Water Pollution:How clean is your water?

Chapter 22 By Lakshmi

Read wastewater treatment system in Arcata, California and list the effective use of the system followed in Arcata.

What is water pollution?

• Any physical, biological or chemical change in water quality that adversely affects living organisms or makes the water unsuitable for desired uses

• Two Major Categories

–Point source pollution–Non-point source pollution

Can you give some examples?• Non-point source pollution

• Point source pollution

Point Source pollution

• Water pollution that can be traced to a specific origin. It is discharged into the environment through pipes, sewers, or ditches from specific sites such as factories or sewage treatment plants.

• A cyanide spill contaminated the Tisza and Danube rivers in Europe in 2000, killing millions of fishes and shutting off downstream water supplies.

Nonpoint source pollution• It is also called polluted runoff, and is caused by land

pollutants that enter bodies of water over large areas rather than at a single point. It occurs when precipitation moves over and through the soil, picking up and carrying away pollutants that eventually are deposited in lakes, rivers, wetlands, groundwater, estuaries, and the ocean.

• It includes agricultural run off(such as fertilizers, pesticides, livestock wastes, and salt from irrigation), mining wastes, municipal wastes, and construction sediments. Soil erosion, logging operations, eroding stream banks, and construction sites is a major cause of nonpoint source pollution.

Eight categories of water pollutants

The main water pollution issue is lack of disease-free drinking water. water pollutants are divided into eight categories:

• Sewage• Disease causing agents• Sediment pollution• Inorganic plant and algal nutrients• Organic compounds• Inorganic chemicals• Radioactive substances• Thermal pollution.

Pollution problems caused by Sewage

• Carries disease-causing agents and poses a threat to public health.

• Causes two environmental problems• A) enrichment and b) oxygen demand• Enrichment is by the addition of high levels of plant

and algal nutrients such as nitrogen and phosphorus.• Decomposition of the sewage requires oxygen and use

up most of the dissolved oxygen, leaving little for fishes and other aquatic organisms. At extremely low oxygen levels, fishes and other animals leave or die.

Sewage and BOD

• Biochemical oxygen demand (BOD), or biological oxygen demand is usually expressed as milligrams of dissolved oxygen per liter of water for a specific number of days at a given temperature.

• A large amount of sewage in water generates a high BOD, which robs the water of dissolved oxygen.

• When dissolved oxygen levels are low, anaerobic microorganisms produce compounds with unpleasant odors, further deteriorating water quality.

Eutrophication• Eutrophication is a natural process that

increases the nutrient load of lakes over time as sediment washes into them

• Artificial or cultural eutrophication is when human activities speed up this process

Eutrophication: An Enrichment Problem

• Lakes, estuaries, and slo-flowing streams that have minimal levels of nutrients are unenriched or oligotrophic. Such lakes have clear water and support small populations of aquatic organisms.

• Eutrophication is the enrichment of a lake, estuary by inorganic plant and algal nutrients such as phosphorus, and such a water body is said to be eutrophic. This increases photosynthetic productivity.

Organisms in oligotrophic and eutrophic lakes

What is cultural eutrophication?

• Excess fertilizer, human or animal waste and sediments act as fertilizer in aquatic ecosystems and cause an algal bloom.

What Eutrophication Looks Like

Next step…• When the algae die, they sink to the lake bottom to

be eaten by decomposers. Decomposers deplete oxygen and create Hypoxia (low oxygen levels) or Apoxia (no oxygen).

• This kills the organisms in the water and creates a “dead” zone

• What can be done? Aerate the water, like the fountains in our lakes and Glenwood Lake

Disease causing Agents

• Municipal wastewater usually contains many bacteria, viruses, protozoa, parasitic worms that cause human or animal diseases.

• In the year 1993, a microorganism (Cryptosporidium) contaminated the water supply in the greater Milwaukee area. About 370,000 developed diarrhea, making it the largest outbreak of a waterborne disease ever recorded in the United States.

• In 2000, the first waterborne outbreak in North America of the deadly strain of Escherichia coli occurred in an Ontario town (Walkerton) in Canada.

Some human diseases Transmitted by Polluted waterDisease Infectious Agent Type of organism Major symptoms

Cholera Vibrio cholerae Bacterium Severe diarrhea, vomiting

Dysentery Shigella dysenteriae Bacterium Infection of the colon causes painful diarrhea with mucus and blood in the stools

Enteritis Clostridium perfringens Bacterium Inflammation in the small intestine causes general discomfort, loss of appetite, and diarrhea.

Typhoid Salmonella typhi bacterium Headache, fever, followed by rash and sometimes with hemorrhaging in the intestines

Infectious hepatitis Hepatitis virus A Virus Inflammationof liver causes jaundice, fever, nausea.

