The aquaculture industry requires solutions to several environmental challenges in order to become sustainable, including adequate wastewater management. Aquaculture wastewater (AWW) is rich in nitrogen, phosphorus, organic carbon, and other elements essential for microalgae. Due to the potential for AWW to be used as a microalgal growth medium and the potential of Chlorella sorokiniana to remediate wastewater, the growth of this species in AWW was evaluated. The microalgal growth in AWW was compared to the growth in a modified BG11 growth medium containing similar nutrient concentrations as the AWW. The effect of pH regulation and air-lifting the cell suspension at different airflow rates was also studied. As a result, it was found that C. sorokiniana can grow successfully in AWW; however, its cultivation required pH regulation. This microalga species can reach a biomass concentration of up to 476 mg/L and a biomass productivity of 140 mg/L/day. Furthermore, up to 78% of the nitrogen, 77% of the phosphorus, 70% of the magnesium, 90% of the zinc, and 99% of the nickel contained in the AWW were assimilated by the microalgae. The results of this study show that microalga cultivation in wastewater has great potential to reduce contamination while generating economic benefits.

This paper shows how an extended Kalman filter can be applied to the parameter estimation in continuous time heat exchanger models. The model is based on lumping of the heat exchanger. It is on state space form where the temperature in each section is a model state. By letting the model parameters be functions of the massflows and the temperatures one obtains a model that is capable of accurately describing the dynamics of the heat exchanger for all relevant working conditions. Since the parameters are functions of temperature, the model is nonlinear in the states and an extended Kalman filter is applied to the state estimation. Empirical relations of the heat transfer coefficients are incorporated in the model parameters in order to cope with the massflow and temperature dependence. Some of the parameters in the empirical relations are also estimated, thereby adjusting the formulas to the specific heat exchanger.