Contaminated Sewage Sludge Research Articles

Impact of heavy metal amended sewage sludge on forest soils as assessed by bacterial and fungal biosensors

Bacterial and fungal bioluminescence-based biosensors were used as indicators of potential heavy metal toxicity to microorganisms in the needle litter of a mature Pinus radiata forest under heavy metal contaminated sewage sludge. Sewage sludge was amended with increasing concentrations of Cu, Ni and Zn and applied to the surface of a mature P. radiata forest. The response of the bacterial and fungal biosensors to soluble Cu, Ni and Zn in needle litter extracts was investigated. The bioluminescence response of the bacterial biosensor Escherichia coli HB101 pUCD607 declined as water-soluble Zn concentrations increased. The effective concentrations that gave a 50% reduction in bioluminescence (EC50 values) for water-soluble Zn and total litter Zn were 1.3 mg l−1 and 3700 mg kg−1, respectively. The bioluminescence response of the fungal biosensor Armillaria mellea declined as soluble Cu concentrations increased. The EC50 values for water-soluble Cu and total litter Cu were 0.12 mg l−1 and 540 mg kg−1, respectively. No decline in bioluminescence was noted for either the bacterial or fungal biosensor on exposure to increasing concentrations of water-soluble Ni. The use of a combination of bacterial and fungal biosensors offers a rapid and sensitive tool for assessing toxicity of heavy metals to microorganisms and, thus, elucidating the environmental impact of contaminants in sewage sludge on litter dwelling microorganisms.

Polycyclic Aromatic Hydrocarbons Content in Shoots and Leaves of Willow (Salix viminalis) Cultivated on the Sewage Sludge-Amended Soil

The aim of the present study was to investigate the uptake of 16 PAHs by willow (Salix viminalis) from soil amended with contaminated sewage sludge. Uptake experiments were conducted on field plots using sludge applications of 0, 30, 75, 150, 300, and 600 Mg ha−1. The total PAH content of control soil and sludge were 49.6 μg kg−1 and 5713 μ g kg−1, respectively. The concentrations for the 16 PAHs listed as priority pollutants were measured for soil and plant tissue samples obtained at 0.5, 1.5, 2.5, and 3.5 years. Soil total PAH content decreased significantly within the first half year, followed by minimal changes over the subsequent three years of treatment. PAH analysis was carried out on a HPLC-UV. Total PAH content in control plants was 3.6–7.3 μ g kg−1 for shoots and 13–27 μ g kg−1 for leaves. Treated plant tissue content was higher with shoots and leaves containing ∼5.5–17.6 and 13.5–33.8 μg kg−1, respectively. Plant total PAH content did not show a significant trend relative to controls with respect to time. However, uptake did increase in relation to an increased sludge application. Bioconcentration factors (BCF), adjusted by control values, were calculated for total PAH content. BCF values were highest for the initial sampling (6 months) and did not show a significant temporal relationship. BCF values did decrease with increasing sludge application. With respect to individual PAHs, elevated plant tissue concentrations were measured for “light” PAH (e.g. naphthalene, phenanthrene, acenaphthalene) with leaf BCF values correlated with solubility and organic partitioning coefficients.

Competing perspectives on public involvement: Planning for risk characterization and risk communication about radiological contamination from a national laboratory

Public involvement is increasingly emphasized as part of government agencies' responses to environmental health hazards, including risk characterization and risk communication. For example, there is a growing body of literature on health and risk communication proposing best practices and evaluating processes, yet there has been little attention to the ways that preferences for process features and criteria for evaluating success may vary among stakeholders and between stakeholders and government agency staff. This paper reports on a study into how participants associated with an effort to address public health risks from the distribution of plutonium contaminated sewage sludge in Livermore, California, think about the most appropriate way to conduct a process integrating public involvement. Using Q method this paper identifies five perspectives about what constitutes a good collaborative process in this case. The lessons for organizers and participants of risk characterization and risk communication efforts when people subscribe to different (sometimes competing) perspectives about process are discussed.

The application of sludge on agriculturally used soils and the problemof persistent organic pollutants

A set of 45 samples of the sludge from wastewater factories in the area of the Czech Republic was completed. The selection of wastewater factories reflected the extent of observed area as well as the occurrence of the industrial wastewater. The contents of persistent organic pollutants (POPs) were determined in the samples. Moreover, the contents of polychlorinated dibenzo-p-dioxins and dibenzofuranes (PCDD/F) were detected in 16 samples. The set of analytical data summarises the level of sewage sludge contamination by POPs within Czech wastewater factories. The results were compared with the directive of Czech Ministry of Environment, No. 382/2001 Sb. and with the proposed limit values of the EU directive, No. 86/278. Among all the determined substances only the value of the sum of polycyclic aromatic hydrocarbons (PAHs) content exceeded the threshold value given by the proposed EU directive.

