Polyacrylamide based Flocculants and their environmental concerns

In recent times, rapid settling of solids from wastewater using Polyacrylamide based flocculants have become very popular. The flocculant is added and stirred leading to rapid floc formation and subsequent settling; resulting in a clear solution. Their effectiveness in aggregating suspended particles for easy removal is widely appreciated. These synthetic polymers possess high molecular weights and exhibit anionic, cationic, or non-ionic properties, allowing for specific wastewater compositions.

However, the use of Polyacrylamide is not without its own set of environmental concerns. For example, the acrylamide monomers have the potential to leach from the formed agglomerated matrix into surrounding environment. Furthermore, microbial decomposition or hydrolysis of the same can lead to excessive nutrient enrichment in receiving water bodies, leading to increased oxygen demand; a major hazard to the existing aquatic ecosystem. There is also the possibility of microplastic formation due to degradation of larger polymer chains; which could accumulate and enter food chain in the aquatic ecosystem.

At the outset, the benefits may seem to outweigh the disadvantages; particularly considering the daily challenges faced by ETP operators to rapidly clear the wastewater from solids to move on to other unit processes. The long term environmental consequences therefore become part of an ecological conservative concern rather than something of immediate consequence. However, it is concerning to note that while one problem is rapidly resolved, another issue may also be created.

Effective alternate strategies to using chemical based flocculants involve the increased preference for natural polymers (Biopolymers from microbial fermentation) as flocculants, or those sourced from plant and animal sources. Alternate treatment strategies such as Advanced oxidation processes (Ozonation, Photocatalysis) and membrane filtration can also be considered.

Careful balance is needed since the water bodies into which we ultimately dispose is becoming increasingly unstable; and wastewater treatment on one side may be contributing to increased issues for water treatment on the other side; particularly in large cities where water treatment towards potability would be taxing on citizens as complexity of unit processes increase.

#flocculation, #wastewater, #polyacrylamide