Por Mauro Rebelo

Nipping the problem in the bud: the search for a definitive technological solution to the golden mussel problem


In August, Bio Bureau took part in the second stage of the selection process for Solutions for the Golden Mussel from Klabin. More than 30 ideas were presented at the event and 8 of them were selected for presentation. We were happy to be there and curious too: what other ideas would there be? We thought we had a good knowledge of the projects being developed with mussels, but when we saw the names of the other presenters, we knew practically none of them.

The event took place in São Paulo at the beautiful Museu de Ema Klabin. However, the mussels are in Paraná. During the 2020 maintenance shutdown at the Puma unit, mussels were found in the raw water intake, which has a flow rate of 8,000 m3/h. Klabin’s problem is similar to that of the many hydroelectric plants we work with. Taking raw water from the river for cooling is the first check point of the infestation. The water must be filtered before entering the system. The speed decreases, the contact surface and temperature increase and the mussels adhere in large numbers.

These filters then need to be cleaned from time to time. In general, once a month. Sometimes every week. The process involves at least two people and interrupts the hydroelectric plant’s turbine for at least 6 hours.

Check out this recording we made of the cleaning process at CTG’s Tijoa plant.

Controlling mussels in this environment is challenging, but possible.

In the first task force to find control solutions for the golden mussel in 2005 (organized by the MMA/MCT), the options were chlorine (hypochlorite and dichlorine), UV, anti-fouling paints, chemical substances (primary-quaternary amines) and ozone.

All these solutions are much more effective at fighting the larvae than the adults, who realize when there is a chemical substance in the water and close their shells. And they can stay that way for a long time. Perhaps it’s easier to kill them by starvation than by the toxic substance. Even then, not all of them come off the surface. Inevitably, the pipe has to undergo a physical unclogging process.

The Museum of Tomorrow, in Rio de Janeiro, has its cooling pipes with water from Guanabara Bay physically unclogged every 3 months with Roto-Rooter. The mussel is different (because the water is marine), but the problem is the same. And when they manage to remove the mussels, a mountain of biological waste is formed. The smell of decomposing mussels is unpleasant, despite the fact that there is technology for processing and extracting high-value compounds (such as heparin).

But even before the cleaning is finished, new mussels are taking hold again. The metaphor of wiping ice applies, but it’s not perfect. At least the ice won’t grow back. That’s where most of these products come in: killing the larvae to prevent them from becoming embedded in the filters and pipes. All these solutions are more or less effective, with more or less cost-effectiveness.

In 2013, we published a paper showing the potential of microencapsulated pesticides to combat adults in industrial facilities (Calazans et al., 2013). However, the cost of these solutions has always prevented their widespread adoption or their progress beyond pilot tests. Chlorine, on the other hand, which is inexpensive, comes up against regulation: the process of obtaining a license to use it is so laborious that it can take longer than the application time required.

All these solutions aim to solve the problem in industrial facilities. It’s understandable: the problem is specific and the client is well defined. However, none of them really solves the problem, but rather tackles the cause. The biggest proof of this is that the mussel invasion continues to expand and so does the frequency of maintenance stoppages.

Perhaps the problem in industrial facilities cannot be solved without first solving the problem in the environment. Nipping the problem in the bud: we think there is no other solution to the mussel problem.

And that’s the difference between our solution and the others presented at the
pitch day
from Klabin. We want to nip the problem in the bud and that means tackling the problem in the environment and not just in industrial facilities.