Cootes Paradise is a wetland located at the western edge of Lake Ontario, surrounded by the cities of Hamilton and Dundas. The area was once a pristine marsh where aquatic plant and wild life flourished, and remains an important spawning ground for fish. Unfortunately, this sanctuary has been altered in past decades. Where once the area was entirely covered with aquatic plants, now much of the marsh is open water. This degradation is visible to any one driving past Cootes Paradise along highway 403 and highway 6. However, the damage goes far beyond what can be seen. As a recent study found, water quality and biodiversity in the wetland has significantly declined, with adverse affects on the health of plant and animals species.
The study, led by Tatiana Mayer, was conducted by Environment Canada’s Water Science and Technology Directorate. It found that Cootes Paradise contains high levels of phosphorus and of a class of chemicals known as alkylphenolics. Aquatic systems such as lakes and marshes are negatively affected by elevated phosphorus and alkylphenolic levels. High phosphorus content can lead to eutrophication of such systems, where in the water’s oxygen content often declines, and the normal ecosystem is disrupted. Alkylphenolics have been shown to alter the sexual development of many organisms. Male species exposed to these chemicals can adapt female sexual characteristics. Both phosphorus and alkylphenolics are found in a wide range of consumer and industrial products, from detergents to cosmetics to paints.
Mayer and the study team observed these levels in core samples of surface and bottom sediment taken from Cootes Paradise in 2001 and 2002. They took several core samples from different areas around the 250 hectare marsh. Marshes are especially vulnerable to the effects of contaminants, because these toxins accumulate in the sediment where their impacts can be augmented.
Results showed that contaminant levels were highest near creeks and drainage points where discharge from municipal wastewater treatment plants (WTPs) and combined sewer overflows (CSOs) emptied into the marsh. These discharges have been shown in other studies to contain high levels of pharmaceuticals, hormones and other toxins, including alkylphenolics. The study also found that higher levels of these contaminants were deposited after heavy rainfall and rapid snow melt occurred. During these events, high levels of water run off overloads WTPs and CSOs, and water is often not properly treated or processed. As such, many of the contaminants remain in the untreated water. The study showed a distinct connection between the elevated levels of these contaminants and the decline in the marsh's biotic health.
As development and population in the Hamilton-Dundas area continue to grow, new infrastructure for managing wastewater will need to be developed, while current facilities will require upkeep. As Mayer points out, impacts like those on Cootes Paradise are similarly affecting other wetlands in areas around the Great Lakes. It is in these areas that urban development is slated to grow the fastest. Considering the results of this study, it’s clear that the impacts of this wastewater on Cootes Paradise and Great Lakes wetlands should be considered, and ultimately minimized by urban developers in future infrastructure.
Reference:
http://journals1.scholarsportal.info.subzero.lib.uoguelph.ca/details.xqy?uri=/03801330/v34i0003/544_docfmdlcwcpo.xml
Tuesday, October 13, 2009
Treating Leachates from Landfills with Biofilm Processes
A large cause of pollution is from landfills leaching into the soil, groundwater, and surface water. Many landfills that are not managed properly and even ones that are can produce leachate which is polluted wastewater. This wastewater is toxic and can contain hazardous components such as heavy metals. The leachate from landfills causes surface water, groundwater and soil pollution. A study performed by A. Gálvez, L. Giusti, et al. in association with the University of Granada, Spain and the University of the West of England, UK, demonstrated some new ways to control this toxic leachate in order to make landfills cleaner and safer on the environment. The study is called “Stability and efficiency of biofilms for landfill leachate treatment” and it was published in the journal “Bioresource Technology” in 2009.
The purpose of this study was to determine how efficient biological aeration filtrate is for the treatment of leachate. The study concentrated on leachate produced at the Harnfill landfill site in the UK. The study looked at how the leachate from landfills can be treated by a biofilm process. A biofilm is a thin resistant layer of organisms (bacteria) that stick together and form on surfaces. The biofilms are supposed to have a higher resistance to toxic agents and a lower sensitivity to low temperatures, and the study was trying to prove whether this was true or not.
