Water dule04/basics2.htm. Presented by Victor Tibane

Transcription

1 Water dule04/basics2.htm Presented by Victor Tibane

2 Water 1. Water bodies water states 2. Chemistry of water, how it operates naturally and how it is perturbed by human activities 3. Water cycle 4. Water pollution 5. Water treatment

3 What is water? Water is a colourless, transparent, odourless, liquid which forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms. As a chemical compound, a water molecule contains one oxygen and two hydrogen atoms that are connected by covalent bonds. Water is a liquid at standard ambient temperature and pressure, but it often co-exists on Earth with its solid state, ice; and gaseous state, steam (water vapour).

4 Water Water is a need to sustain life Water is a carrier of illness Safe water: cleaned water should be free from: Colour, turbidity, odor, taste, harmful metal ions, nitrates Low in hardness and total dissolved solids Organic chemicals Pesticides Chlorinated solvents

5 Water Bill of Rights, Constitution of South Africa, Section 27 (1) (b): Everyone has the right to have access to sufficient water. White Paper on Water Supply and Sanitation (1994): Basic water provision: 25 l of water per person per day within 200 m of their home. GROUNDWATER

6 Water is a resource and needs to be protected Hence the groundwater surface (resource protection) as well as the well/spring (source protection) are receptors Water is the only transport agent that migrates through all the components of the environmental system GROUNDWATER

7 Types of water resources Water may be found in nature as vapour and humidity in the atmosphere; as a liquid in rain; as surface water in rivers, streams, ponds, lakes, watersheds, and interior seas; or forming part of seas and oceans It is also found as groundwater, in vadose or unsaturated zones, included as interstitial water in the free spaces of soil and sediments, in springs and aquifers, or forming part of minerals as hydrates It exists as a solid in glaciers, icebergs, hail, snow, and ice

8 Water Distribution 97% stored as sea water in oceans. 3% shared between the land and the atmosphere % as vapour 66% of land water is stored as ice in ice sheets, ice caps and glaciers Only 1% of surface and underground water is used by humans

9 Water Distribution Water is by far the most abundant liquid on Earth. It comprises between roughly 90% of the weight of living organisms Nearly 71% of the Earth's surface is covered by water It is obvious that without liquid water, life as we know it would not be possible (Ibanez et al., 2007)

10 Water About 1.5 billion people depend upon groundwater for their drinking water supply (World Bank, 1998). A world of salt... GROUNDWATER

11 Water Quality The composition of water in each site depends on its: solids, liquids, and gases during the water cycle the geochemical nature of the bedrock the weathering regimes the environmental climatic conditions the biogeochemical processes the chemistry of the components of the bedrock

12 Water Quality The most common parameters that define chemical/environmental characteristics of natural waters are: ph, alkalinity, ionic strength, conductivity, salinity, hardness, and the composition and concentration of the different ions or compounds present, usually expressed as parts per million (ppm)

13 Global Freshwater Resources Quantity and Distribution GROUNDWATER

14 Endogeneous water: Water Distribution Water, that is derived locally from rainfall and groundwater Exogeneous water: Water, that originates elsewhere and flows through the area Very important for many regions in SA, which are naturally dry but which are fed by rivers originating in areas with water surplus GROUNDWATER

15 Rainwater Rainwater washes and cleans atmospheric processes through dissolution of gases and salts, and transport of substances and particles onto the surface of the Earth. Particles and micro-organisms, such as bacteria suspended in air through wind erosion, are washout and carried over by rain water.

16 Does your family or community use water? Water is used for many different things: Drinking Cleaning Bathing Cooking Watering the yard and much more Can you think of any other uses

17 Water Overexploitation GROUNDWATER

18 Water Overexploitation: evolution of groundwater use UP 2009 GLY 265 GROUNDWATER

19 Water Stress and Scarcity An area is experiencing water stress when annual water supplies drop < m 3 per person. An area is experiencing water scarcity when annual water supplies drop < m 3 per person. 2.8 billion people in 48 countries will face water stress or scarcity conditions by GROUNDWATER

20 Water Stress and Scarcity Freshwater stress and scarcity in Africa by 2025 UNEP (2002) UP 2009

21 South Africa: Water Stress and Scarcity Semi-arid with relatively low rainfall (average: 450 mm/y) 75% of SA has a rainfall of less than 650 mm/y (minimum necessary for successful cultivation) 30% receive < 250 mm/y (classified as desert) Regions of high runoff are often situated away from areas of maximum water demand Rainfall patterns are erratic, and generally decreases from east to the west GROUNDWATER

