Sewage Sludge Concentrations Research Articles

Getting on with persistent pollutants: Decreasing trends of perfluoroalkyl acids (PFAAs) in sewage sludge

Sewage sludge can be a relevant source of perfluoroalkyl acids (PFAAs) for the environment. In order to reduce emissions from this source, Bavarian authorities enforced in 2008 an analysis of PFAAs from sewage sludge derived from municipal wastewater treatment plants (WWTPs). 4981 sludge samples from 1165 different WWTPs were analyzed between 2008 and 2013 for 11 PFAAs compounds. During this period, 71 WWTPs exceeded the precautionary limit of 125 μg kg−1 dm of total PFAAs in sludge samples at least once with a decreasing tendency. The yearly exceedances of the investigated WWTPs decreased from 6% in 2008 to 0.8% in 2013. At the same time, the percentage of uncontaminated WWTPs increased from 33% to 65%. Perfluorooctane sulfonic acid (PFOS) was the predominant compound found in 41% of all sludge samples. Perfluorodecanoic acid (PFDA) was detected in 19% and Perfluorooctanoic acid (PFOA) in 7%. Very high PFAAs concentrations (>500 μg kg−1 dm) in sewage sludge were generally caused by firefighting foams containing PFAAs or emissions from PFAAs-using industries including metal plating, textile, leather or paper industries. Trend analyses of the six year period show that PFAAs contamination in sewage sludge clearly decreased for 47% of the WWTPs. However, for 16% of the WWTPs an increasing trend was detected, even though the concentration levels were below the precautionary limit. During the six years of investigation the load of total PFAAs in sewage sludge was reduced by more than 90%, from 17 t a−1 in 2008 to 1.5 t a−1 in 2013.

The Different Physiological and Antioxidative Responses of Zucchini and Cucumber to Sewage Sludge Application.

The present study investigates the effect of soil amended with sewage sludge on oxidative changes in zucchini and cucumber plants (Cucurbitaceae) and the consequent activation of their antioxidative systems and detoxification mechanisms. The plants were grown in pots containing soil amended with three concentrations of sewage sludge (1.8 g, 5.4 g and 10.8 g per pot), while controls were potted with vegetable soil. The activities of three antioxidative enzymes, ascorbate peroxidase (APx), catalase (CAT) and guaiacol peroxidase (POx), were assessed, as well as of the detoxifying enzyme S-glutathione transferase (GST). Lipid peroxidation was evaluated by measuring the extent of oxidative damage; α-tocopherol content, the main lipophilic antioxidant, was also measured. Visible symptoms of leaf blade damage after sewage sludge application occurred only on the zucchini plants. The zucchini and cucumber plants showed a range of enzymatic antioxidant responses to sewage sludge application. While APx and POx activities increased significantly with increasing sludge concentration in the zucchini plants, they decreased in the cucumber plants. Moreover, although the activity of these enzymes increased gradually with increasing doses of sewage sludge, these levels fell at the highest dose. An inverse relationship between peroxidases activity and CAT activity was observed in both investigated plant species. In contrast, although GST activity increased progressively with sludge concentration in both the zucchini and cucumber leaves, the increase in GST activity was greater in the zucchini plants, being visible at the lowest dose used. The results indicate that signs of sewage sludge toxicity were greater in zucchini than cucumber, and its defense reactions were mainly associated with increases in APx, POx and GST activity.

Sewage sludge toxicity assessment using earthworm Eisenia fetida: can biochemical and histopathological analysis provide fast and accurate insight?

