Saturday, 13 June 2020

Recent research on Microplastics & Sewage Sludge / Biosolids

Recent Publications on Microplastics and Sewage Sludge / Biosolids

1. "Long-term assessment of nanoplastic particle and microplastic fiber flux through a pilot wastewater treatment plant using metal-doped plastics" June/2020

"nanoplastics and microplastics were tracked through a wastewater treatment plant. Over 98% of plastic particles sequestered into biosolids."
"As the majority of particulate plastic is retained in the sludge, the burden of plastic pollution would shift with sewage sludge application to soil"
" the material that may enter the environment in those locations where sludge is still used as an amendment to agricultural soils."
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2. "Plastic Pollution in Soils: Governance Approaches to Foster Soil Health and Closed Nutrient Cycles " May/2020

"Plastic pollution in soils pose a major threat to soil health and soil fertility, to food security and human health. The highest source of microplastic input into the soil is the direct application of sewage sludge for agricultural fertilization …It is, therefore, to be welcomed—also because of other pollutants in sewage sludge—that in Germany, the direct soil related spreading of sewage sludge will be largely prohibited in the future by the respective command‐and‐control legislation"
 "the potentially high contamination of sewage sludge with a wide variety of pollutants and microplastic particles has already led to an increased focus on indirect, thermal sewage sludge recycling in Germany and the EU. The direct recovery of essential nutrients such as phosphorus from sewage sludge by specific (preferably energy‐efficient) recycling processes is, therefore, seen as future‐oriented. This would also lead to reduced plastic pollution of agricultural soils"

3. "High microplastic levels in soil can halve worm fertility" Oct/2019

“Given we know that microplastics are accumulating in our soils and can stay there for a very long time, we clearly need to understand the effect they are having on our soil ecosystems and the long-term risks they may pose.”
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4. "Municipal sewage sludge as a source of microplastics in the environment" April/2020

"Sewage sludge serves as a source of MPs to the environment, predominantly through the application of biosolids on agricultural lands ... land applied biosolids presents a dangerous opportunity
 for large amounts of Microplastics to enter the environment and accumulate up the food chain"
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5. "Microplastics and pollutants in biosolids have contaminated agricultural soils: An analytical study and a proposal to cease the use of biosolids in farmlands" April/2020

"This study examines the detrimental effects of the existing methods for recycling biosolids. Such methods produce negative consequences in terms of contaminating farmlands with microplastics,
micropollutants, chemicals and pathogens. In addition the negative effects of stockpiling biosolids is likewise be examined."
"The agricultural applications of biosolids produce known biological and health concerns, and contamination of farmland through the accumulation of different types of pollutants is occurring despite governing authorities implementing restrictions to lessen their environmental burden."
"Furthermore emerging pollutants, such as microplastics, nanoplastics, pharmaceutical and industrial chemicals, are leading to further contamination of agricultural soils."
"... although guidelines address known pollutants and place ceiling concentrations upon them in order to mitigate their consequences, emerging pollutants, such as pharmaceuticals and chemicals used in the production of household items, have no such limits placed upon them. Thus they are uninhibited from accumulating in the soils on which they are applied."
"Environmental impact of biosolids stockpiles - while stockpiles remain untouched, they contribute to the wastewater treatment industry's damaging carbon footprint … they present a significant source of greenhouse gas emissions worldwide … and may also be responsible for polluting waterways, thus affecting the aquatic environment in addition to polluting the atmosphere."
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6. "More than 1,200 tonnes of microplastics are dumped into Aussie farmland every year from wastewater sludge" June/2020

"Biosolids have a cocktail of nasty chemicals. It’s not just plastic – many industrial additives and chemicals have been found in wastewater and biosolids. This means they may accumulate in soils and affect the equilibrium of biological systems, with negative effects on plant growth. For example, researchers have found pharmaceutical chemicals in particular can reduce plant growth and inhibit root elongation"
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7. "Microplastic in soil–current status in Europe with special focus on method tests with Austrian samples" April/2020

