In nearly all the cases of biotoxicity studies of silver nanoparticles (AgNPs), AgNPs used often have general dispersibility and wide size distribution, which may inevitably generate imprecise results. Herein, a kind of synthesis method by coupling effects of polyvinylpyrrolidone (PVP) and sodium tripolyphosphate (STPP) was proposed, in order to prepare AgNPs with better dispersibility and a stable size. Based on this, the preparation mechanism of AgNPs and the potential anti-algae toxicity were analyzed. UV-vis analysis showed that the particle size distribution of AgNPs prepared by co-protective agents was more uniform. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX) were used to confirm that the obtained nano silver was of a high purity and stable size (~30 nm in diameter). Zeta potential and Fourier transform infrared spectroscopy (FTIR) analysis results indicated the synthesis mechanism of AgNPs by co-protective agents, more precisely, PVP limited the polynegative effect and prevented the linear induction of P₃O₁₀⁵⁻ produced by STPP during the growth of silver nuclei. Subsequently, Chlorella and Scenedesmus obliquus were utilized to test the toxicity of AgNPs, confirming that AgNPs synthesized through co-protective agents have potential inhibitory ability on algae, but not severe. This study provides a basic theory for the induction of synthetic AgNPs by various factors in the natural environment and a scientific reference for the environmental risk assessment.

Subsurface wastewater infiltration (SWI) is an environmentally friendly technology for the advanced treatment of domestic sewage. Clogging (including physical, chemical and biological clogging) of the porous medium not only directly reduces the hydraulic load (treatment efficiency), but also reduces the service life. Although clogging has become one of the key issues discussed in several reports, there are still several gaps in understanding, especially in its occurrence process and identification. SWI clogging causes, development process and solutions are different from those of constructed wetlands. This article quotes some reports on constructed wetlands to provide technical ideas and reference for revealing SWI clogging problems. Based on the analysis of the clogging genesis, this review gathers the main factors that affect the degree of clogging, and new methods for the identification of clogging conditions. Some preventive and unclogging measures/strategies are presented. Finally, it is suggested that to effectively alleviate the clogging phenomenon and extend the service life, priority should be given to the comprehensive analysis of wastewater quality and solid constituents accumulated in the pores. Then, the effectiveness of in-situ strategies, such as alternating operation will be the main focuses of future research.