THE IMPACT OF EFFLUENTS CONTAINING ZINC AND NICKEL METALS ON
STREAM AND RIVER WATER BODIES: THE CASE OF CHAMBISHI AND
MWAMBASHI STREAMS IN ZAMBIA
F. W. Ntengwe1 and K. K. Maseka
1School
of Technology, Chemical and Environmental Engineering Department,
Copperbelt University, Jambo Drive, Riverside, Box 21692, Kitwe, Zambia. Email:
fntengwe@cbu.ac.zm
Tel: 260 2 228212/97802494
Abstract
The effluents coming from mining operations are a danger to species in the environment
more so to species of waters in streams and rivers. A study was conducted in Chambishi and
Mwambashi Streams in Chambishi District in Zambia with an aim of establishing the
impacts of Zinc and Nickel metals in effluents coming from Chambishi Metals Plc. Samples
were collected at four points at reasonable distances up to 4000m downstream and analysed
for Zinc and Nickel using Atomic Absorption Spectrophotometer (AAS). The impacts on
receiving environment were also taken. The results showed high level of metals, Zinc and
Nickel in water and sediment soils, were found to be reasonably high at the discharge point
(0.18mg/L, 0.83mg/L; 0.73mg/L, 1.36mg/L).
The severity impacts were high upstream and
low downstream.
KEY WORDS: Effluents; Impact; Stream; River; Water; Environment
1
INTRODUCTION
Streams and rivers are a major source of fresh water in Zambia. The Kafue River, for
example, is a major supplier of fresh water to most industries in the Copperbelt region
including the mining and chemical industries where large quantities of water are used to wash
mineral ores in order to extract metals such as Copper and Cobalt. In the process, they
generate effluents, which have potential to pollute the environment.
The effluents are
discharged into streams and rivers as part of conservation strategy to prevent the Kafue River
from drying up and as a way of disposing them as wastes. The wastewaters are pre-treated
before discharging to the surface waters of streams and underground waters through
percolation and to the atmosphere by evaporation. Acid mine drainage, a condition created
by effluents when disposed into stream and river waters, impacts the water quality. Tetra
Tech (2001) reported the impact of acid mine drainage on Ely Brook’s water quality as was
determined by physical and biological factors. McMenemy (2001) reported the non-survival
of fish, which was cropped for one year, in Ely Brook River due to extremely poor survival
and growth conditions. Zinc and Nickel are the metals that are used to judge the water
quality. Boyne Smelters Limited in Gladstone region of Australia uses Zinc and Nickel
among other metals like copper, Iron, Lead and Sodium as parameters for monitoring water
quality. The Gladstone Water Board (GWB) in Australia reported Zinc and Nickel to be
among the metals that any smelting or mining company would use to monitor effluents for
water quality. Fish species are used as one of aquatic environment tools to determine water
quality in streams and rivers in Gladstone area (GWB, 2004). The effluents thus can change
the ecosystems in streams and rivers if they do not meet stream and river water quality. The
result would be that life of species in streams and rivers and man would be impacted. The
growth of fish may be retarded or render fish to be absent altogether. The growth and
2
existence of bacteria and planktons may be severely affected. Man may also be affected by
the poor quality of water. Masters, (1974) supports this argument when he wrote that metals
were toxic to fish and wildlife. Ntengwe (2004) reported cases of not willing to pay bills of
water in Lusaka, Zambia because of poor water quality.
In order to protect ecosystems in the environment, the introduction of treatment at source or
waste reduction at source can be used in addition to the regulations in order to control levels
of pollution agents being released into the environment. The government of the Republic of
Zambia (GRZ) adopted the National conservation strategy in 1985 and passed the
Environmental Protection and pollution control act (EPPCA) in 1990 as a way of controlling
and preventing pollution. This also resulted in the formation of the Environmental Council of
Zambia as the enforcing agency for effluents and the National Water and Sanitation Council
for enforcing the quality of drinking water (GRZ, 1990; WHO, 1993; GRZ, 1995; Katuta,
2004). It was therefore important to study the effects or impacts of wastewater.
