Water Pollution Flashcards
Source of thermal pollution
Power station cooling/condensing water. Hot industrial processes
Effects of thermal pollution
Raising the temperature of water bodies above the range of tolerance for some organisms. Denaturing of enzymes above 40 degrees celsius. Reduction in dissolved oxygen as temperature rises leads to the death of organisms close to the lower end of their range. Increase in metabolic rate reducing energy for growth. Increased rate of development e.g. early egg hatching. Introduced species from warmer habitats. Reduced resistance to disease. Increase in pollutant toxicity as toxins are metabolised more rapidly.
Controls of thermal pollution
Cooling towers (always say this one first), forced draft cooling, cooling ponds
Cooling towers
A method of reducing the temperature of effluent water to reduce thermal pollution and deoxygenation. Warm water is passed through sprays to increase surface area. Heat energy is transferred to the surrounding cool air which rises and is dispersed to the atmosphere. Cool air is drawn in through grids at the base of the tower creating a continuous updraft of cool air. The shower spay also increases dissolved oxygen before water is returned to a local body of water.
Forced draft cooling
Forced Draft Cooling Towers are mechanical draft cooling towers that use fans to force cool air through the system. The airflow is introduced at the base of the tower and moves upward or horizontally to interact with the water, cooling it through direct contact and evaporation. Smaller than traditional cooling towers however require energy for the fans and can be noisy.
Sources of oil pollution
Shipping/oil tanker incidents, Oil exploration/drilling, oil rig incidents, oil pipeline damage, leakage from storage tanks, discharge of oil tank washing water from ships, vehicle engine oil leaks or discarded, industrial machine oil leaks
What naturally happens to oil in the environment?
Lighter fractions will evaporate, medium fractions will be digested by bacteria, heavier fractions will remain as tar balls for years. In open water oil spills will disperse in weeks. Oil spills cause most harm near shorelines and sensitive ecosystems.
Effects of oil pollution
Direct toxins such as benzine, asphyxiation due to oil covering, reduced photosynthesis due to lack of light, damage to birds feathers and insulating properties, reduced dissolved oxygen from the atmosphere due to oil film, reduced feeding and rearing of young due to increased preening, masking of smells that may be required for food or mates
Prevention of oil pollution by tanker operation
Improved navigation systems, use of GPS, Automatic Identification Systems, Improved shipping routes, The use of inert gas systems, improved tank washing procedures, improved oily waste disposal
Improved navigation systems to prevent oil pollution
The use of GPS and AIS to avoid collisions with other ships and the shore as well as grounding in shallow waters
Use of GPS to prevent oil pollution
Global Positioning System, a satellite based radio navigation system which can accurately pinpoint position in relation to a planned route or known hazards
Automatic Identification Systems to prevent oil pollution
The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships. Information provided by AIS equipment, such as unique identification, position, course, and speed, can be displayed on a screen or an electronic chart display and information system. AIS is intended to assist a vessel’s watchstanding officers and allow maritime authorities to track and monitor vessel movements.
Improved shipping routes to prevent oil pollution
Pre planned shipping routes where oil tankers in particular travel at a greater distance from the shore and sensitive ecosystems in order to allow more time to assist in the event of engine failure avoiding collisions with the shore.
The use of inert gas systems to prevent oil pollution
Filling empty fuel tanks with an inert gas such as exhaust gasses to avoid the explosive mix of fuel vapours and oxygen
Improved tank washing procedures to prevent oil pollution
Oil tanks were regularly washed with sea water to remove tar sludges and the water discharged into the sea. Oil is now recirculated in port and sludge removed with cargo.
Improved oily waste disposal to prevent oil pollution
Oily waste water is now unloaded at the oil terminal and oil can be separated from the water prior to discharge.
Prevention of oil pollution by tanker design
Double Hull, Twin engines/rudders/fuel tanks, separate oil and ballast water tanks
Double Hull to prevent oil pollution
All large tankers now have double hulls, two layers of steel between the oil and the sea with a gap of 2 metres. Oil is more likely to be contained within the inner hull upon damage to the outer hull.
Twin engines/rudders/fuel tanks to prevent oil pollution
Having pairs of essential equipment, reduces the chance of a ship drifting and colliding with the shore or other ships in the event of breakdown or failure.
Ballast water
As a ship offloads cargo or uses fuel it must take on ballast water in order to sit low enough in the water for the propeller and rudder to work properly
Separate oil and ballast water tanks to prevent oil pollution
In the past ballast water was carried in empty oil tanks and pumped back into the sea when no longer required carrying residual oil. Modern tankers have separate oil and ballast water tanks to avoid oil pollution.
