Spreading Of Sewage Sludge Research Articles

Removal of Cefuroxime from Soils Amended with Pine Bark, Mussel Shell and Oak Ash

The global increase in antibiotics consumption has caused hazardous concentrations of these antimicrobials to be present in soils, mainly due to the spreading of sewage sludge (or manure or slurry) and wastewater, and they could enter the food chain, posing serious risks to the environment and human health. One of these substances of concern is cefuroxime (CFX). To face antibiotics-related environmental pollution, adsorption is one of the most widely used techniques, with cost-effective and environmentally friendly byproducts being of clear interest to retain pollutants and increase the adsorption capacity of soils. In light of this, in this work, three low-cost bioadsorbents (pine bark, oak ash, and mussel shell) were added to different soil samples (at doses of 12 and 48 t/ha) to study their effects on the adsorption of CFX. Specifically, batch experiments were carried out for mixtures of soils and bioadsorbents, adding a range of different antibiotic concentrations at a fixed ionic strength. The results showed that the addition of pine bark (with pH = 3.99) increased the adsorption to 100% in most cases, while oak ash (pH = 11.31) and mussel shell (pH = 9.39) caused a clearly lower increase in adsorption (which, in some cases, even decreased). The Freundlich and linear models showed rather good adjustment to the experimental data when the bioadsorbents were added at both doses, while the Langmuir model showed error values which were too high in many cases. Regarding desorption, it was lower than 6% for the soils without bioadsorbents, and there was no desorption when the soils received bioadsorbent amendments. These results show that the addition of appropriate low-cost bioadsorbents to soils can be effective for adsorbing CFX, helping in the prevention of environmental pollution due to this emerging contaminant, which is a result of clear relevance to environmental and human health.

Trace element speciation in sludge: a preliminary study to assess contamination levels in the sewage network

The spreading of sewage sludge from wastewater treatment plants and various industries arouses the growing interest due to the contamination by trace elements. Sludges were collected from one sewage treatment plant and two industries in Dhaka City, Bangladesh to assess physicochemical parameters and total and fraction content of trace elements like Cr, Ni, Cu, As, Cd, Pb, Fe, Mn and Zn in sludges. We evaluated the bioavailability of theses metals by determining their speciation by sequential extraction, each metal being distributed among five fractions: exchangeable fraction, bound to carbonate fraction, Fe-Mn oxide bound fraction, organic matter bound fraction and residual fractions. We found that all the analyzed sludges had satisfactory properties from an agronomic quality point of view. The average concentration (mg/kg) of trace metals in sludge samples were in the following decreasing order Fe (12807) > Cr (200) > Mn (158) > Zn (132) > Cu (68.2) > Ni (42.5) > Pb (36.4) > As (35.1) > Cd (3.7). The results of the sequential extraction showed that Cr, Ni, Cu, Fe and Mn were largely associated with the residual fraction where As, Cd and Pb was dominantly associated with the exchangeable and carbonate bound fractions and Zn showed a considerable proportion in carbonate bound fraction. These results showed that regulations must take into account the bioavailability with regard to the characteristics of the agricultural soils on which sludge will be spread.

Life cycle assessment of prospective sewage sludge treatment paths in Germany

Due to the amendment of the sewage sludge ordinance, both a thermal post-treatment and a phosphorous recovery from sewage sludge will become mandatory for large-scale wastewater treatment plants in Germany. This study analyzed four prospective treatment paths for sewage sludge by means of life cycle assessment. In the realm of a gate-to-cradle approach, environmental impacts were quantified for all compartments of the ReCiPe Midpoint (H) 2016 method.The spreading of digested sludge on agricultural soils was considered as the base case (system: AD + spreading). It was compared to the centralized incineration of sludge (system: AD + I), a decentralized hydrothermal carbonization followed by centralized incineration (system: AD + HTC + I) and a decentralized pyrolysis of sludge followed by centralized incineration (system: AD + P + I). For all cases, phosphorous recovery from the ash was included. A comparative evaluation showed that AD + spreading resulted in least environmental impacts in most categories but was subject to a high local immission potential due to sewage sludge spreading. It was found to be only justifiable, if toxicity and eutrophication were not compromised. Alternatively, a thermal post-treatment step is required. Hereby, AD + I and AD + HTC + I showed the overall least environmental impacts, while AD + P + I was characterized by similar or higher environmental impacts throughout all impact categories.Alongside the comparative analysis, a hotspot analysis was carried out and mitigation potentials were identified. For all thermochemical post-treatment paths, it was derived that (i) the share of fossil external energy must be kept to a minimum, (ii) primary or secondary measures to control N2O emissions during the incineration and pyrolysis should be implemented and (iii) the technological approach to recover phosphorous must be carefully selected.

