This study addressed the relative importance of particle coating, sewage sludge amendment, and aging on aggregation and dissolution of manufactured Ag nanoparticles (Ag MNPs) in soil pore water. Ag MNPs with citrate (CIT) or polyvinylpyrrolidone (PVP) coatings were incubated with soil or municipal sewage sludge which was then amended to soil (1% or 3% sludge (w/w)). Pore waters were extracted after 1 week and 2 and 6 months and analyzed for chemical speciation, aggregation state and dissolution. Ag MNP coating had profound effects on aggregation state and partitioning to pore water in the absence of sewage sludge, but pre-incubation with sewage sludge negated these effects. This suggests that Ag MNP coating does not need to be taken into account to understand fate of AgMNPs applied to soil through biosolids amendment. Aging of soil also had profound effects that depended on Ag MNP coating and sludge amendment.

The increasing use of silver (Ag) nanoparticles [containing either elemental Ag (Ag-NPs) or AgCl (AgCl-NPs)] in commercial products such as textiles will most likely result in these materials reaching wastewater treatment plants. Previous studies indicate that a conversion of Ag-NPs to Ag2S is to be expected during wastewater transport/treatment. However, the influence of surface functionality, the nature of the core structure and the effect of post-processing on Ag speciation in sewage sludge/biosolids has not been investigated. This study aims at closing these knowledge gaps using bench scale anaerobic digesters spiked with Ag nitrate, three different types of Ag-NPs, and AgCl-NPs at environmentally realistic concentrations. The results indicate that neither surface functionality nor the different compositions of the NP prevented the formation of Ag2S. Silver sulfides, unlike the sulfides of other metals present in sewage sludge, were stable over a six month period simulating composting/stockpiling.

The influence of sewage sludge (SS) and sewage sludge biochar (SSBC) upon biomass yield and the bioaccumulation of PAHs into lettuce plants grown in contaminated soil (∑16PAH 20.2 ± 0.9 mg kg−1) is presented. All SSBC amendments (2, 5 and 10%) and the 2% SS amendment significantly (P < 0.01) increased lettuce biomass. Both SS and SSBC amendments significantly reduced (P < 0.01) the bioaccumulation of PAHs at all application levels; with reduction in ∑16PAH concentration ranging between 41.8 and 60.3% in SS amended treatments and between 58.0 and 63.2% in SSBC amended treatments, with respect to the control. Benefits in terms of biomass production and PAHs bioaccumulation reduction were greatest where SSBC was used as a soil amendment. At high application rates (10%) SSBC reduced bioaccumulation of PAHs by between 56% and 67%, while SS reduced bioaccumulation of PAHs by less than 44%.

For many years, extended-spectrum-beta-lactamase (ESBL) producing bacteria were a problem mainly located in medical facilities. Within the last decade however, ESBL-producing bacteria have started spreading into the community and the environment. In this study, ESBL-producing Escherichia coli from sewage sludge were collected, analysed and compared to ESBL-E. coli from human urinary tract infections (UTIs). The dominant ESBL-gene-family in both sample groups was blaCTX-M, which is the most prevalent ESBL-gene-family in human infection. Still, the distribution of ESBL genes and the frequency of additional antibiotic resistances differed in the two sample sets. Nevertheless, phenotyping did not divide isolates of the two sources into separate groups, suggesting similar strains in both sample sets. We speculate that an exchange is taking place between the ESBL E. coli populations in infected humans and sewage sludge, most likely by the entry of ESBL E. coli from UTIs into the sewage system.

Anaerobically digested and composted sewage sludge (CSS) has been suggested to be a slow-release fertilizer in forestry and an alternative to quick-release inorganic fertilizers. The effects of CSS with or without added carbohydrate on inorganic nitrogen availability and on soil animals were tested in two Norway spruce plantations. Half of the seedlings were individually fertilized with CSS, and the rest were left as controls. Solid sucrose was added to half of the fertilized and untreated seedlings. Soil samples were taken in the autumn in the first and the second year after the treatments. CSS increased soil NH4–N (2100%), the proportion of soil NO3–N, and the N concentration of spruce needles. CSS greatly reduced the abundances of enchytraeids, tardigrades and collembolans, but increased the proportion and abundance of bacterial-feeding nematodes irrespective of carbohydrate addition. A better stabilization method needs to be developed before CSS can be used as a forest fertilizer.

Temporal changes in soil burdens of selected endocrine disrupting compounds were determined following application to pasture of either sewage sludge or inorganic fertilizer. Soil polycyclic aromatic hydrocarbon and polychlorinated biphenyl concentrations were not altered. Changes in concentrations of diethylhexyl phthalate (DEHP) and PBDEs 47 and 99 differed with season but concentrations remained elevated for more than three weeks after application, when grazing animals are normally excluded from pasture. It is concluded that single applications of sewage sludge can increase soil concentrations of some, but not all classes of EDCs, possibly to concentrations sufficient to exert biological effects when different chemicals act in combination, but patterns of change depend on season and soil temperature. Analysis of soil from pasture subjected to repeated sludge applications, over 13 years, provided preliminary evidence of greater increases in soil burdens of all of the EDC groups measured, including all of the PBDE congeners measured.

