Sludge Disposal Site Research Articles

Heavy metal contamination of faecal sludge for agricultural production in Phnom Penh, Cambodia

To achieve the universal target of ‘safely managed sanitation’ set out in UN Sustainable Development Goal 6, the world needs to increase its rate of progress, since e.g. Phnom Penh, the capital of Cambodia, currently has zero percent safely managed sanitation. One way to promote safer faecal sludge management is to shift to a more circular system with nutrient recycling, but this carries the risk of heavy metal accumulation in the environment. This study analysed the concentrations of heavy metals in raw faecal sludge from various sources and assessed the appropriateness of resource recovery and reuse in relation to the heavy metal and nutrient loads in faecal sludge. A total of 42 samples collected from sludge disposal sites in Phnom Penh during the dry and rainy seasons were analysed for heavy metals and physicochemical parameters. Mean measured concentrations of heavy metals in faecal sludge samples decreased in the order Zn > Cu > Pb > Cr > Ni > Hg > As > Cd in both seasons but were higher in the rainy season, probably due partly to inflow from stormwater drains and run-off from roads during storm events. All elements analysed were within the permissible limits for application to land according to EU standards and USEPA. However, Hg and Zn concentrations exceeded the tolerance limits for local organic fertiliser and Swedish limits for compost. Faecal sludge is thus not an appropriate fertiliser considering the risk of heavy metal accumulation in relation to phosphorus recovered. Options to avoid recirculating pollutants to the environment include upstream prevention of pollution, source separation of household wastewater fractions and use of biosolids as a soil conditioner together with other fertilisers or for soil production. Additional studies are needed on these options if sanitation stakeholders are to close the nutrient loop.

Mapping (mis)alignment within a collaborative network using homophily metrics

Collaborative approaches can overcome fragmentation by fostering consensus and connecting stakeholders who prioritize similar activities. This makes them a promising approach for complex, systemic problems such as lack of reliable, safe water, sanitation, and hygiene (WASH) services in low-income countries. Despite the touted ability of collaborative approaches to align priorities, there remains no comprehensive way to measure and map alignment within a network of actors. Methodological limitations have led to inconsistent guidance on if, and how much, alignment is needed around a common vision (e.g., universal, reliable access to WASH) and/or around an agreed set of activities (e.g. passing a bill to promote water scheme maintenance models). In this work, we first define alignment as the extent to which actors work with others who share priorities. We then develop and test a method that uses social network analysis and qualitative interview data to quantify and visualize alignment within a network. By investigating how alignment of two strong, well-functioning WASH collaborative approaches evolved over three years, we showed that while alignment on a common vision may be a defining aspect of collaborative approaches, some alignment around specific activities is also required. Collaborative approaches that had sub-groups of members that all prioritized the same activities and worked together were able to make significant progress on those activities, such as drafting and passing a county-wide water bill or constructing a controversial fecal sludge disposal site. Despite strong sub-group formation, networks still had an overall tendency for actors to work with actors with different prioritized activities. While this reinforces some existing knowledge about collaborative work, it also clarifies inconsistencies in theory on collaborative approaches, calls into question key aspects of network literature, and expands methodological capabilities.

Isolation and identification of protease‐producing bacteria from sludge and sediment soil around Adama, Ethiopia

Proteases are enzymes used in industries such the production and processing of detergents, food, leather, and silk. The aim of this study was to isolate and identify protease‐producing bacteria from a sludge disposal site and from sediments. Soil samples were collected separately from the selected area. Samples weighing 1 g were serially diluted and spread onto skim milk agar. A total of 16 bacteria species were isolated from the study samples. Four bacterial isolates showed high proteolytic activity and were selected for enzymatic study based on their zone of proteolysis. The isolates were identified based on biochemical tests. The results indicated that the isolated bacteria were E. coli (99.69%), Pseudomonas putrefaciens (Shewanella putrefaciens) (91.61%), Bacillus carboniphilus (92.78%), and Lysinibacillus sphaericus (98.4%). The crude protease enzymes produced by these bacterial isolates showed promising results for application in dehairing and destaining as detergent additives. Bacillus carboniphilus showed the best level of activity and was selected as the most potent protease‐producing bacteria for both dehairing and destaining ability. Soils from sludge disposal sites and sediments from around tannery wastes could be good sources from which to isolate alkaline protease‐producing bacteria.

