a) From the moment insecticide reaches the aquifer from the drain field, calculate the advective travel time to the neighbour's water well. b) A 'breakthrough curve' is a profile of concentration versus time at any selected point along a flow path where a tracer or contaminant is being transported. In this case, the point of interest in the system is the neighbour's water well. Draw schematic breakthrough curves showing concentration versus time at the well under the following conditions. Note that on a breakthrough curve for a continuously released tracer (contaminant), the advective travel time is where C/Co 0.5 and for a finite release of a fixed amount of tracer the advective travel time occurs where C/Co reaches its peak. İ. ii. iii. iv. No dispersion along the flow path, it takes only one day for the insecticide to move through the septic tank Same as i, but dispersion occurs along the flow path No dispersion, it takes 60 days for the insecticide to move through the septic tank Same as iii, but dispersion occurs along the flow path Use common axes for plots I and ii, and for plots iii and iv. It is important to label where C/Co equals 0.5 and 1.0 on the y axis and where t equals the travel time calculated in a). Also, make sure to label any other features of the plots that are important. Part 1: Advection-dispersion of septic-tank effluent in groundwater Septic systems are one of the most common sources of groundwater contamination in rural areas. They are designed to treat sewage effluent from homes and then release the treated water to underlying aquifers. When working correctly, they promote biodegradation of organic wastes and kill harmful pathogens, but the treated water is not pristine. When working correctly, septic systems are significant sources of NO3, Cl- and PO4³- to the groundwater system (and anything else that home owners put down the drain). well groundwater table house sewer pipe Septic Tank access risers discharge to absorption trench or filter bed scum inlet baffle compartment 1 compartment 2 heavy solids final distribution pre- treatment treatment zone percolation saturated soil vel 3.17 x 106 m/s bedrock deep aquifer https://www.ontario.ca/files/2022-10/omafra-septic-smart-understanding-home-wastewater-system-en-2022-10-14.pdf effluent filter fine particles 1. Sewage from the house is pre-treated anaerobically in the septic tank. 2. The effluent flows to a drain field with perforated pipes, allowing it to drain downward. Micro-organisms utilize O₂ in the vadose zone to provide additional aerobic treatment. The scenario represented by the Figure above, with a water well and septic system, is common to all homes in rural Canada that are not connected to a municipal sewer system. When installing these systems, one of the primary concerns is that groundwater should flow from the drain field and away from the well. It is best if the well is screened in a deeper confined aquifer that is not impacted from septic drainage, but this is not always possible. So, it is common that septic-tank effluent drains into the same unconfined aquifer that provides drinking water via the well. Let's assume that water impacted by the drain field flows away from the well, as shown in the figure, but people have neighbours, so here we will assume there is a neighbour, with a water well, 100 m downgradient. Not understanding the connection between the house drains and the aquifer, the homeowner flushes some old garden insecticide down the toilet, which moves conservatively through the septic tank and enters the aquifer from the drain field. It then travels along the 100 m flow path to the neighbour's well. Also assume: - homogeneous and isotropic distribution of K one-dimensional flow path

a) From the moment insecticide reaches the aquifer from the drain field, calculate the advective travel time to the neighbour's water well. b) A 'breakthrough curve' is a profile of concentration versus time at any selected point along a flow path where a tracer or contaminant is being transported. In this case, the point of interest in the system is the neighbour's water well. Draw schematic breakthrough curves showing concentration versus time at the well under the following conditions. Note that on a breakthrough curve for a continuously released tracer (contaminant), the advective travel time is where C/Co 0.5 and for a finite release of a fixed amount of tracer the advective travel time occurs where C/Co reaches its peak. İ. ii. iii. iv. No dispersion along the flow path, it takes only one day for the insecticide to move through the septic tank Same as i, but dispersion occurs along the flow path No dispersion, it takes 60 days for the insecticide to move through the septic tank Same as iii, but dispersion occurs along the flow path Use common axes for plots I and ii, and for plots iii and iv. It is important to label where C/Co equals 0.5 and 1.0 on the y axis and where t equals the travel time calculated in a). Also, make sure to label any other features of the plots that are important. Part 1: Advection-dispersion of septic-tank effluent in groundwater Septic systems are one of the most common sources of groundwater contamination in rural areas. They are designed to treat sewage effluent from homes and then release the treated water to underlying aquifers. When working correctly, they promote biodegradation of organic wastes and kill harmful pathogens, but the treated water is not pristine. When working correctly, septic systems are significant sources of NO3, Cl- and PO4³- to the groundwater system (and anything else that home owners put down the drain). well groundwater table house sewer pipe Septic Tank access risers discharge to absorption trench or filter bed scum inlet baffle compartment 1 compartment 2 heavy solids final distribution pre- treatment treatment zone percolation saturated soil vel 3.17 x 106 m/s bedrock deep aquifer https://www.ontario.ca/files/2022-10/omafra-septic-smart-understanding-home-wastewater-system-en-2022-10-14.pdf effluent filter fine particles 1. Sewage from the house is pre-treated anaerobically in the septic tank. 2. The effluent flows to a drain field with perforated pipes, allowing it to drain downward. Micro-organisms utilize O₂ in the vadose zone to provide additional aerobic treatment. The scenario represented by the Figure above, with a water well and septic system, is common to all homes in rural Canada that are not connected to a municipal sewer system. When installing these systems, one of the primary concerns is that groundwater should flow from the drain field and away from the well. It is best if the well is screened in a deeper confined aquifer that is not impacted from septic drainage, but this is not always possible. So, it is common that septic-tank effluent drains into the same unconfined aquifer that provides drinking water via the well. Let's assume that water impacted by the drain field flows away from the well, as shown in the figure, but people have neighbours, so here we will assume there is a neighbour, with a water well, 100 m downgradient. Not understanding the connection between the house drains and the aquifer, the homeowner flushes some old garden insecticide down the toilet, which moves conservatively through the septic tank and enters the aquifer from the drain field. It then travels along the 100 m flow path to the neighbour's well. Also assume: - homogeneous and isotropic distribution of K one-dimensional flow path

Applications and Investigations in Earth Science (9th Edition)

9th Edition

ISBN:9780134746241

Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa

Publisher:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa

Chapter1: The Study Of Minerals

Section: Chapter Questions

Problem 1LR

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Transcribed Image Text:a) From the moment insecticide reaches the aquifer from the drain field, calculate the advective travel time to the neighbour's water well. b) A 'breakthrough curve' is a profile of concentration versus time at any selected point along a flow path where a tracer or contaminant is being transported. In this case, the point of interest in the system is the neighbour's water well. Draw schematic breakthrough curves showing concentration versus time at the well under the following conditions. Note that on a breakthrough curve for a continuously released tracer (contaminant), the advective travel time is where C/Co 0.5 and for a finite release of a fixed amount of tracer the advective travel time occurs where C/Co reaches its peak. İ. ii. iii. iv. No dispersion along the flow path, it takes only one day for the insecticide to move through the septic tank Same as i, but dispersion occurs along the flow path No dispersion, it takes 60 days for the insecticide to move through the septic tank Same as iii, but dispersion occurs along the flow path Use common axes for plots I and ii, and for plots iii and iv. It is important to label where C/Co equals 0.5 and 1.0 on the y axis and where t equals the travel time calculated in a). Also, make sure to label any other features of the plots that are important.