Microplastics in soils: an environmental geotechnics perspective

Microplastics (MPs) are emerging persistent contaminants in the terrestrial subsurface, and evidence has emerged for significant effects of MPs on the biological and ecosystem functions of soils. Main MP sources include land spreading of sewage sludge and biowaste composts, plastic mulching film used in horticultural fields, waste water irrigation and leachate from the landfills, among others. This updated state-of-the-art review paper describes recent experimental and numerical research and developments in understanding the accumulation and fate and effects of MPs in the soil environment (focusing on their storage, degradation, transportation, leaching to groundwater etc.), followed by mitigation and bioremediation measures, including MP-eating soil bacteria and fungi and the best management practices for reducing MP pollution of soil. Other areas covered are the combined effects of MPs and various other environmental contaminants (heavy metals, organic pollutants and antibiotics) in soil ecosystems and the standardisation of methods for detection, quantification and characterisation of MPs in soils, which is critical for MP research. The paper concludes by identifying knowledge gaps and presents recommendations on prioritised research needs.

Comparative study of response of four crop species exposed to carbon nanotube contamination in soil

Crop plants are exposed to a variety of contaminants through sewage sludge spreading but very little is known about the impact of emerging contaminants such as nanomaterials. To date their impact on plants is still very controversial with many works claiming negative impacts while some authors suggest their use as plant growth regulator in agriculture. In this study, aiming to better understand where these discrepancies may come from, we investigated the influence of plant species (tomato, rapeseed, cucumber and maize) on plant response to a carbon nanotube contamination in soil condition. Our results demonstrate that the same CNT contamination can lead to different effects depending on plant species with positive impacts on cucumber and rapeseed (more than 50% increase in leaf biomass and surface area and 29% increase in chlorophyll for cucumber) but negative impact on maize (−14% for plant height), while tomato was insensitive. FTIR analysis of biomacromolecule composition suggested that these differences could be related with plant cell wall composition (in particular: pectins, xyloglucans and lignins). As a summary, no overall conclusion can be drawn about the toxicity of a specific nanomaterial for all plant species.

Medium-term effects of Ag supplied directly or via sewage sludge to an agricultural soil on Eisenia fetida earthworm and soil microbial communities

The widespread use of silver nanoparticles (AgNPs) in consumer products that release Ag throughout their life cycle has raised potential environmental concerns. AgNPs primarily accumulate in soil through the spreading of sewage sludge (SS). In this study, the effects of direct exposure to AgNPs or indirect exposure via SS contaminated with AgNPs on the earthworm Eisenia fetida and soil microbial communities were compared, through 3 scenarios offering increasing exposure concentrations. The effects of Ag speciation were analyzed by spiking SS with AgNPs or AgNO3 before application to soil. SS treatment strongly impacted Ag speciation due to the formation of Ag2S species that remained sulfided after mixing in the soil. The life traits and expression of lysenin, superoxide dismutase, cd-metallothionein genes in earthworms were not impacted by Ag after 5 weeks of exposure, but direct exposure to Ag without SS led to bioaccumulation of Ag, suggesting transfer in the food chain. Ag exposure led to a decrease in potential carbon respiration only when directly added to the soil. The addition of SS had a greater effect on soil microbial diversity than the form of Ag, and the formation of Ag sulfides in SS reduced the impact of AgNPs on E. fetida and soil microorganisms compared with direct addition.