Inhibition of Verticillium Dahliae and Rhizoctonia Solani Growth by Solid Phosphate Sludge Amendments

Background: In Morocco, phosphate processing generates large quantities of sludge which amass, form fillings, reduce arable land and distort the landscape. Phosphate wash sludge is rich in mineral elements. In order to recover some of these mineral elements including phosphorus, we considered using this sludge in a nursery as a substrate. Objective: The aim of the study was to check the effect of solid phosphate sludge amendment on some of the main soil-borne pathogens: Verticillium dahliae Kleb. and Rhizoctonia solani Kühn. Materials and Methods: The pathogens have been isolated and identified in the laboratory of Plant Pathology and Postharvest Quality of INRA-Kenitra. Phosphate wash sludge used was originated from the Khouribga phosphate treatment sludge disposal site. Different concentrations of phosphate sludge (0, 10, 30, 50, and 100 g/l) were tested on a PDA-based medium, in three replicates. The inhibitory effects on mycelial growth were measured and compared with those on the soil used by nurseries (Maamora forest soil). Petri dishes with PDA alone were used as control. The same concentrations (10, 30, 50 and 100 g/kg) were tested in vivo on two varieties of tomato and on Faba Faba bean for Verticillium dahliae and Rhizoctonia solani, respectively. Results: The results of this study showed that there was significant growth inhibition at different concentrations of solid Phosphate sludge amendments in vitro. The highest inhibition percentage was observed at 100 g/l of phosphate sludge amendments with 42% and 75% for Verticillium dahliae and Rhizoctonia solani. The high concentrations of phosphate sludge have shown lower disease severity of Verticillium dahliae on the tomato plants and a disease index of Rhizoctonia solani on the Faba bean plants. Conclusion: Based on these results, we can recommend that solid phosphate sludge can be used or mixed with other substrates in nurseries.

Methodology of the geoecological functional zoning of territories subjected to anthropogenic disturbance due to waste disposal

In the present contribution, the geochemical relationships of territorial units (landscapes), namely sewage sludge disposal sites and historical municipal solid waste landfills, that can be considered as chemical elements migration models and as dynamic components of ecological-geological systems (landfill site adjacent area recreation area)., is described. Since the study of pollutants migration in multicomponent systems is extremely time-consuming, the development of theoretical methods, able to simulate these processes, is of particular relevance. Therefore, in the present study, a geochemical model for substance migration in anthropogenically modified geoecological bodies and their surrounding was conceived, making use of complex mathematical processes and data analysis methodologies (parallel use of factor, cluster, canonical and discriminant analysis tools), and considering both geochemical specialization/composition of parent rocks and land use (functional geoecological zoning).

Relationships between waste physicochemical properties, microbial activity and vegetation at coal ash and sludge disposal sites

The aim of the study was to assess the relationships between vegetation, physicochemical and microbial properties of substrate at coal ash and sludge disposal sites. The study was performed on 32 plots classified into 7 categories: dried ash sedimentation ponds, dominated by a grass Calamagrostis epigejos (AH-Ce), with the admixture of Pinus sylvestris (AH-CePs) or Robinia pseudoacacia (AH-CeRp), dry ash landfill dominated by Betula pendula and Pinus sylvestris (AD-BpPs) or Salix viminalis (AD-Sv) and coal sludge pond with drier parts dominated by Tussilago farfara (CS-Tf) and the wetter ones by Cyperus flavescens (CS-Cf). Ash sites were covered with soil layer imported as a part of technical reclamation. Ash had relatively high concentrations of some alkali and alkaline earth metals, Mn and pH, while coal sludge had high water and C, S, P and K contents. Concentrations of heavy metals were lower than allowable limits in all substrate types. Microbial biomass and, particularly, enzymatic activity in ash and sludge were generally low. The only exception were CS-Tf plots characterized by the highest microbial biomass, presumably due to large deposits of organic matter that became available for aerobic microbial biomass when water level fell. The properties of ash and sludge adversely affected microbial biomass and enzymatic activity as indicated by significant negative correlations between the content of alkali/alkaline earth metals, heavy metals, and macronutrients with enzymatic activity and/or microbial biomass, as well as positive correlations of these parameters with metabolic quotient (qCO2). Plant species richness and cover were relatively high, which may be partly associated with alleviating influence of soil covering the ash. The effect of the admixture of R. pseudoacacia or P. sylvestris to stands dominated by C. epigejos was smaller than expected. The former species increased NNH4, NNO3 and arylsulfatase activity, while the latter reduced activity of the enzyme.

