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1. Gather, process and present information on the features of the local town water supply in terms of


-Catchment area


-Possible sources of contamination in this catchment


-Chemical tests available to determine levels and types of contaminants


Help with essay on chemistry

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-Physical and chemical processes used to purify water


-Chemical additives in the water and the reasons for the presence of these


CATCHMENT AREA


A catchment is an area where water is collected by the natural landscape. In a catchment, all rain and run-off water eventually flows to a creek, river, lake or ocean, or into the ground water system. Natural and human systems such as rivers, bushland, farms, dams, homes, plants, animals and people can co-exist in a catchment.


Healthy catchments provide;


ɨ clean drinking water


ɨ unspoilt natural areas


ɨ habitats for plants and animals


ɨ healthy vegetation and waterways


ɨ reliable and clean water for stock and irrigation


ɨ opportunities for agribusiness and industry


Our daily activities affect the health of our catchments. The first step towards protecting our catchments in a better understanding of our impact on them. If our catchments become unhealthy, then water quality in our rivers and streams will deteriorate.


HUMAN ACTIVITY IMPACTS ON WATER


SPECIAL AREAS Comprise about 70000 hectares of land surrounding the water storages and the lands containing the canals and pipelines. Special areas protect our water supply because they act as a buffer zone, helping to stop nutrients and other substance that may contaminate the water supply.


The major issues in the catchments are those that impact directly on the quality of Sydney’s water supply. Main sources of contamination


ɨ possible contaminated run off from farmland which may include pesticides, fertilizer or manure.


ɨ unsuitable, damaged or inadequate local sewerage systems


ɨ damage and destruction of natural vegetation by humans and animals, reducing filtration ability.


ɨ possible contamination from current and disguised mining sites.


ɨ accidental fuel and or chemical spills


ɨ feral animals and introduced plant species and uncontrolled fire.


CHEMICAL TESTS AND ADDITIVES


Water filtration at Sydney water. Sydney water regularly conducts tests throughout the Sydney water supply to maintain the standard required in the National Health and Medical Research Council drinking water quality guidelines (16).


1st stage Removal of particulate matter


The filtration process involves the addition of one or more coagulants to the water. Primary coagulant is Ferric Chloride. It is added to overcome the naturally occurring surface charges of particles in the water, it forms a hydroxide precipitate that helps collect the neutralised particles into bigger masses, which assists filtering out this material. a number of polyelectrolyte (long chain polymers) are used in small amounts. They act as a secondary coagulant, as a filter aid and for filter conditioning during back washing of filters.


The pH of the raw water may need to be adjusted to facilitate the coagulation and flocculation steps prior to filtration. Sometimes a pre-oxidant (potassium permanganate or chlorine) is added to oxidise dissolved metals and or dissolved organics, so they can be filtered out and removed.


nd stageInactivation of Microbiological Organisms


Involves disinfection to protect the water from potential recontamination as it travels from the water filtration plant through the distribution system to consumer taps. Using a strong oxidant such as chlorine (chlorine gas, liquid sodium hypochlorite and calcium hypochlorite tablets).


In some parts of Sydney ammonia is added after chlorine in a fixed ratio (to form monochloramine which is less reactive). Trihalomethanes may in turn be produced due to chlorine (trihalomethanes to be below 50 micrograms per litre).


rd stage Fluoridation and Corrosivity Control


Sydney adds fluoride, in the form of sodium silicofluoride or hydrofluosilicic acid to achieve a fluoride content of 1mg per litre.


Lime and carbon dioxide are added where the water is very soft to adjust the buffer the pH of the treated water. Carbon dioxide reacts with lime to form calcium carbonate which buffers the water (increases resistance to changes in pH), increases hardness and reduces the general corrosivity of the water.


BASIC PROCESS-


1. Screening; a sieve-like device removes solid objects such as twigs, weeds, eels and fish.


. Coagulation; chemicals (Iron(III)chloride or aluminium hydroxide) are added to make fine suspended particles dump together so they can be easily filtered.


. Filtration; sand filters remove the coagulated solids. Over 00000 small nozzles, in the bottom of each metres deep bed of sand, filter 4 meters cubed of water per square meter of sand per hour. They are cleaned by back washing with water and air to remove the solid particles. These settle out in tanks, are centrifuged and dried then used for compost.


4. Chemical Treatment; When entering the treatment plant is tested for manganese concentration, pH, algae, true colour, hardness, temperature, turbidity and conductivity. These chemicals are added


ɨ potassium permanganate will oxidise the manganese, converting it to an insoluble form to be filtered out.


