Different Types Of Sewage Sludge Research Articles

Enhancing short-chain fatty acids production via acidogenic fermentation of municipal sewage sludge: Effect of sludge characteristics and peroxydisulfate pre-oxidation.

This study first employed a combined pretreatment of low-dose peroxy-disulfate (PDS) and initial pH 10 to promote short-chain fatty acids (SCFAs) production via acidogenic fermentation using different types of sewage sludge as substrates. The experimental results showed that the yield of maximal SCFAs and acetate proportion after the combined pretreatment were 1513.82±28.25mg chemical oxygen demand (COD)/L and 53.64%, and promoted by 1.28 and 1.56 times higher, respectively, compared to the sole initial pH 10 pretreatment. Furthermore, in terms of the disintegration degree of sewage sludge, it increased by more than 18% with the combined pretreatment compared to the pretreatment of sole initial pH 10. Waste-activated sludge (WAS) from A2/O and Bardenpho processes were more biodegradable, explained by the 1.47- and 1.35-times higher disintegration rate than those from oxidation ditch and they favored acetate dominant fermentation. Correlation analysis revealed a strong correlation (p ≤ 0.01) between SCFAs production and soluble COD, total proteins, proteins in soluble-extracellular polymeric substances (SEPS), total polysaccharides, and polysaccharides in SEPS. Mechanism explorations showed that preoxidation with PDS enhanced the solubilization and biodegradability of complex substrates, and altered the microbial community structure during the fermentation process. Firmicutes and Tetrasphaera were proven to play a key role in improving SCFA production, especially in promoting acetate production by converting additional SCFAs into acetate. Additionally, the addition of PDS greatly promoted sulfur and iron-related metabolic activities. Finally, the combined pretreatment was estimated to be a cost-effective solution for reutilizing and treating Fe-sludge.

Microwave Treatment of Three Different Types of Sewage Sludge Based on Their Solar Drying Exposure Time: Effect on Microorganisms, Water Content and Agronomic Aspects

This study aimed to treat sewage sludge through microwave irradiation at a laboratory scale. The objective was to investigate the effect of microwave irradiation on microorganisms, water content, organic matter, and agronomic nutrients present in sewage sludge. Three types of sewage sludges obtained from a full-scale wastewater treatment plant were considered: Sludge A (raw sludge), Sludge B (subjected to 15 days of solar exposure, achieving 48% dryness), and Sludge C (exposed to solar conditions and left open to the air for 23 months, reaching 94% dryness). These diverse sludges were exposed to microwave irradiation at various power levels (analysed variables: ε (Watts/g), θ (°C), T (min)). The specific exposure powers and temperature levels for the water reduction analysis were: 555, 955, 1355, and 1500 Watts/g and 55, 75, 95, and 105 °C, respectively. On the other hand, microbiological and agronomic nutrient analyses were conducted at 75 °C–1355 W and 95 °C–1355 W. After microwave exposure experiments, the results demonstrated the high effectiveness of microwave technology in eradicating indicator microorganisms of faecal contamination and reducing sludge volume while not affecting trace elements of significant agricultural value. The reduction in Escherichia Coli revealed that 4 min of irradiation was necessary to completely eliminate it to 0 ulog, indicating a 100% reduction, in Sludge A. In Sludges B and C, an additional 1 min was needed under conditions of 75 °C and 1355 W for a mass of 50 g. Moreover, Sludge A (46.27 × 105 or 4.80 ulog of dry matter), Sludge B (1.29 × 106 or 6.11 ulog of dry matter), and Sludge C (8.77 × 104 or 4.94 ulog of dry matter) were heavily contaminated with faecal coliforms. It took 6 min to reduce faecal coliforms to below the detection threshold.

Syngas generation from different types of sewage sludge using microwave-assisted pyrolysis with silicon carbide as the absorbent

In this study, the pyrolysis of sewage sludge was explored through microwave-assisted pyrolysis. Three kinds of sludge (primary sludge, waste-activated sludge, and digested sludge) from a sewage treatment process were used. All three kinds of sewage sludge had a low microwave absorption capacity; therefore, an absorber was added to enable microwave-assisted pyrolysis. By using silicon carbide as the heating element, it was possible to increase the temperature within a short time by applying microwaves. During the microwave-assisted pyrolysis of sewage sludges, the amount of gas generated and the H2 and CO fraction of the produced gas increased as temperature increased. The pyrolysis of waste-activated sludge produced the greatest quantity of gas. However, the primary sludge produced the highest amount of syngas in terms of H2 and CO, which indicate the high-quality of the syngas.