SARS-CoV-2 in soils

Some environmental aspects are being increasingly studied in relation to the COVID-19 pandemic. Specifically, studies focusing on wastewater could be used for early warning, based on wastewater based epidemiology precepts. However, sewage sludge has been poorly studied in this regard up to now. In addition, soils have not been considered in publications related to SARS-CoV-2. In this piece, some comments are included to suggest a discussion regarding the eventual convenience of considering future studies focusing on soils receiving the spreading of wastewater and sewage sludge, as well as on plants growing on them.

Enhanced in situ biodegradation of microplastics in sewage sludge using hyperthermophilic composting technology

Land spreading of sewage sludge is a major source of environmental microplastics (MPs) contamination. However, conventional sludge treatments are inefficient at removing sludge-based MPs. Herein, hyperthermophilic composting (hTC) technology is proposed and demonstrated in full-scale (200 t) for in situ biodegradation of sludge-based MPs. After 45 days of hTC treatment, 43.7% of the MPs was removed from the sewage sludge, which is the highest value ever reported for MPs biodegradation. The underlying mechanisms of MPs removal were investigated in lab-scale polystyrene-microplastics (PS-MPs) biodegradation experiments. The hTC inoculum degraded 7.3% of the PS-MPs at 70 °C in 56 days, which was about 6.6 times higher than that of the conventional thermophilic composting (cTC) inoculum at 40 °C. Analyses of the molecular weight and physicochemical properties of the PS-MPs residuals indicated that hyperthermophilic bacteria in hTC accelerated PS-MPs biodegradation through excellent bio-oxidation performance. High-throughput sequencing suggested that Thermus, Bacillus, and Geobacillus were the dominant bacteria responsible for the highly efficient biodegradation during hTC. These results reveal the critical role of hyperthermophilic bacteria in MPs biodegradation during hTC, highlighting a promising strategy for sludge-based MPs removal from the real environment.

Life Cycle Assessment of Phosphorus Sources from Phosphate ore and urban sinks:Sewage Sludge and MSWIncineration fly ash

Urban sinks accumulate phosphorus and other elements and may serve as sources of secondary raw materials. This paper evaluates phosphorus sources based on their environmental impact. In a life cycle assessment (LCA) the conventional production was used as a yardstick against which to measure the performance of two recycling options: spreading of sewage sludge and phosphorus recovery from municipal solid waste incineration fly ash (MSWA). When compared as three gate-to-gate processes, the sludge spreading had the lowest potential environmental impact, except in the impact categories eco- and human toxicity. In the future, the sludge spreading could potentially outperform the conventional process also with regard to toxicity, provided its Hg and Cu content can be reduced. Phosphorus extracted from the MSWA had the highest impact, except in relation to eutrophication. The benefits of avoiding the conventional production were greater than the sludge recycling impacts for all categories except toxicity. When conventional production is substituted by the MSWA recycling, the eutrophication and land-use impacts are avoided, while the impacts in other categories are considerable. The development needs identified for this method include substitution of HCl, reduced water consumption, and reduction of the product's metal content. Solutions to all of these challenges have been proposed and are currently being tested.

EFFECT OF SEWAGE SLUDGE APPLICATION ON WHEAT CROP PRODUCTIVITY AND HEAVY METAL ACCUMULATION IN SOIL AND WHEAT GRAIN

The present work illustrates the results of a long-term field experiment with sewage sludge used on agricultural land in order to assess the influence of sewage sludge on wheat crop productivity. The experimental research was conducted for three years as following: the evaluation of the agricultural use of sewage sludge in the year of application and its residual effect in grain and in soil for the next two years. The sewage sludge considered in the framework of the study was from Sfantu Gheorghe wastewater treatment plant, Covasna County (non-fermented sewage sludge from the dewatering press), Romania. Through the laboratory work, the heavy metals content in sewage sludge, soil, sewage sludge and soil (mixed sample) and wheat was identified. The attention was mainly focused on heavy metals content of sewage sludge because these kinds of contaminants are currently the most significant factor limiting its reuse in agriculture. In this way, the potential impacts of emerging micro-pollutants as cadmium (Cd) and lead (Pb) existing in sludge have been investigated. The results from our field experiments showed positive results related to sewage sludge spreading on agricultural land. Using chemical fertilizer and different doses of sewage sludge (0, 10, 25 and 40 t/ha), it was observed an improvement in the amount of harvested grain. It was demonstrated that a dose of 25 t/ha sewage sludge application provides highest wheat crop productivity, while Cd and Pb concentration levels in soil and wheat grain were under the maximum values allowed by the regulation.

