ISO 4789:2023

Overview

ISO 4789:2023 - Guidelines for wastewater treatment and reuse in thermal power plants provides technical guidance for classifying, treating and reusing wastewater produced across thermal power plant systems. Applicable to coal‑fired, oil‑fired, gas‑fired (including gas turbines), biomass‑fired, waste‑incineration and IGCC plants, the standard addresses wastewater sources, characteristics, treatment technologies and reuse targets to support water savings and environmental protection.

Key topics and technical requirements

• System-based wastewater classification - divides plant drainage into fuel supply, chemical water treatment, boiler & auxiliary, recirculating cooling, flue gas processing, gasification scrubber and ash handling; wastewater is classified by its system source.
• Wastewater characteristics - describes typical contaminant profiles (e.g., high TSS/COD/turbidity for coal yard runoff; oily wastewater forms; high salinity in RO concentrate; leachate with high COD/ammonia/heavy metals).
• Treatment technology guidance - recommendations for appropriate processes for different streams, including membrane processes (RO, NF, UF), biological and physico‑chemical treatments, and advanced options for TDS reduction and concentrate management.
• Reuse water quality requirements - sets out considerations for matching treated water quality to reuse targets within the plant (e.g., boiler feed, cooling make‑up, ash handling), emphasizing separate treatment where reuse targets differ.
• Design and planning principles - stresses water balance optimization across the whole plant, economic and site considerations, and staged technical/economic review to determine feasible reuse pathways.
• Specific stream guidance - technical approaches for coal wastewater, oily waste, RO concentrate, membrane wash and resin regeneration effluents, boiler blowdown and chemical cleaning waste, FGD/WESP blowdown, gasification scrubber effluent and ash handling water.

Practical applications and users

ISO 4789:2023 is intended for:

• Plant engineers and process designers planning wastewater treatment and reuse schemes.
• Environmental and water‑management teams seeking to reduce freshwater withdrawal and meet discharge limits.
• Consultants and technology vendors designing tailored treatment trains (membranes, biological systems, concentrate management).
• Regulators and sustainability officers evaluating water reuse, zero liquid discharge potential and compliance strategies.

Typical applications include designing boiler blowdown reuse, recycling cooling system blowdown, managing RO concentrate, treating FGD and WESP effluents, and planning whole‑plant water balances to maximize reclaimed water quantities.

Related standards

• ISO 20670 - Water reuse - Vocabulary (normative reference used in ISO 4789).
• Other ISO guidance from ISO/TC 282 (Water reuse) and sector‑specific standards for industrial water management.

Keywords: ISO 4789:2023, wastewater treatment, water reuse, thermal power plants, boiler blowdown, FGD wastewater, RO concentrate, industrial water reuse, IGCC, coal‑fired power plant, zero liquid discharge.