This paper describes a study that was aimed at optimizing the pelletization of fecal sludge-based fertilizers for agricultural use. The process developed is easy to implement and increases the marketability of the products while also addressing a serious health and environmental challenge. The study took place during the period 2011-2012 in Ghana. The fecal sludge, rich in nutrients and organic matter, was dried and used to produce five different fertilizers (i.e., four formulations of compost and one with gamma irradiated material). Each material was then pelletized using locally constructed machinery. Key operating parameters, such as moisture content (10-55% in mass), binder type (clay or starch) and concentration (0-10% in mass), were varied and their impacts on the characteristics of pellets (e.g., amount of fine materials generated, length distribution or stability of pellets, and pellet disintegration rate) were also followed. Given the low analyzing capabilities of developing countries, some simple analytical methods were developed and used to compare pellets produced under different conditions. The results confirmed that the addition of 3% of pregelatinized starch is recommended during pelletization of fecal sludge-based fertilizers. Applicable moisture contents were also identified per fertilizer type, and were found to comprise between 21 and 43%.

Anaerobic digestion is one of the most effective means for the stabilisation of sludge. However, it has a very slow rate-limiting hydrolysis phase which is attributed to the low biodegradability of cell walls and the presence of extracellular biopolymers. This study aims at investigating the effect of ultrasonic, microwave and combined microwave–ultrasonic treatment on biogas production, solids removal and dewaterability of anaerobically digested sludge. A comparison was made between the three pretreatment techniques conducting the digestion tests under similar conditions on the same synthetic sludge sample inoculated by digested sewage sludge. The experimental results depict that the combined microwave–ultrasonic treatment (2,450-MHz, 800-W and 3-min microwave treatment followed by 0.4-W/ml and 10-min ultrasonication) resulted in better digester performance than ultrasonic or microwave treatment. Mesophilic digestion of combined microwave–ultrasonic-pretreated sludge produced a significantly higher amount of methane (147 ml) after a sludge retention time of 17 days, whereas the ultrasonic- and microwave-treated sludge samples produced 30 and 16 ml of methane, respectively. The combined microwave–ultrasonic treatment resulted in total solids reduction of 56.8 % and volatile solid removal of 66.8 %. Furthermore, this combined treatment improved dewaterability of the digested sludge by reducing the capillary suction time (CST) down to 92 s, as compared to CST of 331 s for microwave-treated and 285 s for ultrasonically treated digested sludge samples. Optimisation tests were also carried out to determine the best combination.

A new analytical methodology based on ultra high performance liquid chromatography (UHPLC) after microwave assisted extraction, followed by a clean-up and preconcentration step with solid phase extraction (MAE-SPE) has been developed for the simultaneous determination of 11 endocrine-disrupting compounds (EDCs), including alkylphenolic compounds, bisphenol A, and various synthetic and natural steroidal hormones, in sewage sludge samples. The effects of different variables on MAE-SPE were studied and optimised. The recoveries obtained were higher than 77 %, whereas the relative standard deviations were less than 9 %. The detection limits ranged between 0.1 and 0.7 ng g -1. The developed methodology was successfully applied to the assessment of the presence of EDCs to sewage sludge samples that were collected bimonthly during 1 year and a half from two wastewater treatment plants (WWTPs) located in Las Palmas de Gran Canaria (Canary Islands, Spain). All compounds were consistently found in all the samples under study. © 2013 Springer Science+Business Media Dordrecht.

In this paper, we report on a field experiment being carried out in a Typic Eutrorthox. The experiment was initiated in the 1997–98 agricultural season as a randomized block design with four treatments (0, 5, 10, and 20 t ha⁻¹) of sewage sludge and five replicates. Compound soil samples were obtained from 20 subsamples collected at depths of 0–0.1 and 0.1–0.2 m. Cu, Fe, Mn, and Zn concentrations were extracted with DTPA pH 7.3; 0.1 mol L⁻¹ HCl, Mehlich-I, Mehlich-III, and 0.01 mol L⁻¹ CaCl₂. Metal concentrations were determined via atomic absorption spectrometry. Diagnostic leaves and the whole above-ground portion of plants were collected to determine Cu, Fe, Mn, and Zn concentrations extracted by nitric–perchloric digestion and later determined via atomic absorption spectrometry. Sewage sludge application caused increases in the concentrations of soil Cu, Fe, and Mn in samples taken from the 0–0.1 m depth evaluated by the extractants Mehlich-I, Mehlich-III, 0.01 mol L⁻¹ HCl and DTPA pH 7.3. None of the extractants provided efficient estimates of changes in Mn concentrations. The acid extractants extracted more Cu, Fe, Mn, and Zn than the saline and chelating solutions. The highest concentrations of Cu, Fe, and Zn were obtained with Mehlich-III, while the highest concentrations of Mn were obtained with HCl. We did not observe a correlation between the extractants and the concentrations of elements in the diagnostic leaves nor in the tissues of the whole maize plant (Zea mays L.).