A risk-based methodology for deriving quality standards for organic contaminants in sewage sludge for use in agriculture—Conceptual Framework

This paper describes a systematic methodology (Conceptual Framework) to derive quality standards for organic (anthropogenic) contaminants in sewage sludge added to agricultural land, in the context of revision of EU Sludge Directive 86/278/EEC and the broader Soil Thematic Strategy. The overall objective is to ensure, based on a risk assessment approach, a sustainable use of sludge over a long time horizon. ILSI-Europe’s Conceptual Framework is in essence consistent with the EU Technical Guidance Document (TGD) for Environmental Risk Assessment of Chemicals in the soil compartment, or US-EPA’s Sewage Sludge Use and Disposal Regulations, Part 503 Standards. A ‘checklist’ of different exposure pathways and transfer processes for organic contaminants needs to be considered, and the most sensitive relevant toxicological endpoint and its PNEC need to be identified. The additional complexity specific to deriving Sludge Quality Standards (SQS) is that the toxicity results may need—e.g., for (indirect) human toxicity—to be related back to maximum acceptable soil exposure levels (PEC soil). In turn, the latter need to be back-calculated to the maximum acceptable levels in sewage sludge (PEC sludge) at the time of application. Finally, for a sustainable sludge use, the exposure from repeated addition and potential chemical build-up over time (e.g., 100 years) needs to be assessed. The SQS may therefore vary with the (local) sludge application regime, and/or sludge pretreatment processes.

Lead behavior in soil treated with contaminated sewage sludge and cultivated with maize

Lead (Pb) behavior was studied in soil treated twice with sewage sludge contaminated with lead at interval of 18 months. Soil samples received five different treatments: three with lead [0 (reference); 2,500; 5,000 mug g-1] and two with a mixture of lead and cadmium (interferer) (2,500 + 2,500 and 5,000 + 5,000 mug g-1, respectively). Vases containing treated soil were cultivated with maize in a greenhouse for 75 days. Pb was extracted using nitric perchloric digestion and analyzed by atomic absorption spectroscopy. The soil, containing sewage sludge contaminated by lead presented a higher concentration of Pb. The metal concentration remained constant in all treatments at 20-60 cm depth. No absorption of Pb by the plants was detected.

Comparison of a cultural method with ListerScreen plus Rapid'L.mono or PCR-ELISA methods for the enumeration of L. monocytogenes in naturally contaminated sewage sludge

Cultural methods used to count Listeria monocytogenes in sewage sludge are laborious and time consuming, and alternative methods are needed to reduce analysis time and improve detection limits. In this study, a survey of L. monocytogenes in sewage sludge is presented with a comparative study between a cultural method and immunomagnetic separation using a ListerScreen test followed by identification of L. monocytogenes with Rapid'L.mono agar or PCR-ELISA. These two alternative methods improved the detection of L. monocytogenes in different types of sludge, irrespective of their physical and chemical characteristics. The ListerScreen method coupled with detection of L. monocytogenes on Rapid'L.mono offers the advantage of being less sophisticated than the molecular method and allows isolation of the organism, which may be useful in epidemiological studies. However, ListerScreen coupled with PCR-ELISA proved best for high-sensitivity detection of L. monocytogenes in sewage samples.

Bio-indicators to assess impacts of heavy metals in land-applied sewage sludge

Soils from a pastoral farm that had received large amounts of heavy metal contaminated sewage sludge 6–10 years previously were investigated to determine the impact of heavy metals on Rhizobium. The 8 ha application area was originally divided into five different-sized blocks (blocks 1–5), which received sludge at different times between 1991 and 1994. The response of a lux biosensor based on R. leguminosarum bv. trifolii (Rhizotox-C), was compared with more traditional techniques for measuring the presence of effective strains of Rhizobium (MPN) and nitrogen fixation ( δ 15N natural abundance). Although population size (MPNs), nitrogen fixation and biosensor response varied between treatment blocks, linear regression analysis determined that this block effect could not be directly linked to soil heavy metal concentrations, but was probably due to biological, physical, chemical and environmental compounding factors at the site. In this type of uncontrolled field application, the lux bioassay may provide the most useful information as it measures toxicity to any microorganism exposed to the soil solution, for example, the free living rhizobia.

