Coagulant dosage determination using deep learning-based graph attention multivariate time series forecasting model

•The first deep learning application for sequential data to predict coagulant amount in water treatment.•The first application using long-term data for proper training in deep learning.•Graph attention-based mechanism identifies relevant information from input data.•Multivariate time series approach enhances deep learning performance. Determination of coagulant dosage in water treatment is a time-consuming process involving nonlinear data relationships and numerous factors. This study provides a deep learning approach to determine coagulant dosage and/or the settled water turbidity using long-term data between 2011 and 2021 to include the effect of various weather conditions. A graph attention multivariate time series forecasting (GAMTF) model was developed to determine coagulant dosage and was compared with conventional machine learning and deep learning models. The GAMTF model (R2 = 0.94, RMSE = 3.55) outperformed the other models (R2 = 0.63 - 0.89, RMSE = 4.80 - 38.98), and successfully predicted both coagulant dosage and settled water turbidity simultaneously. The GAMTF model improved the prediction accuracy by considering the hidden interrelationships between features and the past states of features. The results demonstrate the first successful application of multivariate time series deep learning model, especially, a state-of-the-art graph attention-based model, using long-term data for decision-support systems in water treatment processes. [Display omitted]