CPCB SOP for Spent Calcium Chloride Utilization in Pigment Violet Production

Introduction

The Central Pollution Control Board (CPCB), in April 2025, released a detailed Standard Operating Procedure (SOP) for the utilization of spent Calcium Chloride powder—a hazardous waste by-product generated during the manufacturing of Triethyl Phosphite (TEP) and Trimethyl Phosphite (TMP). The SOP is framed under Rule 9 of the Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016. This new SOP supports controlled recovery by converting the waste into Pigment Violet, thereby promoting circular economy and safe reuse.

In this blog, we break down the SOP, facilities required, process flows, compliance duties, and pollution control guidelines—along with over 50 transition phrases to guide your understanding effectively.

Why This SOP Matters

Previously, utilization of spent Calcium Chloride powder lacked uniform standards. Consequently, this led to inconsistent practices, environmental risks, and regulatory delays. With this SOP:

Utilization now follows one approved route
SPCBs and PCCs must verify and authorize only as per CPCB’s norms
Pigment Violet becomes the sole approved end-use product
Pollution control, health safety, and documentation gain strict clarity

Scope of Application

This SOP applies strictly to:

Spent Calcium Chloride powder generated from TEP/TMP production
Its utilization in manufacturing Pigment Violet for industrial use only
- Exclusions: No use in food, pharma, animal feed, healthcare, or cosmetics

Key Conditions for Authorization

Before granting authorization, SPCBs/PCCs must ensure:

The waste matches the same generation source as defined in the SOP
The process flow and product match the approved usage
Units have requisite facilities as per CPCB checklist
Authorization follows manifest protocols for transportation
Passbooks are issued to track inbound and utilized quantities

In case of deviation, SPCBs must refer proposals to CPCB.

Step-by-Step Utilization Process

Spent Calcium Chloride is mixed with crude pigment violet in ball mills
Material is stirred, transferred, filtered, washed, dried, and pulverized
Wastewater is treated; calcium salt is recovered and reused or treated further
Distillate is sent to the Effluent Treatment Plant (ETP)
End product (Pigment Violet) is labeled with a compliance tag

Minimal Facility Requirements

Units must install:

Brick-lined dedicated storage area
Closed and mechanized material handling systems
Ball mill, HDPE vessels, filter press, dryer, and concentrator
Proper air pollution control device (cyclone separator & bag filter)
Ventilation, fire safety, flame-proof electrical fittings
Effluent treatment systems (ETP or CETP compliant)

Safety, Monitoring & Emission Control

Handle in closed sheds with minimal manual contact
Maintain worker safety gear (PPE) as per MSDS
Stack height must be ≥30 meters
Ball milling emissions must meet:
- PM₁₀: 15 mg/m³
- Ammonia: 35 mg/m³
- HCl: 7 mg/m³

Monitor emissions quarterly using ISO 17025 labs and submit results to SPCB.

Waste and Effluent Management

Store hazardous waste in non-reactive containers
Dispose at TSDF, MEE, or authorized facility within 90 days
Manage wastewater via physico-chemical treatment, CETP, or captive facility
Maintain zero discharge if required by SPCB/PCC

Reporting and Recordkeeping

Units must:

Maintain passbooks for every shipment
Keep a logbook of waste source, treatment, and disposal
File returns using Form-3 and Form-4 under Rule 20 of HOWM Rules
Use the National Hazardous Waste Tracking System (NHWTS) daily
Submit biannual and quarterly reports on hazardous waste use to SPCB

Site Selection and Plant Efficiency

Units must operate in notified industrial zones
Maintain scale efficiency:
- 1 MT spent Calcium Chloride → 0.0833 MT Pigment Violet
Install systems based on the above conversion

Product Labeling & Usage

Finished pigment must be labeled as:

“This Pigment Violet has been prepared by utilizing Spent Calcium Chloride powder generated from manufacturing of TEP and TMP.”

Only industrial applications are permitted. The product must also meet BIS standards.

Environmental Accountability

If spills or violations occur, the sender or receiver is fully liable for:

Remediation
Soil/water testing
Compensation under CPCB’s “Liability Guidelines”

All utilization must also align with the Public Liability Insurance Act, 1991.

Conclusion

The CPCB SOP for spent Calcium Chloride utilization ensures a safe, structured, and sustainable pathway to convert hazardous waste into a valuable industrial product. By adhering strictly to the process, monitoring emissions, and maintaining documentation, industries can achieve compliance and circularity. SPCBs must enforce these standards uniformly while industries must upgrade infrastructure as per CPCB norms. This SOP not only safeguards the environment but also builds a traceable and responsible chemical industry.