Land spreading of sewage sludge in forest plantations: effects on the growth of the duckweed Lemna minor and trace metal bioaccumulation in the snail Cantareus aspersus.

Wastewater plants generated annually millions of tons of sewage sludge (SS). Large amounts of this organic residue are spread on agricultural lands as a fertilizer, although it is viewed as a major potential source of contamination, presenting a danger to the terrestrial and aquatic environments. This study was undertaken to evaluate the impact of this practice on the duckweed Lemna minor and the snail Cantareus aspersus. Sludge was applied to soil either at six different loading rates equal to 0, 0.4, 3, 10, 30, and 60tons dry matter (DM) ha(-1) for L. minor test or at three rates equal to 0, 30, and 60tons DMha(-1) for C. aspersus test. At the highest rate of SS application (60tons DMha(-1)), the eluates showed that an increase in pH (6.1) resulted in a decrease in Al levels. Thus, the high stimulation of L. minor growth observed after this high rate of SS application can be explained by (i) a reduction in Al toxicity after precipitation and (ii) macro- and micronutrient enrichment. At a rate of SS application of only 30tons DMha(-1), growth appeared to be slightly significant (p < 0.05), in spite of the significant increase in essential mineral elements. However, it is very difficult to discriminate between Al toxicity and pH effects. For the test with C. aspersus, the snail biomass was not affected by sludge application over the exposure period. Mortality was extremely low, with a rate of less than 4% at the last sampling date. Yet, Cu, Pb, and Cd accumulated significantly in the soft body of snails exposed to SS application, suggesting that the amount of metals excreted is lower than that absorbed. In contrast, Zn levels remain constant, inferring that absorption and elimination of Zn are balanced at the beginning of the experiment.

La gestion du changement institutionnel en matière d'épandage agricole des boues d'épuration en France

Les Organismes Independants (OI) constituent un changement institutionnel impulse par le gouvernement francais pour contribuer a mieux gerer l'epandage en agriculture des boues d'origine urbaine. Il est demontre que l'emergence d'un tel changement institutionnel, a l’echelle d’un territoire, depend a la fois de facteurs exogenes et endogenes a ce territoire en mobilisant deux demarches complementaires : une premiere phase quantitative et exhaustive ; une seconde phase s'appuyant sur quatre etudes de cas departementales (Ain, Haut-Rhin, Haute-Garonne, Aveyron) caracterisees par une variete de contextes agricoles, de relations villes-campagnes et d'agences de l'eau. Les facteurs exogenes resultent notamment de decisions politiques a un niveau supra-territorial, national et europeen. Le decoupage en agences de l'eau mis au point au niveau national exerce en effet un role important dans la creation des OI de deux facons differentes : la strategie retenue par la ou les agences de l'eau concernees par le departement et la localisation geographique du departement sur une ou plusieurs agences de l'eau. Le phenomene peut etre qualifie de changement institutionnel induit et se materialise par la capacite d'action locale a l'interieur de territoires particuliers notamment les effets d'apprentissage resultant d'experiences anterieures proches. Les coordinations territoriales construites dans le cadre de la specification des ressources agricoles et des rapports urbain-rural representent un facteur explicatif endogene majeur. La procedure d'activation des ressources specifiques peut jouer sur deux determinants de la coordination entre acteurs : les registres organisationnel et institutionnel de la coordination. Les etudes de cas departementales ont confirme que la grande diversite des situations locales (surtout departementales) du point de vue de l'emergence d'innovations institutionnelles liees a la gestion des boues s'explique bien sous la double pression des facteurs endogenes et exogenes.