STUDY AREA
The study was conducted in Chambishi
District, which is about 25km North West
of Kitwe and has a population of close to
8,000 inhabitants (CSO, 1990). The study
focussed on the impacts of effluent on
water
quality
of
Chambishi
and
Stream
Mwambashi streams (Fig. 1).
Roads
Fig.1 Chambishi and Mwambashi Streams
3
Chambishi Metals plc is the only major mining company in the area and was originally
developed as an open pit mine for Zambia Consolidated Copper Mines Limited. The pit was
capable of producing 24 tonnes of copper per year. In 1972, the underground mine was
developed. This boosted production to 45,000 tonnes per year. Six years later, the company
began to produce cobalt and sulphuric acid. The total cobalt produced per year was 23,000
tonnes.
In early 1990s the company was sold to Anglova who changed the name to
Chambishi Metals Plc and are running it effectively than the predecessor. The climate in the
area comprises three seasons, a warm and wet season, which starts from October and ends in
April, a cool and dry season, which starts in May and ends in July and a hot and dry season
which begins from August and ends in October. The town lies in the medium rainfall belt of
Zambia. The rain begins in October and ends in April. It is associated with the South West
and North East winds.
The South West Winds blow from the Atlantic Ocean to the
Democratic Republic of Congo (DRC) and is the air that brings heavy rainfall to the area in
the months of December, January and February. The North East Wind is associated with
little or no rainfall. A large percentage of people in the study area are farmers and only a few
depend on mining activities for their livelihood. The crops grown in the area include maize,
tomatoes, onion, carrots, cabbage and rape. Cattle, goats, sheep and chickens are reared by a
few people.
The majority of farmers practice Peasant Farming while a few carry out
Commercial Farming.
OBJECTIVE OF THE STUDY
The purpose of the study was to evaluate the impacts of effluents coming from the
engineering unit operations of Chambishi Metals Plc on the receiving environment. The
specific objectives were to determine levels of Zinc and Nickel in stream water and
4
sediments in order to assess the extent to which they impact the environment, the presence of
living species in the stream water and the water use from the stream.
METHODOLOGY
The impacts on fish and phytoplanktons were obtained by the observation method using
cooked maize husks and microscopic observation respectively.
A questionnaire was
administered to the community around the area in order to obtain responses on the use of
water in the stream by people and animals. The levels of Zink and Nickel were obtained by
collecting water and sediment samples from five sites; the Tailings Dam 6 inlet and outlet,
New Dam, Chambishi Bridge and Mwambashi Stream at distances zero, 1250, 2500, 3500
and 4000 metres respectively and analysing using Atomic Absorption Spectrophotometer
method.
The method is used for quantitative determination of metals.
Firstly, the
wavelength at which the metal could be detected was established. Then the solution was
aspirated into the flame where it was vaporised. Atoms of the metal were excited to higher
levels. The energy absorbed by the metals was measured and the concentration was then read
from the calibration curve obtained by analysing standard solutions. The absorption of
energy followed Beer Lambert’s Law (Skoog et al, 1976). The pH of each sample collected
at each point, for the period of four months, was measured using the pH meter in order to
observe the changes at each point in each month. The results were reported as averages.
IMPACTS OF ZINC AND NICKEL
The sources of Nickel are arsenide and sulphide ores. Nickel is used for alloying, as a
catalyst in chemical reactors, for battery making and metal plating. It is deposited in rivers
5
and streams through discharges of effluents from mining operations. Its route of exposure to
humans, animals, and birds is through drinking contaminated water and dust from the
atmosphere. Its health effects include; the disturbance of respiratory system and asthma,
birth defects, vomiting and damage to Deoxyribonucleic Acid (DNA) at high concentrations.
Lawrence et al (2004) reported negative effect of Nickel on abundance of phototropic
organisms like Algae and Cyanobacteria.
