TECHNICAL ANALYSIS OF ACID MINE WATER CONTROL

ON THE OPERATION OF BATU HIJAU GOLD MINE

BY NEWMONT NUSA TENGGARA CORPORATION

THESIS PROPOSAL

Written by:

RONGGO SHULISTYORAHADI

96.030/TA

MINING ENGINEERING DEPARTMENT

MINERAL TECHNOLOGY FACULTY

PEMBANGUNAN NASIONAL “VETERAN” UNIVERSITY

YOGYAKARTA

2001

A. TITLE

TECHNICAL ANALYSIS OF ACID MINE WATER CONTROL ON THE

OPERATION OF BATU HIJAU GOLD MINE BY NEWMONT NUSA

TENGGARA CORPORATION

B. THE REASON OF TITLE SELECTION

Mining operation almost generally has negative effects and one of the actual

effects is about Acid Mine Water.

If Acid Mine Water carried on an unaccurate way so at the end of the

operation will cause such enviromental polution. The Acid Mine Water contains of

solute metal which will reduce soil fertility, corrosion on the tools and probably

several health problems to the civilian surrounding mine area.

One possibility way to reduce Acid Mine Water is controlling waste material

as well as possible.

C. OBJECTIVES OF THE OBSERVATION

This operation has an object to obtain several input data that is related to

process of Acid Mine Water. Then, the input data will be able to be processed in

certain ways to result one good conclusion.

D. IDENTIFICATION AND APPROACHMENT TO THE PROBLEM

Acid Mine Water is a kind of run-off water which has came up from mine

area and has characteristic of acid and contains of solute material compounds, as a

result from oxidation process on the exposed rock to the air. Generally, the process

of oxidation depends on three main reactan : water, oxygen, and rock material.

Acid Mine Water that has came up from overburden piles and tailing

processing unit has an ability or possibility to come up negative effects to the

environment, especially to the water sources.

Approachment to the problem will be done by collecting data which can be

gained from the observation in the field. To support and provide this thesis then the

writter also combine between theory and the facts in the field so the best

approachment will be useful to solve the problem.

E. THEORY

1. Process of Acid Mine Water.

Acid Mine Water is acid water and contains of solute metal compounds,

especially Fe and sulphide compounds, formed succesfully because of rocks strata

containing minerals such phyrite, marcasite, chalcophyrite that were exposed to the

open air. Generally, the process is based on three main reactan. Those are water,

oxygen, and rock materials. Those rocks were exposed to the surface land as a result

of land opening, rock breaking when the mining operation was continuing. Then

followed by oxidation process, resulting oxide compounds and if these have a contact

directly to the water (either come from water rainfall or mine water) will form

Fe2SO4 or H2SO4.

Unless we neutralize the water then the acid water will flow to the

surrounding area. The oxidation process, unexpectedly, often fasten by

microbiological activities. Several species of the bacteries found in the tailing water

are : Thiobacillus thiooxidans, Thiobacillus ferrooxidans and Ferrobacillus

ferroxidans.

We can describe the oxidation process of sulphides minerals which causing

water acidity with three reaction :

a. Fe S2 + 72 O2 + H2O Fe2+ + 2SO42- + 2H+

b. Fe 2+ + 14O2 + H+ Fe3+ + 1/2 H2O

c. Fe 3+ + 3H2O Fe(OH)3 + 3H+

d. FeS2 + 15/4 O2 + 7/2 H2O 2H2SO4 + Fe (OH)3

and the reaction equation of Acid Mine Water which are based on biological

activities are :

FeS2 + H2O + 7/2 O2 Fe2+ + 2SO42- + 2H+

Fe+2 + 1/4 O2 + 5/2 H2O T. Ferroxidans Fe (OH)3 + 2H+

FeS2 + 7/2 H2O + 15/4 O2 Fe (OH)3 + 2H2SO4

From the equation reaction above, we can analyze how the H2SO4 is finally

formed. So with the existence of H2SO4 will cause water flow has characteristic of

acid and that is what we call Acid Mine Water. Acid water is known as pink or red

from its colour and it came up from Ferri Hidroxide on the bottom of the water flow

and we will be able to recognize it from its sulphuric smell. However, it does not

always happen because some time, we even recognize Acid Mine Water has clean

appearance.

