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Triclocarban (TCC) has a high detection frequency in soil, rivers, sediments, and organisms, and its ecological risks have attracted substantial attention. In this study, we analyzed the fate of TCC in four wastewater treatment plants (WWTPs) in Zhengzhou, China, the biodegradation characteristics during the composting process, and the ecological risks of TCC when entering different environmental compartments. The concentration of TCC in the influent was 731.1–812.4 ng/L. More than 53.4% of TCC was biodegraded during the wastewater treatment process, and less than 2.5% was retained in the effluent. TCC was effectively removed through microbial degradation and sewage sludge absorption, and there were only minor differences in the different wastewater treatment processes. It is worth noting that more than 38% of TCC was enriched in sewage sludge (1430.1–1663.8 ng/g). The corresponding biodegradation rates of TCC were 65.7% and 82.8% in sewage sludge after 17 days of composting treatment with sawdust and straw as bulking agents, respectively. The estimated results showed that effluent discharge into the city rivers was safe. Composting could effectively degrade TCC and decrease the ecological risk of TCC when applied to sewage sludge. [Display omitted] • More than 97% of TCC in wastewater is reduced after treatment. • More than 38% of TCC in wastewater is transferred into sewage sludge. • Composting is an effective way to degrade TCC in sewage sludge. • The risk of TCC is predicted in aquatic and terrestrial environments. [ABSTRACT FROM AUTHOR]

Abstract Composting has been globally applied as an effective and cost-efficient process to manage and reuse sewage sludge. In the present study, four different phosphates as well as a mixture of ferrous sulfate and monopotassium phosphate were used in sewage sludge composting. The results showed that these phosphate amendments promoted an increase in temperature and the degradation of organic matter as well as reduction on nitrogen loss during 18 days of composting. In addition, ferrous sulfate and phosphate had a synergistic effect on reducing nitrogen loss. The contents of total phosphorus and available phosphorus in the compost with addition of 1% phosphate were 40.9% and 66.1% higher than the compost with control treatment. Using the BCR (Community Bureau of Reference) sequential extraction procedure, the addition of calcium magnesium phosphate significantly reduced the mobility factor of Cd, Zn and Cu by 24.2%, 1.7% and 18.8%, respectively. The mobility factors of Pb were increased in all samples, but the monopotassium phosphate treated sample exhibited the greatest Pb passivation ability with the lowest mobility factor increase (1.8%) among all treatments. The X-ray diffraction patterns of compost samples indicated that the passivation mechanism of Cu and Zn may be the forming CuFeS 2 and ZnCu(P 2 O 7) crystals during sewage sludge composting. The germination index showed that the compost of all treatments was safe for agricultural application; the germination index of the calcium magnesium phosphate treatment was 99.9 ± 11.8%, which was the highest among all treatments. Graphical abstract Image 1 Highlights • Phosphate promoted temperature rise and organic matter degradation during composting. • Ferrous sulfate and phosphate had synergistic effect on reducing nitrogen loss. • Total P and available P content increased 40.9% and 66.1% by adding 1% phosphate. • Heavy metals were passivated with the addition of phosphate amendments. • All compost products in this study were safe for land application. [ABSTRACT FROM AUTHOR]

Abstract Volatile organic compounds (VOCs) are the major components of the odor emitted from sewage sludge composting plants and are generally associated with odorous nuisances and health risks. However, few studies have considered the potential ozone generation caused by VOCs emitted from sewage sludge composting plants. This study investigated the VOC emissions from a full-scale composting plant. Five major treatment units of the composting plant were chosen as the monitoring locations, including the dewatered room, dewatered sludge, blender room, fermentation workshop, and product units. The fermentation workshop units displayed the highest concentration of VOC emissions at 2595.7 ± 1367.3 μg.m−3, followed by the blender room, product, dewatered sludge, and dewatered room units, whose emissions ranged from 142.2 ± 86.8 μg.m−3 to 2107.6 ± 1045.6 μg.m−3. The detected VOC families included oxygenated compounds, alkanes, alkenes, sulfide compounds, halogenated compounds, and aromatic compounds. Oxygenated compounds, particularly acetone, were the most abundant compounds in all samples. Principal component analysis revealed that the dewatered room and dewatered sludge units clustered closely, as indicated by their similar component emissions. The product units differed from the other sampling units, as their typical compounds were methanethiol, styrene, carbon disulfide, and hexane, all of which were the products of the latter stages of composting. Among the treatment units, the fermentation workshop units had the highest propylene equivalent (propy-equiv) concentration. Dimethyl disulfide and limonene were the major contributors. Limonene had the highest propy-equiv concentration, which contributed to the increased atmospheric reactivity and ozone formation potential in the surrounding air. To control the secondary environmental pollution caused by the VOC emissions during sewage sludge composting, the emission of limonene and dimethyl disulfide must be controlled from the blender room and fermentation workshop units. Graphical abstract Unlabelled Image Highlights • VOCs released from different units of a full-scale composting plant were evaluated. • The potential ozone formation of VOCs was analyzed during the summer. • Oxygenated compounds had the highest concentration and acetone was the major species. • Propy-equiv concentration was used to weigh the atmospheric reactivity of the VOCs. • DMDS and limonene were the major contributors to potential ozone formation. [ABSTRACT FROM AUTHOR]