SENSOR PLACEMENT IN MUNICIPAL WATER NETWORKS
By Jonathan W. Berry; Lisa Fleischer; William E. Hart; Cynthia A. Phillips; and Jean-Paul Watson
Summary
The findings presented in this paper were to address the concerns of the U.S. Environmental Protection Agency that most of the U.S. water supply is highly susceptible to contamination (either accidental or intentional) and that any contamination would go largely undetected, which would place a high risk on public health. The authors present a model that optimizes the placement of sensors in municipal networks to detect maliciously injected contaminants (Berry 237). The LP method utilized is a mixed-integer program that seeks to minimize the fraction of the population at risk. Three separate networks were tested (two fictional networks taken from EPANET and one real-life network). The result of the research is an MIP model that effectively solves large-scale sensor-placement problems (so claims the authors, although the effectiveness and validity of the findings can always be disputed). It was also demonstrated that noise or uncertainty in the data had very little impact on the results of the analysis.
Discussion
Although several assumptions made in the paper were a little unrealistic (constant flow path and velocity, no variance over time and space of contaminant concentration, etc.), I would deem the overall work both viable and reasonable considering the purpose of the research. I found the paper to be a good follow-up to the previous discussion paper.
The authors speak on how this knowledge will be easily transferable to real-world large-scale sensor-placement problems. I wonder how many public water supply companies 1) are aware of this research; and 2) would know how to go about implementing this work if they did… maybe they could hire us!
Monday, February 23, 2009
Monday, February 16, 2009
Clean Water Monitoring Stuff
OPTIMAL LOCATIONS OF MONITORING STATIONS IN WATER DISTRIBUTION SYSTEM
By Byoung Ho Lee and Rolf A. Deininger
Summary
The passing of the Safe Drinking Water Act in 1974 required monitoring to be instituted in water distribution systems around the country; however, no guidance was given on how the sampling was to be executed. The authors address the best methods to locate monitoring stations in a water distribution network. The paper presents these methods by 1) defining new or relevant concepts 2) providing two examples that demonstrate the methods and concepts in real-world practice. The authors claim that the best set of stations is one that maximizes the coverage (as defined in the paper).
Discussion
This paper seems like it has lots of real-world applicability – after all, nearly every water distribution system in the US is required to monitor and I would bet that most of them are not optimizing their coverage. It has been nearly 17 years since this article was written and I would be interested if any more work has been done optimizing monitoring stations – not just research but have communities actually used this knowledge to expand their system’s coverage. If this information has merely lain on the shelf unused, I would be curious as to why. Is it too costly to implement? Are communities unaware that their systems are relatively ineffective?
By Byoung Ho Lee and Rolf A. Deininger
Summary
The passing of the Safe Drinking Water Act in 1974 required monitoring to be instituted in water distribution systems around the country; however, no guidance was given on how the sampling was to be executed. The authors address the best methods to locate monitoring stations in a water distribution network. The paper presents these methods by 1) defining new or relevant concepts 2) providing two examples that demonstrate the methods and concepts in real-world practice. The authors claim that the best set of stations is one that maximizes the coverage (as defined in the paper).
Discussion
This paper seems like it has lots of real-world applicability – after all, nearly every water distribution system in the US is required to monitor and I would bet that most of them are not optimizing their coverage. It has been nearly 17 years since this article was written and I would be interested if any more work has been done optimizing monitoring stations – not just research but have communities actually used this knowledge to expand their system’s coverage. If this information has merely lain on the shelf unused, I would be curious as to why. Is it too costly to implement? Are communities unaware that their systems are relatively ineffective?