22 Water Stress and Scarcity South African rainfall patterns ca UP 2009 GLY 265 GROUNDWATER

23 South Africa: Water Stress and Scarcity Virtually no fresh water lakes, available sources limited to rivers, reservoirs & groundwater (GW) Limited GW, unevenly distributed across the country and often poor quality Very low ratio between runoff & rainfall due to high evaporation rates Constraint to social & economic development Water is a scarce resource! GROUNDWATER

24 Water Stress and Scarcity European Water Directive (2000): Water is not a commercial product like any other, but rather, a heritage which must be protected, defended and treated as such. Risk Assessment (Impact) Risk assessment: Source Pathway(s) Receptor(s) GROUNDWATER

25 Water Stress and Scarcity You can see why groundwater must be protected from contamination. Before you begin to learn about the problem of groundwater contamination, it is important for you to review where groundwater comes from and how it moves.

26 Risk Assessment Atmospheric pathway External exposure Internal exposure (ingestion & inhalation) Biosphere pathway Surface water pathway Geosphere pathway Groundwater pathway GROUNDWATER

27 Water Pollution Types of water resources Underground Lakes and dams Rivers Oceans

28 Groundwater Contamination The contamination of groundwater, which is a principal source of drinking water, is a serious health and environmental problem in many areas of the United States and the world. During this topic you will learn: What is groundwater contamination? Why is it important for us to know about it? What are the sources of contamination? How does one investigate groundwater contamination? What are some ways to clean up and prevent groundwater contamination?

29 Water Water at risk: Contamination Overexploitation GROUNDWATER

30 Contamination Basics: Contaminants Contaminants are separated into three main categories: Biological Inorganic chemicals Organic chemicals

31 Sources for Water Pollution Sewage Effluent Animals waste Surface run-off from cities into storm water Waste not properly disposed of Acid rain from air pollution Fertilizers and chemicals from agriculture Siltation from erosion Oil and chemicals spills

32 Pesticides Pesticides are used to kill pests such as insects on farm fields. Pesticides can seep into the groundwater and cause kidney and liver damage and cancer in humans who drink the water.

33 Uranium Uranium is a radioactive element used in nuclear power plants. It also exists naturally in small concentrations in the ground. Too much uranium can cause cancer and other illnesses.

34 Nitrates are chemicals present in most fertilizers. Nitrates can contaminate the groundwater, causing serious illness in young children. Over 115 million tons of fertilizer are used in the United States. Nitrates

35 Fecal Coliform Yep, that s right. Human waste contains bacteria that can contaminate groundwater. Fecal coliforms can cause stomach illnesses and diarrhea and if they are present, other pathogens may be there also.

36 Chemical Solvents TCE is an example of a chemical solvent. TCE is used in industries to clean parts and materials. Too much of it in the groundwater can cause cancer in humans.

37 Benzene contamination can come from leaking fuel tanks and industrial waste. Benzene Too much of it can cause cancer, nerve, lung and kidney damage, and blood disorders.

38 One-Time Source Plume vs. Continuous Source Plume Contaminants can enter the groundwater by seeping in from the surface or by flowing in from another part of the aquifer. Once in the aquifer they move with the groundwater flow. As contamination moves it disperses. This means that the concentration decreases as it moves farther away from the source of the pollution. For that reason there are different concentrations of contaminants at different points in the aquifer.

39 One-Time Source Plume vs. Continuous Source Plume The visual representation of these different concentrations is called a contamination plume. How the plume looks depends on the type of contamination source, the specific contaminant(s), where the aquifers are located, and different soils in that area.

40 One-Time Source Plume

41 Continuous Source Plume

42 Area of Contamination When talking about contamination movement it is also very important to talk about the area affected by the spreading of groundwater contamination. A contaminant may be released into the groundwater for only a short time and in a very small area, but as it disperses the contaminant can affect a very large area and number of people.

43 Area of Contamination The animation below shows that even though the one-time source was small in area, the total area that has a dangerous concentration of arsenic is much larger. The area that has a dangerous concentration is from the center of the plume in the direction of the water flow.

44 Real Plume Example Where is the source of the contamination? Is the source continuous or a one-time event? Based on the direction of the plume, which way is the groundwater moving? How far does the contamination travel? What important areas are affected by the contamination?

45 Storm Water System Collects rain water and surface run-off Not allowed to be polluted Not petrol, oil, diesel, thinners, solvents and chemicals may be washed into storm water drains. If storm water drains empty into the natural water resources may cause pollution.