"In wastewater treatment plants 90% of the microplastic–fibers of textiles, particles of cosmetic and hygiene products are transferred into sewage sludge and remains there independent from the treatment procedures"
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8. "Transfer and transport of microplastics from biosolids to agricultural soils and the wider environment" July/2020

"This study reinforces the hypothesis that biosolids are a significant source of MicroPlastics to agrosystems … long-term accumulation of MP fibers in soils on plant growth and soil biota could pose a risk to agricultural sustainability"

9. "Microplastics: from origin to impacts" March/2020

"The large proportion of MPs removed during wastewater treatment may be retained in sewage sludge. Depending on the treatment process applied at wastewater treatment plants and during subsequent treatment, the number of particles in sludge has been seen to vary. Following treatment, a large proportion of sludge becomes biosolids, transferred to terrestrial ecosystems through land application and also landfilling. This presents a further problem; in repurposing sludge, MPs are directly released to the terrestrial environment. Further research into the consequences of sludge application and terrestrial transfer and fate of MPs are urgently required"
"Sewage sludge has been identified as a point source for the release of MPs on land ... the presence of these particles in terrestrial ecosystems may facilitate the transport of organic contaminants in soil … If MPs persist and accumulate in soils, there may be significant direct impacts on agriculture and the functioning and biodiversity of terrestrial ecosystems"

10. "An Overlooked Entry Pathway of Microplastics into Agricultural Soils from Application of Sludge-Based Fertilizers" March/2020

"The quantity of Microplastics in soils exhibited a close correlation with application rate of sludge-based fertilizers... sludge composts may act as a vehicle of MPs into soils, enter soil biota and in turn influence the spread of MPs in the environment"
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11. "A scientific perspective on microplastics in nature and society" February/2020

"Plastic and other particulate matter are removed from the liquid waste stream via sedimentation and end up in sewage sludge. Because sewage sludge is used as a fertilizer, microplastics can thereafter be spread on agricultural lands and thus re-emitted to terrestrial ecosystems"
"Transport of plastic particles to air derived from dried sewage sludge onto agricultural soils has also been postulated, supported by the finding that synthetic clothing fibres persisted in soils up to 15 years after being applied"
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12. "Microplastics making their way to British farms in human sewage fertiliser" Feb/2020

"It warns microplastics could harm soil ecosystems or crops either directly or through hormone-disrupting substances, and contain chemicals that could be released slowly as they break down over hundreds of years"
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13. Government of Canada - "Draft science assessment of plastic pollution"  Jan/2020 - 

"It is estimated that 99% of microplastics are removed from the influent but are retained in sewage sludge ... Microplastics can therefore enter terrestrial environments through the application and use of sewage sludge as fertilizers for agriculture or landscaping purposes"
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14. "Mapping microplastics in sludge" April/2018

" it was estimated that over 500 billion microplastics are released into the environment via sewage sludge application each year, to agricultural soils, green areas and soil producers. This likely represents a significant source of microplastics to terrestrial and marine systems."
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Microbiologist, Dr. Richard Honour - 

