09 PREVENTING POLLUTION OF SOURCES (FINALS)

___________ is the introduction of harmful materials into the environment. These harmful materials are called ____________.

• Pollution

• Pollutants

Give example of pollutants

• Volcanic ash

• Trash

• Industrial Runoff

Although urban areas are usually more polluted than the countryside, pollution can spread to remote places where no people live. For example, _______ and other chemicals have been found in the Antarctic ice sheet. In the middle of the northern Pacific Ocean, a huge collection of microscopic plastic particles forms what is known as the _______________?

• Pesticides

• Great Pacific Garbage Patch

• the release of substances into subsurface groundwater or into lakes, streams, rivers, estuaries, and oceans to the point where the substances interfere with beneficial use of the water or with the natural functioning of ecosystems.

Water pollution

WHAT ARE THE TYPES OF POLLUTION SOURCE?

1. Point Source
2. Dispersed Source

• a pipe or channel (e.g. discharge from an industrial facility or a city sewerage system)

• easier to control than dispersed sources, because the contaminated water has been collected and conveyed to one single point where it can be treated

Point Source

• a very broad unconfined area from which a variety of pollutants enter the water body (e.g. runoff from an agricultural area)

• difficult to control

• continue to cause a large fraction of water pollution problem

Dispersed Source

WHAT ARE THE COMMON WATER POLLUTANTS?

• Domestic Sewage

• Solid Waste

• Toxic Waste

• Sediment

• Heat

• Petroleum

What are the several possible ways by which pollution and contamination of water sources can happen?

• Industrial/Commercial Pollution 

• Municipal and Rural Pollution 

• Private Pollution Sources

What is this?

• “Many rivers in the country are already unsuitable for use in potable water schemes due to this pollution.”

Industrial or Commercial Pollution

What sources were once considered safe from contamination due to overlying layers of earth, but now many ____ which are not properly protected have been found to be contaminated by surface water pollutants

• Groundwater sources

• wells

Identify what are the possible contaminants based on this pollution source.

• Solid waste landfill

Heavy metals, chloride, sodium, wide variety of organic & inorganic compounds

Identify what are the possible contaminants based on this pollution source.

• Liquid waste storage ponds

Heavy metals, solvents and brines

Identify what are the possible contaminants based on this pollution source. 

• Septic tanks/leach fields

Organic solvents, nitrates, sulphates and microbiological contaminants

Identify what are the possible contaminants based on this pollution source.

• Agricultural activities

Nitrates, herbicides and pesticides

Identify what are the possible contaminants based on this pollution source.

• Infiltration of urban runoff

Inorganic compounds, heavy metals and petroleum products

What are the examples of Private Pollution Sources?

• Open well casing allowing animal or human waste to pollute the casing/shallow well directly 

• Lack of sealing around the casing (annular space) allowing unfiltered surface water to drain directly into the filter setting 

• Oil or chemical spillage seeping down (1 liter of oil can make 20 m3of water undrinkable) 

• Over-fertilization of fields

Formation Sealing of Drilled Wells

• The annular space between the borehole and casing provides an open pathway for contamination from the surface or from poor quality aquifers intersected by the bore hole before this reaches the desired aquifer.

• That is why the annular space must be filled up with ______ to protect the aquifer. The _____consists of cement and water plus bentonite to reduce shrinkage.

• A __________ at the well top is also important to protect the well.

1. Grout

2. Grout

3. Reinforced Concrete Well Slab

Sanitary Sealing of Drilled Wells

• The top of the casing must extend approximately_______  above the surface of the ground/floor and be watertight with a tight sanitary well seal where the pump connection enters the well.

• The ____ must close all openings for riser mains, cables and monitoring equipment.

• Any vent pipe should be ______ to prevent entry of insects, snakes and the like.

• The ground level around the well top must be ______ away in all directions from the well to prevent entry of surface runoff.

1. 0.3 m

2. seal

3. screened

4. sloping

Formation Sealing of Dug Wells

• The dug diameter of the well is only a little larger than the _______ and the lower annular space is usually filled up by ______ .

• The annular space around the culvert should first be filled by ______up to the water level or at least up to at _ meters from the surface.

• The balance of the annular space can be filled up with ______? 

1. concrete culvert

2. cave-ins

3. grout

4. 2

5. clay up to the concrete slab
   

FORMATION SEALING OF SPRINGS

• Spring water suitable for drinking is normally located on a _______?

• After installing these pipes, the aquifer should be enclosed in  ____ so that polluting surface water will not infiltrate.

• In constructing the spring box, all surfaces in connection with clay should be sealed with _________?
  

1. hill or mountainside

2. clay

3. cement grout.

If the water source is safely protected against surface contamination but is still supplying polluted water, there are 2 possible major causes of pollution:

1. The groundwater is infiltrated by contaminated ground water.

2. The water source is contaminated by a septic tank or leachate water from a dumpsite

Why is it more practical to develop a new water source elsewhere if there is underground pollution?

Because it is almost impossible or just too expensive.

• When large quantities of rock containing sulphide minerals are excavated from an open pit or opened up in an underground mine, it reacts with water and oxygen to create _____.

• When the water reaches a certain level of acidity, a naturally occurring type of bacteria called _______ may kick in, accelerating the oxidation and acidification processes, leaching even more trace metals from the wastes

• sulphuric acid

• Thiobacillus ferroxidans

• ______ severely degrades water quality, and can kill aquatic life and make water virtually unusable

• is carried from the mine site by rainwater or surface drainage and deposited into nearby streams, rivers, lakes and groundwater

Acid Mine Drainage

• _______ is caused when such metals as arsenic, cobalt, copper, cadmium, lead, silver and zinc contained in excavated rock or exposed in an underground mine come in contact with water.

• As rainwater or groundwater flows over these rocks, it picks up the dissolved metals and carries them downstream, contaminating rivers, lakes, and soil. This is dangerous because heavy metals are toxic to plants, animals, and humans, even in small amounts.

• Although metals can become mobile in neutral pH conditions, leaching is particularly accelerated in the low pH conditions such as are created by ______?

1. Heavy metal pollution

2. Acid Mine Drainage.

• This kind of pollution occurs when chemical agents (such as cyanide or sulphuric acid used by mining companies to separate the target mineral from the ore) spill, leak, or leach from the mine site into nearby water bodies.

• These chemicals can be highly toxic to humans and wildlife

Processing Chemicals Pollution

• Mineral development disturbs soil and rock in the course of constructing and maintaining roads open pits, and waste impoundments. 

• In the absence of adequate prevention and control strategies, erosion of the exposed earth may carry substantial amounts of ______into streams, rivers and lakes. 

• Excessive _______ can clog riverbeds and smother watershed vegetation, wildlife habitat and aquatic organisms

• sediment

• sediment