Specialty Chemicals / Coagulants & Flocculants

Coagulants and flocculant's are formulated to assist in the solids/liquid separation of suspended particles in solution. Such particles are characteristically very small and the suspended stability of such particles (colloidal complex) is due to both their small size and to the electrical charge between particles. Conditioning a solution to promote the removal of suspended particles requires chemical coagulation and/or flocculation.

Wastewater is generated, usually from rinsing or cleaning manufactured products. For non-metal bearing waters these include TSS (total suspended solids), BOD (biological oxygen demand), COD (chemical oxygen demand), pH, etc. For wastewater containing metals (either in solution or insoluble) certain metals limits must be met, along with all the other parameters. This is usually accomplished using pH adjustment, along with a coagulant (aluminum based or iron based). A coagulant is required to help give body to the water. Typically you have a colloidal suspension that requires help in getting the particles to come together and form a larger particle. A coagulant will help neutralize similarly charged particles, allowing them to form small to mid-size particles (sometimes called a pin-floc). This usually occurs in a pH environment between 6-9. Once the pin-floc has formed, a second chemical called a flocculent is required to make even larger particles. Addition of a flocculent occurs at a pH of between 8-10 (depending on the characteristics of the wastewater). Flocculent is added and acts as a net where it gathers up the smaller coagulated particles making a larger particle. This larger particle will slowly drop to the bottom of the container (vessel), forming a sludge.

Many wastewater streams contain metals from the manufacturing processes. These metals can either be insoluble or soluble. Insoluble means that there are actual small particles floating in the water that are too light to settle out without aid. Soluble means that the metals have gone into solution and are actually part of the water. Many times, using hydroxide precipitation, along with the aid of a coagulant most of these metals can be separated from the water. (copper is most insoluble at a pH of 8, nickel is most insoluble at a pH or 10.2, etc.)

Many cleaners contain chelators. These chelators have strong cleaning abilities (citric acid, edta, phosphates,etc). The chelators in the water combine with the metals in the water to form a very strong bond that in many instances cannot be broken with pH adjustment. An additional chemical must be added to cleave the metal/ chelator bond. These products are called precipitants. Precipitants have a stronger attraction to the metal than the chelator, therefore they form a bond and can be separated from the water (i.e.; copper will form copper carbonate when poly thio carbonate is added). Coagulants are required to help these particles combine, along with a flocculent. Typically the precipitant and coagulant can be added at the same pH range of 6-9. The pH needs to be between 8-10 for final flocculation.