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Text and/or other creative content from this version of Sewage treatment was copied or moved into Sewage sludge treatment with this edit on 14 January 2015. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
The contents of the Sewage waste energy page were merged into Sewage sludge treatment. For the contribution history and old versions of the redirected page, please see its history; for the discussion at that location, see its talk page. |
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This article is written in American English, which has its own spelling conventions (color, defense, traveled) and some terms that are used in it may be different or absent from other varieties of English. According to the relevant style guide, this should not be changed without broad consensus. |
I think there needs to be a distinction made between biosolids and sludge. In an activated sludge process, the solids wasted out of the process are biosolids, the colonies of bacteria that eat waste matter). In a standard process with primary and secondary clarification, the resulting solids are literally sludge, whatever settles out is what you get.
With both processes, the biosolids and sludges are usually digested, anaerobically or aerobically. This is to reduce VOC content and also further the breakdown -or- digestion of organic matter. Digested biosolids from an activated sludge process are (usually) 12-15 days old, and are nothing but nutrients (phosphorus, nitrogen, ammonia, zinc, potassium, sulphur, manganese, magnesium, iron, copper, calcium, and a host of other yummy ingredients, including trace amounts of heavy metals and other pollutants). The quality and constituents of digested biosolids largely depends of the community the wastewater was collected from. For example, in a residential suburb, you may derive a very high quality biosolids that can easily be qualified for land application, but in a heavy industrial and urban community, your biosolids may contain much higher concentrations of chemicals and heavy metals, disqualifying their use as a fertilizer. The level of industrial pre-treatment also plays a large role in the quality of biosolids.
Also, a reason as to why some plants use anaerobic digestion and aerobic digestion needs to be made. For example, the capital cost of an anaerobic system is vastly greater than the cost of an aerobic system, but in the long term, the anaerobic system is more cost efficient. Aerobic systems require air pumped into them, needing power hungry blowers.
After digestion I think there needs to be more descriptions of the dewatering processes, such as:
Sludge Drying Beds Drying beds consist of long skinny concrete troughs filled with sand, and have an underdrain system. Sludge is allowed to fill the bed, and the water slowly drains through the sand, leaving the solids on top. The sludge may be left to air dry, sometimes for days, resulting in a solid that can be ~80% solids or higher. The purpose of the troughs being skinny is so that a front-end loader drive down the trough and scoop up the dried sludge, leaving the sand intact for the next batch. The tires of the loader sit on the very short concrete walls between the troughs. Drying beds are a slow dewatering process, and are perfect for plants processing less than 4MGD.
Belt Filter Press A Belt Filter Press is a carryover from the paper pulp industry. basically, it is a machine that has two belt loops that come together at one point, squeezing the water from the sludge. The solids remain between the belts and are scraped off, usually onto a conveyor. A press feature three main zones, the gravity zone, where the sludge is dropped onto the belt, and a majority of the water is drained via gravity through the belt. The shear zone, where the two belts come together and usually the initial drum that the belts travel around after the gravity zone. A lot of water is squeezed out here. Next is the pressure zone where the belts travel through a series of rollers, placing the belts under extreme pressure. This forces out the last amount of water. Belt Filter Presses are the workhorses of the dewatering section of most plants because of their ease of use, year round ability to dewater, and relatively low power consumption. The dewatered "cake" scraped off the belts is usually a wet 10% to spongy 18% solids, dry enough to haul in a dump truck.
Plate Filter Press Similar to a Belt Filter Press, except higher pressures can be obtained and thus, a drier cake in the 25-35% range. This is a slower process than the Belt Filter Press as the Plate Filter Press cannot continually process biosolids. The plate filters must be filled, squeezed together then unloaded.
Centrifuge A centrifuge is also a carryover, but from multiple industries (mainly food!) and tailored for sludge. basically, there is a large spinning drum, which may reach speeds as high as 20k RPM. Inside, there is a screw which turns at a slightly lower speed than the drum, pushing the driest solids to one end for discharge, and the liquid flows out the drum into the casing for dishcharge. Centrifuges can handle higher flow rates than comparable Belt Filter Presses, and also have drier cake, usually a spongy 18% to crumbly 26-40% solids. Centrifuges consume much more power than a belt filter press, but the savings are seen in lowered hauling costs.
Liquid Usually only in the smallest plants, sludge is hauled by tanker truck to another facility for dewatering, or some other direct use.