Enhancement of polycyclic aromatic hydrocarbons removal during anaerobic treatment of urban sludge

Anaerobically stabilized sewage sludge has potential to partially substitute synthetic fertilizers. The main risk with the recycling of urban sludge on agricultural soils is the accumulation of unwanted products, such as trace metals and organic micropollutants. In this context, the polycyclic aromatic hydrocarbons (PAHs) are particularly monitored because of their toxic properties at low concentrations and their high resistance to biological degradation. The aim of the present study was to optimize PAHs removal during anaerobic digestion of contaminated sewage sludge. Thirteen PAHs were monitored in laboratory-scale anaerobic bioreactors under mesophilic (35 degrees C) and thermophilic (55 degrees C) methanogenic conditions. Abiotic losses were statistically significant for the lightest PAHs, such as fluorene, phenanthrene and anthracene. It was shown that PAH removal was due to a specific biological activity. Biological PAHs removal was significantly enhanced by an increase of the temperature from 35 degrees C to 55 degrees C, especially for the heaviest PAHs. Bioaugmentation experiment was also performed by addition of a PAH-adapted bacterial consortium to a non-acclimated reactor. Significant enhancement of PAHs removal was observed. It was finally shown that PAH removal efficiencies and methanogenic performances were closely linked. The rate of biogas production may be used as an indicator of bacterial activity on PAH removal.

Effect of nonylphenol surfactants on fungi following the application of sewage sludge on agricultural soils.

The effect of nonylphenol on fungi following the application of contaminated sewage sludge on agricultural soil was studied in laboratory experiments. Nonylphenol bioavailability and adsorption were determined in the soil alone and soil-sludge mixtures. Mixing the soil with sludge made it possible to measure the nonylphenol concentration in the soil solution, which comprised between 6.6 x 10(-6) and 3.8 x 10(-7) M, according to the sludge. We then examined the dose-response relationship between nonylphenol concentration in the culture medium and both biomass production and germination rate of the spores from several strains of filamentous fungi. When applied in this range of concentration, nonylphenol was without noticeable short-term effect on these endpoints. Long-term exposure of fungi to nonylphenol was also assessed. The most intensive effect was a strong stimulation of spore production and germination in Fusarium oxysporum Schlechtendahl. Biomass production by the Fusarium strains also increased. Finally, nonylphenol was shown to induce laccase production in Trametes versicolor. We conclude that the potential of nonylphenol to adversely affect several soil fungi remains low.

The influence of application form on the toxicity of nonylphenol to Folsomia fimetaria (Collembola: Isotomidae)

The Collembola Folsomia fimetaria L. was exposed in the laboratory to a range of elevated soil and sewage sludge nonylphenol concentrations under three different contamination scenarios. When F. fimetaria were exposed to nonylphenol-spiked soil in a standard test design, a 10% effect concentration (EC10) of approximately 23 mg NP/kg was observed for reproduction. One of the primary sources of nonylphenol to agricultural soils is sewage sludge. Upon addition of nonylphenol to sewage sludge prior to homogeneously mixing this into the soil a 10% effect concentration (EC10) of approximately 6 mg NP/kg soil was observed for reproduction. Within soil core sewage, sludge is often not homogeneously distributed, but rather patchily distributed, enabling organisms to avoid it. To mimick the patchy distribution of sewage sludge, NP-contaminated sewage sludge pellets were distributed in noncontaminated soil and F. fimetaria were exposed to it. Exposed to the contaminated sewage sludge pellet F. fimetaria were affected by nonylphenol concentrations above approximately 19 mg NP/kg soil for reproduction. In this case the dose–response curve was considerably less steep than those of the two above exposure regimes.

Influence of thermal treatment on sequential extraction and leaching behaviour of trace metals in a contaminated sewage sludge

Influence of thermal treatment on sequential extraction and leaching behaviour of trace metals in a contaminated sewage sludge

Speciation, Accumulation of Heavy Metals in Vegetation Grown on Sludge Amended Soils and their Transfer to Human Food Chain - A Case Study

The continuous use of heavy metal contaminated sewage sludge as a fertilizer can result in transfer and accumulation of toxic metals from sludge to soil. The subsequent uptake and accumulation of metals in the edible parts of vegetative tissue results in a direct pathway into the human food chain. Speciation study has great importance for monitoring the entry of heavy metals into the human food chain as these are associated in a variable manner in different phases (or species). To assess the extent of heavy metal contamination of soils and also of the vegetables grown on soil amended with sludge, speciation studies were carried out using BCR sequential extraction scheme proposed by European Commission. The vegetables that were grown on sludge amended agricultural fields were analyzed for toxic heavy metals to assess the extent of uptake of heavy metals by different plants. This study reflects the extent of contamination of soil and vegetation due to application of sludge as manure and element transfer to the human food chain.

