Land Application Of Sewage Sludge Research Articles

A bibliometric perspective on the occurrence and migration of microplastics in soils amended with sewage sludge.

The land application of sewage sludge from wastewater treatment plants has been recognized as a major source of microplastic contamination in soil. Nevertheless, the fate and behavior of microplastics in soil remain uncertain, particularly their distribution and transport, which are poorly understood. This study does a bibliometric analysis and visualization of relevant research publications using the CiteSpace software. It explores the limited research available on the topic, highlighting the potential for it to emerge as a research hotspot in the future. Chinese researchers and institutions are paying great attention to this field and are promoting close academic cooperation among international organizations. Current research hot topics mainly involve microplastic pollution caused by the land application of sewage sludge, as well as the detection, environmental fate, and removal of microplastics in soil. The presence of microplastics in sludge, typically ranging from tens of thousands to hundreds of thousands of particles (p)/kg, inevitably leads to their introduction into soil upon land application. In China, the estimated annual accumulation of microplastics in the soil due to sludge use is approximately 1.7 × 1013 p. In European countries, the accumulation ranges from 8.6 to 71 × 1013 p. Sludge application has significantly elevated soil microplastic concentrations, with higher application rates and frequencies resulting in up to several-fold increases. The primary forms of microplastics found in soils treated with sludge are fragments and fibers, primarily in white color. These microplastics consist primarily of components such as polyamide, polyethylene, and polypropylene. The vertical transport behavior of microplastics is influenced by factors such as tillage, wind, rainfall, bioturbation, microplastic characteristics (e.g., fraction, particle size, and shape), and soil physicochemical properties (e.g., organic matter, porosity, electrical conductivity, and pH). Research indicates that microplastics can penetrate up to 90 cm into the soil profile and persist for decades. Microplastics in sewage sludge-amended soils pose potential long-term threats to soil ecosystems and even human health. Future research should focus on expanding the theoretical understanding of microplastic behavior in these soils, enabling the development of comprehensive risk assessments and informed decision-making for sludge management practices. PRACTITIONER POINTS: Microplastics in sewage sludge range from tens to hundreds of thousands per kilogram. Sludge land application contributes significantly to soil microplastic pollution. The main forms of microplastics in sludge-amended soils are fragments and fibers. Microplastics are mainly composed of polyamide, polyethylene, and polypropylene. Microplastics can penetrate up to 90 cm into the soil profile and persist for decades.

Integrating HYDRUS-2D and Bayesian Networks for simulating long-term sludge land application: Uncovering heavy metal mobility and pollution risk in the soil-groundwater environment

The release of sludge-derived heavy metals (HMs) to soil and their subsequent migration into groundwater poses a significant challenge for safe and low-carbon sludge land application. This study developed a predictive framework to simulate 60-year sludge land application, evaluating the risk of HMs pollution in the soil-groundwater environment and assessing the influence of soil and water properties. HYDRUS-2D simulations revealed that highly mobile Cu, Ni, and Zn penetrated a 10 m soil layer over a 60-year period, contributing to groundwater pollution. In contrast, Cr was easily sequestered within the topsoil layer after 5-years continuous operation. The non-equilibrium parameter α could serve as an indicator for assessing their potential risk. Furthermore, the limited soil adsorption sites for Pb (f = 0.02772) led to short-term (1-year) groundwater pollution at a 0.5 m-depth. Bayesian Networks model outcomes indicated that humic-like organics crucially influenced HMs transformation, enhancing the desorption of Cd, Cu, Ni, Pb, and Zn, while inhibiting the desorption for Cr. Additionally, electrical conductivity promoted the release of most HMs, in contrast to the Mn mineralogy in soil. This study bridges the gap between the macro-level HMs migration trends and the micro-level adsorption-desorption characteristics, providing guidance for the safe land application of sewage sludge. Environmental ImplicationThis study introduces a framework integrating HYDRUS-2D simulations with Bayesian Networks to assess the risks of groundwater pollution by heavy metals (HMs) over a 60-year sludge application. Sludge-derived Cu, Ni, and Zn are found to penetrate soil up to 10 m and exceed safety limits, with the non-equilibrium parameter α serving as an indicator for pollution risk. The importance of nutrients from sludge-amended soil for the transformation of HMs in the subsurface environment highlights the need for enhanced sludge management, specifically through more detailed regulation of nutrient composition. These findings contribute to developing precise strategies for the long-term sludge land application.

