ornamental species, meaning it is safe to use biosolids as fertilizers. The 10% concentration of biosolids also performed the best in nutrient balance efficiency, followed by soil treated with 20% CM. The results indicated that the function of biosolids and CM was significant, and these could be a substitute for biochar and WWC use in soils. Biosolid-amended soil can be one of the methods to relieve the landfill loading problem in Hong Kong.

Graphical abstract This comprehensive study addressed the occurrence, seasonal changes, removal efficiencies, and environmental risk assessments of three macrolide antibiotics in five wastewater treatment plants (WWTPs) with conventional and different additional treatment processes. A 1-year monitoring study was conducted, and influents and effluents were collected from Guangzhou (GZ), Shenzhen (SZ), Tai Po (TP), Shatin (ST), and Stonecutters Island (SI) WWTPs. Solid phase extraction and HPLC-MS/MS were used for the pretreatment and determination. The detection limits for azithromycin (AZI), erythromycin (ERY), and roxithromycin (ROX) ranged from 0.80 to 2.13 ng/L for the influent and effluent water samples. AZI was the most abundant antibiotic found in the influents, with average concentrations ranging from 571 ng/L to 1046 ng/L at all the target WWTPs. The seasonal average AZI concentration was the highest in all five WWTPs with the concentration of 984 ng/L in autumn, 849 ng/L in winter, 741 ng/L in summer, and 533 ng/L in spring. The seasonal AZI removal rates in the WWTPs were similar, with an average removal rate above 63.3% from spring to winter. All the treatments in the five WWTPs showed removal abilities for AZI, ERY, and ROX, regardless of the three phase treatments, namely, the UV disinfection process and conventional or chemically enhanced process within the WWTPs. For ERY and ROX, the average total removal rates were significantly decreased in the spring among all five WWTPs, at 53.1% and 57.8%, respectively. The GZ and SZ WWTPs displayed better removal rates than the TP, ST, and SI WWTPs, because the activity underlying the modified A2/O process in the GZ and SZ WWTPs has important effects on the antibiotic removal because the bacteria could produce compact granules and make the antibiotics settle faster in the wastewater. The additional UV disinfection in the SZ WWTP improved the removal efficiencies of the target antibiotics; it enhanced the biodegradability of residual organic pollutants in the WWTP effluent. Moreover, the corresponding environmental risks have been assessed and are viewed as a necessary component of future research. Supplementary Information The online version contains supplementary material available at 10.1007/s11270-021-05053-y.

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