Sewage sludge fertilization in larch seedlings: Effects on trace metal accumulation and growth performance

The spreading of sewage sludge (SS) among forest plantations may provide interesting results for firewood production. While sludges are good fertilizers, they may nevertheless contain trace metals, which can reduce productivity and lead to environmental risks. We investigated the effects of SS application on nutrient uptake and growth parameters in larch seedlings (Larix decidua) and determined trace metal and mineral distribution. Without incorporation into the soil, sludge was applied to the soil surface at three rates (0, 30 and 60t dry weight DW ha−1). The plants were harvested after 12 months. The results showed significantly increased nitrogen and phosphorus concentrations in the top soil layer in pots amended with sludge, whereas no changes appeared in the lower layers. Similar results were obtained for the Cu, Zn and Cd concentrations. However, no differences were observed for the other measured soil mineral elements. Nitrogen concentrations in needles increased with rising sewage sludge application rates, yet the sludge had no effect on the P, Mg, Zn, Pb and Cd concentrations. In addition, Cu accumulated only in the lateral roots of seedlings that received the highest sludge loading rate. Sludge application improved the net photosynthesis, which resulted in higher chlorophyll contents in the needles. Following application, the dry matter accumulation rate increased due to the excessive availability of N, whereas available mineral elements in the plant tissues were diluted. Furthermore, amending the soil with sewage sludge can promote a higher biomass yield which may result in an increased trace metal bioaccumulation capacity in plants. Though this investigation has established the benefits of municipal SS application, further studies are needed to assess the potential transfer of TM to groundwater and through the food chain.

Distribution and Mobility of Zn, Pb and Cd in a Sewage Sludge-Amended Soil

The distribution of the metallic trace elements (MTE) Zn, Pb and Cd in a sludge-amended soil and their partitioning in specific soil microystems are studied by comparing their contents in amended and control soils. This comparison is achieved at the metric scale of the bulk soil horizons and at the micrometric scale of the weathering microsites (weathering rock-forming minerals and their specific weathered products). The chemical analyses of the MTE in the bulk samples do not show any anthropic contamination of the amended soil with repeated sewage sludge spreading. The chemical analyses of the bulk

Impact of sewage sludge spreading on nickel mobility in a calcareous soil: adsorption–desorption through column experiments

A soil column adsorption-desorption study was performed on an agricultural calcareous soil to determine the impact of sewage sludge spreading on nickel mobility. Ni adsorption experiments were followed by desorption tests involving the following liquid extractants: water, calcium (100mg/L), oxalic acid (525mg/L equivalent to 100mg carbon/L), and sludge extracts (0.5 and 2.5g/L). Desorption tests were also conducted after sewage sludge spreading at three application rates (30, 75, and 150t/ha). According to the breakthrough curve, Ni adsorption was irreversible and occurred mainly through interactions with calcite surface sites. Nickel desorption from the soil column was promoted in presence of significant dissolved organic carbon (DOC) concentration as observed with oxalic acid elution and sludge extract at 2.5g/L. In sludge-amended soil columns, the maximum Ni levels occurred in first pore volumes, and they were positively correlated to the sludge application rate. The presence of DOC in leaching waters was the main factor controlling Ni desorption from the sludge-amended soil columns. This finding implies that DOC generated by sludge applied on calcareous soils might facilitate the leaching of Ni due to the formation of soluble Ni-organic complexes. Thus, sludge application can have potential environmental impacts in calcareous soils, since it promotes nickel transport by decreasing Ni retention by soil components.

Valorization of Organic Wastes Through Agricultural Fertilization: Coupling Models to Assess the Effects of Spreader Performances on Nitrogenous Emissions and Related Environmental Impacts