Application of untreated versus pyrolysed sewage sludge in agriculture: A life cycle assessment

Recycling of phosphorus (P) from waste streams such as sewage sludge to agriculture is essential in order to ensure future food security. Land application of sewage sludge is controversial due to its content of pollutants, such as heavy metals and toxic organic compounds. Pyrolysis is a technology that can eliminate harmful contaminants while enabling the recycling of P in the sludge. Organic pollutants are degraded during pyrolysis, while most of the P remains and approximately 40 % of the carbon is retained in a stable form in the biochar. When performing pyrolysis at a temperature of around 800 °C or more, cadmium is evaporated and can be separated from the biochar. Electricity-driven pyrolysis facilitates this by means of easier temperature control. The aim of the present study was to undertake a Life Cycle Assessment (LCA) to evaluate the environmental impacts of high-temperature electricity-driven pyrolysis of sewage sludge, including the separation of cadmium, and field application of sludge biochar as compared with sewage sludge storage and field application. The results showed that pyrolysis can offer a more climate-friendly solution due to avoided greenhouse gas emissions from the sludge and to carbon sequestration of the biochar. However, field application of untreated sludge resulted in a higher application of nitrogen (N) and more plant-available P. Agricultural modelling tools indicated that this produces higher crop yields than biochar application. In the LCA model, higher crop yields lead to savings in land use and water consumption as the higher yields can replace other crop production. The lower plant availability of biochar P implies a possible risk of lower yields when the P application is restricted based on total P, and a risk of greater P loss with soil erosion to the environment. Overall, the present study stresses the importance of including the long-term agronomic impacts of sludge and biochar field application in LCAs, and highlights the trade-offs that need to be considered in decision-making regarding the implementation of pyrolysis technology.

Effect of biological sewage sludge and its derived biochar on accumulation of potentially toxic elements by corn (Zea mays L.)

The land application of sewage sludge can cause different environmental problems due to the high content of potentially toxic elements (PTEs). The objective of this study was to compare the effect of urban biological sewage sludge (i.e. the waste of activated sludge process) and its derived biochar as the soil amendments on the bioavailability of PTEs and their bioaccumulation by corn (Zea mays L.) under two months of greenhouse conditions. The soil was treated by adding biochar samples at 0 (control), 1, 3, 5% w/w. The diethylenetriamine pentaacetic acid (DTPA)-extractable concentrations of PTEs including Zn, Pb, Cd, Cr, Ni, Fe, and Cu in soil and their accumulation by plant shoot and root were measured. Conversion of the biological sewage sludge into the biochar led to decrease the PTEs bioavailability and consequently decreased their contents in plant tissues. The DTPA extractable metal concentrations of produced biochar in comparison to the biological sewage sludge reduced 75% (Cd), 65% (Cr), 79% (Ni and Pb), 76% (Zn), 91% (Cu) and 88% (Fe). Therefore, the content of Ni, Fe, Zn and Cd in corn shoot was decreased 61, 32, 18 and 17% respectively in application of 5% biochar than of raw sewage sludge. Furthermore, the application of 5% biochar enhanced the physiological parameters of the plants including shoot dry weight (twice) and wet weight (2.25 times), stem diameter (1.70 times), chlorophyll content (1.03 times) in comparison to using 5% raw sewage sludge. The results of the study highlight that application of the biochar derived from urban biological sewage sludge in soil could decrease the risk of PTEs to the plant.

