Performance of triple ditch: effects of duration and periodic operation programs

The periodic variation of operation states in triple ditch (BIO-DENITRO pro cess) was investigated in a pilot-scale and a full-scale triple ditch treat ing raw wastewater containing 70% petrochemical wastewater and 30% domestic wastewater. Mathematical models describing the periodic variation of activ ated sludge concentrations in each ditch were proposed based on theoretical analysis and were verified in the pilot-scale and full-scale triple ditche s respectively. The existence of optimal cycle time and time arrangement of periodic operation programs were demonstrated and discussed according to t he mathematical models and the experimental results of the pilot-scale trip le ditch operated in four different stages. Four rulers determining the dur ation and operation programs are suggested.