Zinc is a metal used in galvanizing and alloying. It is also used in manufacturing electric
goods, dying, insecticides and cosmetics. Zinc makes up 0.0005%-0.02% of earth’s crust. It
is listed as one of the hundred and twenty nine (129) priority pollutants (Roy, 1997). Zinc
has been associated with impairment of river and stream water quality for many years. For
example, the State of Texas (2005) reported rivers as not meeting their aquatic uses due to
toxic metals; Wichita and Middlefork Rivers lost their aquatic uses due to selenium, Neches
River below Lake Palestine due to lead, and Neches River above Lake Palestine due to high
level of Zinc. Peplow (2000) reported that elevated concentrations of Cadmium, Copper,
Selenium including Zinc in stream waters and sediments reduced species diversity and
abundance in aquatic communities. Kramer (1976) found elevated levels of lead, Zinc,
Cadmiun and Copper in Flat River water. Zachritz (1978) and Czarnezki (1987) found
elevated levels of Zinc and Lead in Big River water. Schmitt and Finger (1982) found
elevated copper, iron, lead and Zinc in Big River during periods of high flow. All the above
cases are near mining operations. A study on impacts of treated wastewater to Krka River,
Slovenia, conducted by Cotman et al (2001) recommended a reduction of substances in
industrial effluents like Zinc and non-biodegradable organic compounds that cause toxicity to
aquatic life. The impacts of Zinc on humans include fainting, nausea and stomach disorder.
6
This is the reason why it was necessary to assess levels of Zinc and Nickel in the streams and
because they interfere with water quality.
SOURCES OF EFFLUENTS
Fig. 2 shows the processes in which copper and cobalt were produced at Chambishi Metals
Plc. It also shows areas in which liquid wastes (effluents) were released to the environment.
The feed at the smelter included slag, magnesium oxide, lime and coal. The feed materials at
roaster plant included Zimbabwe Pyrite, Zaire Pyrite, flocculants, water, oxygen and heat.
Magnesium oxide was used as catalyst to catalyse the reaction in which ground slag, lime and
coal were used in the reaction.
Fig. 2 Flow Diagram of Cu and Co Production Showing Sources of Effluents
The reactions in the Smelter Furnace reduce the Nickel bearing mattes such as Copper-Nickel
to Copper and Nickel sulphides. Further treatment removed copper and left Nickel in the
residue, which was sent to the Tailings Dam 6. Newton (1959) demonstrated that in the
Roasting Plant, the sulphide ores are oxidized to oxides (Equations, 1, 2, and 3).
7
2ZnS + 3O2 = 2ZnO + 2SO2
(1)
FeS2+11O2=2Fe2O3+8SO2
(2)
2Cu2S+3O2=2Cu2O+2SO2
(3)
The Roaster, therefore, generated the needed Sulphur Dioxide feed in the production of
Sulphuric Acid at the Sulphuric Acid Plant.
Newton (1959) presented facts about the
roasting process. He explained that, the roasting begins at the surface of particles and it
continues while the particle develops a porous coating through which molecules diffuse into
the inside until the reaction goes to completion. Coulson et al (1994) presented similar
views. In his case a particle was presented as a core model in which the reaction begins at
the surface towards the inside and that each particle decreases its size as reaction proceeds
until it is finally consumed or reacted completely. The time for converting ZnS, FeS, and
Cu2S in the roasters could be determined. This agrees well with Newton’s assertions. Laws
of mass transfer between the two films are also obeyed. The leaching of oxides removed
Copper and the residue containing Zinc and Iron were sent to the Tailings Dam 6. Cobalt and
Copper Ores were treated by reduction smelting in the electric furnace where two layers
formed; a red alloy containing mainly copper and a white alloy containing mainly Cobalt.
Cobalt usually occurs with Copper and Copper-Nickel Ores, for example, CoAsS as
Cobaltite or CoAs2 as Smaltite. The countries with large deposits include the Democratic
Republic of Congo (DRC), the United States of America (USA), Canada and Zambia.