Chemical characteristics and valuation of sewage sludge from four different wastewater treatment plants.

Sewage sludge contains plant nutrients and organic matter in its composition, making it a potential partial substitute for mineral fertilizers if it meets environmental, agronomic, and sanitary standards. The objective was to evaluate the content of nutrients and heavy metals in the sludge generated in four wastewater treatment stations (WWTPs) in Rio de Janeiro state and assess its potential value and usefulness. The samples of 19 batches from the WTTPs Alegria, Barra da Tijuca, Ilha do Governador, and Sarapuí were analyzed. The WWTPs differ in methods and processes used for treating sewage and sludge. The total contents of C, N, P, K, Ca, Mg, Fe, Al, Na, Co, Mn, As, Ba, Cd, Cr, Cu, Ni, Se, Pb, and Zn were evaluated, as well as the ratio C/N, pH, organic matter content, and electrical conductivity. The grouping of sludge samples was assessed using principal components (PCA) and cluster analysis. The economic valuation of sludge was conducted utilizing the substitute goods method, which compared the sludge's N-P-K contents with the prices of consolidated nutrient sources. All the evaluated sludge batches exhibited concentrations of heavy metals below the limits allowed by Brazilian law, along with high levels of nutrients and organic matter. Considering the chemical characteristics, all evaluated materials showed potential for agricultural use, but it is crucial to evaluate the microbiological characteristics of sludge batches before agriculture application. PCA and cluster analysis demonstrated that sludge samples from the same WWTP clustered close to each other, demonstrating higher similarity among themselves than with samples from other WWTPs. The sludge had an average added value of U$ 88.46 per megagram, considering the total contents of N, P, and K in its composition. Land application of sewage sludge can reduce the need to purchase mineral fertilizers, thereby supporting the feasibility of reusing this material in the agricultural sector.

Ecological risk assessment of toxic metal(loid)s for land application of sewage sludge in China

Sewage sludge, including those after biological or thermochemical treatments, has the potential to be used as fertilizers for recycle of resources. However, its potential ecological risk is also of great concern to policy making. This study employed comprehensive ecological risk assessment (ERA) methods to evaluate the risk caused by the toxic metal(loid)s in sewage sludge throughout China. The conventional geo-accumulation index and potential ecological risk index revealed that cadmium (Cd) and mercury (Hg) were of significant concern in treating sewage sludge before land application, but chromium (Cr) and zinc (Zn) were preferred by potential affected proportion (PAF) and overall risk probability (ORP) of species sensitivity distribution (SSD). Because SSD considered both the community and the ecotoxicity of toxic metal(loid)s, it was more advantageous and promising in assessing ecological risks caused by land application of sewage sludge. Based on the predicted no-effect concentration (PNEC) of toxic metal(loid) calculated by hazardous concentration that cause death of 50% of species (HC50) by SSD, the maximum allowable disposal amount (MADA) of sewage sludge in the whole China indicated that chromium (Cr) should be totally eliminated because of its high risks in the present background soil. After excluding Cr, the MADA of sewage sludge in China was 3.24 × 106 t and 6.47 × 107 t under land application scenarios with high and low ecological risks, respectively. Additionally, the MADA could be increased by mixing sewage sludge with deeper soil in wider areas. This study emphasized that local laws and regulations on land application of sewage sludge and the subsequent ERA system need to be addressed in the future.