ɨ sulfuric acid is added to break down colour caused by organic matter and to lower the pH to help coagulation


ɨ lime water (Ca(OH)), sodium carbonate or sodium hydroxide lower the acidity


Water leaving the plant is tested to ensure treatment has been effective. Factors tested include true, colour, taste, colour, pH, conductivity, turbidity and concentration of ions such as fluoride, chloride, iron, manganese and aluminium.


MICROSCOPIC MEMBRANE FILTERS


Membrane filters can be classified according to how they are made as depth filters, surface filters and screen filters. depth filters are made of fibrous materials compressed together to form a maze of flow channels in a thick mat that traps particles. They are mostly used as pre-filters as they can remove a large load of suspended substances economically.


Surface filters are made from lots of layers that stop particles larger than the spaces between the fibres of the filter. Particles accumulate mainly on the surface of the filter. Screen filters are thin membranes that act like a sieve, with pores of a uniform size.


Microfiltration can remove inorganic and biological particles including suspended solids, bacteria, algae etc. a vacuum pump draws water through the filtering surface. Filtration can’t be used to remove particles smaller than about 10-m, so it can’t remove dissolved atoms and ions. Reverse osmosis involves applying pressure to a solution to push water molecules through a membrane and leave everything else behind.


EFFECTIVENESS


Testing during 000-0001 was done for a range of physical, biological and chemical properties. Water quality is measured against a range of guidelines. Overall water in SCA’s major dams remained good throughout the year. Water quality in the catchment rivers was generally good where they flowed into the SCA’s dams. Quality of water in the rivers further upstream was poorer.


Phosphorus exceeded the guideline in the upper reaches of the Wollondilly River. Cryptosporidium and Giardia were also detected in for rivers above Lake Burragorang. Cyanobacteria (blue-green algae) increased in summer, though was found to be primarily non toxic. Change in water quality in most storages has been minimal during the past eleven years. Nutrients and chlorophyll show negligible rates of increase.


Factor being tested Test


Total dissolved solids Gravimetrical analysis- evapourate and weigh


Electrical conductivity


Insolube solids Gravimetric- filter and weigh


Common ions AAS for cations


Gravimetric- with a mixture, adjust pH and


determine which compounds precipitate out


Hardness Ability to lather with soap (water with a carbonate


concentration60 mgL is considered hard)


Gravimetric- precipitate carbonates with NaCO


Turbidity Gravimetric


% light transmitted through standard depth


Depth at which disc can be seen


Acidity Indicators


PH meters


Dissolved Oxygen (DO) Winkler method- titration


Meter with Oxygen sensitive electrode


BOD (Biochemical O Demand) Measure ammount of oxygen that 1L of a sample


will react with under standard conditions.


BOD=DOinitially - DOafter 5 days in the dark


Nitrogen to Phosphorus Ratio Measure nitrogen and phosphorus levels by


Gravimetric


Titration


Instrumental- measuring light absorption and


comparing with values for solutions of known


concentration


Heavy Metals AAS


Bio-assay


. Process information from secondary sources to outline and analyse the impact of the work of Galvani, Volta, Davy and Faraday in understanding electron transfer reactions.


LUIGI GALVANI (177-178)


In the mid-1780’s, anatomist Galvani was studying the effects of atmospheric electrical discharge. One day he fastened brass hooks between the spinal cord of a dissectd frog and an iron railing. To his amazement the frog’s legs began twitching wildly, not only when lightning flashed, but also when the sky was calm.


Galvani interpreted his results in terms of animal electricity (incorrect). Galvani proclaimed that the muscle retained a “nerveo-electtrical fluid” similar to that of an electric eel. The most significant consequence of Galvani’s discovery was the concept of “Galvanism” which refers to the production of electrical current from the contact of two metals in a moist environment.


ALESSANDRO GIUSEPPE VOLTA (1745-187)


Volta was born in Italy and began his first accademic position as principal of the state Gymnasium. In 1777 he was appointed Professor of physics at University of Pavia. He repeated Galvani’s experiments and observed that he had connected brass hooks between the frog’s spinal cord and an iron railing.


According to Volta, the muscle twitches were inuced by current flowing between two dissimilar metals connected by the moist flesh of the frog’s leg. This led him to produce a verticle pile of metal discs (zinc with copper or silver) and separated them from each other with paperboard discs that had been soaked in saline solution. This stack became known as the voltaic pile and was the first ever battery.


The current generated by his primitive batteries led him to develop several new devices. He invented the electrophore, a forerunner of the capacitor, the condensatore, a device that detected weak electrical current; and the straw electrometer, a meteorology tool which measured atmospheric electricity. The term volt, a unit of electrical measurement, is named in his honor.