Plastics in Sewage Sludge
Researchers have also looked into how polyester microfibers may be affecting microorganisms in the soil, especially since sewage sludge is loaded with microfibers. They found that the microplastics did, indeed, lead to changes in the soil, including altering the bulk density, water-holding capacity and microbial activity.
Writing in the journal Environmental Science & Technology, researchers noted that wastewater treatment plants act as receptors for the "cumulative loading of microplastics." The solids and liquids are separated using a settlement process, which results in the majority of microplastics (MP) ending up in sewage sludge.
Different methods of treatment affected the end number of particles found in the sludge, but the study found microplastic amounts ranging from 4,196 to 15,385 particles kg–1 (dry weight) in sludge samples.
The researchers noted, "This study highlights the potential for sewage sludge treatment processes to affect the risk of MP pollution prior to land spreading and may have implications for legislation governing the application of biosolids to agricultural land."
Microplastics may act like sponges for contaminants including heavy metals, persistent organic pollutants, polychlorinated biphenyls (PCBs) or pathogens, for instance, and may cause harm on a cellular or subcellular level,  raising serious questions about the risks of exposing soil to them.
Indeed, wastewater treatment plants are efficient at removing microplastics from sewage, but they become trapped in the sludge. This helps keep them out of waterways, unless they're applied to agricultural soils (which may run off into waterways).
When researchers evaluated 31 fields that had applications of sewage sludge, microplastics were found in the samples at levels ranging from 18 to 41 particles g−1, with a median of 34 particles g−1.16 What's more, the microplastic levels increased on fields with higher rates of sludge applications.
"Our results indicate that microplastic counts increase over time where successive sludge applications are performed," the researchers adding, "Sludge is proposed as a primal driver of soil microplastic pollution."


Update for June 24th

Source, occurrence, migration and potential environmental risk of microplastics in sewage sludge and during sludge amendment to soil”

“Microplastics can adsorb heavy metals, organic pollutants, antibiotics and ARGs, and the mechanism of adsorption mainly relies on physical interaction. MPs that are aged by UV irradiation and weathering will adsorb more pollutants because of the increased specific surface area and oxygen-containing surface groups. Soil amendment with sludge is an important pathway of sludge recycling, but the MPs input with the sludge amendment will accumulate in the soil. The MPs will influence the physicochemical properties of soil such as soluble substance concentration, bulk density and hydrodynamics, and may accumulate in plants. The combination of MPs and the pollutants they adsorb might increase the risk of soil pollution. The desorption and migration of pollutants orginally adsorbed by MPs make them become vectors to transfer pollutants, which increases the risks of spreading heavy metals, organic pollutants, antibiotics and ARGs in soils”

Update for June 25

""Most research has so far focused on agricultural systems, which are expected to contain the largest amount of microplastics because of input pathways including sewage sludge""

Update for June 30th

Our fruits and veggies are sucking up microplastics through their roots

"new research has shown that microplastics can penetrate the roots of crops, traveling up the plant into the parts we eat"


Micro- and nano-plastics in edible fruit and vegetables. The first diet risks assessment for the general population

"Agricultural systems are the final recipients of a number of several pollutants and nanomaterials, including microplastics (MPs), with effects relatively unknown. The general lack of understanding regarding nanomaterial fate and effects in agricultural systems is troublesome given the potential for food chain contamination and for an uncharacterized pathway of human exposure"
"Micro- and nano-plastics in edible fruit and vegetables. The first diet risks assessment for the general population"


Update for August 8th

Microplastics in soils: a review of possible sources, analytical methods and ecological impacts

"The annual amount of MPs that enter soils through the use of sewage sludge on arable lands is larger than that released into the oceans. Furthermore, sewage sludge discharged into agricultural soils is estimated to be one of the largest sources of MPs entering the environment. Applying sewage sludge as a fertilizer to the soil environment leads to pollution by synthetic fibers, which are mobile and persistent."

From the article ... "Microplastics as vectors for pollutants and additives in soils" 

“after plastics enter the soil environment, they release toxic plastic additives (plasticizers, retardants, antioxidants and photostabilizers), which threaten ecosyste
ms and impact long‐term soil quality. Furthermore, the weathered surfaces of MPs can act as high‐capacity carriers by adhering microorganisms (pathogens) and other toxic pollutants (organic contaminants, heavy metals, pesticides, etc.) in the soil to them. Under certain conditions, the slow degradation process of plastics can release these adsorbed toxic chemicals back to the surrounding environment. Moreover, soil organisms can have access to high concentrations of MPs via ingestion; hence MPs are transported to the food chain and act as potential vectors that may carry pathogens and contaminants in soil systems. Therefore MPs, which act as vectors for these chemicals, move along with soil particles and not only threaten the aquatic environment but also the soil environment”


Update for August 17th

"Microplastics, especially polyethylene with high adsorption and desorption potentials may serve as a source and carrier to triclosan, and its amendment can change triclosan's environmental behavior and further risk in soil."