Monday, February 9, 2009
Keep it in your pants - an article concerning restricted baby-making
The Tragedy of the Commons
by Garrett Hardin
Science, 1968
Summary
The Tragedy of the Commons uses the illustration of a common parcel of land shared by herders for the grazing of their cattle to allude to a grander commons – the Earth and its finite resources – and its users, all mankind. Following this analogy, Hardin contest that it is in each herder’s best interest to raise as many cattle as possible because the individual herder gains all the benefit while the cost is distributed amongst all the common’s users. Although this action may be justified on an individual level (any rational person will try to maximize their net benefit), it will eventually bring about the demise of the commons (and all the herdsmen) because when everyone seeks to maximize their benefit, the finite resources provide by the commons are diminished. Hardin claims that, in a similar manner, we are all seeking our own ends by over-breeding and the world’s exponentially increasing population will eventually destroy all “commons” that we share today. Hardin suggest that there is no technical solution in solving this quagmire, but that only a moral and social adjustment can manage and possibly avoid the currently inevitable destruction of all resources and mankind.
In conclusion, Hardin notes that there was benefit in different “commons” throughout history but that circumstances and increasing populations has caused us to abandoned using the commons as a means of food gathering and waste disposal in progression to privately owned agricultural land and designated waste disposal areas. In an effort to ensure the longevity and prosperity of all mankind, the author contest that the next common that should be given over to regulation is that of breeding.
Discussion
Although the paper was written over 40 years ago, I believe it is more applicable today than when it was written. Since the Tragedy of the Commons was written the population has more than doubled to nearly 7 billion people. The worldwide population growth shows no signs of regression, which will place an even heavier burden on our finite resources. Hardin’s recommendation is both compelling and controversial because it seeks to restrict something that mankind has tried to maximize since its dawn – the number of offspring they produce. Although I agree that something needs to be done and his argument makes sense (on a logically level), I don’t think it will ever be implemented. Or maybe I should say this… I don’t believe a breeding restriction will be placed on mankind until it has reached a point where considerable, irreversible damage has been done. Government is typically retroactive, not proactive.
by Garrett Hardin
Science, 1968
Summary
The Tragedy of the Commons uses the illustration of a common parcel of land shared by herders for the grazing of their cattle to allude to a grander commons – the Earth and its finite resources – and its users, all mankind. Following this analogy, Hardin contest that it is in each herder’s best interest to raise as many cattle as possible because the individual herder gains all the benefit while the cost is distributed amongst all the common’s users. Although this action may be justified on an individual level (any rational person will try to maximize their net benefit), it will eventually bring about the demise of the commons (and all the herdsmen) because when everyone seeks to maximize their benefit, the finite resources provide by the commons are diminished. Hardin claims that, in a similar manner, we are all seeking our own ends by over-breeding and the world’s exponentially increasing population will eventually destroy all “commons” that we share today. Hardin suggest that there is no technical solution in solving this quagmire, but that only a moral and social adjustment can manage and possibly avoid the currently inevitable destruction of all resources and mankind.
In conclusion, Hardin notes that there was benefit in different “commons” throughout history but that circumstances and increasing populations has caused us to abandoned using the commons as a means of food gathering and waste disposal in progression to privately owned agricultural land and designated waste disposal areas. In an effort to ensure the longevity and prosperity of all mankind, the author contest that the next common that should be given over to regulation is that of breeding.
Discussion
Although the paper was written over 40 years ago, I believe it is more applicable today than when it was written. Since the Tragedy of the Commons was written the population has more than doubled to nearly 7 billion people. The worldwide population growth shows no signs of regression, which will place an even heavier burden on our finite resources. Hardin’s recommendation is both compelling and controversial because it seeks to restrict something that mankind has tried to maximize since its dawn – the number of offspring they produce. Although I agree that something needs to be done and his argument makes sense (on a logically level), I don’t think it will ever be implemented. Or maybe I should say this… I don’t believe a breeding restriction will be placed on mankind until it has reached a point where considerable, irreversible damage has been done. Government is typically retroactive, not proactive.
Sunday, February 1, 2009
How to get crap out of underground water (laymen terms)
Hydraulic Gradient Control for Groundwater Contaminant Removal
Dorothy Fisher Atwood and Steven M. Gorelick
Journal of Hydrology, 76 (1985) 85-106
Summary
As its title implies, the focus of Atwood and Gorelick’s paper is how to control the hydraulic gradient of an unconfined aquifer as a means of containing a contaminant plume for save and effective removal. Although the research is a hypothetical test, the aquifer that is modeled is a real aquifer under the Rocky Mountain Arsenal near Denver, Colorado.