In electro-refining of Cobalt, Cobalt was deposited on stainless steel cathode in four or five
days after which it was removed by stripping from the cathodes. Cathodes were then dipped
8
in nitric acid to dissolve patches of cobalt and then dipped in gelatine in order to renew them.
The process used direct current to deposit the metal. The residue formed in the reactors was
sent to Tailings Dam 6.
Copper production at the Tank House was also by electro-refining and electro-wining
processes where the copper was removed from anodes, which came from the Smelter and was
deposited at the copper cathodes.
Faradays law of electro-deposition applied (Newton,
1959). Copper was removed from solution while Zinc, Nickel, Iron and Cobalt remained in
solution.
Cobalt was later removed but Iron, Zinc and Nickel were discarded to the
environment with effluent.
Electro-refining reactors have anodes and cathodes with potential applied across them and the
current distributed over the surface. The application of potential across the reactors results in
polarization of the electrodes into anode (positive) and cathode (negative). The polarization
results into the deposition of metal and evolution of gas at cathode and anode respectively.
The cathode reactions reduce the copper and cobalt ions in solution to copper and cobalt on
the cathodes while the anode reactions form copper and cobalt ions which go into solution.
Oxygen is also released at the anode by the reaction of sulphate and water molecules. The
sulphur dioxide reaction with water resulted in sulphuric acid production.
The temperature of Sulphur Dioxide (S02) has to be reduced from 80oC in the roaster in
stages of 50oC, 30oC and finally to 15oC at which it reacts with water to produce Sulphuric
Acid (H2S04) (Newton, 1959).
Spillages of the acid end up as effluent going to the
environment. The pH control was thus essential in order to prevent damage to stream water
life and animals. Lime plays an important role in the neutralization of industrial effluents.
9
Effluents from Copper Tank House and Roaster were mixed and neutralised before the
effluent was discharged to slimes dam for disposal.
THE STUDY MODEL
The assumptions that were made for the study were that the effluent from the mining
operations was carrying the undesired pollutants Zinc and Nickel metals. That the pollutant
concentration was highest at the discharge point. The level of concentration would then
decline as the effluent entered the Tailings Dam 6 (TD6) and Chambishi Stream due to
dilution with water. That the level of the metals would decrease further as the distance
increased from the point of discharge. That Zinc and Nickel would move to the sediments
depending on the pH and the availability of ionic species in water that would react or
associate with them. The impacts would be categorised as severe (Negative) and beneficial
(Positive). The water pollution behaviour was then studied according to synthesised Water
Pollution Declining Model as shown in Fig. 3.
Fig. 3 The Water Pollution Declining Model (WPDM) for Zinc and Nickel pollutants in
effluents from mining operation.
10
RESULTS AND DISCUSSION
The study revealed that there were very few people living in the area. The poor water quality
in the streams had resulted in people opting to settle where the quality of water was good.
The animal population comprised animals domesticated by the people. They included goats,
cattle and chickens. There were no wild animals around the streams. One assumption could
be that animals did not like polluted water because it tasted salty. Although wild pigs for
example, like salty waters, none of this type of animals was observed in the area. The plant
population was found to be scanty and few aquatic lives existed as was demonstrated by the
non abundance of fish in some parts of Chambishi and Mwambashi Streams. The fish counts
revealed a decreasing number towards the discharge point of effluents and an increasing
number down stream (Fig.4). The fish that was found in the dams was not abundant and
almost all exhibited stunted growth as stated by McMenemy (2001). The phytoplankton
counts were found to increase down stream and decrease upstream indicating that the effluent
from the mine had an effect on them but the fish fish increased as plankton increased
downstream. This signified that the fish could not be abundant in areas where planktons
were reduced. The pH was found to be regular during the entire study period (standard pH6
to 9) (WHO, 1993). An observation on the effluents released from the mine to Chambishi
Stream revealed a blackish colour from the source to Tailings Dam 6 indicating turbidity
more than the standard value of 5NTU. The water was clear from Tailings Dam 6 up to
Mwambashi Stream. The blackish colour was reduced because most of the solids settled out
in the dam due to sedimentation.