Several condition are provided to Acid Mine Water forming. Those are :

a). Such sufficient sulphide compounds contents in Acid Mine Water and enable to

react both chemically and biologically, generate acid leachate which have reaction

velocity of acid forming faster than reaction velocity of neutralization by alkali

compounds, inside the tailing.

b). This spesific physical characteristics has allow the water and oxygen to infiltrate,

and resulting acid tailing reaction, both chemically and biologically.

c). The condition of mine area with sufficient humidity will cause some water

rainfall infiltration on tailing pile, then the exist tailing will flow to the

surrounding area.

2. The Acid Mine Water Sources.

The Acid Mine Water, also called Acid Rock Water, has happened as a result

from several complex chemically and phisically process, including several factors in

the mining operation whether it came from surface mining or underground mining.

Commonly, this situation happened because sulphuric minerals inside the rocks were

oxidized naturally when the mine development was continuing. And then, provided

with enviromental humidity condition finally will cause sulphuric oxide become

acid.

The Acid Mine Water sources originated from several activities below :

a). Mining

Water from underground mine

For this kind of Acid Mine Water, it is easier to make an identification which has

characteristic of low pH. It will affect to mining tools with the existence of any

corrosion and become special problems on its operation.

Water from surface mine

The final consequence of stripping overburden is exposed rock strata so that

sulphur contents inside the sulphidize rock will be able to be oxidized and if it

reacts with water then finally will form Acid Mine Water.

b). Water From Waste Rock Processing Unit

The most uncounted waste as a results of mining operation are waste rock. The

number of waste rock increase attend by the increasing of mining activities.

Finally, the abundant waste rock which containing sulphuric compounds will have

more directly contact with open/free air and resulting sulphur oxide compound.

c). Water From Ore Stockpile

The water from this location is the main sources of Acid Mine Water.

d). Water From Tailing Process Unit

Usually, tailing settling pond has low permeability and always filled in with water

contains of tailing from mine area and processing unit. The water has

characteristic of quite high pH because of CaCO3 addition in order to neutralize

acid water. The acid water maybe do the infiltration outside the settling pond then

causing some acid tailing.

3. Identification of Acid Mine Water Potency

Both of existing mine operation or planned operation, it is necessary to have

several test on waste characteristics in order to predict the possibility of Acid Mine

Water.

The objectives of identification Acid Mine Water potency are :

a. Planning on Acid Mine Water preventing system, including reclamation planning

on dumping acid materials, reclamation on mined out area and planning on mine

drainage area.

b. Planning on Acid Mine Water management system, including drainage structure

design, settling pond design and water treatment system.

c. Planning the alternative management, phisically, such Acid Mine Water recycle

and another advantages.

The first accurate prediction of tailing characteristics which has potency to

cause Acid Mine Water will be useful to reduce enviromental damages and even on

its management and operational costs.

Based on several procedures of exist Acid Mine Water forming, there are four

(4) statistic test, five (5) kinetic test and the others are test which have a goal to

obtain some information related to natural characteristics of materials whether it is

phyrite rock or carbonaceous rock.

The difference between ability to neutralize (Neutralize Potential = NP) and

ability to form such acid (Acid Potential = AP) then called as Net Neutralization

Potential (NNP). And it has negative symbol. The Net Neutralization Potential

describes potential sources from Acid Mine Water.

The calculation of rock ability to result Net Acid Producing Potential (NAPP)

is a method used to identify the acidity of rock. From those calculation, we can

determine whether the rock have an ability to result acid condition or not.

These are some principles to calculate NAPP :

Using a simple method to determine ability value to result acid from rock sample.

Acid Producing Potential (APP)

By determining sulphur contents using leco furnace method.