HUMPHRY DAVY (1778-18)


He was appointed Professor of Chemistry at The Royal Institution in London. In his first scientific work, Davy investigated the possible therapeutic value of inhaling various gases. Since nitric oxide (laughing gas) and carbon monoxide were among the gases studied. Davy used the voltaic pile to lay the foundations of electrochemistry.


Davy isolated elemental potassium which was soon followed by sodium, barium, calcium, strontium, and magnesium. Davy later isolated boron and silicon. In 181 he set out on a tour of Europe accompanied by young Michael Faraday. Though Faraday was to succeed Davy at the Royal Institution.


MICHAEL FARADAY (171-1867)


He left school at the age of 1, and was essentially self-taught. Davy was Faraday’s mentor in his early years of physics and electrochemistry research. Faraday began his career in 181 as Davy’s Laboratory Assistant.


He achieved scientific prominence of his own for the First Law of Electrochemistry, developed in 184 “The chemical power of a current of electricity is in direct proportion to the absolute quantity of electricity which passes.” The Second Law of Electrochemistry, also defined by Faraday, states “Electrochemical equivalents coincide, and are the same, with ordinary chemical equivalents.” The work that led to these laws resulted in the modern electrochemical terms- electrode, electrolyte, and ion, to name a few- all coined by Faraday.


Faraday didn’t consider himself an electrochemist; he preferred the title of being a “natural philosopher” and devoted his life to proving the interconnection of natural forces. His electrochemical research was one outcome of this effort, exploring the connection between the chemical and electrical forces of the voltaic battery.


. Identify data, gather and process information from first-hand or secondary sources to trace historical developments in the choice of materials used in the construction of ocean-going vessels with a focus on the metals used.


Primitive societies used canoes made with skin for water transport. At around 000BC some societies began to constuct wooden ships. This became the most common material used in ship building until the nineteenth century. Early vessels, like in Indonesia were made of bamboo.


Metals were used in some very early ships for example, the Viking longboats have been found with fittings made of wrought iron and bronze. Fittings such as anchors, keels, rudders and canons were routinely constructed of iron and bronze in the middle ages. Rigging also used metal parts. Copper and brass sheathing was also sometimes used in wooden ships in order to protect the wood from attack by marine organisms. This is due to the fact that copper is poisonous to living organisms.


At around 1500AD the development of iron nails made it possible to connect the ships wooden planks frames. This made the hull stronger and less flexible, though the nails were subject to rust.


As shipbuilding wood became scarce, iron became more available, so they were increasingly constructed by iron. By the early 1800s composite ships were being built using wood and iron as part of the ship materials. The first ship to be of all iron was the British ship Vulcan, a passanger carrying barge, launched in 1818. After this more than 0% of ships in the UK were made of iron by 1870.


Iron needed constant maintainence to prevent rusting. Iron had advantages over wood; iron could be produced as sheets or beams, shaped more easily than wood and joined by welding. They were stronger, safer, more ecconomical and easier to repair than wooden ships. Iron ships could also carry more cargo because they could be built longer and with less bulky framework, leaving more room inside the ship. This in turn led to bigger profits made by merchant ships of the day as they were able to carry larger loads.


It was an advantage to build warships out of steel. Once navies started to use guns that fired shells instead of canon balls, it would be a disadvantage to use wooden ships since the impact of these shells would set it alight. By the late 1800s shipbuilder had already begun to use steel alloys. Steel gave them even more advantage because of it being lighter than iron. The Titanic was one of the many ships at this time that was constructed of steel.


During the twentieth century there has been a progressive improvement in steel alloys, incorporating aluminium, chromium, titanium and zinc. Modern steels are lighter, stronger and more corrosion-resistant that earlier steels.


SURFACE ALLOYS


Instead of forming a metal alloy such as stainless steel, which has the same composition throughout, a cheaper carbon steel is treated by ion bombardment to produce a thin layer of stainless steel, or other desirable alloy on the surface.


In this process a plasma or ion gas of the alloying ions is formed at high temperatures and directed onto the surface of the metal.


NEW PAINTS


Rustmaster paint is a water-based polymer that prevents corrosion in two ways


ɨ firstly, the polymer layer forms a barrier impenetrable to both oxygen and water vapour.


ɨ Secondly, the chemicals in the coating react with the steel surface to form a complex mineral inter-layer called pyroaurite between the metal and the polymer coating.