11
20
No.
15
10
5
0
-5
0
1250
2500
3500
4000
Distance from discharge of effluent (m)
pH
Fish
Plankton
Fig. 4 Variations of pH, fish and Planktons with distance from discharge of effluent
The effluent discharge from Chambishi Metals Plc was found to contain 0.73 mg/L of Nickel
and 0.18 mg/L of Zinc. The pollution load to the dams and streams was also represented by
the same levels at the point of discharge. The daily and yearly pollution loads would depend
on the flow rate of effluent and the concentration load of the elements in the effluent.
The levels of Zinc in water samples were found to be highest at the inlet of Tailings Dam6
(0.18ppm) and lowest at Mwambashi Stream (0.05ppm) as can be observed in the results in
Fig.5. This demonstrated that there was some form of treatment both at the Tailings Dam 6
and along the stream; a process called self cleansing and dilution effect.
The sedimentation process removed solid particles and reduced turbidity living the water
fairly clear.
As the effluent was released into the stream, dilution effect lowered the
concentration of Zinc in the stream water. The concentration of Zinc was reduced further as
the water travelled along the stream. The level of Nickel was found to be higher than that of
Zinc at all the sampled points in the streams and was found to be declining, like those of
Zinc, with distance away from the discharge point (Fig. 5). Nickel levels were also found to
be higher at the inlet of Tailings Dam 6 and lowest at Mwambashi Stream. The results
12
therefore suggest that the effort of treatment by the dams was bearing fruit. However, the
effort seemed to be inadequate because the level of Nickel released into the Chambishi water
was higher than the values recommended by the World Health Organization (WHO) and
Government of the Republic of Zambia (GRZ) Statutory Instruments of 14th May 1993
(WHO, 1993; GRZ, 1993). The WHO recommendation is 0.05mg/L for Zinc and Nickel if
the water is to be used for drinking.
Metal Level (mg/L)
The results therefore indicate that after
4000m down the stream from the point of
discharge, the water complies with WHO
requirements for Zinc and Nickel and if
2
1.5
1
0.5
0
0
1250
2500
3500
4000
Distance from discharge (m)
consumed by man and animals, would
Znsed
Znswat
Nised
Niswat
induce little undesirable effects associated
Fig. 5 The variation of Nickel and Zinc
with them.
with distance from the discharge.
The impact score based on a scale of 1 to 100% revealed that the quality of environment was
impacted 50% negatively (severity) particularly on vegetation in Chambishi Stream. The
impact on surface water and sediments was based on the results analysis.
Further
examination of the impacts revealed that the level of severity (Negative) impacts was higher
than positive (beneficial) impacts upstream while the beneficial impacts were higher than
severity down stream in all the cases. The individual impacts can be seen in Fig.6 and 7.
13
Severity or beneficial (%)
Severity or benefit (%)
100
80
60
40
20
0
SevUS
BenefUS
Swat
SevDS
Sed.
