Activated sludge process control - development of operational diagrams

Hindered batch settling experiments were performed on activated sludge generated from dairy wastewater and combined (Dairy-Domestic mixture 1:3) wastewater for different initial Mixed Liquor Suspended Solids (MLSS) concentrations from 2g/L to 20 g/L for varied Mean Cell Residence Time (MCRT) for 5 to 15 days. Bio kinetic coefficients of combined wastewater were determined using a bench scale Continous Flow Stirred Tank Reactor (CFSTR). Vesilind parameters were also determined experimentally. Operational diagrams for long-term fluctuations in plant inflow and substrate concentration have been prepared. The allowable overflow rate to prevent process failure can be predicted from the chart. The adjustments to be made in recycling ratio and MCRT in case of fluctuations could also be predicted from the operational diagrams. From the operating diagrams plotted for both dairy and combined wastewater, it was noticed that, combined wastewater treatment provide greater operational flexibility than treating dairy waste separately.