce fresh water
demand. However, before tailings water can be returned to the process, levels of acidity and
soluble contaminants Fe, Mn, chloride (Cl) and sulphate (SO4) must be reduced.
In an attempt to remediate these problems, a Reverse Osmosis (RO) plant was established on
site and was, initially, highly effective in reducing levels of Cl and SO4. However, the RO
system had difficulty in coping with the high acidity and membranes were quickly blinded by
the deposition of Fe and Mn. It was felt that if the acidity and levels of soluble Fe and Mn
were reduced, the RO plant would again function effectively.
Following a site visit, Virotec Europe were commissioned to investigate the use of ViroMine
Technology to remediate tailings lagoon water with respect to acidity and levels of soluble Fe
Samples of contaminated tailings water were assessed at Virotec Europe’s laboratory facility
in Newcastle upon Tyne, UK. Test liquors were colourless and odourless with a pH of 3.5.
This section covers the use of ViroMine media in the powder form as a direct addition method.
Figure 1 – Direct addition experimental set up
Virotec Europe have also looked at the pelletized form of media as a passive, permeable
barrier (see Supplementary Investigation). Initial investigations focussed on the selection of the appropriate blend by titration of tailings
water, using ViroMine media at dose rates 2.5 – 5.0g/litre and reaction periods 10 – 120
minutes. Mixing was effected by the use of magnetic stirrers and pH readings were taken
using a Schott bench meter – see Figure 1.
Appendix Tables 1 -3 outline the results of titration investigations.
Samples were then selected, filtered using GF/A filter papers and submitted for analysis of
soluble Fe and Mn, using ICP-MS.
Table 1 shows details of the results of analysis.
Results and Discussion
Analytical data has shown that the most effective treatment of tailings water is seen with the
application of C5 blend at 2.5g/litre over a reaction period of 60 minutes. Levels of soluble
Fe have been reduced from 7.662 to 0.109mg/litre. Levels of soluble Mn have been reduced
from 2.701 to 0.153mg/litre. Acidity has been effectively neutralised.
It should be noted however, that during the reaction period the pattern of pH drift was quite
different when comparing test data for each blend type (see Appendix Tables 1 – 3).
Following the addition of A and T blends, tailings water pH slowly increased over the
reaction period. However, when adding C blends, the pH rapidly increased during the first 10
minutes then slowly decreased over the remainder of the mixing period.
Table 1 – Results of Analysis, Batch Testing
Sample Media type
Soluble metals by ICP-MS
Fe (mg/l) Mn (mg/l)
Input NA NA 3.47 7.662 2.701
Treated A2 60 7.82 0.261 2.350
Treated T5 60 9.34 0.143 1.100
Treated T15 60 9.78 0.152 0.220
Treated T30 60 9.22 0.118 1.665
Treated T30 120 9.56 0.132 0.373
Treated T50 60 9.49 0.137 1.006
Treated T50 120 9.65 0.135 0.111
Treated C4 60 8.67 0.166 0.549
Treated C5 60 9.14 0.109 0.153
In previous projects where C blends have been applied, particularly acidic waters, the
continuous (or semi-continuous) feeding of ViroMine media has shown improved treatment
efficiencies when compared to batch processes. Therefore further test work was performed
using a C5 media blend on a semi-continuous basis, adding 2.5g/litre over a period of 60
minutes, maintaining pH conditions of pH 9.7 – 9.91 over the reaction period. After 60
minutes, no further media was added but the mixing was continued for an additional 30
minutes. Table 2 gives details of the analytical data from this work. Table 2 – Results of Analysis, semi-continuous C5 media Testing
Soluble metals by ICP-MS
Fe (mg/l) Mn (mg/l)
Input NA 3.47 7.662 2.701
Treated 30 9.73 0.048 0.119
Treated 60 9.91 0.040 0.008
Treated 90 9.85 0.008 0
The results of analysis show that removal efficiencies have been improved by the addition of
a C5 blend on a semi-continuous basis, with the greatest improvement seen on the removal
efficiency of Mn. This is due in part to the maintenance of pH at higher levels throughout the
reaction period. Previous work has demonstrated that Mn reduction can be more effective at
pH values >9.