Sewage sludge (SS) is a complex organic by-product of wastewater treatment plants. Deposition of large amounts of SS can increase the risk of soil contamination. Therefore, there is an increasing need for fast and accurate assessment of SS toxic potential. Toxic effects of SS were tested on earthworm Eisenia fetida tissue, at the subcellular and biochemical level. Earthworms were exposed to depot sludge (DS) concentration ratio of 30 or 70%, to undiluted and to 100 and 10 times diluted active sludge (AS). The exposure to DS lasted for 24/48h (acute exposure), 96h (semi-acute exposure) and 7/14/28days (sub-chronic exposure) and 48h for AS. Toxic effects were tested by the measurements of multixenobiotic resistance mechanism (MXR) activity and lipid peroxidation levels, as well as the observation of morphological alterations and behavioural changes. Biochemical markers confirmed the presence of MXR inhibitors in the tested AS and DS and highlighted the presence of SS-induced oxidative stress. The MXR inhibition and thiobarbituric acid reactive substance (TBARS) concentration in the whole earthworm's body were higher after the exposition to lower concentration of the DS. Furthermore, histopathological changes revealed damage to earthworm body wall tissue layers as well as to the epithelial and chloragogen cells in the typhlosole region. These changes were proportional to SS concentration in tested soils and to exposure duration. Obtained results may contribute to the understanding of SS-induced toxic effects on terrestrial invertebrates exposed through soil contact and to identify defence mechanisms of earthworms.

Assessment of Heavy Metals in Spinach (Spinacia oleracea L.) Grown in Sewage Sludge–Amended Soil

ABSTRACTThe assessment of heavy metals in spinach (Spinacia oleracea) grown in sewage sludge–amended soil was investigated. The results revealed that sewage sludge significantly (P < 0.01) increased the nutrients and heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), and zinc (Zn) in the soil. The contents of metals were found to be below the maximum levels permitted for soils in India. The most agronomic performance and biochemical components of S. oleracea were found at 50% concentrations of sewage sludge in both seasons. The contents of Cd, Cr, Cu, Mn, and Zn in S. oleracea were increased from 5% to 100% concentrations of sewage sludge in both seasons. The order of contamination factor (Cf) of different heavy metals was Mn > Cd > Cr > Zn > Cu for soil and Cr > Cd > Mn > Zn > Cu for S. oleracea plants after application of sewage sludge. Therefore, use of sewage sludge increased concentrations of heavy metals in soil and S. oleracea.

Effects of Different Sewage Sludge Concentrations on the Soil Microorganism Sensibility and Metals Accumulation during Helianthus annuus L. Cultivation

Effects of Different Sewage Sludge Concentrations on the Soil Microorganism Sensibility and Metals Accumulation during Helianthus annuus L. Cultivation

Effects of Different Sewage Sludge Concentrations on Soil and Cultivated Raphanus sativus L

Effects of Different Sewage Sludge Concentrations on Soil and Cultivated Raphanus sativus L

The fate of mercury in municipal wastewater treatment plants in China: Significance and implications for environmental cycling

Municipal wastewater treatment plants (WWTPs) play an important role in controlling pollutant discharges to surface waters. Previous studies suggested that the removal of mercury (Hg) by WWTPs was strongly correlated with solid removal. However, conclusions regarding possible transformations of Hg species within WWTPs were not consistent across those studies. We characterized total Hg (THg) and methylmercury (MeHg) concentrations and loads in a WWTP located in Jiaozuo, China, to further understand Hg fate and transformations in WWTPs. THg and MeHg were primarily associated with wastewater solids, and removal of both were greater than 90%; concentrations in the sewage were (2.0±2.7)×103ng/L and 7.5±5.8ng/L, respectively. A mass balance calculation revealed that 80% of the THg input to the WWTP ended up in the sewage sludge (SS), while more than 70% of the influent MeHg mass was degraded, indicating WWTPs are an important sink for sewage-borne Hg. THg and MeHg concentrations in SS were (3.9±1.4)×103ng/g and 6.3±2.3ng/g, respectively, suggesting SS could be a significant source of THg and MeHg to the environment if not handled properly. The significance of sewage and SS in the biogeochemical cycling of THg and MeHg in China is discussed.