Pyroaurite has the form [M1-X ZX (OH)]X+ where M is a + ion (Mg+, Fe+, Zn+, Co+ or Ni+), Z as a + ion (Al+, Fe+, Mn+, Co+, or Ni+) and x is a number between 0 and 1. The anions in it are typically CO-, Cl- and/or SO4-.


The pyroaurite layer grows into the neighbouring polymer layer preventing the movement of ions between the anodic and cathodic areas on the surface of the steel.


THE PROCESS OF RUSTING


4. Gather and process information to identify applications of cathodic protection, and use available evidence to identify the reasons for their use and the chemistry involved.


Cathodic protection is used to protect steel in buried fuel tanks, pipelines and ships. A metal such as magnesium (active metal) is connected by a wire to the tank creating an electrochemical cell in which moist soil becomes the electrolyte. Magnesium becomes an anode and is preferentially oxidised, thus donating electrons to the steel and maintaining it in the reduced state. Thus the steel is the cathode.


In cathodic protection, the metal being protected is made the inert cathode of the electrochemical cell. The hulls of ships are protected in the same way by using bars of titanium steel as anodes, connected by wire to the hull.


e.g.


anode Mg Mg+ +e


cathode O + HO +4e 4OH-


overall Mg + O +HO Mg++ 4OH-





Much of Australias infrastructure is located in marine exposed areas or within 1- kilometers of the sea. Direct splashing of seawater and windborne spray results in highly corrosive situations. The chlorides in the water are extremely reactive to steel, initiating corrosion and rapid breakdown of paint systems. Many structures are exposed to aggressive soil conditions often resulting in pitting attack due to the presence of chlorides. Affected structures are plant lines, underground fuel tanks and aboveground storage tanks.


Heat Exchangers, Chillers and Process Plants








In most cases impressed current is suitable but in some instances sacrificial anodes may be used. In refineries many internal protection applications exist and very often these include the internal protection of large diameter water pipelines.


Most large buildings have chiller systems where cathodic protection is used for the protection of internal surfaces of end boxes. Small diameter steel water pipes can also be protected using internal anode systems. In breweries pasteurisers can be protected using impressed current systems. Sacrificial anodes are not normally recommended as they are unable to produce sufficient protective current.


SHIPS


The external surfaces of the hulls of a large variety of ships are cathodically protected. Sacrificial anode systems using zinc or aluminium are frequently used, especially for smaller vessels. Anodes are supplied with cast inserts which are either welded directly or bolted to studs welded to the hull. Anodes are normally platinised titanium, platinised niobium or lead/silver.


OFFSHORE STRUCTURES


Sacrificial anodes have been used extensively for the protection of offshore platforms. The greater water depth of recent oil fields has forced operatore to consider impressed current. Impressed current systems are usually more ecomomic for shallow water rigs.


Impressed current anodes are normally mixed metal oxide. Anodes are usually mounted to the structure but recent systems employ anode sleds that are anchored a short distance from the structure. Impressed current systems are usually atomatically controlled from zinc or silver/silver chloride reference cells.


SEWAGE TREATMENT PLANTS


Sacrificial anodes are generally used within clarifier tanks for protection of steel brake arms and other steel components where the tank may be constructed from reinforced concrete. All steelwork should be well coated thus the cathodic protection is a supplementary form of corrosion protection.


POWER STATIONS


Cathodic protection systems are used throughout modern power station complexes to protect intake screens, pen stocks and condenser boxes as well as station pipework and fire services, etc. some reiforced concrete structures are also exposed to severe corrosive conditions such as mill foundations. These structures can be readily protected against long term corrosion using cathodic protection.


SERVICE STATION TANKS





Underground service station petrol and LPG tanks are normally protected using cathodic protection. The tanks have coating applied and cathodic protection provides back up protection for any areas of coating deterioration. In most instances sacrificial anodes are used, zinc anodes where the soil is very aggressive and resistivities are low. More commonly however, magnesium anodes are utilised due to high driving voltage.


LPG STORAGE TANKS


It is important to apply cathodic protection to mounded storage tanks as they are readily exposed to the filtering of corrosive water through upper layers of the mound. Connection of these tanks via pipework and earthing systems to other structures in a plant makes them susceptible to accelerated corrosion unless cathodic protection is applied.