Influence of thermal treatment on sequential extraction and leaching behaviour of trace metals in a contaminated sewage sludge

The losses of weight and organic matter of a sludge caused by thermal treatments at 180°C, 300°C and 400°C were determined in order to assess how the possibilities of sludge use were influenced. The sludge heated at 180°C lost small amounts of weight and organic matter (9.8%) but the losses from the two other treatments were large enough (92.2% and 99.9% in organic matter) to preclude the use of the sludges as organic amendments. The concentration and potential lability and leachability of Cr, Cu, Fe, Mn, Ni, Pb and Zn in the native sludge and in the thermal-treated sludge samples were studied by means of a five-step chemical fractionation method and a column experiment. As a consequence of heating, the trace metals were more strongly fixed in the treated sludges, as could be seen by the decrease with temperature of the ratio between the sum of the first two sequential-extracted fractions and the residual fraction. The leaching results showed that, for the native sludge, the quantities of studied metals leached were larger than for the sludge heated to180°C. The order of leachability of metals was the same in both cases, and the same equation could be used to calculate the quantities of metals leached. The amounts of metals leached correlated significantly with the first extracted fraction (exchangeable metals) and an equation could be used to calculate the quantities leached, as a function of that fraction.

Trace metal concentration in durum wheat from application of sewage sludge and commercial fertilizer

Repetitive application of commercial fertilizer continually introduces potentially toxic trace metals to the soil. Such metallic elements are not biodegradable, accumulate in the soil, and are subsequently taken up by food crops. Sewage sludge, often disposed of in landfills, contains high nutrient and organic contents and is now being recycled and beneficially applied to agricultural land worldwide in increasing amounts. Metals in sewage sludge are generally organically bound and generally less available for plant uptake than the more mobile metal salt impurities found in commercial fertilizers. The purpose of this project was to determine the regions of metal accumulation within the wheat plant and to compare metal uptake by plants receiving a high metal load through the application of contaminated sewage sludge with that by plants receiving a commercial fertilizer and a metal-free control. Results of this research indicate that despite the high metal load received by the sludge-applied replicates, metal concentrations in those plants were similar to the concentrations resulting from application of the commercial fertilizer and the metal-free nitrogen control. Little or no change in metal concentration was seen between plants grown with fertilizer addition in comparison to the control plants.

Experimental assessment of bio-reduction of Di-2-thylhexyl phthalate (DEHP) under aerobic thermophilic conditions

The reduction of organic contaminants in sewage sludge is of great importance for a further sludge disposal or agricultural utilization. Laboratory scale batch experiments were performed to assess the potential use of the aerobic thermophilic treatment technique to reduce the concentration of difficult to degrade organic chemicals. Di-2-ethylhexyl phthalate (DEHP) was chosen as a model representative of these chemicals. The effect of the sludge temperature and aeration rate on the reduction of DEHP concentration as well as on the reduction of the organic dry solid (oDS) was investigated. With a specific air flow rate of 16 m 3/m 3.h and a thermophilic temperature of 63 °C it was possible to achieve up to 70% reduction of the DEHP concentration and 61% of oDS within 96 hours. The maximum degradation of the oDS matter occurred within the first 24 hours of operation whereby only little oDS was degraded afterward. During the experiments the reactor content was routinely monitored for pH, COD, along with the ammonia nitrogen and orthophosphate concentrations. Their variations are discussed in this paper.

Organic contaminants in sewage sludge and their ecotoxicological significance in the agricultural utilization of sewage sludge

The screening of sewage-sludge for organic pollutants was carried out in the state of Brandenburg, Germany. Samples were taken both in summer and winter. The waste water treatment plants were classified in three groups depending on the types of sewage treated (domestic, municipal and industrial waste water). The content of polychlorinated terphenyls, naphthalenes, chloropesticides, halogenated hydrocarbon solvents, aromatic hydrocarbon solvents (BTEX), chlorobenzenes, polyaromatic hydrocarbons, phenols, chlorophenols, phthalates, petroleum hydrocarbons, surfactants, organotin compounds and 2,4-dichloroaniline was estimated. Data from terrestrial ecotoxicology were used to estimate tolerable levels of soil contamination. This yields the so-called “standard values” for concentrations of organic pollutants in sewage sludge. The concentrations of most pollutants in sewage sludge were found to be below the standard value. However, surfactant and toluene concentrations exceeded the standard value.

