Why would you use ferrous chloride over safer treatments?
Ferrous chloride is a hazardous product and when used incorrectly, can potentially cause damage to infrastructure. But, what are the advantages of ferrous chloride dosing?
Why would you choose to use a chemical, classified as dangerous, over other treatments that seem safer? When handled appropriately, it can have huge benefits:
Ferrous chloride can be injected anywhere in the wastewater network, because the chemical action occurs after septicity has already set in.
It is not overly sensitive to the conditions of the wastewater (e.g. temperature), and remains effective even in conditions of high septicity. It begins work immediately by binding with dissolved sulphides thus reducing the formation of H2S.
Dosing is automatically controlled, to match the flow of wastewater. Ferrous chloride dosing is the most robust solution to odour issues in wastewater streams.
Is ferrous chloride dangerous?
As a corrosive substance, ferrous chloride is covered by the Dangerous Goods Act of 1985. Standards Australia provides a Code of Practice for the storage and handling of dangerous goods (AS 3780). OdourPro supplies ferrous chloride dosing units that are designed to adhere to these regulations.
When handled correctly, ferrous dosing units are greatly effective against H2S. All of OdourPro's units are designed to best adhere to Australia's dangerous goods and corrosive substance regulations.
Best practices for handling ferrous chloride
Use automation technologies. These limit human interaction with the chemical and ensure safe use. OdourPro dosing units are secured against unauthorised access to prevent accidental contact with the chemical.
Have a bunded loading area to prevent spills from polluting the environment.
Only add ferrous chloride when the wastewater stream is flowing to prevent corrosion of piping and equipment.
Eye protection must be worn at all times when handling ferrous chloride.
Wear gloves. Skin should always be protected.
If you are in contact with ferrous chloride, immediately wash thoroughly.
The science behind ferrous chloride dosing
Ferrous chloride reacts with dissolved sulphides in wastewater forming a reaction almost immediately after dosing. Once the sulphides are effectively removed from the water stream through this reaction, they can no longer form the “smelly” H2S gas. Ferrous chloride dosing therefore breaks the chain of reactions that lead to the formation of odours.
Compared to ferrous chloride, magnesium hydroxide dosing systems are more problematic in an operations sense. Also the rise in wastewater pH caused by magnesium hydroxide can be incompatible with biological nutrient removal treatment processes. Calcium nitrate dosing is only effective if it is dosed upstream of septic conditions. It is less capable of dealing with severe septicity compared with ferrous chloride.
Finally, calcium nitrate effectively provides an alternative food source for bacteria. Bacteria target nitrates in preference to sulphates that are present in the wastewater stream. As long as the sulphates remain unconverted into sulphides, no H2S will be formed and odours will be controlled.Meanwhile, magnesium hydroxide raises the pH of the wastewater above the neutral level that bacteria prefer. High pH inhibits bacteria from feeding on the sulphates in the wastewater and therefore limits the production of sulphides. A higher pH also tends to keep H2S gas dissolved in the wastewater rather than being released into the atmosphere.
What are the alternatives?
There are three main options for chemical dosing wastewater streams to control odours. Magnesium hydroxide, calcium nitrate, and ferrous chloride dosing have all proved effective in various applications.
A disadvantage of magnesium hydroxide is the need to manage the viscosity of the chemical. It tends to solidify and plug up the dosing systems. To overcome this, special storage vessels with continuous mixing and flushing water are required. Magnesium hydroxide also has a limited shelf life of only three months.
Calcium nitrate is the most sensitive of the dosing chemicals. Changes in the conditions of the wastewater reduce the effectiveness of the dosing. It is also less effective when dosed into wastewater that is already septic.
Contact OdourPro for more information about ferrous chloride dosing systems
OdourPro has extensive experience in chemical dosing for odour control. Our ferrous chloride systems comply with AS 3780 standards to ensure protection for employees, wastewater network infrastructure, and the environment. We have technical experts and proven solutions that help your business overcome the challenges of odours emitted from sewers.
Find out more about ferrous chloride dosing systems or call our expert team on 1800 510 704 today to arrange a consultation.
OdourPro on 21 November 2016
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