Effects of sulfidation of silver nanoparticles on the Ag uptake kinetics in Brassica rapa plants

Land application of sewage sludge containing increasing levels of silver nanoparticles (AgNPs) raises concerns about the risk for plant exposure. This study compared the uptake kinetics and distribution of Ag in Brassica rapa seedlings grown in Lufa 2.2 natural soil spiked with 20 nm Ag2S NPs, with those from 3 to 8 nm AgNPs, 50 nm AgNPs and AgNO3 exposures (10 mg Ag/kg dry soil). A two-compartment model was used to describe the uptake kinetics of Ag in plants, distinguishing two stages: stage I with increasing Ag uptake followed by stage II with decreasing Ag uptake. The concentration of Ag in roots from Ag2S NPs was about 14 and 10 times lower than for the other AgNPs and AgNO3 exposures, respectively, at the end of stage I, with root translocation rate constants being higher for Ag2S NPs. In stage II, Ag uptake occurred only for the 50 nm AgNPs. The distribution of Ag in B. rapa exposed to pristine, ionic and sulfidized AgNPs differed at the end of exposure. This study shows that Ag uptake and distribution in plants depends on the Ag form in soil, highlighting the importance of studying the environmentally relevant chemical species in NPs risk assessment.

Microplastic Pollution in Agricultural Soils and Abatement Measures – a Model-Based Assessment for Germany

Microplastic pollution in soils is a recent environmental problem and the lack of knowledge about the impacts and the extent of the problem are raising questions and concerns among researchers and politicians. Using a normative simulation model, we assess the extent of microplastic pollution in German agricultural soils originating from the land application of sewage sludge and compost. We estimate the microplastic concentration in German agricultural soils, the area of polluted land, and we compare the efficiency and effectiveness of some selected abatement measures. For 2020, we estimate that microplastic concentration in agricultural soil reaches a maximum concentration of between 30 and 50 mg/kg dry weight on 2% of utilised agricultural area and a marginal concentration on 22% of utilised agricultural area. Without the implementation of abatement measures, we expect the microplastic concentration to increase two to three times by 2060. Assessing the abatement measures, we find that for sewage sludge, thermal recycling is a more efficient and effective than equipping washing machines with microplastic-filters in private households. The use of plastic detection systems in the biowaste collection process reduces the plastic content of the compost and thus the release of microplastic into the soil. Detection systems are a more efficient measure for compost than thermal recycling. Concerning sludge, the findings indicate that the German strategy of thermally recycling sewage sludge is an efficient and effective measure to reduce microplastic pollution in soils. Reducing the plastic content of collected biowaste complies with the principles of a circular economy.

Sorption of Co2+, Zn2+, Cd2+ and Cs+ ions by activated sludge of sewage treatment plant

Sludges are byproducts of sewage treatment process. Land application of sewage sludge is one of the final steps of waste water treatment, but solubilization of toxic metals restricts this method of sludge disposal. In our paper cobalt, zinc, cadmium and cesium sorption by suspension of non-treated activated sewage sludge (14 g/dm3, dry wt.) from waste water spiked with 60CoCl2, 65ZnCl2, 109CdCl2 or 137CsCl were determined in laboratory experiments at 20°C. Activated sludge supplied by the municipal sewage treatment plant in Zeleneč (Trnava region, Slovakia) showed high efficiency to sorb Co2+, Zn2+, Cd2+ and Cs+ ions from waste water pH 6-7. The process can be characterized by the concentration equilibrium (Csolid/Cliquid) typical for sorption processes. Efficiency of the sorption increased in the order Cs < Co < Zn < Cd. Metal sorption process was not inhibited by pretreatment of the sludge with 0.2% formaldehyde or thermal inactivation at 60°C, what confirms that the process was not dependent on metabolic activity of the sludge. Cobalt, zinc, cadmium and cesium were easily removable from the
 sludge by washing with diluted HCl, EDTA or water solutions of the corresponding metal ions, but with low efficiency by deionized water.