46 Effluent It represents processed water and dirty surface run-off. It usually drains into the municipal sewer. Effluent must be treated before can be released into a water resource. Permits are required to release effluent into the water resource or into municipal sewer.

47 Sewage (i) Consists of human waste and wash water or gray water from kitchen and bathrooms. Goes to municipal sewage line Then get treated at sewage farm to clean and recover water If municipal sewage is not available, septic tanks (large underground tanks that need cleaning) are used. They need regular emptying

48 Sewage (ii) Oil traps recover oil from water Collect for disposal or recycling Usually at wash bays, workshops and before surface water runs into storm water drains. Collection systems often need proper maintenance.

49 Water Treatment Plant Improve water quality prior to release into sewer system or natural resource. Certain water quality standards must be met. Maintenance is important. Usually expensive to operate.

50 Water Treatment Water and wastewater treatment Surface and underground water contamination Hazardous waste management Radioactive waste management Air toxics emissions Acid rain Ozone depletion Global climatic changes

51 Water Pollution and Law Water pollution is illegal. Fines and jail sentences are prescribed. Polluters can be personal liable. Permits and licenses are needed to dispose of effluent into a water resource or sewer. Water use is regulated.

52 Health Problems Associated with Organic Chemicals Cancer, birth defects, Central nervous system disorder, Disruption endocrine system, Heart diseases Non-corrosive Non-scale forming

53 Minimize Pollution and Save Water Use less water Re-use water (recovered or clarified) Recycle water after treatment. Safe waste disposals Industries should use more water efficient processes Keep surface water clean. Do not pour or wash any chemicals, oil or paint into drain.

54 Wastewater and Water Pollution Control Nitrogen and organic (ammonia) is kept within limits of oxygen resource of water. Leaking underground storage tanks Minimize industrial Organic chemicals and heavy metals Minimize agricultural wastes. Nitrogen fertilizers

55 Wastewater and Water Pollution Control Minimize the quantity of waste produced by product substitution. Waste recovery and recycling

56 Industrial and Hazardous Wastes Required knowledge of: Inorganic and organic chemistry, Physical or colloidal, Biochemistry, Radiochemistry.

57 Cleaning Up Contamination So now we know that there can be contamination of the groundwater supply. What do we do about it? Groundwater can sometimes be difficult to clean up due to its location. Many times the water is pumped up a well, cleaned, and then sent back down the well into the aquifer. Sometimes an additive is placed in the groundwater that either makes the contaminants less harmful or destroys them.

58 Cleaning Up Contamination When there is contamination, not only does the water need to be cleaned, but often the soil as well. If the soil wasn't cleaned, then the contaminants could just seep back into the water. Thus, cleaning is a very, very expensive and time consuming process. Sometimes it might be impossible or too expensive to clean up the contamination at all!

59 Bioremediation Bioremediation involves using bacteria to clean up the contamination by "eating" it. Usually nutrients are pumped down into the contaminated area. The nutrients help bacteria, which are already in the groundwater, to grow and destroy the contamination.

60 Soil Vapor Extraction In SVE, air is pulled through the ground in order to pull certain contaminants out of the groundwater. This method also increases air movement underground so that the helpful bacteria in the ground can "breath" better and destroy more contaminants. The air that is pulled out of the ground then needs to be treated also.

61 "Pump and Treat" Systems Sometimes groundwater is cleaned by pumping it to the surface and cleaning it above ground. The clean water is then pumped back into the ground. This is sometimes is a problem, as there might not be anywhere to put it while it is being cleaned up. Another issue is that while the water is now clean, the contaminant still needs to be disposed of safely somewhere. This can take even more time and effort.

62 Prevention of Contamination What is the best clean-up method? It depends on the situation, but most would agree that the best way to deal with groundwater contamination is not to contaminate it in the first place! This brings us to the very important topics of groundwater protection and prevention of contamination.

63 Prevention of Contamination Clean-up methods take a lot of money and time to accomplish, and they usually can't clean up everything. We must try to do our best to protect groundwater from contamination in the first place. There are many different ways that you can prevent contamination. These depend on where the groundwater is located, where it is used, and what dangers of contamination exist.

64 Prevention of Contamination Prevention includes all of the following and more: Using strong containers for fuel and wastewater tanks. Knowing where to store chemical wastes so that they don't hurt anyone or the environment. Making sure that solid waste landfills are used properly and that there are warning systems to tell people if there is a leak.