Cooling water blowdown (CWBD) is wastewater effluent from cooling towers that are used in industry for various purposes including cooling systems[1]–[3]. In the State of Qatar, district cooling facilities are used to supply large-scale cooling needs in high density developments such as business districts, commercial communities, university campuses, etc.Water quality of CWBD changes and depends on the quality of make-up water, the number of cycles of concentration (COC) and chemical additives used for reducing scaling and corrosion [4]. High concentrations of these contaminants in CWBD streams deem them unsuitable for discharge into surface water and wastewater treatment plants; and in some cases, may require pre-treatment. Therefore, the discharge regulations of the CWBD become more stringent to control the amount discharged to the eco-system, reduce makeup water requirements and to recycle and reuse as much water as possible. Hence, in the presented paper we investigate the existing and emerging water treatment technologies for the treatment of CWBD. We present the contaminants in CWBD and their corresponding impacts on the ecosystem; and we compare membrane and nonmembrane based conventional and emerging treatment technologies based on performance, cost, and limitations along with other factors. The membrane-based technologies reviewed in this article include membrane distillation (MD), reverse osmosis (RO), nanofiltration (NF), and vibratory shear enhanced membrane process (VSEP). For the nonmembrane-based technologies, electrocoagulation (EC), ballasted sand flocculation (BSF), and electrodialysis (ED) processes will be also discussed. EC and VSEP processes are emerging technologies with high performance and can be considered as the most suitable technologies for the treatment of CWBD compared to other processes. However, they are energy intensive and that can be controlled by utilizing renewable sources of energy. The study also compares international and regional (Gulf states) policies and regulations related to the standards for water contaminant discharge levels into waterbodies including surface water. Such regulations will help in delineating the limits of contaminants concentrations, consequently determining the most suitable technology for the treatment of these contaminants. The paper findings will guide the development of suitable policies for the management and discharge of CWBD into surface water and wastewater treatment plants.
References
[1] H. I. Abdel-shafy, M. A. Shoeib, M. A. El-khateeb, A. O. Youssef, and O. M. Hafez, “Electrochemical treatment of industrial cooling tower blowdown water using magnesium-rod electrode,†Water Resour. Ind., vol. 23, p. 100121, 2020.
[2] O. M. Hafez, M. A. Shoeib, M. A. El-Khateeb, H. I. Abdel-Shafy, and A. O. Youssef, “Removal of scale forming species from cooling tower blowdown water by electrocoagulation using different electrodes,†Chem. Eng. Res. Des., vol. 136, pp. 347–357, 2018.
[3] E. A. Anwer and B. A. Abdul Majeed, “Different Electrodes Connections in Electrocoagulation of Synthetic Blow down Water of Cooling Tower,†Iraqi J. Chem. Pet. Eng., vol. 21, no. 1, pp. 1–7, 2020.
[4] J. Ahmed, Y. Jamal, and M. Shujaatullah, “Recovery of cooling tower blowdown water through reverse osmosis (RO): review of water parameters affecting membrane fouling and pretreatment schemes,†Desalin. Water Treat., vol. 189, no. June, pp. 9–17, 2020.