Organic waste land application generates nitrogenous emissions that have impacts on acidification, eutrophication and global warming. To assess these impacts with Life Cycle Assessment, emission factors are commonly used without taking into account neither the type and performance of land application techniques nor the type of organic waste applied. This paper proposes a methodological framework to assess the nitrogenous emissions by coupling technological performances of spreader and biophysical models, focusing on sewage sludge spreading in different weather and soil conditions. The first step consists of creating several spreading scenarios by combining a cropping system and a “spreader/sewage sludge” couple. The second step consists of testing the technological spreader performances regarding spatial distribution, application rate and soil compaction with a spreading simulator and the COMPSOIL model. Nitrogenous emissions are then simulated with STICS and DEAC models for different application rates and soil bulk densities. Finally, the simulated nitrogen losses from the models are linked with the real amounts of sewage sludge applied and the compacted soil due to spreader performances. Our approach shows that ammonia emissions during sewage sludge spreading can be directly linked to the spreader performances whereas nitrate leaching depends more on the soil and on the weather conditions. Nitrous oxide emissions mostly depend on the spreader weight and to the soil and the weather conditions. This method paves the way to new approaches: integrating technological performances of machines into biophysical and agricultural models in order to assess environmental impacts of agricultural practices.

Transport of Sulfadiazine in Undisturbed Soil Columns: Effects of Flow Rate, Input Concentration and Pulse Duration

Antibiotics reach soils via spreading of manure or sewage sludge. Knowledge on the transport behavior of antibiotics in soils is needed to assess their environmental fate. The effect of flow rate and applied mass, i.e., input concentration and pulse duration, on the transport of 14C-sulfadiazine (SDZ; 4-aminoN-pyrimidin-2-yl-benzenesulfonamide) was investigated with soil column experiments and numerical studies. Sulfadiazine was applied in pulses (6.8, 68 or 306 h) under steady-state (0.051 and 0.21 cm h(-1)) and intermittent flow conditions and at two input concentrations (0.57 and 5.7 mg L(-1)). Breakthrough curves (BTCs) of 14C were measured and for one experiment concentrations of SDZ, and its transformation products 4-(2-iminopyrimidin-1(2H)-yl)aniline (An-SDZ) and N(1)-2-(4-hydroxypyrimidinyl)benzenesulfanilamide (4-OH-SDZ) were determined. After finalizing the leaching experiments, 14C was quantified in different slices of the columns. A lower flow rate led to remarkably lower eluted masses compared with the higher flow rates. All BTCs could be described well using a three-site attachment-detachment model for which a common set of parameters was determined. However, the BTC obtained with the high input concentration was slightly better described with a two-site isotherm-based model. The prediction of the concentration profiles was good with both model concepts. The fitted sorption capacities decreased in the order SDZ > 4-OH-SDZ > An-SDZ. Overall, the experiments reveal the presence of similar mechanisms characterizing SDZ transport. The dependence of model performance on concentration implies that although the three-site attachment-detachment model is appropriate to predict the transport of SDZ in soil columns, not all relevant processes are adequately captured.

Cadmium in soils and cereal grains after sewage-sludge application on French soils. A review

Recycling sewage sludges as fertilisers on soils for crop production has several potential benefits such as providing large amounts of phosphorous and organic matter. However, the spreading of urban sewage sludge is a constant cause of controversy because it is known to introduce potentially toxic trace metals into the soil, particularly cadmium. In order to clarify this debate, this review article presents a synthesis of the results of several studies carried out in France on the impact of sewage-sludge spreading. This article reports mainly Cd results but also some results on other trace metals such as Cr, Cu, Hg, Ni, Pb and Zn. Two kinds of data are presented: (1) soil data including total metal contents and data from partial extraction to evaluate the phytoavailable fractions, and (2) plant data including metal content of wheat, a major agricultural crop. The field experiments involved very different amounts of applied sewage sludges and Cd. Indeed, three categories of experiments stand out, the first and second involving high amounts of applied Cd, and the third involving low amounts of applied Cd: (1) during the 1970s and ’80s, sludges with a high trace metal content, especially Cd, were spread at the INRA trials at Couhins experimental farm on sandy soils and in the Vexin area on silty topsoils. The quantities of applied Cd were very high, ranging from 3600 g to 641 000 g per ha. Here, the results show a notable impact on total Cd contents of topsoil and cereal grains. (2) Sludges containing high levels of industrial cadmium were spread on acid soils in the Limousin region for more than twenty years up to 1998. Topsoil Cd contents were measured in fields where the cadmium input was highest, of 300 to 600 g Cd per ha. Here, a clear increase in the Cd content of cereal grains was found. (3) During the 1990s and 2000s, numerous experiments with sewage-sludge applications compatible with the new French regulations of 1998 were implemented. The amounts of applied Cd were therefore much lower, from 0.6 to 270 g/ha. Here, no impact was detected on the composition of cereal grains. This review article concludes that the application of huge quantities of sewage sludges in the 1970s and ’80s had a clear and long-lasting effect on both soil and grain Cd compositions. Nonetheless, spreading sewage sludge in accordance with the new French regulations had no significant impact on soil and cereal-grain Cd concentrations.