And even after de-watering, you have the disposal methods.
Landfill Many plants dispose of their de-watered sludge in sanitary landfills (in the U.S.). This option does have its costs, but sometimes there is no other alternative.
Land Application Depending on the quality of sludge, the dewatered sludge or biosolids can be used as a fertilizer on crops not intended for human consumption. This is by far the cheapest option, as most municipalites give it away to farmers and some even spread it themselves on the farmers fields at no charge. In the U.S. biosolids must meet "Class B" criteria for land application, which has to do with the levels of contaminates in the biosolids.
Deep Well Injection Rarely practiced, liquid sludge may be injected deep into the earth.
Given away or sold to consumers For lawn and garden use. Very stringently drawn rules and regulations govern this practice, ans the only biosolids qualified for this are "Class A" and have had their pathogenic content reduced to near nothing. "Class A" biosolids are made by cooking the "Class B" biosolids cake from the dewatering process. This is accomplished trhough a variety of means, mainly gas-fired rotating drum ovens, microwaves, and sunlight. The prohibitive cost of this makes it unattainable by most municipalities.
Ocean Dumping This practice is now illegal in the U.S. and U.S. waters, not sure about the world.
Incineration Fairly expensive because of the fuel requirement, but incineration reduces biosolids down to about 10% of its original mass and volume, making the ash very cheap to landfill. This is an option when the sludge does not meet the quality requirements for land application or even direct landfilling.
Please feel free to tear this apart. Thanks JAK83 17:37, 5 February 2007 (UTC)
The section on disposal should be moved to the sewage sludge page because this article is about treatment, not about disposal. However, when looking at it more closely, one can see that it doesn't actually talk about disposal but also about treatment... Therefore it needs to be integrated into the body of the article, or a different header chosen. I think some of it is dublication, was probably copied from another article. Could someone tidy this up? EvM-Susana ( talk) 10:38, 14 January 2015 (UTC)
A persistent problem with broad concept Wikipedia articles are recurring efforts by special interest editors to inappropriately emphasize emerging technologies. Neutrality requires coverage to accurately reflect present and historical trends. The emerging technologies section of this article is intended to recognize and provide a brief mention of promising technologies; and while there will not be room for a full description of all of them, descriptions of a few broadly successful technologies will ultimately be integrated into the main article as their use becomes widespread. To avoid inappropriately weighting this article with descriptions of little-used treatment methods, I propose to restrict the emerging technologies section to a brief sentence describing those technologies with notability established by a separate article.
In the absence of an alternative organization proposal with appropriately verified notability precedence, I suggest a single alphabetical bullet listing of the emerging technologies by article name to avoid an inappropriately long table of contents unduly weighted toward emerging technologies. I suggest emerging technologies might be considered those applied to less than ten percent of sludge volume and at fewer than ten percent of sludge treatment facilities. Thewellman ( talk) 01:46, 19 February 2015 (UTC)
Hello, Katana0182 I would like to speak to you and others about how we want to deal with the "biosolids" issue in this article. I am not really in agreement with your recent changes (last paragraph of the lead). The citation for the term biosolids that I had given is the well respected textbook by Metcalf and Eddy. You have only provide one reference from 2002, yet you spoke of "studies". I also don't like the term "sewage treatment industry" - there is no industry, it is simply local governments etc. But I know the whole debate in the US is different than e.g. in Europe. Much more heated over there... You only need to look on the page on sewage sludge and its talk page to see the whole level of controversy there.... I suggest that we tone done the sentences about biosolids, that we move it to further down in the article (take it out of the lead), and generally keep it very short and rather refer to the article on sewage sludge - so that we don't have two pages that explain the issue with biosolids but only one, i.e. the page on sewage sludge. But I think at least once in this article the term "biosolids" needs to be mentioned because of literature (not just the "propaganda literature" but also normal textbooks, like Metcalf and Eddy) use this term. EvM-Susana ( talk) 21:24, 23 April 2015 (UTC)