Leachate samples were collected from the Harnfill landfill site and they were brought back to a laboratory for analysis. The leachate samples were put in four identical biological aerated filters and they were tested for biofilm that was forming on them. Some tests were done on the columns to determine what the biofilms could withstand. Some of these tests included testing for the pH, conductivity and heavy metal levels. The columns were also tested under several different temperatures and these included 20⁰C, 30⁰C, 40⁰C, and 45⁰C. The results of the study showed that the biofilm had a high resistance to antibiotic and other toxic agents and it was very adaptable to a wide range of conditions.
The biological aerated filters were found to produce biofilms which reduce the toxins of the leachate. This therefore makes the landfills less harmful for the environment and safer for the people that live near the landfills. Because of the tests done with different temperatures, the biological aerated filters are now known to operate efficiently in temperatures between 20 ⁰C and 45⁰C without showing toxic effects. The study performed by A. Gálvez, L. Giusti, et al proved that using biological aerated filters to remove biodegradable parts of organic matter contained in leachate was a very feasible, cost efficient and environmentally friendly process. As said in the study, “This demonstrates the flexibility of the biofilm process as it is able to treat leachates of different origin and composition.” (Gálvez et al. 2009). This discovery is very important because it will mean that landfills can continue to function without being harmful to the environment and to the society.
Resources
Gálvez, A., Giusti L. et al. Stability and efficiency of biofilms for landfill leachate treatment (2009). Bioresource Technology. 3 June 2009. http://journals1.scholarsportal.info/tmp/2868637342054989626.pdf. Accessed 13 October 2009.
The purpose of this study was to determine how efficient biological aeration filtrate is for the treatment of leachate. The study concentrated on leachate produced at the Harnfill landfill site in the UK. The study looked at how the leachate from landfills can be treated by a biofilm process. A biofilm is a thin resistant layer of organisms (bacteria) that stick together and form on surfaces. The biofilms are supposed to have a higher resistance to toxic agents and a lower sensitivity to low temperatures, and the study was trying to prove whether this was true or not.
Leachate samples were collected from the Harnfill landfill site and they were brought back to a laboratory for analysis. The leachate samples were put in four identical biological aerated filters and they were tested for biofilm that was forming on them. Some tests were done on the columns to determine what the biofilms could withstand. Some of these tests included testing for the pH, conductivity and heavy metal levels. The columns were also tested under several different temperatures and these included 20⁰C, 30⁰C, 40⁰C, and 45⁰C. The results of the study showed that the biofilm had a high resistance to antibiotic and other toxic agents and it was very adaptable to a wide range of conditions.
The biological aerated filters were found to produce biofilms which reduce the toxins of the leachate. This therefore makes the landfills less harmful for the environment and safer for the people that live near the landfills. Because of the tests done with different temperatures, the biological aerated filters are now known to operate efficiently in temperatures between 20 ⁰C and 45⁰C without showing toxic effects. The study performed by A. Gálvez, L. Giusti, et al proved that using biological aerated filters to remove biodegradable parts of organic matter contained in leachate was a very feasible, cost efficient and environmentally friendly process. As said in the study, “This demonstrates the flexibility of the biofilm process as it is able to treat leachates of different origin and composition.” (Gálvez et al. 2009). This discovery is very important because it will mean that landfills can continue to function without being harmful to the environment and to the society.
Resources
Gálvez, A., Giusti L. et al. Stability and efficiency of biofilms for landfill leachate treatment (2009). Bioresource Technology. 3 June 2009. http://journals1.scholarsportal.info/tmp/2868637342054989626.pdf. Accessed 13 October 2009.
Singapore Waste Solutions
The issue of domestic waste management has always been controversial; yet we don’t give much thought to the garbage we throw away. Most of us have at least a baseline idea of what happens to it afterwards but very few people actually care. Landfills are by far the most popular and the cheapest supposed solution. Dumping garbage into its own reserved area where many will never have to see it again is a very appealing idea. There are of course a number of more environmentally friendly options, but not every country can afford them. This is a common dilemma, balancing environmental impacts with the costs of the overall process of disposing of waste. A study done in January 2009 by the Institute of Chemical and Engineering Sciences analyzed Singapore’s methods of dealing with municipal solid waste.
