Zero-discharge treatment process for desulfurization wastewater

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Desulfurization wastewater is mainly the effluent from the absorption tower in the wet desulfurization process of boiler flue gas. To maintain the material balance in the slurry circulation system of the desulfurization unit, prevent the soluble components in the flue gas – namely the chlorine concentration – from exceeding specified levels, and ensure the quality of gypsum, it is necessary to discharge a certain amount of wastewater from the system; this wastewater primarily comes from the gypsum dehydration and cleaning systems. Water quality characteristics of desulfurization wastewater: (1) High corrosivity; (2) High salt content; (3) High hardness, prone to scaling. At present, the wet desulfurization wastewater treatment systems in most thermal power plants in China use traditional chemical dosing and flocculation sedimentation processes, but their overall operational efficiency is very low. After treatment by conventional systems, the concentrations of SS and COD in the desulfurization wastewater are high, and Cl- in the water cannot be removed. Due to the high concentration of Cl-, the treated wastewater cannot be reused. Due to environmental protection requirements and economic considerations, adopting advanced treatment technologies to achieve zero wastewater discharge is an inevitable trend in wastewater treatment. Although desulfurization wastewater can basically meet the requirements for compliant discharge after undergoing the aforementioned conventional physical and chemical treatment, its scope of reuse is very limited. With the growing emphasis on water resources, zero-emission technologies have been widely adopted worldwide. Therefore, to reuse the wastewater from desulfurization processes in coal-fired power plants and achieve true zero wastewater discharge, the wastewater must be subjected to advanced treatment. Based on the differences in emission standards of connection and zero discharge, wastewater treatment processes are divided into conventional treatment processes for desulfurization wastewater and zero-discharge treatment processes for desulfurization wastewater. Zero emissions do not mean no water is released; rather, it means that harmful substances are not discharged into the natural environment through water bodies. The water used in power plant operations is either released into the environment in the form of steam or remains within the plant’s internal water circulation system. This **improves the efficiency of water use, prevents pollution of natural water bodies, and ensures the safety of water supply for residents. From the perspective of sustainable development, water resources will remain relatively scarce in the present and in the future; zero wastewater discharge is an inevitable trend in industrial development. Zero emissions place extremely high demands on water treatment technologies, requiring significant technical investment; therefore, substantial financial funding along with strict management and supervision systems are essential. The principle of zero discharge of desulfurization wastewater by Jiangsu Pasma Environmental Technology Co., Ltd. is as follows: The water resulting from conventional treatment enters the EDR unit for concentration and fresh water separation; the fresh water then goes into a regulation tank where it mixes with water from the circulation system, domestic wastewater, pre-treated industrial wastewater, and initial rainwater. This mixture is sent to an AO biological treatment tank for biological nitrogen removal. The water output from this biological treatment process is processed using a \"UF+RO\" technology for reuse as reclaimed water. The RO-produced fresh water is fed into the feedwater side of the boiler make-up water treatment system, while the RO-concentrated water is returned to the inlet of the EDR unit, where it is fed into evaporation and salt separation equipment.