Update for August 26

Microplastics removal in wastewater treatment plants: a critical review

"reported that successive sludge application on agricultural fields resulted in microplastic accumulation over time. Microplastic content in sludge of the agricultural fields ranged from 18 000 to 41 000 particle per kg. It is expected that microplastics in soil enter the aquatic environment through surface runoff, irrigation or wind"
"The majority of plastics removed during sewage treatment are retained in sewage sludge ... Large numbers of plastic particles enter the terrestrial environment where sludge is reused for agriculture. More research is needed on the environmental fate and impact of plastics in sludge-amended soils, in particular where agricultural reuse of sewage sludge is common practice"


August 26th

Microplastics in Sewage Sludge -
Dr. Scott Coffin - "over time our agricultural soils may become toxic with the addition of these biosolids"
Microplastics in Sludge -starts around the 34 minute mark.

August 26th

Environmental fate and impacts of microplastics in soil ecosystems: Progress and perspective

 "we assessed the ecotoxicological consequences of microplastics contamination on soil ecosystems, including the effects on soil physiochemical properties, terrestrial plants, soil fauna, and soil microbes"


Are Agricultural Soils Dumps for Microplastics of Urban Origin?

"Based on new Microplastic emission estimates in industrialized countries, we suggest that widespread application of sewage sludge from municipal wastewater treatment plants (WWTPs) to farmlands is likely to represent a major input of MPs to agricultural soils, with unknown consequences for sustainability and food security."
" We expect that none of the common processing steps (e.g., drying, pasteurization, composting, etc.) to produce biosolids from WWTP sludge for agricultural use will remove the MP load."
"Reports are emerging about the occurrence and impacts of MPs in soil, both from breakdown of plastics and sludge additions. Reproduction of worms was recently shown to be impacted at MP exposure levels possibly representative of those in agricultural soils receiving sewage sludge application"
"MPs can potentially impact soil ecosystems, crops and livestock either directly or through the toxic and endocrine-disrupting substances added during plastics manufacturing."
"Studies assessing the scale of contamination of agricultural soils by MPs are notable for their absence while farm soils may arguably represent one of their largest environmental reservoirs."


Update September 2nd

Microplastic pollution devastating soil species, study finds

“We call for a reduction in the use of plastics and to avoid burying plastic wastes in soils, as this may bring adverse ecological consequences on soil communities and biogeochemical cycling in terrestrial ecosystems.”


Microplastics in farm soils: A growing concern

"Microplastics arrive on farms through processed sewage sludge used for fertilizer ... alarming potential impacts of this contamination on all aspects of agricultural systems from soil quality to human health"


Update - Sept. 8th

Inhibitory effect of microplastics on soil extracellular enzymatic activities by changing soil properties and direct adsorption

"Microplastics (MPs), as a new type of environmental pollutant, pose a serious threat to soil ecosystems ... MPs competed with soil microorganisms for physicochemical niches to reduce microbial activity and eventually, extracellular enzyme activity"

Microplastics In Farm Soils Have Adverse Effects On Wheat Crops

"Microplastics in soils have recently been linked to increased cadmium uptake and root damage in wheat plants ... microplastics were able to damage the roots of the wheat plants by clogging soil pores and preventing water uptake"

("The highest source of microplastic input into the soil is the direct application of sewage sludge for agricultural fertilization")

Microplastics Mitigation in Sewage Sludge through Pyrolysis: The Role of Pyrolysis Temperature

"Sewage sludge is an important source of introducing microplastics into the environment, and thus, effective mitigation of microplastics in the sludge is in urgent need ... Polyethylene and polypropylene, the two most abundant microplastics in sewage sludge, were entirely degraded when the pyrolysis temperature reached 450 °C"

The Persistence of Plastic

"With a roughly 95-99% removal efficiency, all but the tiniest microplastics are caught in the sludge, which is treated and turned into biosolids, and “predominantly used in land applications,” as fertilizer and soil amendments.
“So then it becomes a terrestrial pollution issue,” Geyer pointed out. “We just turned it into a different environmental pollution issue rather than having actually solved it.”

