Contamination of organic nutrient sources with potentially toxic elements, antibiotics and pathogen microorganisms in relation to P fertilizer potential and treatment options for the production of sustainable fertilizers: A review

Soil contamination with antibiotics in a typical peri-urban area in eastern China: Seasonal variation, risk assessment, and microbial responses

The prevalence and persistence of antibiotics in soils has become an emerging environmental issue and an increasing threat to soil security and global public health. The problem is more severe in areas undergoing rapid urbanization; however, the ecological risks of antibiotics, seasonal variability, and associated soil microbial responses in peri-urban soils have not been well-explored. The seasonal soil sampling campaigns were conducted in a typical peri-urban watershed in eastern China to investigate distribution of antibiotics. The results demonstrated higher mean concentrations of most antibiotic compounds in winter than in summer in peri-urban soils. The seasonal variations of norfloxacin, enrofloxacin, and ciprofloxacin were more significant than those of other antibiotics, due to their higher migration ability and bioavailability. An ecological risk assessment demonstrated that chlortetracycline, ciprofloxacin, doxycycline, and ofloxacin can pose high risks to soil microorganisms. Furthermore, the coexistence of multiple antibiotics obviously poses higher risks than individual compounds. A redundancy analysis demonstrated that tetracyclines mainly showed negative correlations with Firmicutes and Chloroflexi, and quinolones showed obviously negative correlations with Acidobacteria, Gemmatimonadetes, and Nitrospirae, suggesting potential inhibition from antibiotics on biological activities or biodegradation processes. However, the persistence of antibiotics in soil results in a significant decrease in bacterial diversity and a change in dominant species. Our results provide an overview of the seasonal variability of antibiotics and the associated effects on bacterial communities in peri-urban soils. The results can provide scientific guidance on decreasing soil contamination with antibiotics to enhance soil security in similar areas.

Sanitary and environmental aspects of sewage sludge management

Currently, sewage sludge management is a huge challenge in the field of environmental engineering. New effective solutions for the treatment of wastewater led to an improvement of the quality of the final effluent but considerably increased the volume of produced sewage sludge, which increases each year. Two points of view conflict regarding the recycling of those “wastes.” Primarily, dehydrated sewage sludge is considered a reservoir of nutrients and organic matter that can be used as a fertilizer in agriculture or as an organic amendment in the remediation of contaminated sites or to build “anthroposoils.” On the other hand, recycled sewage sludge is seen as a potential source of soil contamination by organic and inorganic pollutants and pathogens; potentially toxic elements (such as zinc, copper, cadmium, lead, silver, etc.); polycyclic aromatic hydrocarbons (PAH); polychlorobiphenyls (PCB); biocides and phytopharmaceuticals; pharmaceuticals, personal care products (PPCP), and residuals; synthetic hormones; microplastics; nanotechnology life cycle end products; and microorganisms such as Escherichia coli O157:H7 or Salmonella typhimurium.

This chapter will focus on these aspects, highlighting the health and ecotoxicological risks associated with the presence of such contaminants in sludge. The environmental dangers of sludge spreading on soils will be presented as well as their possible treatment scenarios to propose an acceptable reuse of sewage sludge in a circular economy.

Persistence and availability of veterinary antibiotics in soil and soil-manure systems

