Can water quality indicators and biomarkers be used to estimate real-time population?

The precise population estimation, short-term or real-time, is crucial to social and civil management, such as public resource distribution, education budgets, health care, and public safety. In this paper, we reviewed the methods for estimation of real-time population. For real-time population estimation, especially for a certain wastewater treatment plant catchment, many water quality indicators and biomarkers were selected as potential markers and their stability, consumption coefficient, and uncertainty were assessed. The conventional water quality indicators, such as wastewater discharge volume, chemical oxygen demand, biochemical oxygen demand, ammonia nitrogen, and total phosphorus, were used to calculate the serving population within a WWTP catchment. These parameters are all affected by the behavior, living habits and health conditions of people in different regions. Among them, wastewater discharge volume and ammonia might be more suitable for population estimation than the other parameters which may be influenced by additional industrial discharge. Moreover, acesulfame could be used to estimate the general population, while caffeine, tobacco, and carbamazepine could be applied as biomarkers for a specific population. Furthermore, the per capita loading differ should be considered and measured independently. To reduce the uncertainty of population, comprehensive model with multi-parameters should be developed and applicability should be checked.