Human diseases contd..

• Cryptosporidiosis caused by Cryptosprodium sp a protozoan. Symptoms include diarrhea and cramps.

• Amoebic dysentry caused by Entamoeba histolytica, a protozoan. Symptoms: infection of the colon causes painful diarrhea with mucus and blood in the stools.

• Schistosomiasis caused by Schistoma sp. a fluke. It is a tropical disorder of the liver and bladder causes blood in urine, diarrhea, abdominal pains.

• Ancylostomiasis caused by hookworm. Symptoms are anemia and bronchitis.

Effects of Sewage on Human Health

• Untreated or raw sewage can transmit disease such as cholera, dysentery and typhoid

• About 4 billion cases of diarrhea per year cause 1.8 million deaths, over 90 per cent of them (1.6 million) among children under five (data from UNICEF, 2010)

• Famous Case of Typhoid Mary

http://cythereabast.wordpress.com/category/typhoid-mary-mallon/You can make use of the above link to know about the famous case of Typhoid Mary

Effects of Sewage on Ecosystems

• As sewage is eaten by decomposers, it reduces the dissolved oxygen (D.O.) content of the water.

• All aquatic species have a range of tolerance for D.O. and if the level is too low, they die. This can result in fish kills.

Dissolved Oxygen Levels• Healthy water has a high level of dissolved oxygen (>

8ppm)• Oxygen-poor water (<2ppm) only supports detritivores• Oxygen is added to the water by diffusion from air

(affect of temperature) and photosynthesis• Oxygen is removed by respiration of plants and

animals• The addition of sewage and wastes stimulates oxygen

consumption by detritivores

How do you know if water is safe to swim in?

• A test called the fecal coliform test tests for E. Coli bacteria present in feces.

• one colony of bacteria per 100ml or greater is considered unsafe to drink

• Safe swimming water should have no more than 200 per 100 mL of water

• Recreational water should have nor more than 2000 per 100 mL of water.

• Raw sewage may contain several million coliform bacteria per 100 mL of water

• A good rule to follow: don’t go to the beach after it rains

Monitoring for sewage

• Bacterial source tracking (BST) attempts to make the proper identification. It has successfully identified the source of coliform bacteria in several cases.

Sediment and suspended solids

• Largest pollutant by volume in most parts of world

• 25 billion metric tons of topsoil from runoff and erosion

• 50 billion from grazing, construction etc.• Erosion of agricultural lands, forest soils

exposed by logging, degraded stream banks, overgrazed rangelands, strip mines…

Effects of sediment pollution• Reduces light penetration, covers aquatic organisms, brings

insoluble toxic pollutants into the water, and fills in waterways.• Makes the water turbid, which inturn decreases the light

penetration.• This in turn reduces productivity.• Extreme turbidity reduces the number of photosynthetic organisms

which in turn results in decrease in number of consumers.• Sediments can clog gills of organisms• Adversely affect water quality by carrying toxic chemicals.• Disease causing agents are also transported into water via

sediments.

Red Tide

• When some pigmented marine algae experience explosions or blooms, their great abundance colors the water orange, red, or brown.

• Some of the algal species that form red tides produce toxins that attack the nervous systems of fishes leading to massive fish kills.

• Water birds like cormorants which eat the contaminated fish die.

• The toxins work their way up the food web to marine mammals and people.

Red tide (Read more on Red Tide Page number 512)

The Dead Zone in the Gulf of Mexico

Every spring and summer, fertilizer runoff from midwestern fields and manure runoff from livestcok operations in states such as Iowa, Wisconsin,Illinois, find their way into the Mississippi River and from there into theGulf of Mexico.

Other than bacteria no lifeExists in the Dead Zone. TheWater does not have enoughDissolved oxygen. This oxygen-Free condition is known as Hypoxia, when algae grow rapidlyAnd are decomposed.

What do we do?

• Reduce nitrogen runoff coming down the Mississippi River.

• Modify farming methods so that less fertilizer is needed.

• Reduce phosphorus as well.• Sewage treatment plants and airborne nitrogen

oxides from automobile emissions to be addressed.• Restoring former wetlands will retain nutrients such

as nitrogen and phosphorus.

Organic Chemicals• Pesticides, oils, plastics, pharmaceuticals, pigments,

detergents, cleaning solutions, and paints Some are carcinogenic and some act as endocrine disruptors

and cause hormonal effects.Alternative organic compounds which are less toxic and

degrade more readily so that they are not persistent in the environment can be developed.

Tertiary water treatment effectively eliminates many synthetic organic compounds in water.