It was suggested above to have a separate biosolids page. At the moment, biosolids redirects to sewage sludge. The curent page on sewage sludge is an absolute mess. It contains the word biosolids on about 80 occasions - so I think that IS a biosolids page already, full of descriptions of the controversies... So I don't see how a separate biosolids page could help - unless we actually rename the sewage sludge page to "biosolids" and create a new sewage sludge page which is purely focussed on the technical aspects. At the moment, I have a similar paragraph about biosolids at the end of the lead section of the "sewage sludge" article but I am wondering if either the same wording that we have used here now should be copied across, or if a terminology section would also be good there. - I guess the whole debate about biosolids fits better on the page of sewage sludge than on the page of sewage sludge treatment - at least that's how it's set up at the moment. EvM-Susana ( talk) 09:33, 24 April 2015 (UTC)
Can we tidy these references up? I don't like the split between refs and the further reading section. Also, are there really no good references since the 1970s? I find that very hard to believe. JMWt ( talk) 08:21, 24 April 2015 (UTC)
This article needs a paragraph or new section/sub-section describing thermal hydrolysis, a process employed at some sewage treatment plants around the world. I'm not sure where in the article to add this. Suggestions? Moreau1 ( talk) 04:24, 20 August 2016 (UTC)
I've just come across the new article on sewage waste energy. I don't think it is very good and the term itself is also not well established. I suggest to merge any worthwhile content to here, as it really is about sewage sludge treatment with energy as a side product. EvMsmile ( talk) 20:55, 3 January 2017 (UTC)
I have revereted a recent addion about CECs by AndrewDrouin for severla reasons. Firts let me state clearly that I too have significant concernes about organic micro-pollutants in the environment and the risks that they pose to human and animal health and growth and their potential to seriously adversly affect the environment. However, I take issue with the tone of the addition and the quality of the references.
Surely there must be quality references out there from the UN, the EPA or the Environment Agency ? Velella Velella Talk 03:38, 10 February 2018 (UTC)
My name is Andrew Drouin, I have twice edited the "Controversy" section of the Sewage Sludge Treatment page - only to twice have it reverted back to it's former, plainly soft-pitch position.
I've spent the past five years studying this topic, and am about as knowledgeable on it as anyone else on this site.
I provided solid, peer-reviewed scientific articles from the USGS and the EPA to back up my positions, only to have them frankly dismissed by the subsequent re-editors.
For example, the first edit contained these links:
https://toxics.usgs.gov/highlights/biosolids.html https://www.epa.gov/sites/production/files/2016-11/documents/8-jay_gan.pdf
The second edit, which I didn't save a copy of (but can easily recreate) contained additional peer-reviewed, US University and US Gov. studies - which were also offhandedly dismissed...
I'm Canadian, not an American as alluded to above - the reason that I cite US documents is that the Americans have conducted a great deal more scientific study on the topic than we have in Canada.
My recent re-edit contained a list of organizations that advocate for a review of how solid waste is managed - only to have the editor offhandedly dismiss it as "a list of supposed concerned citizens group worldwide (unreferenced)" A minute or two of Google searching would have shown the editor that all of the groups in the list are legitimate organizations, and all exist - not "supposed"...
What ever happened to the addition of "[citation needed]" subedits to an editor's post? As opposed to wholesale dismissal / deletion?
The type of hatchet-editing that my submissions have been subject to is biased and reeks of industry handiwork.
How can a category be titled "Controversies" when it does not present any actual controversy aside from an allusion to propaganda ?
Also, no mention is made on the page of Gasification and Pyrolysis technologies, nor the scientifically accurate phrase "Contaminates of Emerging Concern" which details the main controversy with the contents of sewage sludge. These, in my opinion, are critical oversights. — Preceding unsigned comment added by AndrewDrouin ( talk • contribs) 20:21, 10 February 2018 (UTC)
. A more encyclopedia-appropriate version might read something likeAs sludge ("biosolids") are routinely spread throughout communities by municipal governments, spread on school-grounds and parks, sold to landscapers and even provided to citizens, many of whom use it in gardens to grow vegetables. These practices provide ample opportunities for minute quantities of these countless toxins to enter the food-chain and / or directly interface with humans and animals.
Even that isn't particularly good, but it's at least not an obvious attempt to slant the debate.Municipal governments distribute sewage sludge to communities citation needed. It is spread on schoolgrounds and parks citation needed, sold to landscapers citation needed, and provided to citizens, who may use it to grow vegetables. citation needed The toxins may [even this is a weasel word] thereby enter the food chain or be consumed by people and animals.