The authors chose to use a two-stage approach in modeling the problem so to avoid nonlinearities that would otherwise prohibit the use of linear optimization technique. The two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water (Atwood 85). The first stage of the test involved determining the plume boundary location as a function of time by combining a groundwater flow and solute transport model. The second stage used a linear program to determine the optimal (as defined by minimal pumping and recharge) well selection and pumping/recharge rates.
Two different optimization strategies were used: 1) Sequential optimization, which relies primarily on the previous pumping period for its initial conditions and 2) Global optimization, which optimizes the system over the entire 32 pumping periods. The total pumping/recharge rates are comparable for the two optimization strategies; however, the well selection and pumping schedules are very different (Atwood 102). The research shows that the cumulative pumping/recharge rates of the global solution are approximately 10% better (as deemed by pumping/recharge volumes) than the sequential solution. However, the authors urge that although the global optimization produces a better solution than the sequential strategy, the solutions are similar enough that other factors such as economic or social conditions should be considered.
Discussion
The number of groundwater contaminant incidents will continue to increase over the next several decades as we begin to reap some of the pitfalls of industrialization and ineffective environmental safeguards. This article is not only interesting but also useful because it gives an effective and generalized method for handling groundwater contaminant plumes. With that being said, I would have liked to seen the author extend the scope of the research and model the impacts of having multiple wells that remove the plume. To be quite candid, I know little about groundwater contaminant removal but my intuition tells me that 16 years of pumping to remove the groundwater pollutants is not only an extremely long period but very expensive – something that most communities who would be paying for this would not appreciate. I would like to see further research that would optimize the pumping cost and time with multiple wells removing the contaminate plume.
Dorothy Fisher Atwood and Steven M. Gorelick
Journal of Hydrology, 76 (1985) 85-106
Summary
As its title implies, the focus of Atwood and Gorelick’s paper is how to control the hydraulic gradient of an unconfined aquifer as a means of containing a contaminant plume for save and effective removal. Although the research is a hypothetical test, the aquifer that is modeled is a real aquifer under the Rocky Mountain Arsenal near Denver, Colorado.
The authors chose to use a two-stage approach in modeling the problem so to avoid nonlinearities that would otherwise prohibit the use of linear optimization technique. The two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water (Atwood 85). The first stage of the test involved determining the plume boundary location as a function of time by combining a groundwater flow and solute transport model. The second stage used a linear program to determine the optimal (as defined by minimal pumping and recharge) well selection and pumping/recharge rates.
Two different optimization strategies were used: 1) Sequential optimization, which relies primarily on the previous pumping period for its initial conditions and 2) Global optimization, which optimizes the system over the entire 32 pumping periods. The total pumping/recharge rates are comparable for the two optimization strategies; however, the well selection and pumping schedules are very different (Atwood 102). The research shows that the cumulative pumping/recharge rates of the global solution are approximately 10% better (as deemed by pumping/recharge volumes) than the sequential solution. However, the authors urge that although the global optimization produces a better solution than the sequential strategy, the solutions are similar enough that other factors such as economic or social conditions should be considered.
Discussion
The number of groundwater contaminant incidents will continue to increase over the next several decades as we begin to reap some of the pitfalls of industrialization and ineffective environmental safeguards. This article is not only interesting but also useful because it gives an effective and generalized method for handling groundwater contaminant plumes. With that being said, I would have liked to seen the author extend the scope of the research and model the impacts of having multiple wells that remove the plume. To be quite candid, I know little about groundwater contaminant removal but my intuition tells me that 16 years of pumping to remove the groundwater pollutants is not only an extremely long period but very expensive – something that most communities who would be paying for this would not appreciate. I would like to see further research that would optimize the pumping cost and time with multiple wells removing the contaminate plume.
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