Estimation and control of activated sludge processes in zone-aerated treatment facilities

A complex wastewater treatment process is considered that usually takes place in a large-scale treatment basin which is aerated by sections differently. Three basic processes: carbon removal, nitrification and denitrification can be activated there in different sections. A stochastic model of the process is proposed for description of the growth and oxidation processes in time and along the basin, and the state estimation and control methods. The estimation method is proposed for online estimation of the biomass and growth substrates in any local area along the basin by the dissolved oxygen and ammonia concentration measurements and by the outlet gas flow rate and composition measurements. The online estimation accuracy is relatively high because of data smoothing in time and by state-space coordinates along the basin. The estimation accuracy is evaluated in a simulation experiment in close to real conditions. The control algorithm is proposed for the sludge-load, sludge-loading and concentration control and for the water quality control. The sludge recycling and removal flows are considered as control parameters as well as their distribution along the basin and the water-feeding distribution.