Occurrence of Cryptosporidium and Giardia in sewage sludge and solid waste landfill leachate and quantitative comparative analysis of sanitization treatments on pathogen inactivation

Circulation of Cryptosporidum and Giardia in the environment can be facilitated by spreading of sewage sludge on agricultural or livestock grazing lands or depositing in landfills. Solid waste landfill leachate and sewage sludge samples were quantitatively tested for C. parvum and C. hominis oocysts, and G. lamblia cysts by the combined multiplexed fluorescence in situ hybridization (FISH) and immunofluorescent antibody (IFA) method. Subsequently, the effects of four sanitization treatments (i.e., ultrasound and microwave energy disintegrations, and quicklime and top-soil stabilization) on inactivation of these pathogens were determined. The landfill leachate samples were positive for Giardia, and sewage sludge samples for both Cryptosporididium and Giardia. The overall concentration of G. lamblia cysts (mean; 24.2/g) was significantly higher ( P<0.01) than the concentration of C. parvum and C. hominis oocysts (mean; 14.0/g). Sonication reduced the load of G. lamblia cysts to non-detectable levels in 12 of 21 samples (57.1%), and in 5 of 6 samples (83.3%) for C. parvum and C. hominis. Quicklime stabilization treatment was 100% effective in inactivation of Cryptosporidium and Giardia, and microwave energy disintegration lacked the efficacy. Top-soil stabilization treatment reduced gradually the load of both pathogens which was consistent with the serial dilution of sewage sludge with the soil substrate. This study demonstrated that sewage sludge and landfill leachate contained high numbers of potentially viable, human-virulent species of Cryptosporidium and Giardia, and that sonication and quicklime stabilization were the most effective treatments for sanitization of sewage sludge and solid waste landfill leachates.

Fate of organic pollutants after sewage sludge spreading on agricultural soils: a 30-years field-scale recording

Toxic organic compounds, such as the surfactants linear alkylbenzene sulfonates (LAS) and nonylphenol polyethoxylates (NPE), Polycyclic aromatic hydrocarbons (PAH) and residues derived from plastics (PAE-phthalates) end up in sewage sludge. In order to evaluate and quantify the potential environmental risks associated with the xenobiotic introduction into biological life cycle, the EU BIOWASTE project (QLK5-CT-2002-01138) devotes one task to the study of the fate of xenobiotic in a sandy soil after sludge spreading on a 30-year field-scale record experiment. Experimental maize crop fields from Bordeaux (France) have been amended with 100 tons per hectare each 2 years from 1974 to 1992. From 1992 to 2004, the fields were maintained and cropped with maize. This experiment shows that the concentration fluctuations in the sludge amended soil follow the same pattern of those in the sewage sludge showing that there is a real impact of the present xenobiotics in the sewage sludge on the concentration of the xenobiotics in the soil. Nonetheless, 12 years after the last addition of sewage sludge, the residual concentrations remain from 2 to 10 times higher than the content of the control soil, even though these levels are inferior to the Predicted Non Effect Concentration (PNEC). Only LAS level went back to the level in the control soil. However, only the LAS concentration is above the PNEC during all the experiment due to the very high level of LAS in the sludge (20 g/kg dry weight). These results show that even though this compound is much more degradable than NPE and PAE, it may have a long term effect in soil if high quantities are spread. To conclude, this study underlines the importance to fix maximum level for xenobiotic compounds for sewage sludge spreading on agricultural land, and also the central role of the sewage sludge processes in reducing the xenobiotic concentrations before spreading.