The waste liquid mentioned in this text refers to that generated during Wastewater Monitoring. It contains a variety of harmful substances and shall not be directly discharged into sewers or via other channels. Proper handling is therefore essential, and great caution shall be exercised during the process, with relevant precautions duly observed. Key points are briefly introduced as follows.

Different treatment methods are applied for waste liquid with varying pollutants, and certain details shall be noted in the treatment process, as specified below:

1. Recover solvents from waste liquid to the greatest extent for reuse on the premise of not affecting normal operations.
2. Conduct proper collection and classification. Main categories include: a) non‑flammable substances; b) water‑containing waste liquid; c) flammable substances; d) solid substances, etc.
3. Water‑soluble substances may easily escape in aqueous solution, so special attention shall be paid during recovery. Solvents such as methanol and ethanol are readily decomposed by bacteria. Dilute solutions of such solvents may be discharged after adequate dilution with large volumes of water.
4. For waste liquid containing heavy metals, organic matters shall be decomposed first before carrying out treatment for inorganic waste liquid.
5. Waste liquid must be treated when its concentration exceeds specified limits. Where complete treatment facilities are available, allowable concentration limits for waste liquid treatment may be relaxed accordingly.
6. Separate treatment of different waste liquid is preferred. If waste liquid is stored together, collected compounds shall be treated in a unified manner in principle despite different treatment approaches.
7. For waste liquid containing complex ions, interfering components shall be collected separately.