Solid-Embedded Microplastics from Sewage Sludge to Agricultural Soils: Detection, Occurrence, and Impacts

Microplastics (MPs) have been increasingly identified as a global concern because of their ubiquitous distribution and the threats they pose. MPs embedded in the solid matrix remain an underexplored field compared to MPs in aquatic environments. This review focuses on solid-embedded MPs in a binary system consisting of sewage sludge and agricultural soils, which are interconnected through land application of sewage sludge to agricultural soils. The detection, occurrence, and impacts of MPs were summarized for sewage sludge and agricultural soils. Specifically, the latest techniques for detecting solid-embedded MPs are summarized and compared. The occurrence of MPs is presented from three aspects, i.e., the origin, transformation, and properties. Lastly, the impacts of solid-embedded MPs on sewage sludge treatment processes and the agroecosystem are reviewed. As a cutting-edge overview of the current knowledge, this review proposes key challenges to be further investigated with respect to solid-embedded MPs, including a uniform detection procedure, worldwide monitoring programs, rigorous assessments of potential risks, and mitigation measures through collaborative efforts by related liable parties.

Thickening and Storage of Sewage Sludge Contribute to the Degradation of LAS and EOX and the Humification of Organic Matter

Land application of sewage sludge on agricultural soils can be sustainable only if pollutant contents and organic matter quality meet the requirements imposed by minimization of environmental risks. This study investigated the degradation of linear alkylbenzene sulfonates (LAS) and extractable organic halogens (EOX) and the formation of humic substances (HS) during the thickening and storage phases of sewage sludge treatment. Changes in spectroscopic properties (UV-Vis, FT-IR, and excitation-emission matrix (EEM) fluorescence) of HS were also evaluated to assess the occurrence of biological activities during these curing phases of sewage sludge (SS). Humic acids (HA), fulvic acids (FA), EOX, and LAS were extracted from sewage sludge sampled from four municipal wastewater treatment plants of different size and treatment sequence, before and after 90 days of aerobic or anaerobic storage. During storage, the loss of organic C in the SS ranged from almost null to 31%. No significant changes of FA were registered, whereas HA increased in almost all samples, up to 30%. The amount of humic substances synthesized during storage correlated with the percentage of C lost. Spectroscopic changes of FA and HA showed an increase in their aromaticity, with a corresponding decrease in the aliphatic contribution. These changes show the improved agronomical quality of SS. LAS decreased during storage up to 30%, surprisingly more under anaerobic than aerobic conditions, whereas EOX decreased significantly in all samples, even up to 81%. In conclusion, although storage may be normally considered not influencing the quality of SS, their organic matter quality improved and contamination decreased during 90 days of storage, whatever the conditions of oxygen availability applied.

Land application of sewage sludge: Response of soil microbial communities and potential spread of antibiotic resistance.

The effect of land application of sewage sludge on soil microbial communities and the possible spread of antibiotic- and metal-resistant strains and resistance determinants were evaluated during a 720-day field experiment. Enzyme activities, the number of oligotrophic bacteria, the total number of bacteria (qPCR), functional diversity (BIOLOG) and genetic diversity (DGGE) were established. Antibiotic and metal resistance genes (ARGs, MRGs) were assessed, and the number of cultivable antibiotic- (ampicillin, tetracycline) and heavy metal- (Cd, Zn, Cu, Ni) resistant bacteria were monitored during the experiment. The application of 10tha-1 of sewage sludge to soil did not increase the organic matter content and caused only a temporary increase in the number of bacteria, as well as in the functional and structural biodiversity. In contrast to expectations, a general adverse effect on the tested microbial parameters was observed in the fertilized soil. The field experiment revealed a significant reduction in the activities of alkaline and acid phosphatases, urease and nitrification potential. Although sewage sludge was identified as the source of several ARGs and MRGs, these genes were not detected in the fertilized soil. The obtained results indicate that the effect of fertilization based on the recommended dose of sewage sludge was not achieved.