Singapore is a small country, lacking the land for extensive landfills. Its one main landfill is predicted to last until 2030 . They have turned to a number of processes to handle their waste problems, most of which revolve around incinerating MSW (Municipal Solid Waste). They have also begun trying to harness some of the product gas produced as usable electrical energy. Of Singapore’s eight main waste managing methods it was determined that the steam gasification of wood and pyrolysis gasification of waste was the most effective. Gasification consists of shredding waste wood to produce a product gas, then combusting the gas to create electrical energy, making it the most environmentally friendly yet at the same time the most costly. Pyrolysis gasification of waste created the least amount of waste. However all methods of incineration cost a considerable deal, first to heat the waste and second to pretreat and deal with the product.
The study determined that the costs of these methods in comparison to land filling were almost double. For example the gasification of shredded wood was roughly 95 USD/ton feedstock, while land filling was 55 USD/ton feedstock. A number them had high global warming potential, thermal cracking gasification scored highest, with the addition of pretreatment for the waste amounted to almost 2700 kg_Co2 – eq. The study tested a number of different impacts including eutrophication levels and photochemical ozone formation levels. Gasification and pyrolysis was the second most expensive, yet it’s estimated that the trade off of energy produced by the product waste could make it more affordable and beneficial for the environment. Hopefully more alternative methods of waste management will be considered more internationally, improvements in technology should make the transition simpler. However there is a long way to go before we can manage waste in an environmentally sustainable way that is also cost effective, thought the near future holds many possibilities.
Resources:
Life cycle impact assessment of carious waste conversion technologies. Khoo H. Hsien. January 20, 2009. Waste Management V. 29 I. 6. Accessed October 9, 2009. From: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VFR-4VDSCVJ-8&_user=1067211&_coverDate=06%2F30%2F2009&_alid=1046587035&_rdoc=1&_fmt=high&_orig=search&_cdi=6017&_sort=r&_st=4&_docanchor=&_ct=48&_acct=C000051237&_version=1&_urlVersion=0&_userid=1067211&md5=cee5e4a2470c102220e1cd856bc564be.
Monday, October 12, 2009
Human Hair: An Indicator of Contaminant Exposures in E-waste Recycling Areas
Due to the increase in demand and production for electronic products in the past decades, many problems become apparent regarding the whereabouts of the ever rising amount of electronic waste (e-waste). A growing supply of this waste is illegally exported to recycling facilities in developing countries in order to salvage reusable materials and traces of precious metals. In these foreign facilities, open burning and acid stripping practises take place, but along with recovering the prize comes the release of pollutants and toxic heavy metals. Not only do these contaminants cause health problems for the site workers, they also negatively affect the surrounding environment, including fields, rivers, soils, and sediments (Wang et al., 2009).
A recent study on human exposure to heavy metals in an electronic waste recycling area, published in Bioresource Technology during 2009, suggests that scalp hair can be used as an indicator on the exposure of heavy metals and toxic elements to humans. The six researchers, Thanh Wang, Jianjie Fu, Yawei Wang, Chunyang Liao, Yongqing Tao, and Guibin Jiang, believe that since studies on the potential exposures (both occupationally and environmentally) due to e-waste recycling activities are inadequate, it is important to be able to examine these residential exposures using the least invasive and hazardous, but most convenient techniques. They proposed that human hair scalp could be used to assess the amounts of e-waste contaminants that are exposed and state that their study is one of the very few that deals with “human exposure to trace elements and heavy metals associated in areas with e-waste recycling” (Wang et al., 2009).
The study was purposefully chosen to take place in the south eastern Chinese province Taizhou, where residents have been directly or indirectly involved with a local e-waste recycling site that has been in existence for almost two decades. Hair samples, which were collected from volunteer participants during their routine sessions at nearby barber shops, were analyzed using the external standard calibration method to detect total concentrations of arsenic, barium, cadmium, chromium, copper, manganese, nickel, lead, and, vanadium (Wang et al., 2009). These samples were then compared with samples from two cities located about 130km north and 160km northwest of Taizhou.
The results showed that all of the mentioned elements above were found at higher levels than those in the controlled areas except for arsenic and vanadium. The researchers also stated that compared to non-occupationally exposed populations in Sweden and France, the element levels were all greater, especially lead, which proved to show 80 times higher levels (Wang et al., 2009).