Synthesis of Biogas Supply Network Based on Experimental Data from Lab-Scale Anaerobic Digestion of Sewage Sludge and Organic Waste

The aim of this work was to perform synthesis of biogas supply network based on the experimental data from laboratory-scale anaerobic digestion (AD) experiments. Experiments were performed with various types of organic waste and sewage sludge, such as different types of sewage sludge from municipal and industrial wastewater treatment plants, waste from vegetable oil, wine, dairy and meat processing industry, lignocellulosic waste and bio-plastic waste. The synthesis problem was formulated as a mixed-integer linear program (MILP) and was solved by using General Algebraic Modelling System (GAMS) software with the main objective of maximizing economic profit. The synthesis is demonstrated on an illustrative case study of up to three biogas plants in Slovenia. Three scenarios were considered with different prices of waste materials. The study showed good agreement between the model and experimental results. Results demonstrated that biogas production could be profitable by using considered waste materials only if biogas plant was paid for processing the substrates. Up to 6 GWh/y of electricity could be produced with the profit of about 2·106 $/y where prices of waste materials were around 80 $/t.

Different pyrolysis kinetics and product distribution of municipal and livestock manure sewage sludge

Thermogravimetric analysis and pyrolyzer-gas chromatography/mass spectrometry measurements were taken to examine the kinetic behavior and product distribution on the thermal and catalytic pyrolysis of different types of sewage sludge. Compared to livestock manure sewage sludge (LMSS), municipal sewage sludge (MSS) had larger ash (30.3%) and lower fixed carbon (7.9%) contents. The peak intensities for the 1st decomposition region (200–380 °C) on the derivative thermogravimetric curve of MSS were higher than those of LMSS. In contrast, the peak height in the 2nd temperature region (>380 °C) of MSS was lower than that of LMSS. The activation energy for the pyrolysis of MSS (Avg. 186.5 kJ/mol) was lower than that of LMSS (Avg. 263.4 kJ/mol) over the entire conversion range. MSS produced larger amounts of fatty acids and cholesterol than LMSS. The in-situ catalytic pyrolysis of MSS over HBeta using a pyrolyzer-gas chromatography/mass spectrometry also produced larger amounts of aromatic hydrocarbons than LMSS, suggesting that its better feedstock properties strongly influence the final product oil quality.

Fertilisation with biosolids in a silvopastoral system established with Pseudotsuga menziesii (Mirb.) Franco in Galicia (NW Spain)

In Europe, sewage sludge has to be stabilised before its use as fertiliser in agricultural land. Stabilisation processes can cause differences in the concentration of heavy metals in sewage sludge, such as that of zinc (Zn), one of the heavy metals with the highest proportion in sewage sludge. This study was undertaken to examine during a five-year period the effects of fertilisation with different types of sewage sludge (anaerobic, composted, and pelletised) on the concentration of total and available Zn in the soil, tree growth, pasture production, and concentration of Zn in the pasture when compared to control treatments (i.e. no fertilisation and mineral fertilisation) in a silvopastoral system (SS) under Pseudotsuga menziesii (Mirb.). The results of this experiment revealed that pelletised sewage sludge enhanced the levels of Zn in soil and pasture and the production of pasture without reducing the tree growth. Therefore, the use of this type of sewage sludge as organic fertiliser should be promoted in SSs established under tree species and edaphoclimatic conditions similar to those in this study. Moreover, regardless of the type of sludge used for fertilisation, the levels of Zn in the soil never exceeded the maximum values set by Spanish regulations and did not cause harmful effects on plants and animals.