Acid Neutralizing Capacity (ANC)

By measuring degree of soluble metal of Ca, Mg, Mn in acid solution, with the

assumption that those metals seem to be exist as carbonate and the Acid

Neutralizing Capacity is equalized as CaCO3.

Finally, the NAPP is calculated by reducing the potency of acid forming with

Acid Neutralizing Capacity.

We can use the calculation to determine ANC and APP as seen down below :

(1). ANC Determination

Transforming % Ca, Mg, and Mn into CaCO3, based on calculation below :

% Ca x Mr CaCO3/Ar Ca = % Ca x 100,09/40,08 = % Ca x 2,497 …..(1)

% Mg x Mr CaCO3/Ar Mg = % Mg x 100,09/24,32 = % Mg x 4,116 ..(2)

% Mn x Mr CaCO3/Ar Mn = % Mn x 100,09/54,94 = % Mn x 1,822...(3)

Total ANC (as CaCO3) = (%Ca x 2,497) + (%Mg x 4,116) + (%Mn x 1,822 )

(2). APP Determination

Potency to result acid is :

= % S x H2SO4 / 5 x CaCO3 / H2SO4

= % S x CaCO3 / 5

= % S x 3,122 ………..(4)

(3). NAPP Determination

Since the data of rock sample analysis have been accepted, then those will be put

into equation (1(, (2), (3), and (4). So at the end :

NAPP = APP – ANC

If the output shows positive value, then the rock is classified into acid (PAF) and

if it shows negative, it will be classified into non-acid rock (NAF).

4. pH Solution and Acid Neutralization

a. pH Solution

There is a simple way to determine solution acidity by using pH and pOH. It

will show the number of H+ ion and OH- ion inside the solution.

pH = - log (H+) pOH = - log (OH-)

in the pure water, H+ and OH- concentration is equal, that is10-7, so that :

pH = -log (H+) = -log 10-7 = 7

pOH = -log (OH-) = -log 10-7 = 7

if pH < 7 = acid solution

if pH = 7 = neutral solution

if pH > 7 = base solution

So the lower its pH become then the solution will have characteristic of acid.

The relation between pH and pOH :

PH + pOH = 14

Lakmus universal indicator is a media used to indicate whether the water is

acid or base. We can recognize it from the transformation of the colour.

b. Acid Neutralization

Neutralization process is necessary to control Acid Mine Water. The process

by using alkali material (in this case generally has a form of FeS2) will be

raised its pH. So, the process need alkali or carbonaceous material to raise the

pH such :

- limestone (CaCO3)

- dolomite (MgCO3)

- mangan carbonate (MnCO3)

- quicklame (CaO)

- dry hydrate

- ash coal

Below are the chemical reaction of acid water neutralization and chemical

reaction with another alkali or carbonaceous material :

a) FeS2 + 7/2 H2O + 15/4 O2 + CaCO3 Fe (OH)3 + 2SO4-2 + 2H2CO3 +

2Ca+ CaSO4 + CO2 + H2O

b) MgCO3 + H2SO4 MgSO4 + CO2 + H2O

c) Mn CO3 + H2SO4 MnSO4 + CO2 + H2O

d) CaO + H2SO4 CaSO4 + H2O

e) Ca(OH)2 + H2SO4 CaSO4 + 2H2O

f) NaCO3 + H2SO4 NaSO4 + CO0 + H2O

g) 2NaOH + H2SO4 Na2SO4 + 2H2O

5. Control Of Acid Mine Water

Commonly the control of Acid Mine Water is divided into :

a. Prevention

Prevention has goals to prevent or reduce degree of acid forming by retaining

sulphide oxidation. The main element in the process of acid forming are :

Rock or soil which has sulphide contents.

Oxygen

Water

Overcoming acid forming could be done by reducing at least one or more

elements of acid forming so that exist acid stay on a safe level.

Several prevention act, those are :

(1). Isolation of sulphide mineral

by separating materials contain of sulphide mineral from water and or

free air, it will retain from oxidation process.