Sewage sludge treatment: evaluation of the energy potential and methane emissions with COD balancing

Sewage sludge is an important resource for the generation of electricity and heat within a wastewater treatment plant (WWTP). Taking a holistic approach to such use involves considering the greenhouse gas emissions. In particular, for anaerobic sludge treatment, methane emissions are a matter of concern. Therefore, the utilization of a carbon balance, based on the chemical oxygen demand (COD), will be a focus for evaluating the magnitude of methane losses within the sludge treatment. In addition to biogas production and use in combined heat and power plants (CHPs), dissolved methane in digested sludge, as well as the methane slip, have to be considered. Measurements of dissolved methane concentrations in sewage sludge from digesters of various WWTPs show a concentration of about 17–37 mg CH4/L. The COD balance indicates a ratio of the methane emissions (methane slip, dissolved methane and residual gas) of &amp;lt; 4% of the total methane production during digestion. Considering the electricity generation by CHPs and the higher global warming potential of methane, compared to carbon dioxide, emissions of approximately 300 g CO2-equ./kWhel result, which is in a similar range to greenhouse gas emissions caused by electricity generation by fossil fuels.

The Increase in Bismuth Consumption as Reflected in Sewage Sludge

As the use of dangerous substances in consumer products increases, these substances may also be found in society’s end products, among them sewage sludge. Measuring concentrations in sewage sludge can be a way to reflect the consumption of a substance. By using substance flow analysis, the inflow, stock and outflow of the specific substance to, e.g. a city region, may be analysed. Bismuth is a heavy metal that is found in increasing levels in sewage sludge in Swedish wastewater treatment plants (WWTPs) and a similar increase cannot be excluded for WWTPs around the world. This study aims to examine possible sources that could explain the amounts measured in one Swedish WWTP. Household products such as cosmetics (24 %) and plastics (14 %) are found to be major sources of Bi measured in sewage sludge. The remaining unidentified amounts in this study (approximately 50 %) are most likely found in effluent waters from industries or sources outside the household. There is, however, no information on measurements of Bi released by industry available and there is no legislation in place that may encourage industry to conduct such measurements.

Effects of sewage sludge used as fertilizer on the yield and chemical contents of common vetch (Vicia sativaL.) and soil

This study was conducted to determine the effects of sewage sludge (SS) used as fertilizer at different concentrations [Control, 20 kg ha–1 nitrogen (N), 30 ton ha–1 SS (S1), 60 ton ha–1 SS (S2) and 90 ton ha–1 SS (S3), 20 kg ha–1 N + 30 ton ha1 SS (N + S1), 20 kg ha–1 N + 60 ton ha–1 SS (N + S2) and 20 kg ha–1 N + 90 ton ha–1 SS (N + S3)] on common vetch yields and chemical features. For this purpose, an increasing level of SS was applied to the soil samples. The residuals of some heavy metal (Hg, Cr, Fe, Ni, Zn, Mn, Cd, Pb, Cu, Co, and Se) and macro element (K, Ca, Na, Mg, C, and S) concentrations were measured in leafs, seeds and soils. According to the results of this study, SS, when applied to soil in increasing amounts, raised the mineral matter contents of the plants, which favorably affected plant growth. Accordingly, it affected the herbage yield, increasing the yield in parallel with the increasing SS concentrations. Applying N with the SS positively influenced the heavy metal contents on leafs and seeds of common vetch and residue in the soil. Besides, the heavy metal contents were found at below critical levels in the soil, leaf and seeds. Therefore, SS application as fertilizer used in appropriate concentrations did not pollute the soil very much, but did lead to an increase in plant products.

Methodology for the quantification of greenhouse gas emissions during land application of sewage sludge

Land application of sewage sludge improves soil physical, chemical and biological properties, minimizes the mineral fertilizer application and reduces maintenance of soil. In this work, various methods to estimate greenhouse gas (GHG) emissions due to land application of sewage sludge described in the literature were summarized and their limitations were presented. Moreover, an improved methodology to evaluate GHG emissions due to the land application of sewage sludge was proposed. Further, based on the proposed methodology, GHG emissions due to land application of sewage sludge at lower, higher and average concentrations of nutrients (carbon, nitrogen and phosphorus) were assessed. The results revealed that GHG emissions substantially decreased when higher nutrients containing sewage sludge were applied to land. For methodologies presented in the literature, GHG emissions or reductions due to land application did not change with nutrients concentrations of sewage sludge. However, based on the proposed me...