Proposing policy changes for sewage sludge applications based on zinc within a circular economy perspective

Sewage sludge production has been increased in the last years because the wastewater treatment is mandatory in urban areas with more than 2000 inhabitants since 2005. Most adequate disposal of sewage sludge should be agricultural soils to improve their fertility and fulfill bioeconomy and circular economy requirements. However, the higher level of heavy metals in sludge than in soils makes necessary to consider the inputs of heavy metals in soil as have been done by regulation 86/278/EEC and more recent documents (EU 3rd Draft Directive or the Environmental, economic and social impacts of the use of sewage sludge on land). Sewage sludge application is restricted by the mean amount of heavy metals applied with sewage sludge in soil in a 10-year period and the concentrations of heavy metals in the sludge and soils. The aim of this study was to evaluate the current and foreseeable limits of the application of different types of sewage sludge (anaerobic, pelletised and composted) considering the current and the possible future legislation of the most abundant heavy metal in the sewage sludge, which is Zinc (Zn) and taking into account the existing levels in acid soils in Galicia (NW Spain). Main results highlighted the adequacy of using composted sludge as amendment, while anaerobic and pelletised sludge as fertilisers to reduce future possible soil contamination. Sewage sludge regulations should aim to reach mean values of Zn to ensure soil microbial health and sustainability adequate levels of Zn in crops or pasture. Low quality sewage sludge application should be reduced in frequency or doses, allowing soils to get benefits of increasing soil organic matter without strong changes in Zn soil contents.

Investigation of NO conversion by different types of sewage sludge chars under low temperature

Different types of sludge chars, i.e. the original (S1), HNO3 washed (S2), KOH activated (S3), and H2 reduced chars, were prepared to investigate their performances for NO conversion under low temperature. Results indicated that the surface area of the sludge chars did not play key role on NO conversion. S1 showed the higher NO conversion performance than S2 and S3, due to the reducing effect of iron components in S1 (mainly FeS and Fe2P). Both H2 reduction at high temperature and the followed cooling atmosphere (H2 or N2) have great influences on the activity of S1. H2 reduction can promote the reducing capacity of the iron components, thus the performance of S1 for NO conversion was also significantly enhanced. However, NO conversion over S1 decreased in the presence of O2, because the iron components were more quickly oxidized in O2 atmosphere. Results of duration tests showed that the activity of S1 decreased with time, but it can be recovered by calcination in N2. The profiles of the temperature programmed desorption (TPD) of CO and CO2 indicated that CO and CO2 emissions are mainly from the decomposition of oxygen functional groups (OFGs), including anhydrides, phenols, esters, and carboxylic acid. Furthermore, mechanisms of NO adsorption and conversion by S1−S3 were explored by an in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). It was found that NO adsorbed on the sludge chars mainly transferred into NO2 species at 50 °C, and then NO2 species were gradually oxidized to nitrate species with the increase of temperature. Finally, the possible reaction routes for NO conversion were proposed based on experimental data.

Removal of Phenolic Compounds from Water Using Sewage Sludge-Based Activated Carbon Adsorption: A Review.

Due to their industrial relevance, phenolic compounds (PC) are amongst the most common organic pollutants found in many industrial wastewater effluents. The potential detrimental health and environmental impacts of PC necessitate their removal from wastewater to meet regulatory discharge standards to ensure meeting sustainable development goals. In recent decades, one of the promising, cost-effective and environmentally benign techniques for removal of PC from water streams has been adsorption onto sewage sludge (SS)-based activated carbon (SBAC). This is attributed to the excellent adsorptive characteristics of SBAC and also because the approach serves as a strategy for sustainable management of huge quantities of different types of SS that are in continual production globally. This paper reviews conversion of SS into activated carbons and their utilization for the removal of PC from water streams. Wide ranges of topics which include SBAC production processes, physicochemical characteristics of SBAC, factors affecting PC adsorption onto SBAC and their uptake mechanisms as well as the regeneration potential of spent SBAC are covered. Although chemical activation techniques produce better SBAC, yet more research work is needed to harness advances in material science to improve the functional groups and textural properties of SBAC as well as the low performance of physical activation methods. Studies focusing on PC adsorptive performance on SBAC using continuous mode (that are more relevant for industrial applications) in both single and multi-pollutant aqueous systems to cover wide range of PC are needed. Also, the potentials of different techniques for regeneration of spent SBAC used for adsorption of PC need to be assessed in relation to overall economic evaluation within realm of environmental sustainability using life cycle assessment.