(2). Control of water flow

Preventing from infiltration of the surface water flow into acid

material

Preventing from infiltration of the rainfall water on acid material

Preventing from infiltration of the underground water flow on acid

material location

b. Control of acid water migration

The main reason of control acid water migration is preventing dissemination

of acid water flow. By doing several action such :

Development of drainage system alongside location acid water flow

Installation of drainage pipe system under location material pile

c. Acid water neutralization

Settling pond is a media used to catch acid water. This media has a function

as a supervision tool in order to supervise the water quality, and also used as

a media to neutralize acid water before it will be released into the

environment.

F. SURVEY METHODOLOGY

1. Data Acquisition

It is a part of step of the survey which has certainly goal to collect data from

many sources related to this topic and will be use to complete the thesis. Those

data are :

a. Acid Mine Water management method

b. Water content inside material

c. Specification and dimension of tailing settling pond

d. Sulphuric mineral due to Acid Mine Water forming

e. Waste yield

f. Pure water quality (pH)

g. Mining method

h. Complementary data, consist of :

- regional geological data and geology history

- lithology data, topography and water rainfall

- geology map

- condition and surrounding environment

2. Step of the survey

a. literatur study

b. survey on the field

c. data acquisition

(see sub chapter F no. 1)

d. data processing

data processing consist of some calculation and description. It is continued

by presentation of tables, graphics or serial calculation to solve certain

process.

e. analysis

The data will be processed in order to obtain hypothesis and then the

hypothesis will be followed by another processing and talked on

discussion chapter.

f. conclusion

The conclusion will be obtained after doing correlation between data

processing and observed problem. This will be final result from all aspect

that has been discussed before.

G. ADVANTAGES

Base on final result from the survey, we hope that identification potency of exist

Acid Mine Water might be recognized earlier so that preventing action can be

prepared as soon as possible. Else, the first accurate control of Acid Mine Water will

give Newmont Nusa Tenggara Corporation an opportunity to do its enviromental

eligible operation with low cost.

On the other effect, it supports the company to achieve optimal production target

because heavy machinery can work optimally without any problem cause of any

corrosion or damage.

H. TIME SCHEDULE

No. Activity Time ( Week )

1. Literatur Study

2. Field Introductary

3. Data Acquisition

4. Data Processing

5. Draft

I. CONTENTS

SUMMARY

PREFACE

FIGURE LIST

TABLE LIST

ADDITIONAL LIST

I. INTRODUCTARYA.BackgroundB. ObjectivesC. ProblemsD.Survey MethodologyE. Result

II. GENERAL PREVIEWA.GeographyB. GeologyC. Mining OperationD.ProcessingE. DrainageF. Enviromental Effect

III. THEORY

A. Process Of Acid Mine WaterB. Acid Mine Water SourcesC. Control Of Acid Mine WaterD. Prevention Of Acid Mine Water Forming On Waste Dump

IV.ANALYSIS OF ACID MINE WATER ON THE FIELDA.Water From Waste Rock Processing UnitB. Water From Ore StockpileC. Water From Tailing Processing Unit

V. DISCUSSIONA. Preventing Action From Acid Mine Water B. Management Of Acid Mine Water C. Control Of Acid Mine Water On Tailing Settling PondD. Preventing Action From Negative Effect On Tailing Settling Pond

VI. CONCLUSION AND SUGGESTIONA. ConclusionB. Suggestion

REFERENCIES

ADDITIONAL

J. REFERENCIES

1. C.G Down, PhD. And J. Stocts B.DS., “Enviromental Impact of Mining”, ARSM., C.Eng., Departement of Resources Engineering Royal School of Mines, London.

2. F. Gunawan Suratno. 1993, Analisis Dampak Lingkungan. Yogyakarta Gadjah Mada University Press.

3. Ir. Hadiyah, MT, “Air Asam Tambang”, Dosen Pengajar Jurusan Teknik Pertambangan Fakultas Teknologi Mineral UPN “Veteran” Yogyakarta, Diktat Kuliah, 1997.

4. Jefrey. G. Skouser and Paul F.Z, “Acid Mine Water Control and Treatment”, West Virginia University and the National Mine and Land Reclamation Centre, 1995.