Synthetic microfiber emissions to land rival those to waterbodies and are growing

"terrestrial environments are emerging as an increasingly important initial compartment of microfiber emissions, which is due to improved access to WWTPs and the application of biosolids to terrestrial environments"

September 28 update

Adsorption of polyethylene microbeads and physiological effects on hydroponic maize

"Plastic bioaccumulation in the rhizosphere caused a significant decline in transpiration, nitrogen content, and growth. Our results indicate that plastic particles may accumulate in the rhizosphere, impairing water and nutrient uptake, and eventually reaching root eaters. "

November 17

Release of Plastics to Australian Land from Biosolids End-Use

"Plastics are contaminants of emerging concern that can enter the environment via land application of treated biosolids. Biosolids samples collected from 82 wastewater treatment plants ...Ninety nine percent of the samples contained plastics"


December 2020 update - 

Impacts of polyethylene microplastics on bioavailability and toxicity of metals in soil

"MPs increased the bioavailability of metals in the soil and the toxic effects to earthworms. These findings provide insights regarding the impacts of MPs on the bioavailability of metals and the combined toxic effects of these two kinds of pollutants on terrestrial animals"

Dec 17 2020

A probabilistic risk assessment of microplastics in soil ecosystems

"An agriculture practice that can be a significant source of microplastics to agricultural soil is the land application of biosolids ... This probabilistic assessment showed that microplastics could pose a considerable risk to soil biota. This assessment underscores the need for further data on the potential effect of environmentally-relevant concentrations and mixtures of microplastics on soil biota and the fate of microplastics in soil ecosystems ... This class of contaminant does not readily degrade (t1/2 ~100–1000 years), consequently, the concentration in soil will likely only increase, unless significant changes are made to the volume of use and/or waste management of plastic. A conclusion that can be made with certainty is that as the concentration of microplastics in soil rises, the potential risk to soil biota and soil function will rise"


Update - January 10 2021

Analysis of the polyester clothing value chain to identify key intervention points for sustainability

"Microfibers that are successfully removed from wastewater are retained in the sewage sludge. This means that 63,000–430,000 tons of microplastics are added to European farmlands every year via sludge applications"


Wastewater treatment alters microbial colonization of microplastics

"Sewage sludge is commonly applied to land in the U.S. , and there is no regulatory framework to assess or limit sludge microplastics. Thus, microplastics in sludge may be a concern for soil ecosystems"


"The highest scientifically proven source of microplastic input into the soil is the direct application
of sewage sludge for agricultural fertilisation" (Weithmann et al,2018)

"Microplastics in the soil can destroy the soil structure, reduce infiltration of rainwater and irrigation water, and negatively impact the water holding capacity of the soil" (Liu et al,2014)

" Microplastics can affect the diversity of the soil microbial community, thereby affecting the physical and chemical properties of the soil" (Bandopadhyay et al,2018)

"Microplastics have a negative impact on soil organic carbon (C) and nitrogen (N) cycles, soil microbial activity, and nutrient transfer" (Cao et al, 2017)

"Microplastics can inhibit the growth of corn (Wang et al., 2020), cress, and tomatoes (Bosker et al., 2019), and are toxic to rice seedlings" (Dong et al., 2020a)


Update - Feb. 5 2021

A Growing Concern: Microplastic Pollution on Farm Fields

"The researchers conclude that 92 percent of all microfiber emissions on land come from these biosolids"

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