The occurrence of a variety of organic pollutants has complicated wastewater treatment; thus, the search for sustainable and effective treatment technology has drawn significant attention. In recent years, bulk nanobubbles, which have extraordinary properties differing from those of microbubbles, including high stability and long residence times in water, large specific surface areas, high gas transfer efficiency and interface potential, and the capability to generate free radicals, have shown attractive technological advantages and promising application prospects for wastewater treatment. In this review, the basic characteristics of bulk nanobubbles are summarized in detail, and recent findings related to their implementation pathways and mechanisms in organic wastewater treatment are systematically discussed, which includes improving the air flotation process, increasing water aeration to promote aerobic biological technologies including biological activated carbon, activated sludge, and membrane bioreactors, and generating active free radicals that oxidise organic compounds. Finally, the current technological difficulties of bulk nanobubbles are analysed, and future focus areas for research on bulk nanobubble technology are also proposed.

Small-sized microplastics (MPs) pose concerns about potential risks to both the environment and human health. However, research on MP pollution is hampered by limitations in the detection techniques. Also, few studies have provided insight into the release of small-sized MPs from disposable polyethylene terephthalate (PET)-bottled drinks for outdoor usage. Thus, PET bottles’ potential to release small MPs sized 1–100 μm outdoors was studied in relation to physical and chemical parameters (temperature, sunlight irradiation, and drink characteristics) using flow cytometry and Nile Red dye. The results showed that temperatures below 80 °C had little effect on the release of MPs from PET bottles. Sunlight irradiation and alkalinity were prone to promote the generation of MPs, mostly 1–5 μm in size. Moreover, the combined impact test implied that two pairings—acidity with temperature and alkalinity with sunlight—positively affected MP release, with maximum releases of 21,622 ± 2477 particles/L and 31,081 ± 7173 particles/L, respectively. Based on the rapid quantification of small-sized MPs using flow cytometry after Nile Red selection, the results hereby presented will assist researchers in reducing MP release and aid them in the evaluation of MPs’ contamination of aquatic environments.

The existence of odors in drainage pipelines is one of the most prominent environmental problems that urban residents complain about nowadays. Odorous substances in sewage can cause corrosion and erosion in drainage pipelines, and even lead to great harm to the human body and environments. Ideas for in situ odor control can be divided into two main categories: the elimination of odorous substances and the inhibition of the production of odorous substances. However, there is a lack of comprehensive summary of in situ overall deodorization techniques, which has limited the wide application of these methods. We conducted a systematic review to summarize recent advances in in situ overall deodorization. Firstly, the main odorous substances in drainage pipelines and their basic characteristics are concluded. Special attention has been paid to volatile sulfur compounds (VSCs) and nitrogen-containing compounds, as the main odorous substances. Subsequently, typical sources of these odorous substances are summarized based on their formation mechanisms. Then, in situ deodorization techniques (including pipeline condition optimization techniques, odor source control techniques, chemical control techniques, and biological control techniques) are introduced. Finally, upcoming research efforts on deodorization mechanism improvement, research gap supplementation, and economic efficiency enhancement to meet practical conditions are proposed.