This article is rated C-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||||||||||||
|
Text and/or other creative content from this version of Sewage treatment was copied or moved into Sewage sludge treatment with this edit on 14 January 2015. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
The contents of the Sewage waste energy page were merged into Sewage sludge treatment. For the contribution history and old versions of the redirected page, please see its history; for the discussion at that location, see its talk page. |
This is the
talk page for discussing improvements to the
Sewage sludge treatment article. This is not a forum for general discussion of the article's subject. |
Article policies
|
Find sources: Google ( books · news · scholar · free images · WP refs) · FENS · JSTOR · TWL |
This article is written in American English, which has its own spelling conventions (color, defense, traveled) and some terms that are used in it may be different or absent from other varieties of English. According to the relevant style guide, this should not be changed without broad consensus. |
I think there needs to be a distinction made between biosolids and sludge. In an activated sludge process, the solids wasted out of the process are biosolids, the colonies of bacteria that eat waste matter). In a standard process with primary and secondary clarification, the resulting solids are literally sludge, whatever settles out is what you get.
With both processes, the biosolids and sludges are usually digested, anaerobically or aerobically. This is to reduce VOC content and also further the breakdown -or- digestion of organic matter. Digested biosolids from an activated sludge process are (usually) 12-15 days old, and are nothing but nutrients (phosphorus, nitrogen, ammonia, zinc, potassium, sulphur, manganese, magnesium, iron, copper, calcium, and a host of other yummy ingredients, including trace amounts of heavy metals and other pollutants). The quality and constituents of digested biosolids largely depends of the community the wastewater was collected from. For example, in a residential suburb, you may derive a very high quality biosolids that can easily be qualified for land application, but in a heavy industrial and urban community, your biosolids may contain much higher concentrations of chemicals and heavy metals, disqualifying their use as a fertilizer. The level of industrial pre-treatment also plays a large role in the quality of biosolids.
Also, a reason as to why some plants use anaerobic digestion and aerobic digestion needs to be made. For example, the capital cost of an anaerobic system is vastly greater than the cost of an aerobic system, but in the long term, the anaerobic system is more cost efficient. Aerobic systems require air pumped into them, needing power hungry blowers.
After digestion I think there needs to be more descriptions of the dewatering processes, such as:
Sludge Drying Beds Drying beds consist of long skinny concrete troughs filled with sand, and have an underdrain system. Sludge is allowed to fill the bed, and the water slowly drains through the sand, leaving the solids on top. The sludge may be left to air dry, sometimes for days, resulting in a solid that can be ~80% solids or higher. The purpose of the troughs being skinny is so that a front-end loader drive down the trough and scoop up the dried sludge, leaving the sand intact for the next batch. The tires of the loader sit on the very short concrete walls between the troughs. Drying beds are a slow dewatering process, and are perfect for plants processing less than 4MGD.
Belt Filter Press A Belt Filter Press is a carryover from the paper pulp industry. basically, it is a machine that has two belt loops that come together at one point, squeezing the water from the sludge. The solids remain between the belts and are scraped off, usually onto a conveyor. A press feature three main zones, the gravity zone, where the sludge is dropped onto the belt, and a majority of the water is drained via gravity through the belt. The shear zone, where the two belts come together and usually the initial drum that the belts travel around after the gravity zone. A lot of water is squeezed out here. Next is the pressure zone where the belts travel through a series of rollers, placing the belts under extreme pressure. This forces out the last amount of water. Belt Filter Presses are the workhorses of the dewatering section of most plants because of their ease of use, year round ability to dewater, and relatively low power consumption. The dewatered "cake" scraped off the belts is usually a wet 10% to spongy 18% solids, dry enough to haul in a dump truck.
Plate Filter Press Similar to a Belt Filter Press, except higher pressures can be obtained and thus, a drier cake in the 25-35% range. This is a slower process than the Belt Filter Press as the Plate Filter Press cannot continually process biosolids. The plate filters must be filled, squeezed together then unloaded.
Centrifuge A centrifuge is also a carryover, but from multiple industries (mainly food!) and tailored for sludge. basically, there is a large spinning drum, which may reach speeds as high as 20k RPM. Inside, there is a screw which turns at a slightly lower speed than the drum, pushing the driest solids to one end for discharge, and the liquid flows out the drum into the casing for dishcharge. Centrifuges can handle higher flow rates than comparable Belt Filter Presses, and also have drier cake, usually a spongy 18% to crumbly 26-40% solids. Centrifuges consume much more power than a belt filter press, but the savings are seen in lowered hauling costs.
