Number
090-EN
Section
General Section
Use
Sector
Manufacture of bulk, large scale chemicals (including petroleum products)
Manufacture of fine chemicals
Health services
Electricity, steam, gas water supply and sewage treatment
Function
pH regulating agent
Process
Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions.
Product category
Processing aids such as pH-regulators, flocculants, percipitant, neutalization agents
Application
Waste water treatment
Abstract
Waste water with a high content of ammonia was previously neutralised with strong acids such as hydrochloric acid and sulfuric acid. These strong acids were replaced by carbon dioxide (CO2).
Substituted substances
Hydrogen chloride
CAS No. 7647-01-0 EC No. 231-595-7 Index No. 017-002-00-2
Chemical group
Inorganic acid
Classification: hazard statements
H331 Toxic if inhaled
H314 Causes severe skin burns and eye damage
Other adverse effects
Strong inorganic acid mists: 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Sulphuric acid
CAS No. 7664-93-9 EC No. 231-639-5 Index No. 016-020-00-8
Chemical group
Inorganic acid
Classification: hazard statements
H314 Causes severe skin burns and eye damage
Other adverse effects
Strong inorganic acid mists: 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Alternative Substances
Carbon dioxide
CAS No. 124-38-9 EC No. 204-696-9 Index No.
Chemical group
Carbonyl compounds
Reliability of information
Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication
Reason substitution
ecotoxicity
physical hazards
Hazard Assessment
Substances to be substituted: The original substances are classified as hazardous. The alternative is not hazardous. Hydrogen chloride is toxic if inhaled and causes severe skin burns and eye damage. Sulphuric acid causes severe skin burns and eye damage. The substance is listed on the Substance Database according to SUBSPORTplus Screening Criteria as: Strong inorganic acid mists: 1 carcinogen (IARC). Alternative substance: The alternative, carbon dioxide has no harmonised classification according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation).
Description of Substitution
During the production of pharmaceutical products a by-product is waste water with a very high pH and high ammonia content. The local Danish environmental authorities require that waste water effluent has to be neutralised before it is diverted to the sewers and for this neutralization strong acids were used. In addition to the health and safety risks these products represented, a strong heat was generated when acid and water reacted. Through optimization and systematic review of well-defined and publicly available "unit operations" for the chemical industry, the company came up with the idea of using carbon dioxide (CO2) instead of strong acids. CO2 is now applied through a closed tank, where a pH sensor is connected to the CO2 injection. The pH of the waste water is hereby kept constant. After treatment the waste water can be disposed directly to the sewers without further purification. Advantages: Without waste water neutralization, the company would have large expenses for transportation of waste water and external waste water treatment. The health and safety risks are reduced due to the fact that there is no more handling of strong acids. Moreover the closed system for application of CO2 prevents ammonia fumes in the surroundings. Apart from neutralising the alkaline waste water, the CO2 addition also reduces unpleasant odour from the ammonia content. Disadvantage: A disadvantage are the costs for establishing new tank facilities as well as a system for automatic dosing of CO2.
Case/substitution evaluation
In this case story the company changed from handling hazardous acids to an automatic process with a not-classified substance. The chemical alternative was assessed against hazards in hazardous Substance Database according to SUBSPORTplus Screening Criteria (SDSC) and passed. CO2 is a greenhouse gas. An automatic dosing system helps limiting overdosing. Due to the effective substitution the risks for human health are reduced. This case study from 2010 describes the substitution of hydrogen chloride by using CO2 when lowering the pH value in wastewater treatment. The BVT Information Sheet "Wastewater / Waste Gas Treatment" from 2016 describes the use of "CO2" to lower the pH value, not as a substitute but as an equivalent.
State of implementation
Full capacity
Date and place of implementation
1990 Denmark
Type of information supplier
User
Contact
http://www.leo-pharma.com www.leo-pharma.com
Date, reviewed
December 11, 2020