BIBLIOGRAPHY


Surfing Textbooks; Shipwrecks to Salvage & Chemical Monitoring and Management


Conquering Chemistry Textbook, by Smith.


http//www.sydneywater.com.au/html/education/schools/Wfiltt.cfm


http//www.sca.nsw.gov.au/water/wq_monitor.html


http//fccjmail.fccj.org/~ethall/electro/electro.htm


http//www.solcor.com.au/divisions/marine_plants/sewagetreatment.html


1. Gather, process and present information on the features of the local town water supply in terms of


-Catchment area


-Possible sources of contamination in this catchment


-Chemical tests available to determine levels and types of contaminants


-Physical and chemical processes used to purify water


-Chemical additives in the water and the reasons for the presence of these


CATCHMENT AREA


A catchment is an area where water is collected by the natural landscape. In a catchment, all rain and run-off water eventually flows to a creek, river, lake or ocean, or into the ground water system. Natural and human systems such as rivers, bushland, farms, dams, homes, plants, animals and people can co-exist in a catchment.


Healthy catchments provide;


ɨ clean drinking water


ɨ unspoilt natural areas


ɨ habitats for plants and animals


ɨ healthy vegetation and waterways


ɨ reliable and clean water for stock and irrigation


ɨ opportunities for agribusiness and industry


Our daily activities affect the health of our catchments. The first step towards protecting our catchments in a better understanding of our impact on them. If our catchments become unhealthy, then water quality in our rivers and streams will deteriorate.


HUMAN ACTIVITY IMPACTS ON WATER


SPECIAL AREAS Comprise about 70000 hectares of land surrounding the water storages and the lands containing the canals and pipelines. Special areas protect our water supply because they act as a buffer zone, helping to stop nutrients and other substance that may contaminate the water supply.


The major issues in the catchments are those that impact directly on the quality of Sydney’s water supply. Main sources of contamination


ɨ possible contaminated run off from farmland which may include pesticides, fertilizer or manure.


ɨ unsuitable, damaged or inadequate local sewerage systems


ɨ damage and destruction of natural vegetation by humans and animals, reducing filtration ability.


ɨ possible contamination from current and disguised mining sites.


ɨ accidental fuel and or chemical spills


ɨ feral animals and introduced plant species and uncontrolled fire.


CHEMICAL TESTS AND ADDITIVES


Water filtration at Sydney water. Sydney water regularly conducts tests throughout the Sydney water supply to maintain the standard required in the National Health and Medical Research Council drinking water quality guidelines (16).


1st stage Removal of particulate matter


The filtration process involves the addition of one or more coagulants to the water. Primary coagulant is Ferric Chloride. It is added to overcome the naturally occurring surface charges of particles in the water, it forms a hydroxide precipitate that helps collect the neutralised particles into bigger masses, which assists filtering out this material. a number of polyelectrolyte (long chain polymers) are used in small amounts. They act as a secondary coagulant, as a filter aid and for filter conditioning during back washing of filters.


The pH of the raw water may need to be adjusted to facilitate the coagulation and flocculation steps prior to filtration. Sometimes a pre-oxidant (potassium permanganate or chlorine) is added to oxidise dissolved metals and or dissolved organics, so they can be filtered out and removed.


nd stageInactivation of Microbiological Organisms


Involves disinfection to protect the water from potential recontamination as it travels from the water filtration plant through the distribution system to consumer taps. Using a strong oxidant such as chlorine (chlorine gas, liquid sodium hypochlorite and calcium hypochlorite tablets).


In some parts of Sydney ammonia is added after chlorine in a fixed ratio (to form monochloramine which is less reactive). Trihalomethanes may in turn be produced due to chlorine (trihalomethanes to be below 50 micrograms per litre).


rd stage Fluoridation and Corrosivity Control


Sydney adds fluoride, in the form of sodium silicofluoride or hydrofluosilicic acid to achieve a fluoride content of 1mg per litre.


Lime and carbon dioxide are added where the water is very soft to adjust the buffer the pH of the treated water. Carbon dioxide reacts with lime to form calcium carbonate which buffers the water (increases resistance to changes in pH), increases hardness and reduces the general corrosivity of the water.


BASIC PROCESS-


1. Screening; a sieve-like device removes solid objects such as twigs, weeds, eels and fish.


. Coagulation; chemicals (Iron(III)chloride or aluminium hydroxide) are added to make fine suspended particles dump together so they can be easily filtered.


. Filtration; sand filters remove the coagulated solids. Over 00000 small nozzles, in the bottom of each metres deep bed of sand, filter 4 meters cubed of water per square meter of sand per hour. They are cleaned by back washing with water and air to remove the solid particles. These settle out in tanks, are centrifuged and dried then used for compost.


4. Chemical Treatment; When entering the treatment plant is tested for manganese concentration, pH, algae, true colour, hardness, temperature, turbidity and conductivity. These chemicals are added


ɨ potassium permanganate will oxidise the manganese, converting it to an insoluble form to be filtered out.