Prevention of oil spills on land
Bund walls, oil interceptors, collection and recycling of industrial, engine and cooking oil
Bund wall to prevent oil pollution
A wall that surrounds a tank which would contain the contents if the tank leaks or bursts.
Oil interceptors to prevent oil pollution
used for drainage systems on major roads and car parks, oil flows from the surface into a separate oil tank whilst water flows from the base into drains
Collection and recycling of industrial, engine and cooking oil
used oil is collected and contaminants removed and distilled to produce oil that can be reused. Cooking oil can be repurposed into biodiesel. Heavily contaminated oil can be burnt as fuel.
Treatment and cleanup of oil
Booms, Skimmers, Absorbent materials, detergents and dispersants, polymerising agents, steam washing, bioremediation.
Oil cleanup - Booms
Inflatable/floating tubes used to contain oil with a skirt that extends below the surface to contain oil in the event of gentle currents/waves. Only work well in sheltered areas reducing oil from reaching sensitive shoreline ecosystems.
Oil cleanup - Skimmers
Rotating metals disks that pick up and scrape oil from the water surface for disposal or incineration.
Oil cleanup - Absorbent materials
High surface area materials can be used to absorb oil and removed for disposal or incineration. Examples of good natural oil absorbers: straw, wool, cotton
Oil cleanup - Detergents and dispersants
detergents are often applied by aircraft and break up the oil into many droplets to aid dispersal. Does not actually reduce the amount of oil but may speed up breakdown by bacteria
Oil cleanup - Polymerising agents
Product developed that solidifies oil into a material that is more easily collected and removed. Can be burnt after as a fuel.
Oil cleanup - Steam washing
The use of hot water, usually on the shore line to reduce viscosity (make the oil more runny) and wash off into the sea. Does not reduce the amount of oil, just moves it to a less sensitive area. Steam washing can harm organisms in the area.
Oil cleanup - Bioremediation
Some bacteria naturally break down oil. Rate of breakdown can be increased by increasing temperature, oxygen availability and nutrients, these factors are more easily manipulated on land.
Properties of pesticides
toxic, persistent, specific, bioaccumulation, biomagnification
Sources of pesticides
runoff from agricultural land, consumed via food, inhalation via household use
Direct effects of pesticides
Toxic to target species and sometimes non-target species. Bioaccumulation leading to biomagnification in higher trophic levels. Can cause eggshells to thin and sterility reducing reproductive success. Often causes nervous system problems
Indirect effects of pesticides
loss of predator or prey species or other interdependencies or services such as pollination or seed dispersal.
Different pesticide groups
Organochlorines, Organophosphates, Pyrethroids, Neonicotinoids.
Organochlorines
Hydrocarbon-based compounds that include chlorine. They include pesticides such as DDT and industrial chemicals such as PCBs. Their use is now banned or restricted. High toxicity to insects, low toxicity to mammals, high persistence, liposoluble (bioaccumulation and magnification). DDT use led to the decline of the golden eagle. The famous book “Silent Spring” released in 1962 led to the banning of DDT in America (read it!)
Organophosphate pesticide
Insecticide group eg parathion, malathion. They are not persistent but have high mammalian toxicity. They are neurotoxins that damage nerve function. Sarin is an organophosphate developed as a weapon in WWII. Their use increased after organochlorines were banned however farm workers are at risk of acute exposure. Long term (chronis) exposure at low doses can cause ADHD, Alzheimers, memory problems, depression, and may also be carcinogenic.
Pyrethroids
Synthetic insecticide pesticides, based on the natural chemicals originally extracted from chrysanthemum flowers (pyrethrins). They are not persistent and have low mammalian toxicity. Do not bioaccumulate or biomagnify. Toxic to fish, should not be used near water bodies.
Neonicotinoids
A widely used group of insecticides. They have been linked with the deaths of bees, especially when they act synergistically with some fungicides. Neurotoxins (for insects) reducing the ability to navigate, are water soluble and can be taken up into the plant. Some neonicotinoids are now banned in Europe and the UK.
Systemic pesticides
A substance that is absorbed and transported throughout an organism eg by sap in plants.
Contact pesticides
A pesticide that is sprayed onto the outer surface of the organism, can be washed off in the rain.
