Turbidity prediction of lake-type raw water using random forest model based on meteorological data: A case study of Tai lake, China.

Turbidity is an indication of water quality and enables the growth of pathogenic microorganisms. For drinking water treatment plants (DWTPs), violent fluctuations in turbidity are highly disruptive to operational performance due to the lag in process parameter adjustments. Such risks must be carefully managed to guarantee safe drinking water. Machine learning techniques have been proven to be effective for modeling complex nonlinear environmental systems, and this study adopted such a technique to develop a model for predicting source water turbidity for DWTPs to allow DWTPs to make proactive interventions in advance. A random forest (RF) model used preprocessed (empirical mode decomposition and quartile rejecting) meteorological factors (wind speed, wind direction, air temperature, and rainfall) as the input variables, to establish the turbidity prediction of a lake with significant turbidity in China's South Tai Lake. The modeling process included four main stages: (1) source data analysis, (2) raw data preprocessing, (3) modeling and tuning, and (4) model evaluation. The results of the RF model indicated that the correlation coefficient between the predicted and actual sequences is over 0.7, and more than 55% of the predicted values could control the errors within 20% compared to the actual measured values, suggesting that machine learning techniques are suitable for predicting the turbidity of raw source water. It was found that the RF model can provide a modest performance boost because of its stronger capacity to capture nonlinear interactions in the data. The findings of this study can inform the development of turbidity prediction models using readily available meteorological forecast data. The model can be applied to other DWTPs using similar shallow lakes as water sources.