ɨ sulfuric acid is added to break down colour caused by organic matter and to lower the pH to help coagulation


ɨ lime water (Ca(OH)), sodium carbonate or sodium hydroxide lower the acidity


Water leaving the plant is tested to ensure treatment has been effective. Factors tested include true, colour, taste, colour, pH, conductivity, turbidity and concentration of ions such as fluoride, chloride, iron, manganese and aluminium.


MICROSCOPIC MEMBRANE FILTERS


Membrane filters can be classified according to how they are made as depth filters, surface filters and screen filters. depth filters are made of fibrous materials compressed together to form a maze of flow channels in a thick mat that traps particles. They are mostly used as pre-filters as they can remove a large load of suspended substances economically.


Surface filters are made from lots of layers that stop particles larger than the spaces between the fibres of the filter. Particles accumulate mainly on the surface of the filter. Screen filters are thin membranes that act like a sieve, with pores of a uniform size.


Microfiltration can remove inorganic and biological particles including suspended solids, bacteria, algae etc. a vacuum pump draws water through the filtering surface. Filtration can’t be used to remove particles smaller than about 10-m, so it can’t remove dissolved atoms and ions. Reverse osmosis involves applying pressure to a solution to push water molecules through a membrane and leave everything else behind.


EFFECTIVENESS


Testing during 000-0001 was done for a range of physical, biological and chemical properties. Water quality is measured against a range of guidelines. Overall water in SCA’s major dams remained good throughout the year. Water quality in the catchment rivers was generally good where they flowed into the SCA’s dams. Quality of water in the rivers further upstream was poorer.


Phosphorus exceeded the guideline in the upper reaches of the Wollondilly River. Cryptosporidium and Giardia were also detected in for rivers above Lake Burragorang. Cyanobacteria (blue-green algae) increased in summer, though was found to be primarily non toxic. Change in water quality in most storages has been minimal during the past eleven years. Nutrients and chlorophyll show negligible rates of increase.


Factor being tested Test


Total dissolved solids Gravimetrical analysis- evapourate and weigh


Electrical conductivity


Insolube solids Gravimetric- filter and weigh


Common ions AAS for cations


Gravimetric- with a mixture, adjust pH and


determine which compounds precipitate out


Hardness Ability to lather with soap (water with a carbonate


concentration60 mgL is considered hard)


Gravimetric- precipitate carbonates with NaCO


Turbidity Gravimetric


% light transmitted through standard depth


Depth at which disc can be seen


Acidity Indicators


PH meters


Dissolved Oxygen (DO) Winkler method- titration


Meter with Oxygen sensitive electrode


BOD (Biochemical O Demand) Measure ammount of oxygen that 1L of a sample


will react with under standard conditions.


BOD=DOinitially - DOafter 5 days in the dark


Nitrogen to Phosphorus Ratio Measure nitrogen and phosphorus levels by


Gravimetric


Titration


Instrumental- measuring light absorption and


comparing with values for solutions of known


concentration


Heavy Metals AAS


Bio-assay


. Process information from secondary sources to outline and analyse the impact of the work of Galvani, Volta, Davy and Faraday in understanding electron transfer reactions.


LUIGI GALVANI (177-178)


In the mid-1780’s, anatomist Galvani was studying the effects of atmospheric electrical discharge. One day he fastened brass hooks between the spinal cord of a dissectd frog and an iron railing. To his amazement the frog’s legs began twitching wildly, not only when lightning flashed, but also when the sky was calm.


Galvani interpreted his results in terms of animal electricity (incorrect). Galvani proclaimed that the muscle retained a “nerveo-electtrical fluid” similar to that of an electric eel. The most significant consequence of Galvani’s discovery was the concept of “Galvanism” which refers to the production of electrical current from the contact of two metals in a moist environment.


ALESSANDRO GIUSEPPE VOLTA (1745-187)


Volta was born in Italy and began his first accademic position as principal of the state Gymnasium. In 1777 he was appointed Professor of physics at University of Pavia. He repeated Galvani’s experiments and observed that he had connected brass hooks between the frog’s spinal cord and an iron railing.


According to Volta, the muscle twitches were inuced by current flowing between two dissimilar metals connected by the moist flesh of the frog’s leg. This led him to produce a verticle pile of metal discs (zinc with copper or silver) and separated them from each other with paperboard discs that had been soaked in saline solution. This stack became known as the voltaic pile and was the first ever battery.


The current generated by his primitive batteries led him to develop several new devices. He invented the electrophore, a forerunner of the capacitor, the condensatore, a device that detected weak electrical current; and the straw electrometer, a meteorology tool which measured atmospheric electricity. The term volt, a unit of electrical measurement, is named in his honor.