Evaluation of “Classic” and Emerging Contaminants Resulting from the Application of Biosolids to Agricultural Lands: A Review

ABSTRACTThe presence of detectable amounts of contaminants in treated sewage sludge (concentrations μg/kg – mg/kg) has led to concerns that land applications of biosolids may result in an accumulation of contaminants in the soil and their subsequent translocation through the food chain. Despite advances in wastewater management (e.g., anaerobic, thermophilic, and mesophilic digestion), many compounds and their metabolites remain intact following treatment. This review looks at the main risk factors relating to the occurrence of “classic” (persistent organic pollutants [POPs]) and emerging pollutants (pharmaceuticals and personal care products) in biosolids. Relevant EU legislation and risk assessment strategies for the control of emerging contaminants are also considered. Organic pollutants regulated under the Stockholm Convention on POPs along with PPCPs were identified as contaminants of concern based on the risk factors: persistence, bioaccumulation, and toxicity (PBT). PPCPs were recognized as being of particular concern as their high transformation/removal rates are compensated by their continuous introduction into the environment. This study highlights the growing concern in relation to emerging contaminants in biosolids and highlights risk assessment strategies that can be used to characterize potential human/environmental risks.

Preliminary Comparison of Radioisotope Concentration in Sewage Sludge after the Fukushima and Chernobyl Accidents

Radioisotope concentrations (Cs-137 and I-131) in sewage sludge, obtained on a daily basis in the Fukushima city wastewater treatment plant from end of April 2011 until end of December 2013, have been analysed for their evolution with time, and the time series have been compared to similar data from central Europe after the Chernobyl accident. Additionally, daily rainfall data have been considered for Fukushima.The long-term trends for Cs-137 are very similar between Japan and Europe, indicating a decrease of concentration with an initial half-life of about 1 year with a tendency towards a slower decrease at later times. Short-term Cs-137 data indicate a dominating influence of rainfall – each significant rainfall event leads to a sharp increase of sludge Cs-137 concentration. Absolute values (maximum: ca. 6000 Bq kg-1) are relatively low compared to Europe after 1986 – this is attributed to the different types of sewer systems: separated in Fukushima, collecting only small amounts of rainfall with the wastewater, mixed in many cities in Europe, collecting rainwater and wastewater in the same sewer. I-131 was detectable during short intervals and at relatively constant maximum concentration (ca. 1000 Bq kg-1) during the whole observation period. The origin is suspected to be routine medical application of the isotope, which has been shown to contribute significantly to sewage sludge concentration wherever it is in use.

Application of Hydrothermal Treatment to High Concentrated Sewage Sludge for Anaerobic Digestion Process

Tomato and seaweed were produced by utilizing CO2 and heat discharged from power generation using biogas in Toyogawa biomass park, Japan. The biogas was obtained by anaerobic digestion with hydrothermal treatment. The hydrothermal treatment was applied to the high concentrated sewage sludge (22 % total solids (TS) dewatered sludge). The purpose of this study is to clarify the effect of hydrothermal treatment on the qualities of high concentrated sewage sludge, by analyzing particulate organic carbon (POC) and dissolved organic carbon (DOC). The hydrothermal treatment was investigated under 10-60 min of treatment time, 180-200 °C of temperature, 10-22 %-TS of sewage sludge concentration. The results showed that the DOC in each conditions increased through hydrothermal treatment. The highest DOC obtained was 67 % of total carbon concentration, when the temperature was 180 °C, treatment time was 60 min and sewage sludge concentration was 10 %-TS. Furthermore, the viscosity of treated sewage sludge was decreased by hydrothermal treatment. In batch anaerobic digestion test, methane gas production was confirmed. In addition, this study evaluated the energy balance of this system. Thus, the results of this study indicated that the possibility of application of hydrothermal treatment to high concentrated sewage sludge for anaerobic digestion process.

