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Biodegradable plastics have been increasingly used as a solution to the problem of plastic pollution in recent years. However, there are few studies on the negative effects of biodegradable microplastics. Triclosan, a widely used disinfectant, is a highly toxic substance. In the present study, the adsorption and desorption processes of triclosan on a type of biodegradable plastics, polyhydroxybutyrate (PHB), were investigated and also compared with one conventional plastic type, polyethylene. The adsorption equilibrium quantities of polyethylene and PHB were 3431.85 and 9442.27 μg/g, respectively. The adsorption rate and equilibrium adsorption capacity of triclosan on PHB are much higher than on polyethylene. Physical adsorption of triclosan on PHB and polyethylene microplastics may play a dominant role in this process. The desorption hysteresis indices are all less than zero; this indicates that triclosan is easily released from PHB and polyethylene microplastics under physiological conditions. Our results indicate that biodegradable PHB microplastics are stronger carriers for triclosan than the conventional polyethylene microplastics in the aquatic environment.

Occluded water is water that remains inside corrosion scales within deteriorating distribution pipes. The accumulation of iron and manganese in the occluded water is a potential risk for water quality. Thus, this study investigated the change in metal (iron, manganese, copper and chromium) concentration in occluded water, the effect of these metals on the flowing water, and the source of iron and manganese in the occluded water using a simulation device. The results showed that total iron and total manganese were enriched in the occluded water, while the concentrations of total copper and total chromium in the occluded water gradually decreased over time. The iron and manganese in the occluded water migrate to the flowing water causing pollution in the flowing water. Also, copper and chromium adsorb on the corrosion scales within the pipes. The iron and manganese in the occluded water mainly came from the corrosion of the metal pipes, and the corrosion scales had a certain obstructive effect on the outward migration of iron in the occluded water but had less hindrance to the migration of manganese. Occluded water plays a critical role in the pollution of drinking water, and additional work is needed to control metal accumulation and release.