Possible reasons for a loss of efficiency in your sludge dewatering process

As Lavoisier so aptly put it: Nothing is lost, nothing is created, everything is transformed.

When using settling and or floatation-based processes as part of the physical-chemical treatment of industrial wastewater, all of the contaminants being removed accumulate to form a residue of waste material, often referred to as “sludge”.

If sludge volumes and disposal costs get excessive, mechanical dewatering can be used. Within mechanical dewatering processes, polymers are added to condition the solids, promote the release of excess water, and transform the sludge into a dry cake. When applied properly, the reduction of a facility’s waste footprint and by default its operational spend can be significant. It is not uncommon for Aquasan to get urgent calls from facilities that are struggling with their dewatering efficiency and by default, are looking for some technical support to get a better understanding of what can be done to correct it.

The link below provides a case study where Aquasan was called in to solve a problem that was caused by the presence of bacteria in a polymer solution tank of an injection system.

Aquasan Case Study – Dewatering Application – Loss of Dewatering Efficiency – Proliferation of Bacteria in Polymer Solution Tank.

In addition to the aforementioned case study, another potential cause for the loss of mechanical dewatering efficiency can be the acidification of the waste sludge. 

This problem tends to be most common amongst our customers who operate in the agri-food industry. Within this industrial segment, the pH of these sludges will drop drastically if stored and left untreated for an extended period of time, typically in excess of 24 hours. The acidification of these sludges will inevitably lead to a lack of polymer performance (flocculation/sludge conditioning) and a significant loss of mechanical dewatering efficiency.

The illustrative example below summarizes some of the polymer testing that took place on a sludge sample that had been collected from an Aquasan customer within the agri-food industry and had been aged for a period of 24 hours. Within the 24-hour period, the pH of the sludge sample dropped down to 5.45. After doing so, the sludge conditioning polymer was incapable of dewatering the sludge, even at much higher dosages. It was only after the pH of the sludge was adjusted back above 7.0 with caustic soda that the polymer regained its ability to condition the solids and effectively dewater within the equipment being used.

Series	pH of Sludge and Flocs	Screen	Filtrate and Turbidity of Filtrate
Series 13 AQ-8560 375 mg/L		—	—
Series 14 AQ-8560 375 mg/L

Our Aquasan team is highly technical and more than willing to share the knowledge and experience they have accumulated from the many industries we serve, including municipal.  When you do business with AQUASAN, our technical expertise and support can make all the difference in maintaining your wastewater treatment and sludge dewatering operation.