Harmful Effects of Nitrogen-Containing Fertilizers on Aquatic Ecosystems - Assignment Example

1) In what forms is nitrogen (N) found in sewage? Briefly discuss three (3) reasons why excessive quantities of nitrogen can be of concern in waterways. In raw domestic sewage, the predominant forms are organic nitrogen and free ammonia. Organic nitrogen corresponds to amina groups. Ammonia is mainly derived from urea, which is rapidly hydrolysed and rarely found in raw sewage. [1]Heavy use of nitrogen fertilizers in agricultural areas causes runoff into waterways, which leads to nitrogen pollution. [2] According to a report from the Ecological Society, nitrogen pollution causes "changes in the composition and functioning of [aquatic] ecosystems and contributes to long-term declines in coastal marine fisheries" and biodiversity. [3] Nitrogen fertilizers contribute to the acidification of freshwater, causes extreme plant growth, and can accumulate to toxic levels. (2) What is the effect of acid rain on a.1. Plants The roots are damaged by acidic rainfall, causing the growth of the plant to be stunted, or even in its death. Nutrients present in the soil, are destroyed by the acidity. Useful micro organisms which release nutrients from decaying organic matter, into the soil are killed off, resulting in less nutrients being available for the plants. The acid rain, falling on the plants damages the waxy layer on the leaves and makes the plant vulnerable to diseases. Plant germination and reproduction is also inhibited by the effects of acid rain. a.2. Materials (such as limestone, steel roof) Acid rain erodes limestone and carbonate stones which are used as building materials upon acid deposition. Though stainless steel and aluminum are more resistant to acid rain, other materials such as carbon-steel, nickel, zinc, copper, paint, and some plastics, paper, leather, and textiles are vulnerable to corrosion by acid rain. (b) List 2 specific measures to reduce the acid rain problem in an economic manner. b.1. Clean Air Act amendments required that power plants make significant cuts in sulfur dioxide and nitrogen oxides emissions (by installing "scrubbers" in their smokestacks and switching to low-sulfur coal.) Also Reduce nitrogen oxide emissions from stationary sources, through the use of better burner designs and the chemical additives. b.2 Through the market-based allowance trading system, utilities regulated under the Acid Rain Program decide the most cost-effective way to use available resources to comply with the requirements of the Clean Air Act. Utilities can reduce emissions by employing energy conservation measures, increasing reliance on renewable energy, reducing usage, employing pollution control technologies, switching to lower sulfur fuel, or developing other alternate strategies. (3) i) Compare the global warming potential (GWP) of HFC, Perflourocarbon (CF4) and sulphur hexa flouride (SF6) HFCs have a 100-year GWP range between 124 and 14,800 CO2e CF4 contains 100-year GWPs between 7,390 to 17,700 CO2e Sulfur hexafluoride (SF6) has a 100-year GWP potential of 22,800 CO2e ii) What are the sources of CF4 and SF6 CF4 - aluminum production and solvents used for electronics and metals SF6 – is emitted when electric transmission and distribution equipment is damaged or opened during repair or disposal; magnesium production and casting are also SF6 sources. (4) (i) What is the unit of measurement of ozone in the atmosphere? Dobson unit (DU) - One Dobson unit represents the amount of atmospheric ozone that would form a uniform layer 0.01 millimeter (10 micrometers) thick at standard temperature (0 °C) and pressure (1 atmosphere or 1013.25 millibars). (ii) Compare the ozone depletion potential of CFCs, HCFs and HFCs. CFCs and HCFCs have ODPs (ozone depletion potential) that range from 0.01 to 1.0. HFCs have zero ODP because they do not contain chlorine. (iii) Compare the effect of HFCs in global warming and ozone depletion. Because they do not contain chlorine or bromine, HFCs do not deplete the ozone layer (ODP = 0). Some HFCs have high GWPs and are revealed as extremely powerful greenhouse gases which could account for up to 19% of global warming by 2050. (5) What is biophysical alteration? Give 2 examples to illustrate this phenomenon. Biophysical Alteration refers to alteration in biological processes, or composition through the application of physical methods and theories derived from physics. Alteration of Tropomyosin Function and Folding by a Nemaline Myopathy-Causing Mutation and Biophysical alterations of hippocampal pyramidal neurons in learning, ageing and Alzheimers disease. (6) What adverse impacts result from the excessive discharge of the following pollutant sources into rivers? (i) untreated sewage It either percolates into the ground and in turn contaminates the groundwater or is discharged into the natural drainage system causing pollution in downstream areas. It can often be washed into streams and lakes as well. Toxic chemicals from sewage water transfer to plants and entire