BenefDS
100
80
60
40
20
0
SevUS
Man
BenefUS
Animal
SevDS
Fish
BenefDS
Biota
Fig. 6 Impact on Surface water (Swat),
Fig. 7 Severity/ beneficial impacts on
man and sediments (Sed)
animals, fish and other biota (Plankton)
This signified that any living thing that used water in the streams would accumulate high
levels of metals. It could also imply that the fish in the dams and streams accumulated a lot
of metals to levels that could be toxic to predators. The Agency for Toxic Substances and
Disease Registry (ATSDR) (2000) reported that Nickel accumulates significantly in some
aquatic organisms including phytoplankton and sea weeds and that if such levels adversely
affect the ecology then size and quality of fish catches would be impacted. A fish advisory in
Vermont recommended reduced consumption of fish by the community because of fish
toxicity from metals. The Vermont Department of Health (VDH) (2000) and VDEC (1992)
then issued Health Alert that people should limit the consumption of fish caught in Vermont
Waters. The Chambishi scenario could not be different from the Vermont one. Some
humans in the area fished from the dams but were not able to use water from the stream for
domestic use within the 4km distance. The fish in streams were found to be stunted in
growth, as stated earlier, when compared to the same type of fish in Lwangwa River which
does not receive discharges of effluents from mining operations. This implied that the water
was unsuitable for healthy fish habitation (Sadar, 1996). The fish abundance was tested
using cooked solid husks of maize. The handful lumps of cooked husks were placed in the
14
water half a metre from the bank of the stream in order to call the fish. The fish came to eat
the husks but the numbers differed from point to point. The numbers of fish that came to eat
husks increased at points down the Chambeshi Stream and decreased at points up the stream
in a ratio of seven to three except the dams downstream where the fish increased in numbers.
The decrease of fish upstream represented a severity impact of 70% upstream and 30% down
stream for surface water. The numbers of fish that came to eat husks at the New Dam were
found to be more than those from Tailings Dam 6 (TD6) in a ratio of four to one. This meant
that the severity impact was 75% for TD6 and 25% for the New Dam. The severity of water
use by the community represented 75% for non use and 25% for fishing and other uses. Only
15% of the animals domesticated by the community had access to Chambeshi and
Mwambashi Stream waters while 85% relied on other sources such as borehole water.
The levels of phytoplankton in water samples taken at different points revealed a decrease of
nine to one upstream representing 90% and 10% severity upstream and downstream
respectively. In general the impacts were high upstream and low down stream. When
compared to the decreasing levels of Zinc and Nickel in water and sediments in the
downstream, the results of severe impacts were also found to decrease downstream.
Therefore, a direct link between level of Zinc and Nickel to the severity of impacts was
established. The severity of impacts on soil sediments was based on phytoplankton counts
which showed a severity ratio of four to one upstream and the same beneficial impact ratio
downstream.
Acid mine drainage is also one of the frequent causes of poor water quality apart from metals.
Although neutralisation is practiced at Chambishi Metals Plc, the effects of fluctuations in
neutralisation could be observed in Chambishi Stream. In almost all areas accommodating
15
mining operations in the world, the studies have revealed high levels of metals particularly
Zinc and Nickel.
The Ely Copper Mine Report in Vershire, Vermont revealed levels of Zinc and Nickel in Ely
Brook River to be 1300mg/L and 73mg/L for surface water respectively and 160mg/L and
26mg/L for sediments taken from the river (VDEC, 1992). The values were found to exceed
the Ambient Water Quality Criteria (AWQC) standards (USEPA, 1993, 1999). Brigden
(2002) observed that the 2001 data in the Kishon River Masterplan Report showed that Zinc
and Nickel levels were above the discharge limits and that effluents still contained significant
quantities of metals including Zinc and Nickel. In Nigeria, the recommended limits for
discharge into surface water are 0.1mg/l for Zinc and <1mg/L for Nickel (FEPA, 1991). A
typical concentration of Zinc in the stream of Arizona was found to be 0.05mg/L above an
open pit mine (Roy, 1997). The Zambian discharge limits into surface water are 10mg/L for
Zinc and 0.5mg/L for Nickel (GRZ, 1993). The results of the study showed that Zinc level
complied with the Zambian standard but Nickel did not. The Nigerian standard is stricter
than the Zambian one while the World Health Organization standard was met by Zinc level
but not that of Nickel. The pH values were higher upstream than downstream (Fig.4). It
could therefore be observed that streams and rivers receiving effluents from mining
operations do not retain the natural existence due to the impacts associated with metals.