From these results, Wang and his co-researchers concluded that human scalp hair can be used to determine the exposure of toxic heavy elements and metals to residential and occupational personnel directly or indirectly involved with e-waste recycling areas. It provides a non-invasive and cost-effective method, and is beneficial because by knowing the levels of exposure, scientists can further their knowledge on the negative effects of unregulated recycling practises such as open burning and acid stripping.
Reference
Wang, T. et al. (2009) Use of scalp hair as indicator of human exposure to heavy metals in an electronic waste recycling area. Environmental Pollution, issue 157, March 2009. http://journals2.scholarsportal.info/tmp/12866323311903835193.pdf. Accessed 08 October 2009.
A recent study on human exposure to heavy metals in an electronic waste recycling area, published in Bioresource Technology during 2009, suggests that scalp hair can be used as an indicator on the exposure of heavy metals and toxic elements to humans. The six researchers, Thanh Wang, Jianjie Fu, Yawei Wang, Chunyang Liao, Yongqing Tao, and Guibin Jiang, believe that since studies on the potential exposures (both occupationally and environmentally) due to e-waste recycling activities are inadequate, it is important to be able to examine these residential exposures using the least invasive and hazardous, but most convenient techniques. They proposed that human hair scalp could be used to assess the amounts of e-waste contaminants that are exposed and state that their study is one of the very few that deals with “human exposure to trace elements and heavy metals associated in areas with e-waste recycling” (Wang et al., 2009).
The study was purposefully chosen to take place in the south eastern Chinese province Taizhou, where residents have been directly or indirectly involved with a local e-waste recycling site that has been in existence for almost two decades. Hair samples, which were collected from volunteer participants during their routine sessions at nearby barber shops, were analyzed using the external standard calibration method to detect total concentrations of arsenic, barium, cadmium, chromium, copper, manganese, nickel, lead, and, vanadium (Wang et al., 2009). These samples were then compared with samples from two cities located about 130km north and 160km northwest of Taizhou.
The results showed that all of the mentioned elements above were found at higher levels than those in the controlled areas except for arsenic and vanadium. The researchers also stated that compared to non-occupationally exposed populations in Sweden and France, the element levels were all greater, especially lead, which proved to show 80 times higher levels (Wang et al., 2009).
From these results, Wang and his co-researchers concluded that human scalp hair can be used to determine the exposure of toxic heavy elements and metals to residential and occupational personnel directly or indirectly involved with e-waste recycling areas. It provides a non-invasive and cost-effective method, and is beneficial because by knowing the levels of exposure, scientists can further their knowledge on the negative effects of unregulated recycling practises such as open burning and acid stripping.
Reference
Wang, T. et al. (2009) Use of scalp hair as indicator of human exposure to heavy metals in an electronic waste recycling area. Environmental Pollution, issue 157, March 2009. http://journals2.scholarsportal.info/tmp/12866323311903835193.pdf. Accessed 08 October 2009.
Chasing Nature
If someone were to ask you, ”What do helicopters, hypodermic needles, airplane wings and sonar have in common?”, do you think you could come up with the answer? At first glance the answer may not seem clear, but upon closer inspection a hidden similarity emerges. While all of these items do represent enormous leaps in human technological advancement, the design behind them is by no means original. Millions of years before the notion of these technologies were even conceived, dragonflies and hummingbirds hovered in midflight, vipers injected venom through hollow fangs into unsuspecting prey and dolphins used echolocation to locate fish. In fact a vast majority of modern technology is directly copied from designs in nature. Despite our best attempts, these imitations always pale in comparison to the real thing. It is really not much of a surprise then, when technology fails to match the most complex biological processes which, in themselves took millions of years to develop through evolution
