Deep learning model based on urban multi-source data for predicting heavy metals (Cu, Zn, Ni, Cr) in industrial sewer networks

• Published in: Journal of hazardous materials 2022-06, Vol.432, p.128732-128732, Article 128732
• Main Authors: Jiang, Yiqi, Li, Chaolin, Song, Hongxing, Wang, Wenhui
• Format: Article
• Language: English
• Subjects: China; Deep Learning; Deep learning model; Environmental Monitoring - methods; Heavy metal prediction; Industrial sewer networks; Metals, Heavy - analysis; Sensitivity analysis; Sewage - chemistry; Shapley value; Water Purification; Zinc - analysis
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.128732

The high concentrations of heavy metals in municipal industrial sewer networks will seriously impact the microorganisms of the activated sludge in the wastewater treatment plant (WWTP), thus deteriorating the effluent quality and destroying the stability of sewage treatment. Therefore, timely prediction and early warning of heavy metal concentrations in industrial sewer networks is crucial. However, due to the complex sources of heavy metals in industrial sewer networks, traditional physical modeling and linear methods cannot establish an accurate prediction model. Herein, we developed a Gated Recurrent Unit (GRU) neural network model based on a deep learning algorithm for predicting the concentrations of heavy metals in industrial sewer networks. To train the GRU model, we used low-cost and easy-to-obtain urban multi-source data, including socio-environmental indicator data, air environmental indicator data, water quantity indicator data, and easily measurable water quality indicator data. The model was applied to predict the concentrations of heavy metals (Cu, Zn, Ni, and Cr) in the sewer networks of an industrial area in southern China. The results are compared with the commonly used Artificial Neural Network (ANN) model. In this study, it was shown that the GRU had better prediction performance for Cu, Zn, Ni, and Cr concentrations, with the average R2 significantly increased by 12.35%, 11.94%, 9.21%, and 8.13%, respectively, compared to ANN predictions. The sensitivity analysis based on Shapley (SHAP) values revealed that conductivity (σ), temperature (T), pH, and sewage flow (Flow) contributed significantly to the prediction results of the model. Furthermore, the three input variables including air pressure (AP), land area (A), and population (Pop.) were removed without affecting the prediction performance of the model, which maximized the modeling efficiency and reduced the operational cost. This study provides an economical and feasible technical method for early warning of abnormal heavy metal concentrations in urban industrial sewer networks. [Display omitted] •This study reveals the variation of Cu, Zn, Ni, and Cr concentrations in industrial sewer networks.•Deep learning method based on multi-source data can predict heavy metal concentrations in sewers.•The Gated Recurrent Unit model has superior prediction performance with more than 93% accuracy.•The Shapely value method identifies the key indicators for predicting heavy metals.