CONCLUSION AND RECOMMENDATIONS
The results showed that the absence of abundant aquatic life in Chambishi Stream suggested
that Zinc and Nickel levels had a long term effect on the ecosystem. The non-use of water
from the stream by the community also signified that they were aware that the water was
16
unsuitable for domestic use. The results further demonstrated that levels of Zinc and Nickel
could be high in animals and birds that drunk water from the streams. For example, dogs,
goats, birds and cattle. The levels of Nickel were found to exceed the local and international
standards by s mall margin. However, the metals were found to be decreasing down-stream
and increasing upstream as postulated by the Water Pollution Declining Model (WPDM)
developed for the study.
The self purification process of the stream was found to be
inadequate upstream but good downstream. The high level of Nickel seemed to suggest also
that the removal process using dams or lagoons was marginally ineffective.
While the Mining Company should be commended for her efforts to ensure that the
environment is not impacted by the effluents coming from her engineering operations as
demonstrated by the construction of dams that are used to treat the effluent naturally, sludge
which is disposed through indiscriminate methods around the plant area are carried by rain
water to Chambishi Stream and hence pollute the water.
The dams were not able to
adequately reduce levels of Nickel down to levels recommended by both the World Health
Organization (WHO) and the Environmental Council of Zambia (GRZ, 1993; 1995). This,
therefore, calls for an improvement to the system so that it can be efficient.
There are many ways in which the system could be improved. One of the methods could be
to reduce the concentration of metal carrying solids at the source as sludge, which could then
be disposed at Landfills. This can be achieved by putting a sedimentation tank between the
source and Tailings Dam 6. The unit uses Stokes Law which states that particles will settle
under gravity with a velocity equal to the terminal settling velocity in order to settle out the
solids (Coulson et al, 1991). Neutralizers, flocculation agents and precipitators may be added
as required in order to enhance the removal of solids and metals and hence turbidity. Zinc
17
and Nickel can be precipitated in order to reduce the level in the effluents. This method
works well at the International Metals Company (INCO) in Ontario Canada where they are
treating wastewater from mining operations and sending it to the environment in its natural
state. The second method could be to construct additional dams with adequate retention
times and with plants that can enhance the removal and retention of metals so that the
effluent from the dams leaves with low levels of metals and solids. This method not only
reduces turbidity but also encourages the restoration of a healthy ecosystem. The third
method is to recycle the effluents back into the engineering operations so that more Nickel
could be removed from the effluents. Recycling is one of the many methods used in reducing
pollutants in effluents. Rawlings (2002) elaborated the bio-processing of Zinc and Nickel
using the Thiopaq Process. The process was used to treat Zinc contaminated ground waters
at Budelco Zinc Refinery in Netherlands and Kennecott Bingham Canyon Copper Mine in
Utah where recovery of more than 99% copper at pH 2.6 was achieved (Boonstra et al).
Rowley et al, 1997 reported a bio-sulfide process that uses both chemical and biological
methods that operate independently in the removal of metals such as Zinc and Nickel.
As the major metals being processed at Chambishi Metals are Copper and Cobalt only, the
removal of metals such as Zinc and Nickel could be a challenge to Chambishi Metals or other
investors who would wish to consider investing in Zinc and Nickel production in the area. It
is, therefore, hoped that Chambishi Metals would consider the given recommendations in
addition to what currently exists at the plant in their future strategies of protecting the
environment. It is a known fact that even if the effluents are treated with the application of
high costs that go in the efforts to lower undesirable elements that reduce the quality of
stream and river water, the full restoration of ecosystems can only be achieved in the long
term and not in the short term. The treatment of acids and removal of metals supported by
18
the plantation of acid resistant grass and trees would help to restore the quality of streams in
the area.
ACKNOWLEDGMENT
We would like to thank Chambeshi Metals Company and her workers for allowing and
assisting us to conduct the study at their premises and mine area. We are also grateful to the
Copperbelt University for providing us with facilities that were used during the study. We
finally wish to thank Katuta Bruce, the technologist, for assisting in analysing the samples.
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