By Dr. Alexandre Arenzon – 08/24/17 (updated 10/16/23)
The quality of surface water used for public supply has become a major concern in recent times. Ongoing debates aim to assess whether the criteria established to monitor this water, as well as the limits imposed by Brazilian legislation, are sufficient to ensure its purity and safety.
Domestic and industrial effluents, regardless of whether they have undergone treatment, are constantly released into surface waters. Surprisingly, these are the same waters drawn to supply our taps. While these rivers, lakes, or reservoirs have the capacity to purify the waste they receive, it is essential to remember that this capacity has its limits. As urban populations grow, the amount of waste discharged into rivers increases, not only in volume but also in the number of compounds present.
The concern here should not be limited only to monitoring the quality of the water we consume but also to the direct relationship between this quality (or lack thereof) and the constant influx of waste that these waters receive.
Just as population growth compels us to release ever-increasing volumes of effluents, we should consider making a gradual improvement in the quality of these discharges mandatory. Setting goals for reducing organic or toxic loads, for instance, could contribute to the self-purification of rivers by reducing the volume of waste they receive.
The state of Rio Grande do Sul was a pioneer in enacting environmental legislation that required a gradual reduction in effluent toxicity (CONSEMA 129/06). At the end of a 16-year adaptation period, all effluents released into surface waters in the state were to be free of toxicity. This legislation was in effect for a decade and primarily encouraged the industrial sector to conduct research, invest, and make adjustments to reduce toxicity. By reducing toxicity, it is certain that the compounds causing it would also be reduced, thereby decreasing the impact on the rivers.
Regrettably, this environmental resolution was revoked at the end of 2016, to be replaced a year later by Ordinance 66/2017. The new Ordinance enforces the application of the federal legislation CONAMA 430/11 in the state of Rio Grande do Sul, treating each effluent as unique, to be received and purified by the river, without considering the pollution load discharged by surrounding establishments, let alone establishing a gradual reduction in these loads.
It is important to note that simply adding more parameters to the monitoring list does not guarantee an improvement in the quality of water bodies by itself. Often, this only serves to keep an updated record of what can be found in the waters. Similarly, imposing stricter limits on monitored parameters may result in an even longer list of requirements that are challenging to meet without addressing the root of the problem.
It is crucial to acknowledge that surface waters will remain under constant pressure until a substantial change occurs in the standards of effluents discharged into these areas. Only then can we envision a true improvement in the quality of these natural resources.
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