in the food chain and affect public health. Pathogens occurring in the sewage water directly affect the mammals causing severe diseases. (ii) wastewater from a sanitary landfill Harmful chemicals in the wastewater may seep through a nearby soil and be absorbed in the skin after contact with contaminated soil, and vegetables and other edible plants grown in such soil can absorb chemicals as well. Health effects from exposure to hazardous waste from a poorly maintained landfill can include: Cancer Birth defects Genetic mutations (7) Indicate the important water quality constituents in the following wastewater streams— (i) storm water Suspended Solids (sediment), Nutrients, Metals, Oxygen Demanding Substances, Oils, Greases and Hydrocarbons, and Pathogens. (ii) wastewater from a sanitary landfill BOD, TOC, COD, sulphates, chlorides, ammonia-N, organic-N, phosphates, and certain metals. (8) A particular wastewater stream has dissolved oxygen (DO) concentration of 2.0 mg / L and a discharge rate of 0.5 m3 / s. The river into which it is being discharged has DO equal to 8.3 mg / L, a flow rate of 4.35 m3 / s and a temperature of 20 C. The saturated value of DO at 20 C is 9.1 mg / L. (a) Assuming complete and instantaneous mixing, estimate the initial dissolved oxygen deficit of the mixture of wastewater and river water just downstream from the discharge point. C0 = (Qr Cr + Qw Cw) / (Qr + Qw) = [(4.35)(8.3) + (0.5)(2.0)]/(4.35 + 0.5) C0 = 7.651 mg/L D0 (deficit) = D0sat - C0 = 9.1 - 7.651 D0 (deficit) = 1.449 mg/L (b) Assuming the critical DO condition occurs at 4 km downstream, draw a graph to show the trend of the variation of the DO at 2 km and 10 km downstream of the discharge point (calculation not necessary). Saturation DO (DOsat) DO (mg/L) 2 4 6 8 10 12 14 16 18 20 distance from the discharge point (km) (c) What are the main factors that affect the DO concentration given by Streeter-Phelphs equation? The factors are dissolved oxygen deficit (mg/L), first-order reaeration rate coefficient (d-1), distance (m), average velocity (ms-1), first-order deoxygenation rate constant (d-1), and CBOD (mg/L). (9) Suggest a technology that can be used to treat the following wastes (a) particulates from a Cement factory (about 0.1 microns particles) Cloud Chamber Scrubber (CCS) – using highly charged water droplets as collectors; energy efficient (b) particulates from a Flour factory (about 5 microns particles) Use of Automatic Self-Cleaning Filters to remove the bulk of the suspended solids through a weavewire screen mesh woven from 316-L stainless steel. (c) organic pollutants from air in the Painting industry Effluent removal using Wood Ash – a natural adsorbent, with very low price; maximizes Pb-removal up to 96.1% & maximizes Co-removal up to 99% (d) SO2 from the air in the chemical industry Flue Gas Desulfurization (FGD) systems to scrub SO2 acid gas from the flue gas (10) A jet engine has a sound pressure level of 90 dB, as heard from a distance of 30 m. A ground crew member is standing 30 m away from a four-engine jet. What sound pressure level (SPL) reaches his ear when the first engine is turned on? Then when the second is started, so that two engines are running? When the third begins and then when all four are running?. Assume there is no background noise. (Use the chart provided in the class notes). When the first engine is turned on, a sound pressure level of 90 dB reaches the crew members ear. (11) In a big city of 1 million population, the waste management authority (WMA) is asked to prepare a report on solid waste management practices. You are the project officer in the WMA. Assume the city has similar socio-economic condition as Sydney. (a) Estimate the amount of solid waste produced per year Approximately 23 million tonnes of solid wastes in the city are being generated and disposed through considerable quantities of waste from human consumption and activities related to the construction, operation, maintenance, and renewal of human settlements. (b) Explain a material recovery facility you will adopt in this city A state-of-the-art biological treatment facility would be proposed to mechanically process the solid wastes from two municipalities by integrated sorting, biological digestion, and composting processes. This facility shall enable separation and cleaning of the organic fraction of household waste from which to produce renewable energy. Furthermore, the project would seek to optimize output at maximum possible recovery of recyclables, compost, energy, and carbon credits as well as minimize emissions of greenhouse gas and process leachates seeping through soil and groundwater. (c) The conventionally used sanitary landfill is not suitable for the city due to the non-availability of land. Suggest alternative technological solutions to economically handle the solid waste generated in the city. In the absence of landfill due to non-availability of land, the project would adopt the alternative of task requisites by imploring government provision for every household and manufacturing