HUMPHRY DAVY (1778-18)


He was appointed Professor of Chemistry at The Royal Institution in London. In his first scientific work, Davy investigated the possible therapeutic value of inhaling various gases. Since nitric oxide (laughing gas) and carbon monoxide were among the gases studied. Davy used the voltaic pile to lay the foundations of electrochemistry.


Davy isolated elemental potassium which was soon followed by sodium, barium, calcium, strontium, and magnesium. Davy later isolated boron and silicon. In 181 he set out on a tour of Europe accompanied by young Michael Faraday. Though Faraday was to succeed Davy at the Royal Institution.


MICHAEL FARADAY (171-1867)


He left school at the age of 1, and was essentially self-taught. Davy was Faraday’s mentor in his early years of physics and electrochemistry research. Faraday began his career in 181 as Davy’s Laboratory Assistant.


He achieved scientific prominence of his own for the First Law of Electrochemistry, developed in 184 “The chemical power of a current of electricity is in direct proportion to the absolute quantity of electricity which passes.” The Second Law of Electrochemistry, also defined by Faraday, states “Electrochemical equivalents coincide, and are the same, with ordinary chemical equivalents.” The work that led to these laws resulted in the modern electrochemical terms- electrode, electrolyte, and ion, to name a few- all coined by Faraday.


Faraday didn’t consider himself an electrochemist; he preferred the title of being a “natural philosopher” and devoted his life to proving the interconnection of natural forces. His electrochemical research was one outcome of this effort, exploring the connection between the chemical and electrical forces of the voltaic battery.


. Identify data, gather and process information from first-hand or secondary sources to trace historical developments in the choice of materials used in the construction of ocean-going vessels with a focus on the metals used.


Primitive societies used canoes made with skin for water transport. At around 000BC some societies began to constuct wooden ships. This became the most common material used in ship building until the nineteenth century. Early vessels, like in Indonesia were made of bamboo.


Metals were used in some very early ships for example, the Viking longboats have been found with fittings made of wrought iron and bronze. Fittings such as anchors, keels, rudders and canons were routinely constructed of iron and bronze in the middle ages. Rigging also used metal parts. Copper and brass sheathing was also sometimes used in wooden ships in order to protect the wood from attack by marine organisms. This is due to the fact that copper is poisonous to living organisms.


At around 1500AD the development of iron nails made it possible to connect the ships wooden planks frames. This made the hull stronger and less flexible, though the nails were subject to rust.


As shipbuilding wood became scarce, iron became more available, so they were increasingly constructed by iron. By the early 1800s composite ships were being built using wood and iron as part of the ship materials. The first ship to be of all iron was the British ship Vulcan, a passanger carrying barge, launched in 1818. After this more than 0% of ships in the UK were made of iron by 1870.


Iron needed constant maintainence to prevent rusting. Iron had advantages over wood; iron could be produced as sheets or beams, shaped more easily than wood and joined by welding. They were stronger, safer, more ecconomical and easier to repair than wooden ships. Iron ships could also carry more cargo because they could be built longer and with less bulky framework, leaving more room inside the ship. This in turn led to bigger profits made by merchant ships of the day as they were able to carry larger loads.


It was an advantage to build warships out of steel. Once navies started to use guns that fired shells instead of canon balls, it would be a disadvantage to use wooden ships since the impact of these shells would set it alight. By the late 1800s shipbuilder had already begun to use steel alloys. Steel gave them even more advantage because of it being lighter than iron. The Titanic was one of the many ships at this time that was constructed of steel.


During the twentieth century there has been a progressive improvement in steel alloys, incorporating aluminium, chromium, titanium and zinc. Modern steels are lighter, stronger and more corrosion-resistant that earlier steels.


SURFACE ALLOYS


Instead of forming a metal alloy such as stainless steel, which has the same composition throughout, a cheaper carbon steel is treated by ion bombardment to produce a thin layer of stainless steel, or other desirable alloy on the surface.


In this process a plasma or ion gas of the alloying ions is formed at high temperatures and directed onto the surface of the metal.


NEW PAINTS


Rustmaster paint is a water-based polymer that prevents corrosion in two ways


ɨ firstly, the polymer layer forms a barrier impenetrable to both oxygen and water vapour.


ɨ Secondly, the chemicals in the coating react with the steel surface to form a complex mineral inter-layer called pyroaurite between the metal and the polymer coating.


