Accurate parameter prediction is necessary for nonlinear, long-delayed water treatment process to raise water quality. To improve the prediction model precision and computational efficiency, a cascade broad learning system based on the sparrow search algorithm and slow feature analysis is proposed in this paper. First, the slow feature analysis method is introduced to extract the essential characteristics of water monitoring data as the input of the prediction model. Then, a cascaded broad learning system is adopted to establish a prediction model for residual chlorine in water works effluent. The cascade broad learning can deal well with online prediction. Furthermore, the sparrow search algorithm is utilized to obtain the optimal hyperparameters of the established model, which can avoid the complex and time-consuming manual parameter tuning process. Finally, the comparison experiment with several methods is carried out. The experiment results show that the proposed method saves more computing resources and makes some improvements in prediction accuracy. Its prediction accuracy is much higher than majority traditional deep learning models such as LSTM, RNN, GRU.