The availability and persistence of various antibiotics in soil and soil amended with composted poultry manure were investigated through laboratory incubation assays. Six veterinary antibiotics (one fluoroquinolone, two tetracyclines, two sulfonamides and one lincosamide) and one active metabolite (ciprofloxacin) were studied. The incubation assays were conducted at a controlled temperature of 25 °C with different water regimes, such as constant moisture content (80% of water holding capacity) and drying-rewetting cycles. The studied antibiotics were determined in soil and soil aqueous phase samples by LC-MS/MS using internal standards. The results indicated that the highest levels found in the soil aqueous phase were for sulfamethoxazole, followed by sulfamethazine and lincomycin, being very low the levels of chlortetracycline, doxycycline, ciprofloxacin and enrofloxacin (≤1.8%). A positive correlation was observed between the antibiotic concentrations and the content of the dissolved organic carbon in soil aqueous phase with the incubation time. An increase in the apparent sorption coefficients of these antibiotics, except chlortetracycline and lincomycin, was observed when the soil was amended with composted manure. Except for fluoroquinolones, with remaining residues around 70% after 90 days of incubation, a fast dissipation of antibiotics was observed during the assay, with half-lives ranging from 8 to 27 days. These values increased between 6% and 53% in manure amended soil; nevertheless, half-lives remained short (9 days and 27 days for lincomycin and sulfamethazine, respectively). Similar results were obtained with soil under drying-rewetting cycles showing somewhat lower values in soil aqueous phase and slightly shorter half-lives in some cases. The results obtained pointed out that the route of entry of antibiotics into the soil, through recycled water or manure, may have an important effect on their behavior, particularly regarding their availability in soil.

Pharmaceuticals and illicit drugs - A new threat to the application of sewage sludge in agriculture

The occurrence of 93 pharmaceuticals, illicit drugs and their metabolites has been investigated in stabilized sewage sludge from five municipal wastewater treatment plants (WWTPs) in the Slovak Republic. The total population connected to the tested WWTPs was approximately 600,000 p.e. which represents >20% of the Slovak population connected to public sewer systems. The sludge production from the five tested plants was >8100tons in 2016, which is approximately 15% of the total Slovak sewage sludge production in 2016. The highest total concentration of all pharmaceuticals was found in WWTP Bratislava Devínska Nová Ves (DNV) and Senec - 11,800 and 11,300ng/g dry matter (DM), respectively. Among individual pharmaceuticals, the highest concentrations were recorded for fexofenadine (mean 2340ng/g DM, maximum 5600ng/g DM in Bratislava DNV) and telmisartan (mean 1170ng/g DM, with a maximum of 3370ng/g DM in Senec). A principal component analysis revealed differences between pharmaceutical patterns in aerobically and anaerobically stabilized sludge. The worst-case scenario based on no further degradation of pharmaceuticals between sludge production and field application was used to predict pharmaceutical mass loads in agriculture. For the result, we estimated an annual load to soil in the Slovak Republic of up to several hundred kilograms of pharmaceuticals and drugs, with the maximum for fexofenadine (120kg/year) and verapamil (29kg/year).

Catalytic degradation of sulfaquinoxalinum by polyester/poly-4-vinylpyridine nanofibers-supported iron phthalocyanine

Iron (II) phthalocyanine (FePc) supported on electrospun polyester/poly-4-vinylpyridine nanofibers (PET/P4VP NFs) was prepared by stirring in tetrahydrofuran. The resulting product was confirmed and characterized by ultraviolet-visible diffuse reflectance spectroscopy, attenuated total reflection Fourier transform infrared spectra, X-ray photoelectron spectroscopy, gas chromatography/mass spectrometry, and ultra-performance liquid chromatography. More than 95% of sulfaquinoxalinum (SQX) could be removed by the activation of hydrogen peroxide in the presence of FePc-P4VP/PET with a PET and P4VP mass ratio of 1:1. This system exhibited a high catalytic activity across a wide pH and temperature range. The degradation rates of SQX achieved 100, 95, and 78% at a pH of 3, 7, and 9, respectively, and the degradation rates of SQX are more than 80% at the temperature ranging from 35 to 65 °C. DMSO₂ could be detected by gas chromatography/mass spectrometry after the addition of DMSO, suggesting the formation of the high-valent iron intermediates in this catalytic system. In addition, the electron paramagnetic resonance experiments proved that free radicals did not dominate the reaction in our system. Therefore, the high-valent iron intermediates were proposed to the main active species in the FePc-P4VP/PET/hydrogen peroxide system. In summary, the heterogeneous catalytic processes with non-radical catalytic mechanism might have better catalytic performance for the removal of organic pollutants, which can potentially be used in wastewater treatment.