Zinc bioaccumulation by microbial consortium isolated from nickel smelter sludge disposal site

AbstractHeavy metal pollution is one of the most important environmental issues of today. Bioremediation by microorganisms is one of technologies extensively used for pollution treatment. In this study, we investigated the heavy metal resistance and zinc bioaccumulation by microbial consortium isolated from nickel sludge disposal site near Sereď (Slovakia). The composition of consortium was analyzed based on MALDI-TOF MS of cultivable bacteria and we have shown that the consortium was dominated by bacteria of genus Arthrobacter. While consortium showed very good growth in the zinc presence, it was able to remove only 15 % of zinc from liquid media. Selected members of consortia have shown lower growth rates in the zinc presence but selected isolates have shown much higher bioaccumulation abilities compared to whole consortium (up to 90 % of zinc removal for NH1 strain). Bioremediation is frequently accelerated through injection of native microbiota into a contaminated area. Based on data obtained in this study, we can conclude that careful selection of native microbiota could lead to the identification of bacteria with increased bioaccumulation abilities.

Reduction in greenhouse gas emissions from sludge biodrying instead of heat drying combined with mono-incineration in China

ABSTRACTSludge is an important source of greenhouse gas (GHG) emissions, both in the form of direct process emissions and as a result of indirect carbon-derived energy consumption during processing. In this study, the carbon budgets of two sludge disposal processes at two well-known sludge disposal sites in China (for biodrying and heat-drying pretreatments, both followed by mono-incineration) were quantified and compared. Total GHG emissions from heat drying combined with mono-incineration was 0.1731 tCO2e t−1, while 0.0882 tCO2e t−1 was emitted from biodrying combined with mono-incineration. Based on these findings, a significant reduction (approximately 50%) in total GHG emissions was obtained by biodrying instead of heat drying prior to sludge incineration.Implications: Sludge treatment results in direct and indirect greenhouse gas (GHG) emissions. Moisture reduction followed by incineration is commonly used to dispose of sludge in China; however, few studies have compared the effects of different drying pretreatment options on GHG emissions during such processes. Therefore, in this study, the carbon budgets of sludge incineration were analyzed and compared following different pretreatment drying technologies (biodrying and heat drying). The results indicate that biodrying combined with incineration generated approximately half of the GHG emissions compared to heat drying followed by incineration. Accordingly, biodrying may represent a more environment-friendly sludge pretreatment prior to incineration.

Non-Ferrous Metal Industry Waste Disposal Sites As A Source Of Poly-Extremotolerant Bacteria

Abstract Waste disposal sites from non-ferrous metal industry constitute environments very hostile for life due to the presence of very specialized abiotic factors (pH, salt concentration, heavy metals content). In our experiments microflora of two waste disposal sites in Slovakia – brown mud disposal site from aluminium production near Ziar nad Hronom and nickel sludge disposal site near Sered - was analyzed for cultivable bacteria. Isolated bacteria were characterized by a combination of classical microbiological approaches and molecular methods and the most of isolated bacteria shown a poly-extremotolerant phenotype. The most frequently halotolerant (resistant to the high level of salt concentrations) and alkalitolerant (resistant to the high pH level) bacteria belonging to the Actinobacteria class were detected. The most of bacteria shown very high level of heavy metal resistance e.g. more than 500 μg/ml for Zn2+ or Cu2+. Based on our data, waste disposal sites thus on one side represents an important environmental burden but on other side they are a source of new poly-extremotolerant bacterial strains and species possibly used in many biotechnology and bioremediation applications.

English

Ghana lags behind the Millennium Development Goals’ target for sanitation, despite widespread effort by the central government. Most households in peri-urban communities in Ghana lack improved sanitation facilities, and access to faecal sludge disposal sites is also problematic. This study investigates farmers’ attitude and perception toward excreta reuse for peri-urban agriculture in Shai-Osudoku district, Ghana. Data were collected on 400 randomly selected respondents using questionnaires and focus group discussions. The study found that a majority of the respondents ‘disagree’ that excreta are a waste and are willing to use excreta as fertilizer, although a majority ‘agrees’ that excreta can pose health risks. Perceptions toward excreta reuse for agricultural purpose however differ among households. There is the need for more open discussions on the benefits and risks of excreta reuse in agriculture; this could help enrich farmers’ knowledge on the appropriate use of excreta as fertilizer. Further research on the factors that influence farmers’ decision to use excreta as fertilizer and their perceptions on the health risks is recommended.   Key words: Sanitation, excreta reuse, farmers’ perception, peri-urban agriculture, Ghana.

