Investigating the research and development status and trends of constructed wetlands: A bibliometric and patent analysis

Constructed wetlands (CWs) have been globally studied over the past few decades as promising energy-efficient and cost-effective green technology. As a result, it is critical to monitor the research and development (R&D) trend, research and innovative hotspots, sustainability status, development limitations, and key contributors at the forefront of this green infrastructure. The current study employs bibliometrics of research publications and patent analysis as the most effective carrier of technological information and significant R&D metrics to track the R&D trends in the field. Using the logistic model for S-curve analysis we predicted the technological life cycle of CW. Results from the study showed that (1) scientific publications and patents on CWs have experienced a steady growth at an annual rate of 22.2 % and 17.9 % respectively (2) China had the highest research and patent publications 77.6 % and 84 % respectively. However, the USA stood out as the most international collaborator in the field. (3) The analysis of co-occurrence keywords indicates that the significant hotspot of constructed wetlands research includes: "removal efficiency", "performance", and "wetland plants". Whereas "sedimentation tank", "inlet water pipe", and "filter bed" were observed to be the innovative hotspots for CW development. (4) The S-curve analysis from the articles and patents shows technical saturation points of 4706 and 251 respectively with an estimated remaining time, an average of 15 years, which implies that presently the growth of CW is almost stagnant and has barely little potential for further growth. The current limitations of CW development and directions for future studies were outlined.