Overview
SIST EN 12255-2:2026 defines the key requirements for storm water management systems within wastewater treatment plants. Developed by the Slovenian Institute for Standardization (SIST), this European standard focuses on the separation, storage, treatment, discharge, and return of storm water that arrives at wastewater treatment facilities. It does not cover storm water management for collection and conveyance networks (sewer systems), which are addressed in standards such as EN 752 and EN 16933.
The objective of compliant storm water management systems at wastewater treatment plants is to mitigate excessive hydraulic loading during storm events, ensure proper treatment before discharge, and minimize environmental impact. These systems are an essential element for plants where upstream sewer networks do not sufficiently control storm water flow.
Key Topics
The standard covers several essential areas for effective storm water management at treatment plants:
- Flow Management Systems: Methods for separating normal and excess flows, including the use of flow measurement devices and bypass systems.
- Storm Tank Design and Operation: Guidelines for the number and types of storm tanks, design features, overflow arrangements, and means of isolating tanks. The importance of floor slopes, cleaning provisions, and sizing methods are also highlighted.
- Return of Storm Water: Procedures for returning stored storm water to the treatment process when capacity allows, including controls to prevent plant overload or untimely return.
- Storm Tank Cleaning: Requirements for cleaning methods according to plant size, including manual and automated options. Ensures prevention of solids accumulation and promotes operational efficiency.
- Measurement and Control: Necessity for monitoring and recording storm water flows, using level sensors, flow meters, and appropriate control systems depending on plant capacity.
- Additional Requirements: Recommendations for further treatment, such as screening and sediment removal, and considerations for minimizing environmental impact.
Applications
Storm water management systems described in SIST EN 12255-2:2026 deliver practical solutions for:
- Wastewater Treatment Plant Operators: Ensuring plant resilience to storm events by managing flows that exceed hydraulic design capacity, thus maintaining effluent quality and protecting downstream ecosystems.
- Design Engineers and Consultants: Providing a framework for planning, sizing, and specifying storm water tanks, return systems, and automation based on plant scale and expected loading conditions.
- Regulatory Bodies: Supporting compliance with environmental protection regulations by enforcing effective management and treatment of storm water within treatment facilities.
- Public Utilities and Municipal Authorities: Guiding investment and operational strategies for infrastructure upgrades, especially where upstream collection networks lack storm flow controls.
The standard is most applicable to treatment plants designed for domestic and municipal wastewater and is particularly relevant for facilities serving populations greater than 2,000, where robust storm water infrastructure is critical.
Related Standards
To complete a robust storm water and wastewater management program, refer to the following standards:
- EN 752: Covers sewer and drainage system management outside buildings, including flow limitation.
- EN 12255 Series: Other parts address general construction, preliminary and primary treatment, lagooning, sludge management, automation, and safety (including EN 12255-1, -3, -4, -10, -11, -12).
- EN 16932 and EN 16933: Offer additional requirements for pumping and design in external drainage and sewer systems.
- ISO Standards: For flow measurement and terminology (e.g., ISO 4359, ISO 12242, EN ISO 20456).
By implementing SIST EN 12255-2:2026 alongside the related standards, organizations can achieve environmentally sound and operationally efficient storm water management at wastewater treatment facilities.
Keywords: wastewater treatment, storm water management, storm tanks, water storage, storm water return, storm water treatment, flow management, environmental protection, SIST EN 12255-2:2026, standardization.