Methods of reducing pesticide pollution
Restriction of use, use of non-persistent pesticides, use of more specific pesticides, use of systemic pesticides, timing of application, use alternatives to pesticides
Pesticides - restriction of use
Some pesticides have been banned (DDT) or their use is now restricted and only allowed to combat a serious issue such as malaria. Other pesticides are used in agriculture and industry but not in a domestic setting (eg not sold in B&Q)
Use of non-persistent pesticides
these pesticides breakdown quickly and are less likely to become concentrated or travel long distances eg organophosphates are less persistent that organochlorines
Use of more specific pesticides
Pyrethroid are a specific pesticide that are toxic to insects but not mammals
Use of systemic pesticides
Pesticide is taken up into the plant tissue and therefore is not washed off into water bodies however may enter the food chain when the plant/crop is consumed.
Timing of pesticide application
Spray on still days to reduce drift, use weather forecast to avoid precipitation and runoff, spray at night to reduce impact on bees
Non-pesticide techniques / alternative to pesticide use
Crop rotation to reduce disease, use of companion crops which deter pests, encourage natural predators by protecting habitats such as hedges, dry stone walls, beetle banks, introduction of biological control, the use of steriles males, use of pheromone traps, use of CWRs and GM for disease resistance
Sources of Inorganic nutrient pollution
NPK washed off farmland from artificial fertiliser use, phosphates from sewage effluent, phosphates from detergent use.
Effects of inorganic nutrient pollution in humans
Nitrates cause blue baby syndrome and are linked to digestive tract cancers
Haemoglobin
The protein in red blood cells that carries oxygen.
Nitrates and cancer
Gut bacteria convert nitrates to nitrites, these may be further converted to nitrosamines which are carcinogenic and may cause stomach cancer.
Blue baby syndrome (Methemoglobinemia)
A health problem with several possible causes, where the haemoglobin in a baby’s blood does not carry enough oxygen. Nitrates in drinking water can be converted to nitrites which reduce the ability of haemoglobin to carry oxygen.
Effects of inorganic nutrient pollution in water bodies
Eutrophication
The process of eutrophication
The process by which nutrient levels in a water body increase to excessive levels such that the growth and subsequent die-off of plants and algae cause deoxygenation.
1 Excess nutrients enter a water body
2 Increase in algae and plant growth - algal bloom
3 Light blocked causes plants to die
4 Anaerobic decay of plants causes depletion of dissolved oxygen
5 Other organisms die due to oxygen depletion - dead zone
Control/prevention of inorganic nutrients
reduce the use of nitrate fertilisers, avoid ploughing at times of heavy rain, use slow release fertilizers, reduce the cultivation of crops with high nitrogen requirement - replace wheat for triticale, reduce reliance on artificial fertiliser by growing legumes
Example of a crop with lower nitrogen (and therefore fertiliser) requirements
Triticale (alternative to wheat)
How does growing legumes reduce reliance on fertilizer use?
Legumes naturally increase nitrogen availability in the Soil. Nitrogen fixing bacteria live symbiotically on the root nodules of legumes and reduce nitrogen to ammonia. Legumes include beans, nuts and pulses.
Physical removal of inorganic nutrients
addition of iron (III) sulphate during water treatment removes (precipitates) phosphates, adding iron sulphate to lakes to remove soluble phosphates (use as a binding agent) and dredging lakes to remove phosphate rich sediments
Sources of organic nutrient pollution
Human waste (sewage), animal waste (manure), paper mills, dairy industry, leather tanneries, processes involving animal and plant products
Effects of organic nutrient pollution
Pathogens, spread of disease such as cholera, typhoid, dysentery, deoxygenation of water due to increase in microorganisms feeding of waste, release of inorganic nutrients which may lead to eutrophication.
Pathogens
Organisms that cause disease, often found in sewage and animal waste.
How is deoxygenation of water by organic nutrients different to that of inorganic nutrients?
Deoxygenation of water caused by organic nutrients is initially caused by the increase in aerobic microorganisms that feed upon animal waste rather than an increase in aerobic bacteria that break down dead organic matter during eutrophication
Organic nutrients pollution and eutrophication
Organic nutrients do not cause eutrophication directly as nutrients are not utilised initially by algae or plants however the breakdown of organic nutrients may release inorganic nutrients that would then cause eutrophication
Reduction of organic nutrients to water
separation, storage and treatment of organic waste before release or leaching into water occurs.