(Page 514-List of synthetic organic compounds found in polluted water)

Toxic Inorganic materials• Heavy metals:– mercury, lead, cadmium and nickel– mining wastes, mine drainage– Arsenic in ground water

Lead

• Source – lead based paint, lead containing anti-knock agents in gasoline.

• Effects : develop hypertension.• High levels of lead in pregnant women increase the

risk of miscarriages, premature deliveries and stillbirths.

• Children will suffer from a variety of mental and physical impairments, including hearing loss, attention deficit, lowered IQ, and learning disabilities.

• Lead accumulates in bone.

Mercury • Source: coal-fired power plants release the largest amount

of mercury.• Municipal waste and medical waste incinerators also

release mercury. Fluorescent lights and thermostats are examples of municipal wastes that contain mercury, whereas thermometers and blood pressure cuffs are examples of medical waste.

• Smelting of metals such as lead, copper, and zinc.• Mercury is used in the chemical plants that manufacture

chlorine and caustic soda. Some of the mercury vaporizes and enters the atmosphere.

Contd..

• Once mercury enters a body of water it settles into the sediments where bacteria converts it to methyl mercury compounds, a more toxic form that enters food web. (biomagnification occurs)

• Exposure to methyl mercury causes kidney disorders and damages the nervous and cardiovascular systems.

• The exposure of the developing fetuses to mercury is linked to diminished cognitive function, cerebral palsy, and developmental delays.

• Low levels caues headache, depression.

Effects of thermal pollution

• Less oxygen dissolves in warm water than in cold water. when the level of dissolved oxygen is lowered due to thermal pollution, a fish ventilates its gills frequently and puts a great deal of stress on the fish.

• It also affects the reproductive cycle, digestion rates, and respiratory rates.

• At warmer temperature fishes require more food to maintain body weight.

• In extreme themral pollution they die.

Thermal Pollution• Water temps are usually stable so organisms

are poorly adapted to rapid change• oxygen solubility decreases as temperature

increases• most happens in industrial cooling

• Power plants release warmed water into rivers

Water pollution from Agriculture

• Fertilizer runoff causes water enrichment.• Animal wastes and plant residues in waterways

produce high BODs and high levels of suspended solids as well as water enrichment.

• Chemical pesticides used in agriculture may leach into the soil and from there into waterways.

• Soil erosion from fields and rangeland cause sediment pollution in waterways.

What is going into the water from farm operations?

•Pesticides•Fertilizers•Manure•sediments

What is going into the water from urban runoff?

• Salt from roadways• Untreated garbage• Animal wastes, organic wastes, leaves• Construction sediments and traffic emissions.• Zinc from weathering of aging pipes and gutters• Copper from brake linings, worn pipings• Used motor oil• Fertilizers

Industrial wastes in water

• Food processing industries produce organic wastes that are readily decomposed but have a high BOD.

• Paper and paper mills produce waste that have high BOD and also toxic compounds and sludge. The paper industries have however begun using methods of production of paper without the use of chlorine as a bleaching agent and that produce less toxic effluent.

• The electronics industry uses special techniques such as ion exchange and electrolytic recovery method to reclain the toxic metal such as copper, lead and manganese.

Water Quality: DO

Sewage Treatment

Treatment of Human Waste

• Primary treatment: taking out solids– grating (removes debris)– moving screen (takes out smaller pieces)– grit tank (sand and gravel settle)– primary sedimentation tank (sludge settles)

Secondary treatment: biological degradation

– aeration tank (or filter bed, sewage lagoon)– fluid is mixed with a bacteria rich slurry– air is pumped in which promotes bacterial growth– bacteria and sludge is removed off the bottom (some is

returned to inoculate the aeration tanks)– water is sometimes chlorinated to kill bacteria, then

released

Tertiary Treatment: removal of plant nutrients

– removal of nitrates, phosphates and other nutrients which can cause algal blooms

– this can be accomplished by passage through a wetland or lagoon

• Sewage treatment works well except:– water in storm drains gets no treatment– during storms, raw sewage is dumped– treated water still has environmental effects

Septic Tanks

• A house-by-house alternative to sewer systems• Water is pumped into a tank– oils rise to top, solids to bottom– middle water is pumped into a series of pipes

where it can evaporate and be worked on by bacteria

• Works well if maintained, but can leak into ground water

Septic Tank and Field

Combined sewer system

• It is one in which human and industrial wastes are mixed.

• Is it good to have this practice or not? Explain• (Refer to Page number 519)• Read the article Preventing water pollution

and how you can make a difference and discuss with your partner as to whether you are practicing or plan to practice.