Upper and Lower Concentration Thresholds for Bulk Organic Substrates in Bioremediation of Acid Mine Drainage

Acidic pit lakes can form in open cut mine voids that extend below the groundwater table. The aim of this research was to determine what bulk organic material concentrations best stimulated sulphate-reducing bacteria (SRB) for acid mine drainage (AMD) treatment within a pit lake. An experiment was carried out to assess the effect of different substrate concentrations of sewage sludge on AMD bioremediation efficiency. Experimental microcosms were made of 300 mm long and 100 mm wide acrylic cores, with a total volume of 1.8 L. Four different concentrations of sewage sludge (ranging from 30 to 120 g/L) were tested. As the sewage sludge concentration increased, the bioremediation efficiency also increased, reflecting the higher organic carbon concentrations. Sewage sludge contributed alkaline materials that directly neutralised the AMD in proportion to the quantity added and therefore played a primary role in stimulating SRB bioremediation. The lowest concentration of sewage sludge (30 g/L) tested proved to be inadequate for effective SRB bioremediation. However, there were no measurable beneficial effects on SRB bioremediation efficiency when sewage sludge was added at concentrations >60 g/L. We compared our results with existing literature data to develop a conceptual model for remediation of AMD in pit lakes through organic material amendments. The model indicated that labile organic carbon availability was more important to the bioremediation rate than AMD strength, so long as iron and sulphate concentrations were not limiting. The conceptual model also indicates that bioremediation may still occur when only low concentrations of organic carbon are present in the pit lakes, albeit at a very slow rate. The model also demonstrates the presence of an organic material amendment threshold where excess organic carbon does not measurably influence the final outcome. The conceptual model defined is well supported by the results of the microcosm experiment.

Induction of suppressiveness to Fusarium wilt of chrysanthemum with composted sewage sludge

The effectiveness of composted sewage sludge incorporated into Pinus bark-based substrate with or without biofertilizer, fish hydrolyzate, chitosan and Trichoderma asperellum was evaluated for the control of Fusarium wilt in chrysanthemum. The substrate was obtained from pots containing chrysanthemum plants killed by the pathogen. Half of the substrate was sterilized prior to the incorporation of sewage sludge (0, 10%, 20% and 30% v/v). These substrates were or were not supplemented with the following: biofertilizer, fish hydrolyzate and Trichoderma. The mixtures were transferred to pots, and the chrysanthemum was transplanted. For all treatments, half of the plants were sprayed weekly with chitosan. Assessment of severity was performed on the 8th, 12th, 15th and 20th week after transplanting. In the 12th week, microbiological and chemical analysis of the substrate was performed. The incorporation of composted sewage sludge into the Pinus bark-based substrate significantly reduced Fusarium wilt, which was progressively decreased as the concentration of sewage sludge increased. The addition of biofertilizer, fish hydrolyzate, chitosan and Trichoderma had no effect on the disease. The microbial community was greater in non-disinfested substrates. The results indicate that suppressiveness is related to the interaction of chemical and microbiological factors.

Modeling human off-site aerosol exposures to polybrominated flame retardants emitted during the land application of sewage sludge

Elevated sewage sludge concentrations of polybrominated diphenyl ethers (PBDEs) are due to their broad utilization in textiles and polymers, their resistance to biological degradation, and also their hydrophobic nature—which drives partitioning into wastewater solids. This study estimated the total U.S. emissions of PBDE due to sewage sludge land application and then determined the human inhalation exposure to sludge-associated PBDEs as a function meteorological conditions and downwind distances from an application site. These aerosol exposures have also been incorporated into pharmacokinetic models to predict contributions to steady-state body burden. Our results suggest that while the amount of PBDEs aerosolized during the land application process is small compared to aerosol emissions associated with product use, the application of sludges onto U.S. soils constitutes a major source of PBDEs entering the outdoor environment. Regarding aerosol exposure to nearby residents, the maximum daily inhalation dosages from a common land application scenario occur immediately after sewage sludges are applied and were 137, 27, 1.9, and 81pg/day for significant congeners PBDE-47, -99, -153 and 209 respectively. These doses are 1–2 orders of magnitude less than the standard daily inhalation exposure to the same PBDEs associated with home indoor air and are similar to doses from inhalation of urban and rural outdoor air. Under the worst-case atmospheric transport scenario, the dosages are reduced by approximately 1 order of magnitude when the setback distance between the sludge aerosolization source and human receptor is increased to 200m. Though the health implications of low-level exposures are not well-understood, these sludge-derived PBDE dosages contribute less than a tenth of 1% to the estimated total body burden of PBDE produced from inhalation of indoor and outdoor air, exposure to house dust, and exposure to PBDE from food and water intake. Overall, the inhalation of PBDE aerosols from sludge-applied fields does not represent a significant contribution to human exposure compared to other common indoor exposures. However, land application is a major environmental source of PBDEs and sludge health impact analyses should focus on the practice's impacts on other exposures, such as biomagnification in aquatic and terrestrial food webs.

