Standard test methods for urban sludge
1Key Takeaways
This document specifies the terms, definitions and test methods for the detection indicators of urban sludge quality. Note: The sludge quality detection indicators in this document include: organic matter content and ash, organic matter, loss on ignition, moisture content, sludge settling ratio, sludge volume index, mi…
2Expert Interpretation
A comprehensive analysis of the CJ/T 221-2023 urban sludge inspection standard, covering 51 inspection methods for 32 new indicators and technical points of 24 revised methods, including sample collection, determination of physical and chemical indicators, and quality assurance system.
Core content of the standard revision
| Comparison dimensions | CJ/T 221-2005 | CJ/T 221-2023 |
|---|---|---|
| Number of detection indicators | 34 items | 66 items |
| New inspection methods | - | 51 kinds (including heavy metal forms, polycyclic aromatic hydrocarbons, etc.) |
| Number of revised methods | - | 54 kinds |
Key technological breakthroughs
Sample preparation innovation
The standard specifies for the first time the processing specifications for three types of samples:
- Mixed solution of biochemical system (need to be refrigerated at 4℃ and ≤24h)
- Volatile components (air drying is prohibited, and must be tested immediately)
- Stable metals (natural air drying is allowed)
Vacuum freeze-drying conditions: direct sublimation and dehydration at -40℃/10Pa to avoid component loss
Analysis of key detection methods
Determination of organic matter content (Section 5.1)
Use the triple constant weight method: evaporate to dryness in a water bath → bake to constant weight at 105℃ → burn in a muffle furnace at 550℃, calculation formula:
Organic matter content (ω1)=(m2-m3)/(m2-m1)×100%
Precision requirement: Parallel sample deviation ≤10%
Mixed liquor sludge concentration (Section 5.2)
Critical control points:
- Use 0.45μm filter membrane or quantitative medium-speed filter paper
- Wash with distilled water three times (10mL each time)
- Dry at 103-105℃ to constant weight (±0.001g)
Implementation suggestions
Quality control system requirements
| Parallel sample ratio | ≥10% (do 1 sample if there are less than 10 samples) |
| Moisture content determination deviation | ≤5% |
| Heavy metal detection | Morphological analysis is required (new requirement) |
Note: All testing equipment needs to undergo regular metrological certification