Most low-temperature evaporation residues (crystallized salt / dry slag) are hazardous waste, and only a small number can be classified as general industrial solid waste; the classification mainly depends on the source industry, composition, toxicity / corrosivity, and must be legally identified and disposed of in accordance with the *National Catalogue of Hazardous Wastes (2025 Edition)* and the GB5085 identification standards.

I. First Identification: Hazardous Waste or General Industrial Solid Waste?

1. Directly Identified as Hazardous Waste (Included in the Catalogue, No Identification Required)

HW11 Distillation Residues (including 252-001-11, etc.)

Evaporation / distillation residues from chemical, petrochemical, pharmaceutical, and coking industries

HW17 Surface Treatment Waste

Evaporation slag from high-salinity wastewater in electroplating, passivation, and pickling processes (containing nickel, chromium, cadmium, lead, etc.)

HW34 Waste Acid / HW35 Waste Alkali

Salt slag from evaporation of acid-base wastewater (pH ≤ 2 or ≥ 12.5)

HW49 Other Wastes

Evaporation slag from high-concentration wastewater containing organic solvents, pesticides, dyes, tar, phenols, etc.

2. Requiring Identification (Not Included in the Catalogue)

Testing in accordance with the GB5085 series of standards:

Corrosivity: Leachate pH ≤ 2 or ≥ 12.5 → hazardous waste

Toxicity leaching: Excessive levels of heavy metals (lead, arsenic, mercury, cadmium, hexavalent chromium), benzene homologues, VOCs → hazardous waste

Compliance with any of the criteria for acute toxicity, flammability, or reactivity → hazardous waste

3. Classifiable as General Industrial Solid Waste (Extremely Rare)

Sources: Domestic sewage, ordinary circulating cooling water, pure inorganic salts (NaCl/Na₂SO₄)

Conditions: Free of heavy metals and toxic organic substances, all leaching indicators meet standards, pH 6–9

Still requires an identification report + confirmation from the local ecological and environmental authority

II. Legal Disposal: Separate Paths for Hazardous Waste and General Industrial Solid Waste

(1) Hazardous Waste Residues (Most Common)

Classification and Codes

Chemical / pharmaceutical / coking industry: HW11 (252-001-11)

Electroplating / surface treatment: HW17

Waste acid-base salt slag: HW34/HW35

Other organic / toxic residues: HW49

Collection and Storage (Mandatory)

Airtight, seepage-proof, rain-proof, and dust-proof containers

Affix hazardous waste labels and keep ledger records (generation volume, destination)

Storage area complies with GB18597

Transfer and Transportation (Red-Line Requirements)

Entrust qualified hazardous waste transportation entities

Use the national hazardous waste transfer manifest (electronic manifest)

Inter-provincial transfer requires approval from the ecological and environmental department

Disposal Methods (By Licensed Entities)

Incineration (high organic content): Temperature ≥ 1100℃ with flue gas purification

Stabilization + secure landfill (high salinity / heavy metals): Solidified before landfilling in hazardous waste landfills

Co-disposal in cement kilns (organic substances + heavy metals): High-temperature decomposition and heavy metal solidification

Resource utilization of waste salt (purification and refining): Only applicable for residues free of toxic organic substances and low in heavy metals; products meeting standards can be reused

(2) General Industrial Solid Waste Residues

Disposal: Landfill at general industrial solid waste landfills / comprehensive utilization (brick making, building materials, road base courses)

Management: Ledger records, seepage-proof storage, and legal transfer, but no hazardous waste qualification or manifest required

III. Key Compliance Points for Enterprises (Mandatory Actions)

Qualify Before Classification

Provide wastewater composition, industry sector, and evaporation process

Entrust qualified third-party institutions to conduct hazardous waste identification (HJ 298)

Retain identification reports, catalogue comparison records, and approval documents for at least 5 years

Separate Collection, Strictly Prohibit Mixed Storage

Separate storage and independent ledgers for hazardous waste / general industrial solid waste

Full-Process Traceability

Generation volume → warehousing → outbound delivery → transfer manifest → disposal receipt → disposal report

Environmental Impact Assessment and Pollutant Discharge Permit

Clarify residue properties, codes, destinations, and disposal volumes

Include in management plans and emergency response plans

IV. One-Sentence Quick Reference (For On-Site Use)

Chemical, pharmaceutical, electroplating, coking industries, high organic content, high acid-base content, heavy metal-containing → hazardous waste (HW11/HW17/HW34/HW35/HW49)

Pure inorganic salts, free of toxic substances, compliant leaching indicators → general industrial solid waste after identification

Identify first, classify second, dispose via licensed entities, complete manifests, and maintain full ledgers