firm to implement domestic and corporate schemes on managing solid wastes. This includes conducting free seminars to instruct comprehensive yet innovative recycling methods then monitoring compliance of both residents and corporate members to ensure enactment and cooperation. The community shall be encouraged as well to reduce waste disposal by employing practical measures as donating or selling stuffs not much worn out at affordable prices instead of disposing them off immediately. In addition, the project would aim to motivate residents to consider composting and reserving slots, if possible, in their backyards to plant trees or expand nearby farm vegetation areas to be sustained by the compost yield. Any remaining funds after the initial plan has been carried out successfully in the course of operation would be allocated for studying plausibility of modifying incineration technology as another option to help manage the rest of the solid wastes. (12) Estimate the moisture content, density and energy content of a solid waste sample with the composition given in Table below. Sample Percentage by mass Moisture (%) Density (kg/m3) Energy (kJ/kg) Food waste 20 70 290 4650 Paper 50 8 85 16700 Garden Trimmings 15 60 110 6550 Wood 5 20 250 18700 Metal cans 10 2 90 500 Total 100 Moisture content = 28.2 kg 108.14 1,124,750 kJ Moisture content = (0.70)(20) + (0.08)(50) + (0.60)(15) + (0.20)(5) + (0.02)(10) = 28.2 kg Volume = (20/290) + (50/85) + (15/110) + (5/250) + (10/90) = 0.9247 m3 Density = (total mass) / (total volume) = 100 / 0.9247 = 108.14 kg/m3 Energy = (4650)(20) + (16700)(50) + (6550)(15) + (18700)(5) + (500)(10) (10) = 1,124,750 kJ (Note: This is based on 100-kg total sample mass.) (13) Explain why it is important to maintain environmental flows in river. Outline why it is especially important to maintain low to very low flows. Environmental river flows or water levels ought to be maintained in order to sustain all the elements of the aquatic ecosystems, such as wetlands and fish populations. Monitoring sufficient flow promotes preservation of fish runs and keeps the estuary at the river mouth healthy. It is especially important to maintain low to very low flows since water extraction and storage are high in dry times and impose long artificial droughts that increase the stress on aquatic plants and animals. Such maintenance employs no water extraction from streams or wetlands in periods of no flow so as to protect specific pools: streams where flow occurs under the sediment surface, natural wetlands with licensed pumps, and where these pools have become deeper or shallower. (14) Explain the difference between regulated rivers and unregulated rivers Regulated rivers refer to rivers where downstream flows are regulated by a major storage, or dam, to supply irrigation water. Unregulated rivers, on the other hand, apply to rivers without major storage, or dams, as well as to rivers where the storage does not release water downstream (in these cases, water is piped to where it is needed, such as metropolitan centers). (15) Describe how past practices has led to some of the problems associated with the provision of environmental flow problems in rivers in New South Wales. Extensive desnagging (removal of large woody debris and living riparian vegetation) and associated river improvement works were conducted in rivers of southeastern Australia (Victoria and New South Wales) between at least 1886 and 1995. This resulted to removal of appreciable amounts of large woody debris from rivers, and regenerating indigenous vegetation was cleared from within designed alignment widths and, ironically, huge numbers of exotic trees were planted. The environmental impacts of desnagging have only been documented on a few impacted rivers but have included increased flow velocity, spatially extensive bed degradation, massive channel enlargement and loss of fish habitat. (16) Outline some new Government initiatives being undertaken to provide environmental flow in rivers. Some of these initiatives are: determining that water will be allocated to the environment to enhance or restore the health of river systems and that this will be undertaken using an integrated catchment management approach; for water quality guidelines to recognise the use of risk-based hierarchical decision frameworks and distinguish between high conservation value ecosystems and disturbed systems; in accordance with the COAG systems, all state agencies now recognise the importance of protecting and rehabilitating estuarine ecosystems. (17) Describe what information can be obtained from models such as HEC RAS that is useful for environmental flow analysis. Such models perform hydraulics computations from which to determine geometry in terms of cross-sections, in bridges and dams, flows and hydraulic coefficients which are eventually useful in verifying ordinary high water elevations, calculating velocities, developing water-surface profiles, and evaluating effects of dam removals. 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