Performance of electro-osmotic dewatering on different types of sewage sludge

The feasibility of pressure-driven electro-dewatering (EDW) on sludge samples taken after different biological processes, stabilisation methods or mechanical dewatering techniques was assessed. First, the influence of potential values on EDW of anaerobically and aerobically stabilised, mechanically dewatered, sludge samples was investigated. Preliminary tests carried out by applying a constant potential (10, 15 and 20V) in a lab-scale device confirmed the possibility to reach a dry solid (DS) content of up to 42.9%, which corresponds to an increase of 15% of the dry content in dewatered sludge without the application of the electrical field. Dewatering increased with the applied potential but at the expense of a higher energy consumption. A potential equal to 15V was chosen as the best compromise for EDW performance, in terms of DS content and energy consumption. Then, the influence of the mechanical dewatering was studied on aerobically stabilised sludge samples with a lower initial DS content: the higher initial water content led to a lower final DS content but with a considerable reduction of energy consumption. Finally, the biological process, studied by comparing sludge samples from conventional activated sludge and membrane bioreactor processes, didn’t evidence any influence on EDW. Experimental results shown that DS obtained after mechanical dewatering, volatile solids and conductivity are the main factors influencing EDW. Anaerobically digested sludge reached the highest DS content, thanks to lower organic fraction.

Effect of various types of thermochemical processing of sewage sludges on phosphorus speciation, solubility, and fertilization performance

Sewage sludge has one of the highest phosphorus (P) recovery potentials of all waste materials. Therefore, P-recycling from sewage sludge could contribute to closing the P-cycle. Recently, various thermal processes for P-recovery have been developed, but there is still a demand for information on the effect of different process parameters (e.g. additives and temperature) on P-speciation and especially on the fertilization performance. In the present study, two common methods (low-temperature conversion at 400–500°C and thermochemical treatment at 950°C) were investigated and combined to produce highly bioavailable P-fertilizers from two different types of sewage sludge based on chemical phosphorus precipitation (Chem-P) and enhanced biological phosphorus removal (Bio-P). The results of P-fractionation, X-ray diffraction analysis, and pot experiments with maize showed that Bio-P sludges attain high P-plant-availability after treatment at low temperatures (400°C). In contrast, Chem-P sludges can adequately be treated at higher temperatures under reductive conditions with sodium additives to form highly bioavailable calcium-sodium-phosphate. Additionally, also highly heavy-metal contaminated sludges can be thermochemically treated at high temperatures to achieve the legal requirements for fertilizers.

Fate of emerging and priority micropollutants during the sewage sludge treatment: Case study of Paris conurbation. Part 1: Contamination of the different types of sewage sludge

This article provides data on the contamination of different kinds of sludge (raw, centrifuged, digested, thermally dried sludge and sludge cake) from Paris conurbation by 71 various pollutants including pharmaceutical products (PHPs), hormones, perfluorinated acids (PFAs), linear alkylbenzene sulfonate (LAS), alkylphenols (APs), phthalates (PAEs), polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs).Very high contents of LAS (0.1–10g/kg dry matter - DM) compared to other compounds were found in all types of sludge followed by DEHP (10–100mg/kg DM) and fluoroquinolones (1–100mg/kg DM). APs were measured at intermediary contents in Parisian sludge, lying in the 2–20mg/kg DM range. Finally, hormones, PAHs, PCBs, PAEs, PFAs and the remaining PHPs were all found at contents lower than 1mg/kg DM.For most compounds (PHPs, PFOS, DEHP, PAHs), no significant differences in the micropollutant contents were found for similar types of sludge from different WWTP in Paris, highlighting the homogeneity of sludge contamination in downstream Paris catchment.The variability of concentration is rather high (coefficient of variation >100%) for several PHPs, PFAs or PCBs while it is moderate (<100%) or low (<50%) for fluoroquinolones, hormones, PAHs, APs or LAS. In addition, digestion seems to have a buffer effect as variabilities are lower in digested sludge for PHPs, PFAs, APs and PCBs. During sludge treatment (centrifugation, digestion, thermal drying, sludge conditioning+press filtration), the hormones, LAS, APs, PAHs, DEHP and PCBs concentrations increased, while those of PHPs and PFAs decreased. In the case of digestion, the increase of content can be explained by no pollutant removal or a lower removal than DM removal (concentration phenomenon) whereas the decrease underlines that the compound is more removed than the DM. In any case, these concentration variations presuppose the mechanisms of dissipation that could be attributed to volatilization, biotic or abiotic transformation (complete or with metabolites production), bound residues formation.In addition, data on sludge liquors - centrifuged (CW) and condensed (TDW) waters - from respectively centrifugation and thermal drying were collected. Several hormones, PHPs, PFAs, LAS, PAEs, APs, PCBs and PAHs were quantified in CW and TDW, displaying a transfer through the water removal. The concentrations observed are rather comparable to those found in wastewater.