Liquid Usually only in the smallest plants, sludge is hauled by tanker truck to another facility for dewatering, or some other direct use.
And even after de-watering, you have the disposal methods.
Landfill Many plants dispose of their de-watered sludge in sanitary landfills (in the U.S.). This option does have its costs, but sometimes there is no other alternative.
Land Application Depending on the quality of sludge, the dewatered sludge or biosolids can be used as a fertilizer on crops not intended for human consumption. This is by far the cheapest option, as most municipalites give it away to farmers and some even spread it themselves on the farmers fields at no charge. In the U.S. biosolids must meet "Class B" criteria for land application, which has to do with the levels of contaminates in the biosolids.
Deep Well Injection Rarely practiced, liquid sludge may be injected deep into the earth.
Given away or sold to consumers For lawn and garden use. Very stringently drawn rules and regulations govern this practice, ans the only biosolids qualified for this are "Class A" and have had their pathogenic content reduced to near nothing. "Class A" biosolids are made by cooking the "Class B" biosolids cake from the dewatering process. This is accomplished trhough a variety of means, mainly gas-fired rotating drum ovens, microwaves, and sunlight. The prohibitive cost of this makes it unattainable by most municipalities.
Ocean Dumping This practice is now illegal in the U.S. and U.S. waters, not sure about the world.
Incineration Fairly expensive because of the fuel requirement, but incineration reduces biosolids down to about 10% of its original mass and volume, making the ash very cheap to landfill. This is an option when the sludge does not meet the quality requirements for land application or even direct landfilling.
Please feel free to tear this apart. Thanks JAK83 17:37, 5 February 2007 (UTC)
The section on disposal should be moved to the sewage sludge page because this article is about treatment, not about disposal. However, when looking at it more closely, one can see that it doesn't actually talk about disposal but also about treatment... Therefore it needs to be integrated into the body of the article, or a different header chosen. I think some of it is dublication, was probably copied from another article. Could someone tidy this up? EvM-Susana ( talk) 10:38, 14 January 2015 (UTC)
A persistent problem with broad concept Wikipedia articles are recurring efforts by special interest editors to inappropriately emphasize emerging technologies. Neutrality requires coverage to accurately reflect present and historical trends. The emerging technologies section of this article is intended to recognize and provide a brief mention of promising technologies; and while there will not be room for a full description of all of them, descriptions of a few broadly successful technologies will ultimately be integrated into the main article as their use becomes widespread. To avoid inappropriately weighting this article with descriptions of little-used treatment methods, I propose to restrict the emerging technologies section to a brief sentence describing those technologies with notability established by a separate article.
In the absence of an alternative organization proposal with appropriately verified notability precedence, I suggest a single alphabetical bullet listing of the emerging technologies by article name to avoid an inappropriately long table of contents unduly weighted toward emerging technologies. I suggest emerging technologies might be considered those applied to less than ten percent of sludge volume and at fewer than ten percent of sludge treatment facilities. Thewellman ( talk) 01:46, 19 February 2015 (UTC)
Hello, Katana0182 I would like to speak to you and others about how we want to deal with the "biosolids" issue in this article. I am not really in agreement with your recent changes (last paragraph of the lead). The citation for the term biosolids that I had given is the well respected textbook by Metcalf and Eddy. You have only provide one reference from 2002, yet you spoke of "studies". I also don't like the term "sewage treatment industry" - there is no industry, it is simply local governments etc. But I know the whole debate in the US is different than e.g. in Europe. Much more heated over there... You only need to look on the page on sewage sludge and its talk page to see the whole level of controversy there.... I suggest that we tone done the sentences about biosolids, that we move it to further down in the article (take it out of the lead), and generally keep it very short and rather refer to the article on sewage sludge - so that we don't have two pages that explain the issue with biosolids but only one, i.e. the page on sewage sludge. But I think at least once in this article the term "biosolids" needs to be mentioned because of literature (not just the "propaganda literature" but also normal textbooks, like Metcalf and Eddy) use this term. EvM-Susana ( talk) 21:24, 23 April 2015 (UTC)
