The Product Testing Process
Dissolved Materials must be transformed from soluble to insoluble before the liquid solid separation process can begin.
Knowing the type of soluble material is key. Time could be wasted while jar testing if you are uncertain on how to precipitate the soluble material. Some soluble material can be removed by biological activity; soluble BOD or COD can be broken down by biological activity. Another method for removal is complexing with another chemistry.
There are three popular chemical methods to precipitate soluble heavy metals: hydroxide precipitation, sulfide precipitation and using proprietary chemistries.
1. Hydroxide Precipitation: Each metal has an optimum pH where it will precipitate as a hydroxide. This method has been tried and is very effective for bulk removal of metals. There are drawbacks to this method, but it can be effective if the discharge limits aren’t too low.
2. Sulfide Precipitation: This is not as pH dependent as hydroxide and can often reach lower discharge limits. While using this process, some environmental and safety issues can occur.
3. Proprietary Chemistries: These chemistries are proving to be cost effective and allow customers to reach new lower limits. Several chemistries are available and should be considered when choosing a jar testing process.
Colloidal Suspension/Oily Wastewater or Suspended Solids?
Once you are certain the contaminants are all insoluble, you must determine where you are on the Application Road Map. Use a simple flocculation test to determine if the contaminants are a colloidal suspension or a simple suspension.
If flocculation occurs and the water produced after settling is acceptable to your customer, you know your particles can be categorized as Suspended Solids. If there is no reaction or if there is some settling but the water is not as clear as the customer needs, your particles can be categorized Colloidal Suspension, or if oil is present then you’re dealing with Oily Wastewater.
The key to proper testing is to know where you are on the Application Road Map. Once you know what you are dealing with, product selection becomes simplified.
SUCCESSFUL JAR TESTING
The images below represent different results when jar testing. A 30% anionic flocculant was added to Jar A. No reaction was seen indicating a coagulant is needed, therefore Jar A is a Colloidal Suspension or Oily Wastewater.
A 30% anionic flocculant was added to Jar B. The particles came together and settled. This indicates Jar B was Suspended Solids.