Toxic metals in soil due to the land application of sewage sludge in China: Spatiotemporal variations and influencing factors

Land application has become a promising method for recycling energy and resources from sewage sludge; however, the changes that occur to the toxic metal concentrations in soil following the application of sewage sludge have been poorly investigated in China. The present study attempted to investigate the spatiotemporal variations of toxic metal concentrations in soil due to the land application of sewage sludge and the critical influencing factors. Overall, the results indicated that an increasing ratio of sewage sludge for land application, the concentrated disposal measures, and a shallower soil may lead to elevated toxic metal concentrations in soil. The worst scenario simulation showed that the cumulative discharge of toxic metals through sludge disposal were ranked as: Zn > Cu > Cr > Pb > Ni > As > Cd > Hg. After sewage sludge was applied to previously unaffected soil, i.e., background soil, the toxic metal concentrations in the soil increased annually over the period from 2006 to 2017. However, with respect to the affected soil, the concentrations of Zn and Cu increased, whereas the concentrations of As, Cd, Cr, and Pb decreased annually over the period from 2006 to 2017. The results indicate that, in practice, the selection of soil for sewage sludge disposal depends on the background and actual concentrations of toxic metals in a soil as well as the stress caused by the amount of sewage sludge application to cultivated land. We propose to use sewage sludge containing relatively lower concentrations of metals than the disposal soil for land application. Furthermore, land application of sewage sludge should be suited to local conditions in the future sewage sludge management.

The Autism Biosolids Conundrum

ABSTRACT
 Before Congress passed the Clean Water Act of 1972, municipalities throughout the United States discharged hazardous municipal and industrial wastes directly into rivers and other waterways. Every chemical and biological agent linked to neurodevelopmental disorders, including those linked to “autism spectrum disorders” (ASDs), spilled into coastal waters and settled on the bottoms of the oceans. The solution to pollution was dilution. To comply with the Clean Water Act of 1972, President Carter created wastewater treatment plants throughout the United States to extract heavy metals and toxic organic chemicals from water and concentrate them in sewage sludges that were dumped offshore and buried in landfills. In 1988, Congress banned ocean dumping of sewage sludges because of their potential for causing vaccine-derived polio epidemics. Suddenly, high concentrations of every heavy metal, toxic organic chemical and vaccine-derived viruses linked to autism, including rubella and cytomegalovirus, had no place to go but land. The solution to pollution shifted from diluting pollutants in water to concentrating them on land at hundreds of thousands to millions of times higher concentrations, including on commercial farms that produce our nation’s food supplies. Now, all of the most dangerous pollutants regulated by EPA no longer require biomagnification up the food chain to harm public health. Promoted by EPA and the USDA as safe and environmentally beneficial, land application practices quickly spread worldwide. Here, the author relies largely, albeit not exclusively, on EPA’s own research to address the implications. As a whole, it indicates that the global shift that EPA’s 503 Sludge Rule created in the accumulation of pollutants from ocean sediments to populated land surfaces is causally related to sharp increases in the incidence of neurodevelopmental disorders worldwide. Autism in its severe infantile form is more or less at the center of this entire class of disorders that appears to have become epidemic beginning in late 1988. EPA dismissed controversial claims linking MMR vaccination to autism, but never addressed the role that widespread land application of sewage sludges (a.k.a. biosolids), which contain highly virulent strains of vaccine-derived measles, rubella and other viruses, may play in autism. Notwithstanding this glaring omission, the global shift that EPA policies on biosolids created in human exposures to complex mixtures of measles, rubella and other viruses derived from live vaccines, combined with high concentrations of potentially every heavy metal and chemical pollutant linked to autism, could explain sharp increases in the incidences of autism and other ASDs that began in 1988.

Effects of co-loading of polyethylene microplastics and ciprofloxacin on the antibiotic degradation efficiency and microbial community structure in soil