Water treatment - pre-treatment
grills to remove large items, grit traps for grit and stones, comminutors to chop up faecal solids
Water treatment - primary treatment
Sedimentation tanks for up to a week where 95% of organic faecal matter sinks and can be removed.
Water treatment - secondary treatment
Aeration tanks where the remaining organic faecal matter is broken down by aerobic bacteria, secondary sedimentation tanks collect the bacteria rich sludge after the aeration tanks and this is fed back into the process. Trickling filter beds are an alternative to aeration tanks to remove remaining organic matter, effluent is trickled through gravel, the high surface area is colonised by bacteria, fungi, algae, fly larvae which digest remaining organic matter
Water treatment - tertiary treatment
only to remove a specific pollutant or to address a public health issue. Addition of iron III sulphate to remove phosphates, use of UV, chlorine or ozone to kill pathogens, addition of fluoride to improve dental health.
Activated carbon filter
A filter that reduces emissions of pollutants such as complex organic molecules that adsorb onto the surface of the activated carbon particles.
Water treatment - sludge treatment
Sludge collected from primary sedimentation can be
1 dispersed in the sea although this is now banned in most countries
2 sent to landfill (wastes nutrient content)
3 incineration, still produces waste
4 Agricultural use as a natural fertiliser
Different types and improved sewage collection systems
In the UK all sewage, waste and effluent water enters the same system. This includes runoff from roads, urban surfaces, roofs, washing water as well as toilet waste. This contaminates all water which requires the same treatment to remove organic matter and pathogens. It would be much more efficient to have two systems, one for sewage and one for other wastewater which requires less treatment.
Sewage storm overflow
Volume of sewage remains fairly stable all year round however extra flow occurs during periods of high precipitation. Most sewage works have overflow tanks however untreated wastewater is often discharged to rivers when these are full. There has been a recent rise in public awareness and opposition to this and the problems caused to wildlife.
Raw sewage in our rivers
https://theriverstrust.org/key-issues/sewage-in-rivers
Cause of acid mine drainage
Many ore rocks which contain valuable metals are sulphides, mining breaks up the rock increasing the surface area. The sulphide reacts with oxygen and water and produces sulphuric acid which becomes acid mine drainage
Effects of acid mine drainage
All the same effects as acid rain
Controls of acid mine drainage
Divert water away from the mine, Block the mine, seal exposed rocks, fill with concrete, most likely option - divert outflowing water to treatment with crushed limestone to increase/neutralise pH.
Biological Oxygen demand (BOD)
A measure of the amount of demand for oxygen in water, high organic matter increases aerobic bacteria which would increase BOD. The test: 1 litre of water is left in the dark at 20 degrees celsius for 5 days. The amount of decrease in dissolved oxygen indicates BOD.
Chemical oxygen demand (COD)
a measure of the amount of oxygen required to chemically oxidise organic substances in water such as ammonia or nitrate
Coliform count
A measure of the number of coliform bacteria (gut bacteria E. coli) which confirms faecal contamination and in turn the increased risk of other pathogens
Monitoring nitrates
Nitrate and the concentration can be confirmed using nitrate test strips and compared with a reference colour chart, alternative methods include colourimetry or ion selective electrodes.
Monitoring turbidity
Method 1 Secchi disk, lower a disk with alternate black and white sections into the water, record the depth at which you can no longer distinguish between the black and white sections. The greater the depth the lower the turbidity. Method 2 Turbidity bottle A standard amount of water is put in the bottle, different hatched circles are placed in the base of the bottle, note made of the coarsest pattern that cannot be distinguished, the more that can be seen clearly, the less the turbidity.
Measuring the effect of pH on seed germination
Place seeds in a number of different trays, standardise the seed species, growing medium, temperature, water, light and nutrient availability. Control the pH of the seed trays to cover a range at which germination is possible. Record % of seeds that germinate at different pHs, repeat and calculate a mean at each pH
The effect of turbidity on light penetration
Electronic turbidimeters give a quantitative rather than qualitative measurement of turbidity. They measure the amount of light scattered by particles suspended in the water, a light meter measures light at 90 degrees from a light source, higher light readings means more scatter, means higher turbidity.
Biotic index
A measure of pollution based on the presence, abundance and state of health of selected living organisms e.g. lichens for acid rain, aquatic invertebrates for water pollution.
Biotic indicators of water pollution
The Trent Index is the most commonly used, some freshwater invertebrate species are very tolerant of organic pollution such as blood worms and rat tailed maggots whereas others are very sensitive such as mayfly and stonefly nymphs.