Pyroaurite has the form [M1-X ZX (OH)]X+ where M is a + ion (Mg+, Fe+, Zn+, Co+ or Ni+), Z as a + ion (Al+, Fe+, Mn+, Co+, or Ni+) and x is a number between 0 and 1. The anions in it are typically CO-, Cl- and/or SO4-.


The pyroaurite layer grows into the neighbouring polymer layer preventing the movement of ions between the anodic and cathodic areas on the surface of the steel.


THE PROCESS OF RUSTING


4. Gather and process information to identify applications of cathodic protection, and use available evidence to identify the reasons for their use and the chemistry involved.


Cathodic protection is used to protect steel in buried fuel tanks, pipelines and ships. A metal such as magnesium (active metal) is connected by a wire to the tank creating an electrochemical cell in which moist soil becomes the electrolyte. Magnesium becomes an anode and is preferentially oxidised, thus donating electrons to the steel and maintaining it in the reduced state. Thus the steel is the cathode.


In cathodic protection, the metal being protected is made the inert cathode of the electrochemical cell. The hulls of ships are protected in the same way by using bars of titanium steel as anodes, connected by wire to the hull.


e.g.


anode Mg Mg+ +e


cathode O + HO +4e 4OH-


overall Mg + O +HO Mg++ 4OH-





Much of Australias infrastructure is located in marine exposed areas or within 1- kilometers of the sea. Direct splashing of seawater and windborne spray results in highly corrosive situations. The chlorides in the water are extremely reactive to steel, initiating corrosion and rapid breakdown of paint systems. Many structures are exposed to aggressive soil conditions often resulting in pitting attack due to the presence of chlorides. Affected structures are plant lines, underground fuel tanks and aboveground storage tanks.


Heat Exchangers, Chillers and Process Plants








In most cases impressed current is suitable but in some instances sacrificial anodes may be used. In refineries many internal protection applications exist and very often these include the internal protection of large diameter water pipelines.


Most large buildings have chiller systems where cathodic protection is used for the protection of internal surfaces of end boxes. Small diameter steel water pipes can also be protected using internal anode systems. In breweries pasteurisers can be protected using impressed current systems. Sacrificial anodes are not normally recommended as they are unable to produce sufficient protective current.


SHIPS


The external surfaces of the hulls of a large variety of ships are cathodically protected. Sacrificial anode systems using zinc or aluminium are frequently used, especially for smaller vessels. Anodes are supplied with cast inserts which are either welded directly or bolted to studs welded to the hull. Anodes are normally platinised titanium, platinised niobium or lead/silver.


OFFSHORE STRUCTURES


Sacrificial anodes have been used extensively for the protection of offshore platforms. The greater water depth of recent oil fields has forced operatore to consider impressed current. Impressed current systems are usually more ecomomic for shallow water rigs.


Impressed current anodes are normally mixed metal oxide. Anodes are usually mounted to the structure but recent systems employ anode sleds that are anchored a short distance from the structure. Impressed current systems are usually atomatically controlled from zinc or silver/silver chloride reference cells.


SEWAGE TREATMENT PLANTS


Sacrificial anodes are generally used within clarifier tanks for protection of steel brake arms and other steel components where the tank may be constructed from reinforced concrete. All steelwork should be well coated thus the cathodic protection is a supplementary form of corrosion protection.


POWER STATIONS


Cathodic protection systems are used throughout modern power station complexes to protect intake screens, pen stocks and condenser boxes as well as station pipework and fire services, etc. some reiforced concrete structures are also exposed to severe corrosive conditions such as mill foundations. These structures can be readily protected against long term corrosion using cathodic protection.


SERVICE STATION TANKS





Underground service station petrol and LPG tanks are normally protected using cathodic protection. The tanks have coating applied and cathodic protection provides back up protection for any areas of coating deterioration. In most instances sacrificial anodes are used, zinc anodes where the soil is very aggressive and resistivities are low. More commonly however, magnesium anodes are utilised due to high driving voltage.


LPG STORAGE TANKS


It is important to apply cathodic protection to mounded storage tanks as they are readily exposed to the filtering of corrosive water through upper layers of the mound. Connection of these tanks via pipework and earthing systems to other structures in a plant makes them susceptible to accelerated corrosion unless cathodic protection is applied.


BIBLIOGRAPHY


Surfing Textbooks; Shipwrecks to Salvage & Chemical Monitoring and Management


Conquering Chemistry Textbook, by Smith.


http//www.sydneywater.com.au/html/education/schools/Wfiltt.cfm


http//www.sca.nsw.gov.au/water/wq_monitor.html


http//fccjmail.fccj.org/~ethall/electro/electro.htm


http//www.solcor.com.au/divisions/marine_plants/sewagetreatment.html





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