Pollutant Load and Water Quality

Abstract

Pollutant load per capita flowing into water body (PLCwb) is an index to evaluate contribution of municipal wastewater pollutant discharge in pollutant load flowing into ambient water body such as coastal zones, bays and lakes. PLCwb is not commonly applied in the fields of environmental engineering or river and coastal water environment management, however, PLCwb should be more widely applied because of its easily understandable characteristics especially for comparison purposes among wastewater treatment methods or systems, among river sub-basins, and among countries, for miscellaneous stakeholders including policy makers, professionals of water environment and wastewater treatment and ordinary citizens. Pollutant discharge per capita (PDC) is an index to simply indicate pollutant discharge amount to ambient water. PDC of municipal wastewater is a function of pollutant generation per capita (PGC) and treatment efficiencies of municipal wastewater treatment systems. In this chapter, estimation methods of PLCwb and their results are explained. Water quality profiles in the past and present are explained to consider the relationships between pollutant discharges and the ambient water quality. The sub-river basin basis analysis of PLCwb has been firstly conducted in the Miyako-gawa River Basin, Chiba Prefecture, Japan, which flows into the Tokyo Bay (Tsuzuki 2006). The indicator, PLCwb, has been quantitatively evaluated by sub-river basin and wastewater treatment method. An example of pollutant discharge calculator of municipal wastewater shows the quantification concept and method of the soft intervention effects on pollutant discharge reductions and ambient water quality improvement.