Toxic potential of different types of sewage sludge as fertiliser in agriculture: ecotoxicological effects on aquatic, sediment and soil indicator species

Purpose Treated and processed sewage sludges (biosolids) generated during the treatment of wastewater usually contain substantial concentrations of nutrients, especially phosphorus, which is essential for plant growth. Sewage sludge therefore can be used as an alternative fertiliser in agriculture. But since sewage sludge could also contain pollutants, analysis and ecotoxicological tests on affected soil and stream water organisms are necessary in order to guarantee its harmless use.

Sewage sludge stabilisation and fertiliser value in a silvopastoral system developed with Eucalyptus nitens Maiden in Lugo (Spain)

Copper (Cu) is one of the heavy metals with highest proportion in sewage sludge. In Europe, sewage sludge should be stabilised before using it as a fertiliser in agriculture. Depending on the stabilisation process, sewage sludge has different Cu contents, and soil Cu incorporation rates. This study was undertaken to examine the effect of fertilisation with different types of sewage sludge (anaerobic, composted, and pelletised) on the concentration of total and available Cu in the soil, the tree growth, the pasture production, and the concentration of Cu in the pasture when compared with control treatments (i.e. no fertilisation and mineral fertilisation) in a silvopastoral system under Eucalyptus nitens Maiden. The results of this experiment show that an improvement of the soil pH increased the incorporation and the mineralisation of the sewage sludge and litter, and therefore, the release of Cu from the soil. Moreover, the concentration of Cu in the pasture and the levels of Cu extracted by the pasture improved when the soil organic matter decreased because the high levels of organic matter in the soil could have formed Cu complex. The composted sewage sludge (COM) increased a) the soil variables studied (pH, total Cu, and available Cu) and b) the Cu extracted by the pasture, both probably due to the higher inputs of cations made with it. In any case, the levels of Cu found in the soil never exceeded the maximums as set by Spanish regulations and did not cause harmful effects on the plants and animals. Therefore, the use of COM as an organic fertiliser should be promoted in silvopastoral systems established in edaphoclimatic conditions similar to this study because COM enhanced the productivity of the system from a viewpoint of the soil and the pasture, without causing any environmental damage.

Retraction Note to: Toxic potential of different types of sewage sludge as fertiliser in agriculture: ecotoxicological effects on aquatic and soil indicator species

Retraction Note to: Toxic potential of different types of sewage sludge as fertiliser in agriculture: ecotoxicological effects on aquatic and soil indicator species

Wet oxidation of sewage sludge from municipal and industrial WWTPs

In the last years, sewage sludge management turned out to be a topic of great interest due to the increasing sludge production and the high cost of sludge treatment and disposal. In this context, several methods are being studied for sewage sludge minimization: among them, wet oxidation (WO) was proposed as an effective hydrothermal oxidation based technology. The aim of this work, carried out within the European project “ROUTES,” was the assessment of the influence of sludge composition on process performance: for this purpose, seven different types of sewage sludge were submitted to WO tests at lab scale. Moreover, each operating condition (temperature, reaction time, and initial oxygen pressure) was varied so as to highlight the effect of process parameters on oxidation efficiency; this was essentially evaluated in terms of chemical oxygen demand (COD), volatile suspended solid (VSS) and total suspended solid (TSS) reduction. COD and VSS abatement varied in the ranges 44–85%, 71–99% depending on reaction time (15–120 min) and 22–79%, 54–99% as a function of temperature (200–250°C), respectively. Furthermore, by comparing WO tests results of the seven types of sludge obtained under the same treatment conditions (temperature = 250°C and reaction time = 60 min), it was highlighted that VSS and COD removal efficiency can be correlated to the initial VSS/TSS ratio.