One of the most complex and intricate of these systems is the digestive tract, specifically that found in ruminants. Since the emergence of grass as a dominant plant species, ruminants have continued to be the dominant group of herbivores. The secret of this success lies in the unique digestive system of this group of animals. Cellulose, is one of the main components of grass and plant cell walls, and since it is primarily comprised of carbohydrates, it has a lot of stored potential energy. The trouble is that cellulose is very difficult to digest and as a result all of that stored energy is virtually unattainable. Ruminants however, have evolved a highly complex digestive system which can digest tough cellulose so that energy may be extracted. Recently, humans have also recognized the enormous energy potential of cellulosic plant biomass specifically in the production of ethanol. Ethanol has many industrial applications, but its primary use is as a fuel additive. When ethanol is added to fuel, the amount of hydrocarbon and volatile organic emissions decreases. Up until recently, corn has been the primary source of ethanol. Unfortunately, corn alone cannot supply the necessary amount of ethanol required for a worldwide demand. Consolidated bioprocessing(CBP) of biomass is a process which utilizes anaerobic bacteria to decompose and ferment cellulose plant biomass into ethanol. Currently, CBP systems still require many improvements before the process can become a viable ethanol production source. Researchers from the University of Wisconsin-Madison and the USDA-ARS-US Dairy Forage Research Center have set out to observe the digestive system of the cow, which has a very efficient cellulose digestive system, in order to determine how CBP systems can be improved. After observation, 3 main areas of improvement were identified:
1. Pre-treatment of the cellulose fibre
2. Anaerobic bacteria
3. Usage of by-products as possible alternate energy sources
Even for the species of bacteria which can produce cellulase, cellulose must first be pre treated in order to weaken the tough protein lignin found in the cell walls of plantcells. In CBP this is achieved chemically, however, the systems and the chemical agents all require significant costs. In addition, chemical pre treatment also results in the loss of some carbohydrate from the mixture as well as waste which requires disposal. The system in cows is much more primitive, yet more effective. By physically grinding the plant material, and then re-chewing the regurgitated cud, cows are able to reduce the particle size so much that there is an estimated 104 fold increase in total surface area(Weimer 2009). However, in order to thoroughly breakdown the cellulose cows were found to chew for 200 min/kg of fibre intake which adds up to 10-13 hours of ruminating per day or as high as 20 hours per day(Weimer 2009)! Remarkably the energy expended in ruminating is actually quite small. But currently there is no mechanical system which matches the efficiency of the cow in grinding plant biomass, so efforts are continuing to be focused on a chemical pre treatment. However, this research may provide the information which could be used in the future to create a more efficient grinding system which closely mimics the cow.
The process of cellulose hydrolysis is made possible by enzymes produced by anaerobic bacteria. In cows these vital bacteria are located in a large organ called the rumen where the chewed plant fibre can remain for up to 72 hours(Weimer 2009). This gives the bacteria in the rumen plenty of time to properly digest the treated plant matter. In the low-no oxygen conditions, fermentation occurs and the main products are volatile fatty acids(VFA), which the cow absorbs through its gut wall(Weimer 2009). The cellulose is degraded faster depending on the available surface area. Plant cell walls are composed of many different components and yet almost every single type of enzyme required to digest the material can be produced by at least one of the bacterial species found in the rumen. In contrast, artificial systems lack this diversity of microflora, and cannot digest plant matter as thoroughly as ruminants.
Perhaps the most important focus of this study was the examination of utilizing the fermentation by products other than ethanol as alternative energy sources. Two of the major by products produced by the fermentation process are methane and VFAs. Methane, which is excreted as gas by ruminants, could be captured in CBP systems and used as an alternate fuel source. VFAs on the other hand have a low volatility, but have a large amount of stored energy therefore have a potential as another energy source. Most systems currently focus on primarily ethanol production however, the addition of these by products could contribute enormously to the biomass energy yield.
Improvements on current CBP systems need to be made before this process becomes a viable source of ethanol. Current research provides a valuable insight regarding the direction to advance this technology. Equally important, the effort towards developing this technology also presents alternatives for waste management. For industries where high cellulose biomass is produced as waste such as agriculture, forestry or even maintenance of green spaces the advancement of CBP systems represents a potentially effective and even beneficial waste management strategy other than composting.
References
Weimer J. Paul, Russell B. James, & Muck E. Richard. (2009). Lessons from the cow: What the ruminant animal can teach us about consolidated bioprocessing of cellulosic biomass. [Lessons from the cow: What the ruminant animal can teach us about consolidated bioprocessing of cellulosic biomass] Bioresource Technology, 100(21), 5323-5331.
