Multi-Pollutants Water Cascade Analysis for Industrial Water Minimization

This research article studies building a Water Cascade Analysis (WCA) method that can rationalize multiple industrial environments that involve multiple pollutants. The method uses an integrated numerical targeting step and network redistribution to minimize freshwater usage as well as wastewater discharge. The method was, thus, applied using the case study by Hashemi et al. (2024) [1], where the analysis first identified a total of three units that accounted for most water consumption: these were the Desalter unit, the cooling tower, and the firewater system. Both Chemical Oxygen Demand (COD) and Total Dissolved Solids (TDS) were adopted as the two main contaminants. The results of the single-contaminant analysis showed that the minimum freshwater requirement was 44.62 m³/h when considering COD, while it decreased to 34.68 m³/h when considering TDS. This reduction amounts to between 19% and 25% of the refinery's total consumption (175 m³/h). The volume of wastewater produced was, therefore, identical to these figures, reflecting the accomplishment of the Pinch Point as evidenced by the cascade tables for each pollutant individually. Next, the sequential contaminant analysis (A→B) and (B→A) was performed. The results of the first scenario showed consumption rising to 44.87 m³/h owing to the need to dilute the concentrations of the second contaminant. On the other hand, the best performance was achieved in the second scenario (B→A) with freshwater requirements as low as 44.83 m³/h. As a result, TDS was identified as the Limiting Pollutant. A comparison between the methodology developed and the Water Pollutant Analysis (WPA) method employed in the reference study revealed that the use of freshwater was lowered from 99 m³/h to less than 45 m³/h in the proposed method, whereas wastewater discharge was reduced from 52 m³/h to about 44.8 m³/h. The findings verify that the proposed methodology serves as a simplified, efficient, and numerical means of water reuse network design in multi-contaminant industrial systems. Besides achieving considerable water savings, it also lessens the environmental impact, thus presenting itself as a suitable instrument for use in oil refineries and industrial facilities with complex water systems.

Keywords : Water Pinch Analysis; Multi-Pollutants Water Cascade Analysis; Wastewater Minimization; Industrial Water Network;