Modification of lignite ash fusion temperatures by the addition of different types of sewage sludge

The effect of the addition of three types of sludge (A, V and F) on the slagging behaviour of a brown lignite was investigated. It was evaluated by determining ash fusion temperatures (AFTs) of lignite, sludge samples and coal-sludge blends of 10 and 50wt.% of each sludge, together with their chemical and mineral composition. The addition of sludge to lignite produces a decrease in the AFTs, the extent of which depends on the percentage of sludge added to the lignite, as well as the sludge additives used (organic polyelectrolyte, lime and/or FeCl3) and their phosphorus content. As a consequence, the addition of sludge to lignite produces an increase in the slagging tendency. Those lignite–sludge blend ashes whose base to acid ratio (B/A(+P)) ranges from 0.7 to 2.0 have the lowest AFTs. In this range, most of the ash compositions are near to those of SiO2–Al2O3–CaO eutectics. Also, an increase in the phosphorus content of the blends, as well as the formation of amorphous silicates and phosphates, reduce the AFTs.

RETRACTED ARTICLE: Toxic potential of different types of sewage sludge as fertiliser in agriculture: ecotoxicological effects on aquatic and soil indicator species

Purpose Treated and processed sewage sludge (biosolids) generated during the treatment of waste water usually contain substantial concentrations of nutrients, especially phosphorus which is essential for plant growth. Sewage sludge therefore can be used as an alternative fertiliser in agriculture. But since sewage sludge could also contain pollutants, analysis and ecotoxicological tests on affected soil and streamwater organisms are necessary in order to guarantee its harmless use.

Consequences of sludge composition on combustion performance derived from thermogravimetry analysis

Wastewater treatment plants produce millions of tons of sewage sludge. Sewage sludge is recognized as a promising feedstock for power generation via combustion and can be used for energy crisis adaption. We aimed to investigate the quantitative effects of various sludge characteristics on the overall sludge combustion process performance. Different types of sewage sludge were derived from numerous wastewater treatment plants in Beijing for further thermogravimetric analysis. Thermogravimetric–differential thermogravimetric curves were used to compare the performance of the studied samples. Proximate analytical data, organic compositions, elementary composition, and calorific value of the samples were determined. The relationship between combustion performance and sludge composition was also investigated. Results showed that the performance of sludge combustion was significantly affected by the concentration of protein, which is the main component of volatiles. Carbohydrates and lipids were not correlated with combustion performance, unlike protein. Overall, combustion performance varied with different sludge organic composition. The combustion rate of carbohydrates was higher than those of protein and lipid, and carbohydrate weight loss mainly occurred during the second stage (175–300°C). Carbohydrates have a substantial effect on the rate of system combustion during the second stage considering the specific combustion feature. Additionally, the combustion performance of digested sewage sludge is more negative than the others.

Sorption of Perfluorinated Compounds onto different types of sewage sludge and assessment of its importance during wastewater treatment

The distribution coefficient (Kd) and the organic carbon distribution coefficient (KOC) were determined for four Perfluorinated Compounds (PFCs) to three different types of sludge taken from a conventional Sewage Treatment Plant (STP). Batch experiments were performed in six different environmental relevant concentrations (200ngL−1to 5μgL−1) containing 1gL−1 sludge. Kd values ranged from 330 to 6015, 329 to 17432 and 162 to 11770Lkg−1 for primary, secondary and digested sludge, respectively.The effects of solution’s pH, ionic strength and cation types on PFCs sorption were also evaluated. Sorption capacities of PFCs significantly decreased with increased pH values from 6 to 8. Furthermore, the divalent cation (Ca2+) enhanced PFCs sorption to a higher degree in comparison with the monovalent cation (Na+) at the same ionic strength.The obtained Kd values were applied to estimate the sorbed fractions of each PFC in different stages of a typical STP and to calculate their removal through treated wastewater and sludge. In primary settling tank, the predicted sorbed fractions ranged from 3% for Perfluorooctanoic Acid (PFOA) to 55% for Perfluoroundecanoic acid (PFUdA), while in activated sludge tank and anaerobic digester sorption was more than 50% for all target compounds. Almost 86% of initial PFOA load is expected to be detected in treated wastewater; while Perfluorodecanoic acid (PFDA), PFUdA and Perfluorooctanesulfonate (PFOS) can be significantly removed (>49%) via sorption to primary and excess secondary sludge. In anaerobic digester, the major part (>76%) of target PFCs is expected to be sorbed to sludge, while almost 3% of initial PFOA load will be detected in sludge leachates.