8. E and 4. Water Quality, Indicators, and Usage

Transcription

1 8. E and 4 Water Quality, Indicators, and Usage

2 How is the health of a water system determined? Balance between physical, chemical, and biological factors Physical variables include: temperature, turbidity, and water movement. Chemical variables include: dissolved oxygen and other gases, ph, nitrates, pollution, and salinity.

3 Physical, Chemical, and biological factors Both natural and man-made forces are constantly changing these variables. Freshwater systems are of particular concern because they are the source of most of the potable water consumed by humans. Testing for the occurrence of chemicals and other factors that can influence water quality, such as nutrients and pesticides in water resources is a normal part of public health maintenance and stewardship of freshwater resources.

4 Potable Water Water that is safe to drink is called potable water, or drinking water, in contrast to safe water, which can be used for bathing or cleaning. In the United States, the Environmental Protection Agency sets maximum levels for the 90 most commonly occurring contaminants.

5 How does temperature affect the health of a water system? Affects the ability of water to act as a solvent Warm water dissolves more solid substance less important gases (oxygen, carbon dioxide) Aquatic life requires specific temperatures to survive in their habitat Human impact on water temperature Global Warming Factory Discharge Chemical Reactions

6 How does turbidity affect the health of water systems? The measure of clarity of water The more dirt suspended in the water the higher the turbidity (less transparent) Impact of high turbidity Blocks out sun High water temperatures Plants and algae cannot perform photosynthesis Water is not clean to consume

7 How does water movement affect the health of a water system? Erosion: gradual wearing away and movement of land surface materials due to the movement of water and wind Stagnant (not moving) water Levels of dissolved oxygen drop anaerobic bacteria can grow The Power of Erosion

8 How do dissolved gases affect a water system? Aquatic life needs oxygen to survive Oxygen (solute) is dissolved in water (solvent) Movement of water and aquatic plants Temperature Temperature = Dissolved Gases = Dissolved Gases Think about chugging a cold soda vs. a warm soda, which one has more bubbles? Dissolved Oxygen and Gases- Soda Example

9 How does dissolved oxygen (DO) affect water systems? DO is a measure of the amount of oxygen in water that is available for chemical reactions and for use by aquatic animals Gets in the water because oxygen is a product of photosynthesis DO levels decline sensitive animals may move away, weaken, or die. High DO levels in potable (drinkable) water usually make it taste better Measuring Dissolved Oxygen

10 How do other dissolved chemicals affect the water? Phosphates Stimulate growth of producers causes water flow to slow down increase in sediment Enter water through Human/animal waste Laundry Cleaning/industrial waste Nitrates Enter water through Fertilizer Sewage Erosion Increased algae growth which can lead to eutrophication

11 How does ph affect a water system? Controls many chemical and biological processes that occur in water A measure of acidity Acid = ph of 1-6 Base = ph of 8-14 Neutral = ph of 7 Variances in ph cause Pollution Death of aquatic animals

12 How does salinity affect water systems? Salinity: A measure of dissolved salts in water Freshwater animals cannot survive in salt water and salt water animals cannot survive in freshwater environments. How does salt enter the environment? Minerals get washed into the environment due to surface runoff and erosion. Human Impact: salted roads during the winter

13 How is the health of a water system determined? Biological Factors (macro-invertibrates) Components of a water system that indicate the health of the water. Living organisms in the water indicate the health of the water, depending on the use of the water.

14 What are bioindicators? Organisms that are studied to indicate the quality of water such as water flow, pollution, and vegetation They indicate the health or sickness of their environment The higher the biodiversity, the healthier the environment Poor water quality is indicated by a few or one type of macroinvertebrates in one place.

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16 Select and Describe One Most Common Water Borne Disease? (Pathogen and Symptoms) Travellers' Diarrhea Giardia and Cryptosporidium Dysentery Salmonella Escherichia coli 0157:H7 (E. coli) Typhoid Fever Cholera

17 What is water quality? Describes the chemical, physical, and biological characteristics of water Described in terms of the propose for which the water is used. Potable water- safe to drink Safe water- an be used for bathing and cleaning

18 What are water quality standards? Outline the water quality pollution control program for a body of water Identify uses of body of water Establishes how to protect uses Establishes provisions for to protect and preserve in long term Mandated by local, regional and federal agencies Drinking water standards: benchmarks established to determine the quality of water

19 What legislation is in place to protect our freshwater? Clean Water Act Safe Drinking Act 1974 Everyone in the developed world has the right to safe drinking water concern shifted to industrial waste and water contamination Water treatment plants adapted Water treatment: the process used to remove contaminants from water and make it usable for humans. Focus on conservation of water systems

20 How is water treated? Water flows through mixers Clumping agents Disinfecting chemicals Clarifying pool Lumps of dirt sink to bottom Filter smaller particles of dirt Coal, sand, gravel Chlorine Added to kill last of the bacteria

21 Carcinogens in Tap Water Studies have shown that the most prominent chemical contaminant (carcinogens) in tap water all over the country is Hexavalent Chromium, also known as Chromium-6. Hexavalent chromium is a known carcinogen and can start eating away at the body after only a relatively small amount of exposure. Other types of carcinogens and neurotoxins found in water supplies include: Benzene Chlorine Fluoride Arsenic Lead Dimethyl disulfide Carbon Disulfide Napthalene Trimethyl Benzene

22 Think Time! Why do you think water treatment is important? What is the impact of good/poor water quality to society?

23 Water Treatment Cycle COAGULATION removes dirt and other particles suspended in water. Alum and other chemicals are added to water to form tiny sticky particles called "floc" which attract the dirt particles. The combined weight of the dirt and the alum (floc) become heavy enough to sink to the bottom during sedimentation.

