Overview
ISO 5815-2:2003, titled Water quality - Determination of biochemical oxygen demand after n days (BODn) - Part 2: Method for undiluted samples, is an international standard developed by ISO for determining biochemical oxygen demand (BOD) in undiluted water samples. BOD is a critical parameter in water quality analysis, reflecting the amount of oxygen consumed by biochemical oxidation of organic and inorganic matter present in water. This standard is applicable to samples with BOD levels greater than or equal to 0.5 mg/l and not exceeding 6 mg/l of oxygen, providing environmental professionals and laboratories with a consistent approach for assessing water quality in surface water bodies, effluents, and receiving waters.
Key Topics
- Scope and Applicability: ISO 5815-2:2003 focuses on determining BOD in undiluted water samples with BOD values between 0.5 mg/l and 6 mg/l. The method is suitable for a wide range of waters, provided certain conditions are met regarding sample composition and BOD level.
- Principle of Determination: The method involves equilibrating the water sample at 20°C, possibly aerating, followed by incubation in a sealed bottle for 5 or 7 days in the dark. The BOD is determined by measuring dissolved oxygen consumed over this period using standard methods.
- Factors Affecting Results: The presence of substances toxic to microorganisms (such as heavy metals, bactericides, or free chlorine) can inhibit oxidation and lead to underestimated values. Conversely, algae or high levels of nitrifying microorganisms may give artificially high results.
- Modification of the Method: Annexes include guidelines for modifying the standard procedure - alternative incubation periods and temperatures (Annex A), use of seeding material, nutrient addition, nitrification inhibition, neutralization, homogenization, and filtration (Annex B), and reliability/precision data (Annex C).
- Control and Quality Assurance: Implementation of duplication, quality control charts, and interlaboratory data help ensure reliable and consistent BOD results.
Applications
ISO 5815-2:2003 is widely used in:
- Routine Water Quality Monitoring: Assessment of rivers, lakes, reservoirs, and wastewater discharges to track organic pollution loads over time.
- Regulatory Compliance: Determining if effluents from industrial facilities, municipal wastewater treatment plants, or stormwater discharges meet national or local environmental requirements.
- Research and Environmental Impact Assessments: Supporting studies on the ecological status of water bodies and evaluating the effects of new developments or remediation measures.
- Validation of Water Treatment Processes: Verifying the efficacy of biological treatment stages in municipal and industrial water treatment systems.
The standard’s ability to work with undiluted samples facilitates analysis when dilution is impractical, sample volume is limited, or the BOD is low.
Related Standards
For comprehensive water quality assessment and BOD measurement, consider the following related ISO standards:
- ISO 5815-1: Water quality - Determination of biochemical oxygen demand after n days (BODn) - Part 1: Dilution and seeding method with allylthiourea addition
- ISO 9408: Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium by determination of oxygen demand in a closed respirometer
- ISO 5813: Water quality - Determination of dissolved oxygen - Iodometric method
- ISO 5814: Water quality - Determination of dissolved oxygen - Electrochemical probe method
- ISO 3696: Water for analytical laboratory use - Specification and test methods
Utilizing ISO 5815-2:2003 helps ensure accurate, reproducible BOD data vital for effective water quality management and environmental protection.