Performance of a Clayey Soil Used for Landfill Liner Material in a Tannery Sludge Disposal Site for Chromium Attenuation

AbstractLaboratory and field investigations were performed in this study to evaluate the efficacy of a fine-grained clayey soil as a low-cost primary liner material for attenuating chrome-laden leachate from a chrome sludge disposal site of a tannery plant. On-site soil and water samples exhibited the existence of Cr6+ in excess of the permissible limit as prescribed for discharging inland surface water. Batch adsorption kinetic results showed that Cr6+ removal in equilibration increases with elevation of temperature. The soil mass in use exhibited reasonable capability of adsorbing Cr6+, and the kinetic results demonstrated that the pseudo second-order kinetic model fitted reasonably well. The triaxial test results revealed a maximum permissible overburden pressure of 3.0 kN/m2 from deposited waste if the clayey soil is to be used as a liner material. The use of a compacted clay soil with a thickness of 600 mm is recommended for effective containment of leachate transmission with regard to a leachable h...

Attenuation of Hexavalent Chromium by In Situ Compacted Clay Liner in a Chrome Laden Tannery Sludge Disposal Site

An investigation in field scale was carried out in a common tannery effluent treatment plant site near Kolkata for evaluating hexavalent chromium migration through the fine-grained clayey soil, for disposal of chrome sludge emanated from cake filter press. The locally available soil was used in situ as a compacted clay liner material as adsorbing candidate. Laboratory batch adsorption results demonstrated about 70–80 % of hexavalent chromium removed after 120 min of equilibration time. Hydraulic conductivity of the soil was found to be decreased by two decimal place due to permeation of hexavalent chromium laden leachate. Field test results also exhibited 63 % of hexavalent chromium was sorbed after 120 days interval. Experimental results were also validated by mathematical analysis with good agreement to test data.

GROWTH PERFORMANCE, BIOMASS AND PHYTOEXTRACTION EFFICIENCY OF <i>ACACIA MANGIUM</i> AND <i>MELALEUCA CAJUPUTI</i> IN REMEDIATING HEAVY METAL CONTAMINATED SOIL

Heavy metals are very toxic and soil contaminated with sewage sludge urgently need remediation in order to avoid related health hazards. Phytoremediation is a low cost and reliable technique to remediate heavy metal contamination. However phytoremediation using timber species was rarely reported and its efficiency was questionable. A field study was conducted to examine the efficiency of two timber species namely Acacia mangium and Melaleuca cajuputi in phytoextraction of Zn, Cu and Cd from contaminated soil. Two hundred of A. mangium and M. cajuputi were planted on sewage sludge disposal site and the growth was recorded for 12 months before at the end total biomass of each species was determined. Results show in 12 months, about 72 and 4 t ha-1 of aboveground biomass can be produced by A. mangium and M. cajuputi, respectively. Both species show potential for phytoremediation, however A. mangium is more efficient compared to M. cajuputi where efficiency of A. mangium to remove Zn was 24.4, 6.2 for Cu and 9.5% for Cd. As for M. cajuputi the efficiency was 1.3, 0.3 and 0.14% for Zn, Cu and Cd, respectively. It is projected that A. mangium require 5, 17 and 20 years to remove 79.82 kg ha-1 of Zn, 46.94 kg ha-1 of Cu and 2.33 kg ha-1 of Cd, respectively.

Butyltin occurrence and risk assessment in the sediments of the Iberian Peninsula

