Environmental Engineering Questions and Answers

1.       Define environment (in terms of mining).

Environment is Conditions that affect working atmosphere and development of mining. Or is the physical condition that exists in mines.

2.       What is mining?

It is the extraction of minerals from the earth.

3.       Why does environment become a subject to mining?

Because serious mine closure issues remain after mine is closed so by taking environment as a subject to mining, the mine closure issues can be addressed and must be known to the local people of what is going on and what preventive measures that can be taken to protect people and the natural environment.

4.       What are main sources of physical impacts by mining operations?

They are: exploration, development and extraction.

5.       What are main sources of chemical pollution due to mining?

Main sources of chemical pollution are cyanide and sulfuric acid for (leaching) and organic reagents (flotation agents) from ore separation processes. Others include mercury, toxic blast chemicals and hydrocarbon products run – off.

6.       What particular problem exists with both ferrous and precious metallic ores?

Acid mine drainage is a particular problem in many mines and both ferrous and precious metallic ores are the main sources of ARD.

7.       What is the main concern of trace metal concentrations?

The main concern of trace metal concentration is that, when they are leached into the river systems and streams it cause bioaccumulation which is a concern to the river systems.

8.       State the magnitude of mineral’s contributions to economic growth in developed and developing nations.

High proportions of minerals are mined in developing countries and so the economy of poor countries depends largely on minerals whereas minerals contribute a small portion to the economy of developed countries like USA, Japan and Great Britain.

9.       What are the effects of increased demand for minerals?

The demand for minerals increased as there was an increased in technology, development and human civilization. As a result, environmental impacts of earth based resource extraction increases.

10.   Why is every mine different and related environmental effects?

Because every mine has different characteristics with respect to environment. These characteristics include;

      Amount of materials removed.

      Deposit depth.

      Ore chemical composition

      Ore process technology/techniques

      Degree of stewardship practiced.

11.   Describe very briefly how mineral is extracted by surface mining methods and underground methods.

In surface mining method, the mineral is extracted by removing the overburden, drilled, blasted, loaded and hauled to the processing plant.

In underground mining methods, mineral deposits are extracted at certain depths. Ore is drilled and blasted stopes, marked and hauled to the surface via hoisting systems or diesel units.

12.   What aspect of operation distinguish surface from underground mining?

Underground mine operations are complex compared to surface operations. Surface mining is easy and cheap to operate because the ore deposit is near surface whereas underground mining is hard and expensive to operate because mineral deposit is at certain depth.

13.   State the natures of environmental impacts caused by mill operation, underground and surface mining respectively.

Riverine Tailings from mill operation is dangerous as most mineral deposits are associated with sulfur. In addition, smelting generate large amount of toxic gas. Smelters cause regional pollutions where SO2 can travel considerable distances and cause “acid rain” and climate change.

Potential sources of water pollution include drainage from surface and underground mines, waste water from beneficiation, and contaminated surface water from toxic blast chemicals and hydrocarbon products run – off.

14.   Why is chemical pollution more serious than physical?

Because chemical means are hard to reverse and these must be controlled at process stage. But environmental impacts through physical impacts can be reclaimed through rehabilitation during mining and post – mine period.

15.   Differentiate tailings and waste rock and describe respectively environmental impacts.

Tailings compose mostly of mud and slurry containing high proportion of fine particles. Mud and slurry tailings once exposed to air and rain cause oxidation, releasing sulfuric acid, causing acid rock drainage. The suspended solids cause river bed sedimentation, diversion of watercourses, flooding and destruction of aquatic life.

Waste rock is solid coarse materials from both surface and underground mines. Waste rock dump occupy large portions of land, often outside the special mining lease under lease for mining Purposes.

16.   If Frieda Copper mine is predicted to produce 1million/year ore at 0.45%Cu, what is the annual waste material generated?

Data: production = 1,000,000 tonness/year

       grade = 0.45%

Annual waste generated =????

Copper concentrate = production x grade = 1,000,000 x 0.0045 = 4500 tonnes copper.

Annual wastes = 1,000,000 – 4,500 = 995,500 tonnes of waste.

17.   If Hidden Valley mine has minable ore of 5minllion tones grading 2.5g/t Au, for mine life of 10 years, the tailings dam should be designed to what capacity?

Data: mineable ore = 5 million

Ore grade = 2.5g/t     mine life = 10 years.

 /year x 2.5g/t = 12,500,000 grams/year.

Total value mineral = 10 years x 12,500,000 gram/year = 125,000,000 grams

 In terms of tonnes = 125 tonnes.

Waste and value minerals = 5,000,000 tonnes /year x 10 years = 50,000,000 tonnes of ore.

Therefore; total waste generated would be = 50,000,000 tonnes – 125 tonnes = 49,999,875 tonnes.

So the tailings dam should be designed in such a way that will cater for 49,999,875 tonnes of waste over the ten year period. If tonnage factor was given then the answer would be expressed in volume.

18.   What is beneficiation? Describe it?

Is the entire process of crushing, grinding, sizing and separation of ore into valuable mineral and waste

In other words it is the process that liberates mineral grains locked in rock/ore which can be separated physically and chemically.

19.   State the two types of mineral separation and examples of each.

Two basic means of separation are physical and chemical.

·         Physical separation involves; - (a) magnetic and (b) gravity separation.

·         Chemical separation methods are: (a) floatation (b) cyanidation (c) amalgamation and (d) heap leaching.

20.   Briefly describe the processes: (a) heap leaching (b) cyanidation & (c) amalgamation.

      Heap leaching – is a process used to extract metal values from run – of – mine ore. The ore is usually porous and readily soluble in aqueous solvent.

      Cyanidation – is a process for extracting gold or silver from ore by treating the ore with a weak solution of sodium cyanide and recovering the metal particles from the resulting solution.

         Amalgamation – is a method of extracting a precious metal from an ore by using mercury to form an amalgam (an alloy of mercury and another metal) with the metal.