One of the most complex and intricate of these systems is the digestive tract, specifically that found in ruminants. Since the emergence of grass as a dominant plant species, ruminants have continued to be the dominant group of herbivores. The secret of this success lies in the unique digestive system of this group of animals. Cellulose, is one of the main components of grass and plant cell walls, and since it is primarily comprised of carbohydrates, it has a lot of stored potential energy. The trouble is that cellulose is very difficult to digest and as a result all of that stored energy is virtually unattainable. Ruminants however, have evolved a highly complex digestive system which can digest tough cellulose so that energy may be extracted. Recently, humans have also recognized the enormous energy potential of cellulosic plant biomass specifically in the production of ethanol. Ethanol has many industrial applications, but its primary use is as a fuel additive. When ethanol is added to fuel, the amount of hydrocarbon and volatile organic emissions decreases. Up until recently, corn has been the primary source of ethanol. Unfortunately, corn alone cannot supply the necessary amount of ethanol required for a worldwide demand. Consolidated bioprocessing(CBP) of biomass is a process which utilizes anaerobic bacteria to decompose and ferment cellulose plant biomass into ethanol. Currently, CBP systems still require many improvements before the process can become a viable ethanol production source. Researchers from the University of Wisconsin-Madison and the USDA-ARS-US Dairy Forage Research Center have set out to observe the digestive system of the cow, which has a very efficient cellulose digestive system, in order to determine how CBP systems can be improved. After observation, 3 main areas of improvement were identified:
1. Pre-treatment of the cellulose fibre
2. Anaerobic bacteria
3. Usage of by-products as possible alternate energy sources
Even for the species of bacteria which can produce cellulase, cellulose must first be pre treated in order to weaken the tough protein lignin found in the cell walls of plantcells. In CBP this is achieved chemically, however, the systems and the chemical agents all require significant costs. In addition, chemical pre treatment also results in the loss of some carbohydrate from the mixture as well as waste which requires disposal. The system in cows is much more primitive, yet more effective. By physically grinding the plant material, and then re-chewing the regurgitated cud, cows are able to reduce the particle size so much that there is an estimated 104 fold increase in total surface area(Weimer 2009). However, in order to thoroughly breakdown the cellulose cows were found to chew for 200 min/kg of fibre intake which adds up to 10-13 hours of ruminating per day or as high as 20 hours per day(Weimer 2009)! Remarkably the energy expended in ruminating is actually quite small. But currently there is no mechanical system which matches the efficiency of the cow in grinding plant biomass, so efforts are continuing to be focused on a chemical pre treatment. However, this research may provide the information which could be used in the future to create a more efficient grinding system which closely mimics the cow.
The process of cellulose hydrolysis is made possible by enzymes produced by anaerobic bacteria. In cows these vital bacteria are located in a large organ called the rumen where the chewed plant fibre can remain for up to 72 hours(Weimer 2009). This gives the bacteria in the rumen plenty of time to properly digest the treated plant matter. In the low-no oxygen conditions, fermentation occurs and the main products are volatile fatty acids(VFA), which the cow absorbs through its gut wall(Weimer 2009). The cellulose is degraded faster depending on the available surface area. Plant cell walls are composed of many different components and yet almost every single type of enzyme required to digest the material can be produced by at least one of the bacterial species found in the rumen. In contrast, artificial systems lack this diversity of microflora, and cannot digest plant matter as thoroughly as ruminants.
Perhaps the most important focus of this study was the examination of utilizing the fermentation by products other than ethanol as alternative energy sources. Two of the major by products produced by the fermentation process are methane and VFAs. Methane, which is excreted as gas by ruminants, could be captured in CBP systems and used as an alternate fuel source. VFAs on the other hand have a low volatility, but have a large amount of stored energy therefore have a potential as another energy source. Most systems currently focus on primarily ethanol production however, the addition of these by products could contribute enormously to the biomass energy yield.
Improvements on current CBP systems need to be made before this process becomes a viable source of ethanol. Current research provides a valuable insight regarding the direction to advance this technology. Equally important, the effort towards developing this technology also presents alternatives for waste management. For industries where high cellulose biomass is produced as waste such as agriculture, forestry or even maintenance of green spaces the advancement of CBP systems represents a potentially effective and even beneficial waste management strategy other than composting.
References
Weimer J. Paul, Russell B. James, & Muck E. Richard. (2009). Lessons from the cow: What the ruminant animal can teach us about consolidated bioprocessing of cellulosic biomass. [Lessons from the cow: What the ruminant animal can teach us about consolidated bioprocessing of cellulosic biomass] Bioresource Technology, 100(21), 5323-5331.
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