Explanation of 47-Year BOD Alternation in a Japanese River Basin by BOD Generation and Discharge

摘要: Average and 75 % biochemical oxygen demand (BOD) in the Yamato-gawa River, Japan, 1963 were smaller than criteria determined 1970 (5 mg l−1); however, they deteriorated up to 22–32 l−1 1970. The deterioration was caused by population increase economic urban development. national-level regulations on ambient water quality pollutant discharge have been established Municipal wastewater is major contributor discharges river basin. Estimated BOD (PD(BOD)) basin reduced level of 2000; average more criteria. Analysis relationship between PD(BOD) resulted five phases 1963–2009. equilibrium conditions changed from phase I II because perturbation excess discharge, self-correcting mechanisms found III, III IV V. comparison estimated based generation (PG) without measures monitored represented following situations 47 years: (1) It took several years before effects centralised WWTPs observed, (2) less 35 t-BOD day−1 for linear BOD, (3) combined treatment, purification facilities soft be about 10 mg-BOD 2010.