Microplastics (MPs) have become a global environmental concern while soil plastic pollution has been largely overlooked. In view of the severe antibiotic contamination in arable soils owing to land application of sewage sludge and animal manure, the invasion of MPs along with antibiotics may pose an unpredictable threat to soil microbial communities and ecological health. In this work, polyethylene MPs and ciprofloxacin (CIP) were applied to a soil microcosm to investigate the CIP degradation behavior and their combined effects on soil microbial communities. Compared with that of the individual amendment of CIP, the co-amendment of CIP and MPs reduced the CIP degradation efficiency during the 35 d cultivation period. In addition, the high-throughput sequencing results illustrated that the combined loading of MPs and CIP in soil significantly decreased the microbial diversity compared with that of individual contamination. As for the community structure, the microbial compositions at the phylum level were consistent among all treatments, and the most dominant phyla were Proteobacteria, Actinobacteria, and Chloroflexi. At the genus level, only one genus, namely Arthrobacter, was remarkably changed in the CIP-amended soil compared with that in the blank control, but four genera were significantly altered in the MPs-CIP co-amended soil. Serratia and Achromobacter were abundant in the combined polluted soil, which might have been involved in accelerated depletion of soil total nitrogen based on redundancy analysis. These findings may contribute to the understanding of bacterial responses to the combined pollution of MPs and antibiotics in soil ecosystems.

Land Application of Sewage Sludge: Physiological and Biochemical Response of the Rio Grande Tomato

Treated wastewater produces sewage sludge as a by-product that may have beneficial implications on agricultural practices. The effects of sludge amendments on growth, morphological and biochemical characteristics of the agro-industrial Tomato cultivar Rio Grande were observed. A pot culture experiment was carried out during 4 months (16 February 2019 to 18 June 2019), at an experimental green house in the locality of Salah Soufi, Guelma, north-eastern Algeria. There were significant differences between soil and sewage sludge samples. Total nitrogen (20.58 mg/kg) was more available in sewage sludge than in soil (N = 2.09 ± 0.3 mg/kg). In contrast, sludge contained less phosphorus and organic matter than soil. The observation of the morphological characteristics of the plants showed significant variations between the treatments. The germination rates for treated soils decreased significantly to reach 50%, compared to the control. Growth patterns (dry and fresh weight of leaves and roots) changed significantly (P <0.05) between the treatments. Chlorophyll contents of plants in treated soils were more than twice as high as those of the control, but started decreasing at 75% amendment rates.

Decreasing reactive nitrogen losses in organic agricultural systems

Excess reactive nitrogen (Nr) in the global system has led to a wide variety of environmental and human health problems. To minimize the negative impacts of nitrogen loss from agriculture, we need to develop more sustainable farming systems that can efficiently produce food for humans while balancing ecological functioning and reducing Nr losses. This paper looks at recent research examining Nr losses in organic systems, using conventional Nr losses in the United States (U.S.) as a baseline to identify leverage points for reducing Nr loss. The paper discusses the sources of Nr used in organic versus conventional farming and highlights the importance of increasing the use of recycled Nr to prevent additional Nr loss to the environment. Specifically, we note that organic production is advantageous when it comes to the creation of new Nr because of its reliance on recycled sources of Nr, improved ability to access nutrients in the soil, and higher residue recycling rates. We also highlight areas where additional research, policies, and protocols are needed to improve Nr efficiency, including increasing organic yields, increased recycling of processing waste, matching nutrient flows, reducing and recycling edible food waste, and examining potential benefits and risks of land application of sewage sludge in organic systems.

Antioxidant Enzyme Activity and Lipid Peroxidation in Aporrectodea caliginosa Earthworms Exposed to Silver Nanoparticles and Silver Nitrate in Spiked Soil.