Biodegradation activity in the soil contaminated with oil products

The current study is aimed to determine how sewage sludge may impact the biodegradation activity of soil contaminated with oil products and what groups of microorganisms are most active in it. Bathihypogleyi-Dystric Albeluvisol (ABd-gld-w) with a texture of sandy loam was selected for laboratory tests. The soil was contaminated with heavy fuel oil 15 and 30 g kg -1 , supplemented with sewage sludge to create three backgrounds: 1) without sludge, 2) 5% (50 g kg -1 ) and 3) 10% (100 g kg -1 ) of sludge for air-dried soil. The trend was determined that when treating soil contaminated with heavy fuel oil the highest treatment efficiency was achieved by supplementing the soil with 10% of activated sewage sludge. Microorganisms which take part in the process of biodegradation of heavy fuel oil demonstrated different levels of activity during the investigation period. Hydrocarbon-oxidizing bacteria and micromycetes are the most important groups of microorganisms involved in the degradation of heavy fuel oil products in the soil. The initial concentration of heavy fuel oil in the soil had no statistically significant differences for all analyzed groups of microorganisms, although the number of bacteria and micromycetes, capable of oxidizing oil products, was statistically significantly influenced by the degradation time. The increasing concentration of sewage sludge statistically significantly affected the total number of bacteria and actinobacteria.

Phytotreatment of Sewage Sludge Contaminated by Heavy Metals and Pahs by Co-Planting Sedum Alfredii and Alocasia Marorrhiza

High concentrations of heavy metals and organic pollutants in municipal sewage sludge are key factors limiting its use in agriculture. The objectives of this study were to decrease the heavy metal and polycyclic aromatic hydrocarbon concentrations in sewage sludge by phytotreatment and to determine, in a field experiment, whether co-planting is more effective than using a mono-crop of Sedum alfredii. Four treatments were used in the plot experiment: no sludge, no plants, S. alfredii and co-planting S. alfredii and Alocasia marorrhiza. The results showed that co-planting produced tubers and shoots of A. marorrhiza that were suitable as a safe animal feed and good organic K fertilizer, respectively. Co-planting was more effective than mono-planting at reducing concentrations of total Zn and diethylenetriaminepentaacetic acid (DTPA)-extractable Zn, Cd, and Cu in the sludge. Co-planting decreased the concentrations of DTPA-extractable heavy metals and benzo[a]pyrene (B[a]P) in the sludge significantly compared with the unplanted sludge. Decreases of 87, 75, 85, 31, and 64% were obtained for B[a]P and DTPA-extractable Zn, Cd, Cu, and Pb, respectively, compared with the fresh sludge. These results indicate that co-planting can reduce significantly the environmental risks associated with heavy metals and B[a]P in sewage sludge for further disposal.

Iodine-131 in Sewage Sludge from a Small Water Pollution Control Plant Serving a Thyroid Cancer Treatment Facility

Iodine-131 (half-life = 8.04 d) is the most widely used radionuclide in medicine for therapeutic purposes. It is excreted by patients and is discharged directly to sewer systems. Despite considerable dilution in waste water and the relatively short half-life of I, it is readily measured in sewage. This work presents I concentrations in sewage sludge from three water pollution control plants (WPCPs) on Long Island, NY. Iodine-131 concentrations ranged from 0.027 ± 0.002 to 148 ± 4 Bq g dry weight. The highest concentrations were measured in the Stony Brook WPCP, a relatively small plant (average flow = 6.8 × 10 L d) serving a regional thyroid cancer treatment facility in Stony Brook, NY. Preliminary radiation dose calculations suggested further evaluation of dose to treatment plant workers in the Stony Brook WPCP based on the recommendations of the Interagency Steering Committee on Radiation Standards.