Under laboratory trial conditions, a ViroMine media dose rate of 2.5g/litre has been employed.
On the full scale application, however, settled sludge from the base of the clarifier can be
recycled back to the reaction tank. This media will still be active and will further absorb
metals in the reaction tank, allowing a reduction in media dose rate whilst still maintaining
plant performance. In other Virotec projects, a reduction in media dose rate of up to 50% has
been achieved. Excess settled sludge can be returned to the tailings lagoon, where it will
continue to treat tailings and tailings water. Over time, there would a gradual remediation of
the lagoon, allowing a further reduction in media dose rate. In addition, there would be zero
discharge of sludge from the MATSA mine site.
Based on the results of this trial, it can be concluded that contaminated process waters at the
MATSA mine site can be effectively treated using ViroMine Technology. Utilizing blend
type C5 at 2.5g/litre on a semi-continuous or continuous basis, acidity is neutralised and
levels of soluble Fe and Mn can be reduced to parts per billion concentrations over a reaction
period of 60 minutes.
Incorporation of a sludge recycling system would result in a significant reduction in ViroMine
media dose rate and hence operational costs.
Implementation of the ViroMine treatment system will greatly improve the operation of the
RO plant for Cl and SO4 reduction, permitting the re-use of tailings water in the production
It is recommended that ViroMine Technology is incorporated into the MATSA site tailings
water treatment process, for the remediation of acidity and the reduction of soluble Fe and Mn.
It is proposed that further discussions are arranged to confirm flow rates, treatment targets and
timescales, leading to the formulation of a conceptual design for the new treatment plant.
David Rayne, Project Manager Virotec Europe. Appendix
Tailings Water Titrations:
Appendix Table 1
Media type (5g/litre)
A2 T5 T15
10 7.39 10 7.95 10 8.41
20 7.65 20 8.27 20 9.08
30 7.76 30 8.56 30 9.39
40 7.78 40 8.88 40 9.59
50 7.81 50 9.20 50 9.71
60 7.82 60 9.34 60 9.78
Appendix Table 2 Appendix Table 3
Media type (2.5g/litre) Media type (2.5g/litre)
T30 T50 C4 C5
10 7.83 10 8.13 10 9.84 10 10.29
20 8.34 20 8.85 20 9.44 20 9.94
30 8.69 30 9.18 30 9.18 30 9.68
40 9.00 40 9.37 40 9.01 40 9.47
50 9.13 50 9.44 50 8.83 50 9.31
60 9.22 60 9.49 60 8.67 60 9.14
120 9.56 120 9.65 Supplementary Investigation
The use of ViroMine pelletised media has been proposed for use as a stand by option to treat
excess tailings water before construction of the new treatment plant.
Tailings water was pumped through a column containing ViroMine pellets in upflow mode
using a calibrated peristaltic pump – Figure 2. Residence time through the media was set at
Figure 2 – Pellet column set up
Samples were taken of inlet and treated for pH and soluble Fe and Mn. Results of analysis are
shown in Table 3.
Table 3 – Results of Analysis
Sample Media type pH
Soluble metals by ICP-MS
Fe (mg/l) Mn (mg/l)
Input NA 3.62 7.137 2.600
Treated Pellets 8.93 0.105 <0.025
Although this only shows a snapshot of information, there appears to be the potential for use
as a possible emergency response when tailings water volumes reach critical levels.
Use of the pelletised media is not seen as a long term option however, as acidity from the
tailings water would affect their physical structure. It is estimated that the functional life span
of the pellets would be around 2 weeks. This would however, give a window for the
construction of other systems to combat excessive volumes of lagoon waters without
breaching site consents. During this 2 week period, ViroMine treated water would be passed
to the RO plant and then returned to production for re-use.