Overview
ISO 11465:2025 specifies standardized laboratory methods for determining the dry residue or water content of sludge and solid environmental matrices and for calculating the dry matter fraction (mass basis). The standard defines two complementary approaches:
- Method A - drying at 105 °C to determine dry residue (applies to solid samples such as sludge, sludge products, treated biowaste, soil and solid waste).
- Method B - direct Karl Fischer titration (volumetric or coulometric) to determine water content (applies to liquid waste and samples suspected to contain volatiles other than water).
ISO 11465:2025 is applicable to samples containing more than 1 % (mass fraction) of dry residue or more than 1 % (mass fraction) of water. Results from either method are used to calculate the dry matter fraction, enabling expression of analytical results on a dry-matter basis.
Key topics and requirements
- Scope and applicability: clear distinction of when to use Method A (solids) vs Method B (liquids/volatile-containing samples).
- Principles: drying to constant mass at (105 ± 5) °C (Method A) and direct Karl Fischer titration for water content (Method B).
- Sample preparation: guidance references to ISO 11464, EN 16179 and EN 15002 for pretreatment and homogenization; phase separation for multiphase wastes when needed.
- Apparatus & reagents:
- Drying oven or equivalent, desiccator, precision balance (≥10 mg accuracy), suitable evaporating dish/crucible.
- Karl Fischer reagents and volumetric/coulometric titration equipment for Method B.
- Interferences & hazards:
- Volatile compounds evaporating at 105 °C can bias Method A; use Method B when volatiles are expected.
- Oxidation or CO2 uptake during drying, and biological/fermentation risks with sludge; consider inert atmosphere (N2) for sensitive samples and follow laboratory safety practices.
- Result expression: procedures for calculating dry residue, water content (field-moist and dry-residue bases) and dry matter fraction; precision and test report requirements included.
Applications and users
ISO 11465:2025 is relevant for:
- Environmental and materials testing laboratories performing compositional analyses.
- Wastewater treatment facilities and sludge management operations (monitoring dry solids).
- Soil and contaminated-site characterization, remediation projects.
- Waste management, composting operations and environmental regulators requiring consistent dry-matter–based reporting.
- Researchers and consultants needing validated, comparable dry-matter or moisture determinations.
Validated matrices include municipal sludge, fresh compost, sludge-amended and contaminated soils, dredged sludge, filter cakes, distillation residues and various wastes.
Related standards
- ISO 11464 (sample pretreatment)
- EN 16179, EN 15002 (sample preparation and phase separation guidance)
- EN 12880, EN 15934 (content merged into this edition)
- ISO/TC 190 (soil quality - technical committee responsible)
Keywords: ISO 11465:2025, dry residue, dry matter fraction, water content, sludge testing, Karl Fischer titration, drying at 105 °C, environmental matrices, moisture determination.
Open preview (PDF)Sludge and solid environmental matrices — Determination of dry residue or water content and calculation of the dry matter fraction on a mass basis