The occurrence of butyltin (BT) compounds in more than 50 recent sediment samples of the Iberian Peninsula, collected in the harbours of the western Mediterranean Sea (Spain) and the North Atlantic Ocean (Portugal), including domestic and industrial sewage disposal sites, has been assessed. The highest levels of tributyltin (TBT) (7673 μg kg −1 dry wt.) were detected in commercial harbours associated with inputs from large vessels. However, relatively high TBT values (about 2150 μg kg −1 dry wt.) were also detected in fishing and recreational boating areas. Spanish marinas and harbours are more polluted in terms of TBT (5–7673 μg kg −1 dry wt.) compared to those in Portugal (4–12 μg kg −1 dry wt.). Generally, the Mediterranean sediments show a BT distribution characterized by the predominance of TBT over the degradation products dibutyl (DBT) and monobutyltin (MBT), indicating the presence of recent inputs, in contrast to the Portuguese coastal distribution. Calculation of butyltin degradation indexes (BDI) confirmed a different trend, depending on the area. Furthermore, a comparative study of the occurrence of BT in different sewage sludge disposal sites shows that domestic primary sewage sludge effluents can contribute to coastal BT pollution, but to a lesser extent when compared with harbours. Historical trends (1995–2003) for Barcelona harbour reveal that BT regulations on the use of TBT-based antifouling paints have not been fully effective. Finally, a comparison against the existing sediment quality guidelines (SQGs) indicated that acute toxic effects could only be expected for TBT in some Mediterranean harbours; conversely, in every North Atlantic Ocean station, a lesser environmental threat for the harbour benthic community is expected.

<i>Short communication</i> Increase in metal extractability after liming of sacrificial sewage sludge disposal soils

A sandy and a sandy clay-loam soil from two dedicated (sacrificial) sewage sludge disposal sites were incubated with a total lime equivalent of 45 Mg·ha-1. Both these soils were acidified (pH 4.0 to 4.2) and had a significant accumulation of organic material (organic C of 2.9 to 3.7 %) compared to non-polluted soils (organic C of 0.6 to 1.0 %). The limed soils did not attain the desired pH of 6.5 after 6 months\' incubation due to a high buffer capacity. After incubation, soil samples were taken from the incubated pots and the levels of Al, Fe, Mn, Cu, Zn, Pb and Cd were determined by atomic absorption spectrophotometry (AAS) after extraction with NH4-EDTA and BaCl2. Most of the metals extracted with BaCl2 (except Mn in the sandy soil and Cd in both soils) decreased after liming. The EDTA-extractable Mn, Fe, and Cd in both soils and Cu and Pb in the sandy clayloam soil increased after liming, whereas Al and Zn, decreased in extractability (Statistically significant differences could not be determined for the trial due to the trial not having been designed for the results that were obtained). Similar results were reported in the literature for EDTA metal extraction but the phenomenon was not elaborated upon, except for Cr. The increased extractability of some of the metals after liming could negatively influence the use of EDTA as an extracting agent in proposed heavy-metal guidelines for similar sacrificial soils. Should liming be considered as a strategy to decrease metal mobility in sacrificial soils, the observed increase in extractability becomes a cause for concern and should receive attention in further research. Water SA Vol. 31 (2) 2005: pp.271-274

Phytoextraction capacity of the plants growing on tannery sludge dumping sites

The study was undertaken to assess the phytoremediation potential of four plants ( Sida acuta, Ricinus communis, Calotropis procera, Cassia fistula) growing at a tannery sludge disposal site. Results showed that maximum amount of K, Fe and Ni was associated with residual fraction, whereas, Zn, Mn, Cr, Pb, Cd and Co was found in Fe–Mn oxide fraction. Cu and Na were mostly associated with organic matter and carbonate fraction, respectively. The results demonstrated that the levels of accumulation of metals was found high in all the studied plants and followed the order; C. procera > S. acuta > R. communis = C. fistula. The principal components analysis (PCA) revealed that translocation behavior of Cu, Zn and Mn, Cr were found similar in the plants. Correlation analysis between metal accumulation in the plants with DTPA extractable metals emphasized that S. acuta and C. fistula provide better value of correlation for most of the tested metals. The values of transfer factor were also found high for most of the tested metals in the plants of S. acuta. Overall, the plants of S. acuta and C. fistula were found suitable for the decontamination of most of the metals from tannery waste contaminated sites.

Sulfur and Carbon Cycling in a Flue Gas Desulfurization Sludge Disposal Site

Products of a power plant flue gas desulfurization scrubber are discharged into a pond as sludge consisting of calcite (initial δ13C 3.2–3.8‰), gypsum (initial δ34S 7.6–8.6‰), and aqueous solution. Reducing conditions exist below a boundary that appears to move vertically as a function of changes in pond water level. Under reducing conditions, bacteria partially reduce aqueous sulfate to low-δ34S sulfide, consuming organic carbon and generating low-δ13C bicarbonate. Under oxidizing conditions, sulfide is converted to sulfate, leading to calcite dissolution, gypsum precipitation, and isotopic re-equilibration of remaining calcite with dissolved bicarbonate near the pond surface. The gypsum has δ34S near 6‰, and calcite has δ13C as low as -1.7‰; the changes from initial values correspond to predictions based on isotopic balance and reaction stoichiometry. The pond largely contains the products of bacterial reduction. After the pond is abandoned, these products may adversely affect attempts to revegetate the site. Future bacterial reduction may be best controlled by dewatering and limiting the supply of organic matter in percolating surface water.