It was suggested above to have a separate biosolids page. At the moment, biosolids redirects to sewage sludge. The curent page on sewage sludge is an absolute mess. It contains the word biosolids on about 80 occasions - so I think that IS a biosolids page already, full of descriptions of the controversies... So I don't see how a separate biosolids page could help - unless we actually rename the sewage sludge page to "biosolids" and create a new sewage sludge page which is purely focussed on the technical aspects. At the moment, I have a similar paragraph about biosolids at the end of the lead section of the "sewage sludge" article but I am wondering if either the same wording that we have used here now should be copied across, or if a terminology section would also be good there. - I guess the whole debate about biosolids fits better on the page of sewage sludge than on the page of sewage sludge treatment - at least that's how it's set up at the moment. EvM-Susana ( talk) 09:33, 24 April 2015 (UTC)
Can we tidy these references up? I don't like the split between refs and the further reading section. Also, are there really no good references since the 1970s? I find that very hard to believe. JMWt ( talk) 08:21, 24 April 2015 (UTC)
This article needs a paragraph or new section/sub-section describing thermal hydrolysis, a process employed at some sewage treatment plants around the world. I'm not sure where in the article to add this. Suggestions? Moreau1 ( talk) 04:24, 20 August 2016 (UTC)
I've just come across the new article on sewage waste energy. I don't think it is very good and the term itself is also not well established. I suggest to merge any worthwhile content to here, as it really is about sewage sludge treatment with energy as a side product. EvMsmile ( talk) 20:55, 3 January 2017 (UTC)
I have revereted a recent addion about CECs by AndrewDrouin for severla reasons. Firts let me state clearly that I too have significant concernes about organic micro-pollutants in the environment and the risks that they pose to human and animal health and growth and their potential to seriously adversly affect the environment. However, I take issue with the tone of the addition and the quality of the references.
Surely there must be quality references out there from the UN, the EPA or the Environment Agency ? Velella Velella Talk 03:38, 10 February 2018 (UTC)
My name is Andrew Drouin, I have twice edited the "Controversy" section of the Sewage Sludge Treatment page - only to twice have it reverted back to it's former, plainly soft-pitch position.
I've spent the past five years studying this topic, and am about as knowledgeable on it as anyone else on this site.
I provided solid, peer-reviewed scientific articles from the USGS and the EPA to back up my positions, only to have them frankly dismissed by the subsequent re-editors.
For example, the first edit contained these links:
https://toxics.usgs.gov/highlights/biosolids.html https://www.epa.gov/sites/production/files/2016-11/documents/8-jay_gan.pdf
The second edit, which I didn't save a copy of (but can easily recreate) contained additional peer-reviewed, US University and US Gov. studies - which were also offhandedly dismissed...
I'm Canadian, not an American as alluded to above - the reason that I cite US documents is that the Americans have conducted a great deal more scientific study on the topic than we have in Canada.
My recent re-edit contained a list of organizations that advocate for a review of how solid waste is managed - only to have the editor offhandedly dismiss it as "a list of supposed concerned citizens group worldwide (unreferenced)" A minute or two of Google searching would have shown the editor that all of the groups in the list are legitimate organizations, and all exist - not "supposed"...
What ever happened to the addition of "[citation needed]" subedits to an editor's post? As opposed to wholesale dismissal / deletion?
The type of hatchet-editing that my submissions have been subject to is biased and reeks of industry handiwork.
How can a category be titled "Controversies" when it does not present any actual controversy aside from an allusion to propaganda ?
Also, no mention is made on the page of Gasification and Pyrolysis technologies, nor the scientifically accurate phrase "Contaminates of Emerging Concern" which details the main controversy with the contents of sewage sludge. These, in my opinion, are critical oversights. — Preceding unsigned comment added by AndrewDrouin ( talk • contribs) 20:21, 10 February 2018 (UTC)
. A more encyclopedia-appropriate version might read something likeAs sludge ("biosolids") are routinely spread throughout communities by municipal governments, spread on school-grounds and parks, sold to landscapers and even provided to citizens, many of whom use it in gardens to grow vegetables. These practices provide ample opportunities for minute quantities of these countless toxins to enter the food-chain and / or directly interface with humans and animals.
Even that isn't particularly good, but it's at least not an obvious attempt to slant the debate.Municipal governments distribute sewage sludge to communities citation needed. It is spread on schoolgrounds and parks citation needed, sold to landscapers citation needed, and provided to citizens, who may use it to grow vegetables. citation needed The toxins may [even this is a weasel word] thereby enter the food chain or be consumed by people and animals.