Screening the environmental fate of organic contaminants in sewage sludge applied to agricultural soils: II. The potential for transfers to plants and grazing animals

This is the second of two papers which screen the environmental fate of sludge or sludge organic contaminants when applied to agricultural land. A simple screening model has been developed to assess the likelihood of organic contaminants accumulating into the food-chain following the application of sludge onto arable and pasture land. The purpose of this exercise is to highlight those compounds that have the potential to accumulate into plants and animal tissues using data on physico-chemical properties of the compounds of interest. Over 300 organic compounds or groups of compounds which have been identified as potential pollutants in sludge have been screened for their potential to transfer from sludge-amended soils to plants via retention by root surfaces, root uptake and translocation, foliar uptake and animal intake via soil and herbage ingestion. Various organic contaminants have been identified as having a high potential to transfer into the food-chain through plant and animal accumulation. Two priority lists have been produced to include (a) those compounds which are shown as being of sufficient or suspected importance, but for which further sludge concentration data and fate studies would be necessary to check on their status, and (b) those compounds which have been highlighted in the screening processes as having a high potential to accumulate up the food-chain. This screening approach can be adapted to other chemicals as information on new chemicals and their physico-chemical properties becomes available.

Monitoring and prioritisation of organic contaminants in sewage sludges using specific chemical analysis and predictive, non-analytical methods

Municipal sludge application on agricultural land (land utilization) is practised widely and accounts for between 30–40% of production in Canada and the UK. Land utilization is subject to public concerns over the potential for deleterious effects of organic contaminants on agricultural productivity and uptake into the foodchain. Consequently, reliable data on the concentrations of organic contaminants in sludge are required to assess risks associated with land use. A detailed monitoring survey has been carried out by WTC to determine the concentrations of a range of industrial organic contaminants in 11 Canadian sewage sludges and one sludge compost. Volatile, base-neutral and acid extractable contaminants seldom exceeded 5 mg kg−1 dry wt., organochlorine pesticides and polychlorinated biphenyls did not exceed 1 mg kg−1 dry wt. and toxaphene and N-nitrosodimethylamine were not detected in the materials analyzed. Mean total PCDD and PCDF concentrations were ≤ 36 μg kg−1 dry wt. (median 6.7 μg kg−1 dry wt.) and mean toxic equivalents were ≤ 0.12 μg kg−1 dry wt. (median 0.02 μg kg−1 dry wt.). It was concluded that in many Canadian sludges the aforementioned organic contaminants represent no significant risk to agriculture and the environment. However, other organic contaminants potentially present in sewage sludge may not be amenable to analysis by the target compound techniques widely used. Consequently, WRc have applied a non-analytical approach to assess which contaminants may occur in sewage sludges and persist in treated soils. Predictions of physicochemical properties using quantitive structure activity relationships (QSARs) have been used to aid the screening and prioritisation of a range of high production volume chemicals (HPVCs) that may enter sewage treatment works. Analytical surveys for organic residues are expensive and this type of approach may assist in identifying further contaminants which should be analyzed in sewage sludges and treated soils.

Screening the environmental fate of organic contaminants in sewage sludges applied to agricultural soils: 1. The potential for downward movement to groundwaters

The potential for organic contaminants present in sewage sludge to leach and cause groundwater contamination following sludge application to agricultural land has been assessed. Models used to predict compound mobility in soil on the basis of physico-chemical parameters were applied to a range of contaminants prioritised and/or detected in sludge and a provisional list of potential ‘leachers’ compiled. In addition, theoretical soil water concentrations following sludge application were calculated using mean reported sludge contaminat concentrations and soil/water partition coefficients. These estimated aqueous phase concentrations were compared with Dutch groundwater quality standards in the absence of appropriate UK standards to identify those compounds which could be present in groundwater at levels of concern. The two prioritised lists were used to identify compounds in sludge which could pose a possible threat to groundwater. Appropriate experimental data were not available to qualify model results. However, the screening exercise indicated that under routine operational practice with typical sludge application rates, and the usual range of compound concentrations detected in sludge, groundwater quality standards were unlikely to be exceeded. However, data variability, reliability and scarcity limited the usefulness of this screening approach.