Modelling of Cd, Cu, Ni, Pb and Zn uptake, by winter wheat and forage maize, from a sewage disposal farm

Abstract. A predictive model of metal concentrations in crops was developed to optimize soil liming and sludge application strategies at a dedicated sewage sludge disposal site. Predictions of metal concentrations in plant tissue were derived from measured values of soil metal concentration, humus content and soil pH. The plant and soil data used to parameterize the model were collected on site using quadrat sampling of mature crop and underlying topsoil. The uptake model was used to map predicted metal concentrations in wheat grain and forage maize based upon a database of soil characteristics (metal content, % humus and pH) measured as part of a routine geochemical survey of the site. The effect of a management strategy to modify uptake of Cd by wheat by changing soil pH was investigated. The effect of soil dust adhering to maize plants at harvest was also simulated to investigate the importance of this pathway for Cd transfer to animal feed such as silage.The model gave satisfactory predictions for uptake of Cd and Zn but less useful simulations for Pb, Cu and Ni. The results for Cd uptake showed a greater dependence on soil pH in the case of wheat in comparison to maize. It is suggested that, for the study site, liming to pH 7.0 will reduce Cd concentrations in wheat grain to within EC legal standards. However the Cd content of maize may still exceed these guidelines, with a relatively minor contribution from contamination with soil dust.

Organotin contamination in sediments from the Western Mediterranean enclosures following 10 years of TBT regulation

Organotin (OT) compounds, namely butyl and phenyl, were measured in 38 recent sediments collected in harbours of the Western Mediterranean Sea (Northern: 4 and Southern: 9) and domestic and industrial sewage disposal sites (Northern: 9 and Southern: 1). Butyltins were the predominant tin species identified as being tributyltin (TBT) widespread in the whole area which suggests recent inputs of OTs. The highest levels of TBT were detected in commercial harbours associated with inputs from large vessels (average value: 5.0 μg TBT g −1). Moreover, relatively high TBT values were also detected in fishing and recreational boating areas (average level ca. 1.0 μg TBT g −1). Phenyltin derivatives occurred at lower levels than butyltins being the monophenyltin the predominant compound (average values 45–945 ng g −1). The large predominance of the phenyltin degradation products (i.e. mono and diphenyltin) over the parent compound (i.e. triphenyltin) suggests that there are almost no recent inputs of these compounds. Furthermore, a comparative study of the OT occurrence in the sewage sludge disposal sites offshore Barcelona and Almerı́a (domestic) and into the Tarragona harbour (industrial) shows that domestic primary sewage sludge effluents can contribute to coastal OT pollution (244 ng TBT g −1). Nevertheless, sewage sludge is a secondary source of OT contamination in the coastal environment in comparison to commercial harbours. In a comparative study with previous data collected in the late 1980s, the present study reveals that OT regulations established in the Mediterranean region in 1991 on the use of TBT-based antifouling paints have been effective in marinas, but reveals a significant TBT contamination in commercial and fishing harbours.

Evaluation of dioxin contamination in sewage sludge discharges on coastal sediments from catalonia, spain

The fate of polychlorinated dibenzo- p-dioxins (PCDDs) and dibenzofurans (PCDFs) in sewage sludges after discharge into the sea was investigated. Sediment samples were analysed at a sewage sludge disposal site as well as in the surrounding areas. Moreover, eight sediment samples from two rivers in Catalonia and three sediment samples from Catalonian Coast were analysed to determine the background levels of contamination. Total international toxicity equivalent (I-TEQ) values for these sediments ranged from 0.42 to 8.01 pg/g, with a mean value of 4.15 pg/g and a median value of 3.69 pg/g. However, the I-TEQ values of sludge-treated areas were higher: 57.04 pg/g at the dumping site, and within a range of 13.42–47.76 pg/g near this site. Thus, European sediment quality objectives were exceeded. The higher concentrations coincided with changes in the ratio between PCDD and PCDF levels, suggesting the influence of the sewage sludge on coastal sediments.