24 Water Treatment Cycle SEDIMENTATION The heavy particles (floc) settle to the bottom and the clear water moves to filtration.

25 Water Treatment Cycle FILTRATION The water passes through filters, some made of layers of sand, gravel, and charcoal that help remove even smaller particles.

26 Water Treatment Cycle DISINFECTION A small amount of chlorine is added or some other disinfection method is used to kill any bacteria or microorganisms that may be in the water.

27 Water Treatment Cycle STORAGE Water is placed in a closed tank or reservoir in order for disinfection to take place. The water then flows through pipes to homes and businesses in the community.

28 Treated Water Treatment for drinking water production - or "water purification" - is the removal of contaminants from untreated water to produce drinking water that is pure enough for the most critical of its intended uses, usually for human consumption.

29 Sewage Treatment System

30 Preliminary Treatment During Preliminary Treatment, the incoming raw sewage, or influent, is strained to removed all large objects that make their way into the sewer system. These objects can be anything from rags and sticks to toys, cans and even snakes. Generally bar screens, which come in a variety of shapes and sizes, are used to remove the items. The influent flows across these screens, objects catch on the screens, are raised out of the water and are then raked (either mechanically or manually) off the screens.

31 Primary Treatment Many plants have a sedimentation stage where the sewage is allowed to pass slowly through large tanks, commonly called primary clarifiers or primary sedimentation tanks. The tanks are large enough that sludge can settle and floating material such as grease and oils can rise to the surface and be skimmed off. The main purpose of primary treatment is to produce both a generally homogeneous liquid capable of being treated biologically and a sludge that can be separately treated or processed.

32 Secondary Treatment Secondary treatment processes can remove up to 90% of the organic matter in wastewater by using biological treatment processes. Attached Growth Processes In attached growth (or fixed film) processes, bacteria, algae, fungi and other microorganisms grow and multiply on the surface of stone or plastic media, forming a microbial growth or slime layer (biomass) on the media. Wastewater passes over the media along with air to provide oxygen, and the bacteria consume most of the organic matter in the wastewater as food. Attached growth process units include trickling filters, bio-towers, and rotating biological contactors. After biological treatment, the water is pumped to secondary clarifiers where any leftover solids and the microorganisms sink to the bottom. These solids are handled separately from the supernatant which continues on to disinfection.

33 Tertiary Treatment DISINFECTION The purpose of disinfection in the treatment of wastewater is to substantially reduce the number of microorganisms in the water to be discharged back into the environment and is almost always the final step in the treatment process regardless of the level or type of treatment used.

34 Tertiary Treatment Chlorination remains the most common form of wastewater disinfection due to its low cost and long-term history of effectiveness. One disadvantage is that chlorination of residual organic material can generate chlorinated-organic compounds that may be carcinogenic or harmful to the environment.

35 Tertiary Treatment Ultraviolet (UV) light can be used instead of chlorine. Because no chemicals are used, the treated water has no adverse effect on organisms that later consume it. UV radiation causes damage to the genetic structure of bacteria, viruses, and other pathogens making them incapable of reproduction. The key disadvantages of UV disinfection are the need for frequent lamp maintenance and replacement

36 Tertiary Treatment Ozonation is also becoming a popular alternative to chlorine. Ozone (O3) is generated by passing oxygen (O2) through a high voltage potential resulting in a third oxygen atom becoming attached and forming O3. Ozone is very unstable and reactive and oxidizes most organic material it comes in contact with thereby destroying many pathogenic microorganisms. Ozone is considered to be safer than chlorine because it is generated onsite as needed and does not have to be stored. Ozonation also produces fewer disinfection by-products. A disadvantage of ozone disinfection is the high cost of the ozone generation equipment and the requirements for special operators.

37 Sewage Treatment System

38 Reclaimed Water Reclaimed water or recycled water, is former wastewater (sewage) that is treated to remove solids and impurities, and used in sustainable landscaping irrigation, to recharge groundwater aquifers, to meet commercial and industrial water needs, and for drinking.

39 What are the types of pollution? Point-source pollution The specific place or thing can be identified as a source of a specific water contamination Example: pollution from factory Non-point source pollution Both the water and air pollution from diffuse (spread out or disseminating) sources Example: Smog, pollution comes from cars, factories, etc. in a city

40 What is stewardship? The act of being responsible for overseeing and protecting, caring for, and preserving something Research and identify one common water pollution in North Carolina or Wake County. Plan for an attainable solution/s to solve this problem?