Silver nanoparticles (AgNPs) from industrial use, discharged via the land application of sewage sludge, are interacting with soil biota, including earthworms. In affected organisms, excessive production of reactive oxygen species can result in lipid peroxidation, shifting the balance between oxidants and antioxidants to cause oxidative stress. We determined selected lower-tier biomarkers such as antioxidant responses and lipid peroxidation in Aporrectodea caliginosa earthworms exposed to soils spiked with AgNPs or silver nitrate (AgNO3 ). Aporrectodea caliginosa were exposed to AgNPs at 0 (control), 0.3, 3, 30, and 300 mg/kg or Ag+ (as AgNO3 ) at 0, 0.03, 0.3, 3, and 10 mg/kg in soil for 4 wk. At 1, 2, 3, and 4 wk, the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, as well as lipid peroxidation (malondialdehyde content), increased as a function of concentration, with a much larger response for Ag+ than AgNPs. Given the likelihood of ever-increasing AgNP concentrations in soil, where AgNPs can transform to ionic Ag (Ag+ ), our findings of antioxidant response to oxidative stress in a common indicator organism even at an environmentally realistic exposure concentration of 0.03 mg/kg demonstrate that AgNPs may affect soil fertility and, thus, agricultural production. Evaluating selected lower-tier biomarkers offers a meaningful assessment of AgNPs and Ag+ effects on terrestrial earthworms. Environ Toxicol Chem 2020;39:1257-1266. © 2020 SETAC.

Potential for phytoremediation of nonylphenol from sewage sludge.

Nonylphenol (NP) is considered a major contaminant that must be removed to enable safe and environmentally friendly land application of sewage sludge. Phytoremediation is a technology in which plants are used to remove and/or stabilize organic and inorganic contaminants present in the soil, municipal wastewater, and sewage sludge. In this study, a 391-d large pot experiment was conducted to remove NP from sewage sludge by phytoremediation using Zea mays L. 'Yunshi-5', Lolium perenne L., and co-cropping of the two plants. The fate of NP in the soil under the sewage sludge was assessed at the same time. At the end of the experiment, the NP levels in sludge from the various treatments were as follows: control (38.60%)>L. perenne (31.27%)>Z. mays (16.25%)>co-cropping (15.28%). Degradation followed an availability-adjusted first-order kinetics with a decreasing order of half-lives as follows: control (88.2 d)>L. perenne (87.3 d)>co-cropping (66.2 d)>Z. mays (59.1 d). The results indicated that Z. mays and co-cropping could both degrade NP. The concentrations of NP in tissues of different plants differed significantly. The mean bioconcentration factors for Z. mays and L. perenne were 0.16 and 3.69, respectively. Direct removal of NP from sewage sludge by plant uptake was negligible, as was downward movement of NP in the system. Moreover, NP was not detected in soils in any treatments at harvest.

A sustainable food security approach: Controlled land application of sewage sludge recirculates nutrients to agricultural soils and enhances crop productivity

AbstractThe food security in today's world is endangered by several threats, including accelerated increases in the world's population, depletion of the Earth's resources, exaggerated environmental pollution, and foreseen climatic changes. As a strategy to diminish these threats, the wise disposal of the huge amounts of sewage sludge (SS) to agricultural soils as a bio‐fertilizer represents a worthy practice for recirculating valuable nutrients to food chains via crop plants. The current study was designed to scientifically test the feasibility of SS application to agricultural soils without causing environmental or health threats. Different SS amendment doses of 0, 10, 20, 30, 40, and 50 g/kg were supplied for soil‐grown barley (Hordeum vulgare L.) plants. Our results show that all of the SS amendment doses improved the postharvest soil properties and enhanced barley growth, with the best results obtained at the 40 g/kg dose. At this amendment dose, the organic matter (OM) content increased to 6.7% compared with 1.4% in control soil. Analysis of the postharvest soils showed that the concentrations of the investigated heavy metals (HMs) (Co, Cu, Mo, Ni, Zn, Cd, Cr, and Pb) were within the allowable limits for agricultural soils at all of the SS amendment doses, except for Co. All of the SS amendment rates enhanced barley growth and yield parameters, including shoot and root lengths and dry weights, spike weight and number of spikes per plant. Up to the 40 g/kg amendment dose, the concentrations of the investigated HMs in the harvested plant tissues were within safe limits, with most of the absorbed HMs persisting in roots. Taking these results together, the current study suggests that controlled application of SS to agricultural soils represents an eco‐friendly SS disposal procedure, which can recycle macro‐ and micronutrients to food chains and hence provide a promising approach for sustainable food security.