The BAP system in tannery and dyeing wastewater: a pioneering approach to wastewater treatment in real environments in the country

Néstor Andrés Urbina Suárez, biotechnology production engineer, graduated from the PhD in Engineering with an Emphasis on Sanitary and Environmental Engineering from the Universidad del Valle. Credit: researcher's courtesy.

Due to industrial discharges, the water basin that supplies drinking water to 80% of the city of Cúcuta and its metropolitan area is currently suffering serious impacts, since most of these industries do not use pretreatment processes. The research proposed to analyze 2 waste effluents from these industries, the tannery sector and the dyeing sector. The purpose of this research was to produce a technology that would allow reducing the impact of pollutants in its interior, by means of an innovative process that is framed in the methodology of advanced oxidation processes coupled with microalgae biotechnology. 

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Advanced oxidation processes and their application to water sources: the case of the tannery and dyeing industry 

The textile industry, which includes tanning and dyeing, is one of the largest sectors worldwide in terms of wastewater generation due to the excessive use of water during its processes. These recalcitrant effluents are highly polluting due to the presence of the so-called emerging pollutants (heavy metals, dyes, etc.) and other materials used. Since these industries do not have wastewater treatment systems, the discharges that are sent to river flows pose a high threat to water resources and public health.  

Based on this scenario, the biotechnological production engineer from the Universidad Francisco de Paula Santander, Master in Biotechnology and Bioengineering from the Center for Research and Advanced Studies of the National Polytechnic of Mexico and in Project Management from the International Cooperative University of Costa Rica and graduate of the Doctorate in Engineering with Emphasis in Sanitary and Environmental Engineering from Universidad del Valle, Néstor Andrés Urbina Suárez, who is also a researcher and full-time professor at the Universidad Francisco de Paula Santander in Cúcuta, carried out a multi-year investigation with the objective of valorizing the compounds of these chemical wastes.  

This research, which was directed by Fiderman Machuca Martínez, professor and researcher at the School of Chemical Engineering of the Universidad del Valle, and co-directed by Andrés Fernando Barajas Solano, professor and researcher at the Universidad Francisco de Paula Santander, in Cúcuta, was based on the innovative use of the BAP (Bicarbonate Activated Peroxide) system -a line of research within the advanced oxidation processes that has been little tested in real wastewater- that seeks to provide an integral technology that allows both the treatment of this wastewater and the use of some of the compounds inside it, for its subsequent use as a culture medium for the production of microalgal biomass with potential production of high value-added metabolites. 

This bet, whose methodology and results were worthy of the first place for the laureate thesis at the International Meeting of Engineering Education ACOFI 2024, aims to address this problem for the communities surrounding the discharges of these industries, and provide an opportunity to obtain additional benefits that contribute to the environment from the recovery of these liquid wastes. 

The research: physicochemical characterization of selected waters 

The research conducted by the researcher Néstor Andrés Urbina Suárez started with the characterization of the wastewater with which he was going to work, given that for this occasion it was decided to use real water from two industries, which implied considering a much more complex matrix due to the multiple compounds in its interior, many of which were unknown. The purpose of using this water source was to obtain information closer to reality and to establish the behavior of the AOPs in the removal of pollutant load and obtaining possible nutrients for their coupling to the microalgal culture. 

For this characterization, researcher Urbina focused on the concentration of nitrogen compounds, since the influent water would later be coupled to a culture with microorganisms (microalgae and cyanobacteria), so it was necessary to determine the amount of nitrate and ammonium in the water, since these are the main source of nutrients for these microorganisms.  

"Knowing the characterization allowed us to establish the degree of contamination of these waters and also to understand how we were going to approach the advanced oxidation processes, so that we could mitigate these contaminants and increase their biodegradability index, because they are waters with a very low index," says researcher Néstor Andrés Urbina Suárez, and reiterates that the difficulty of working with real wastewater led them to consider an experimental treatment design that could cover a greater complexity.  

In order to fulfill the purpose of the research, a process that has been widely studied in the field of advanced oxidation processes, photolysis, was used, which utilizes ultraviolet (UV) radiation together with hydrogen peroxide to make possible the oxidation of the compounds in these waters. 

The BAP system and its unprecedented use in real wastewaters 

In addition to this process, the research also considered the use of another one, called BAP (Bicarbonate Activated Peroxide) system, which uses bicarbonate and hydrogen peroxide to make possible the oxidation process of organic matter in the water. Although there are records of its use in synthetic waters, there are no reports of its use in real wastewater, such as those treated by the researcher Urbina, so the decision to implement it in the research meant a great contribution to the academy at national and international level.  

The reason why the researcher Urbina decided to use this technology, even though it had not been implemented for the treatment of real wastewater, was that it is quite affordable in economic terms, in addition to the ease of operation compared to other AOPs such as photocatalysis, Fenton, Ozone, among others, where more operational variables must be considered that increase costs and operational difficulty. These reasons also contribute to make this system more attractive for use in more complex environments, once the investigations are scaled up from the laboratory to a larger environment, such as the treatment plant of an industry.  

One of the signs of the success brought about by the use of this system is that, as a result of the doctoral research, 3 articles were published that spoke of the effectiveness of the BAP system in real wastewater, which have had a high impact within the academy, as they have quickly become references to study the potential of this method in other research (two of which can be found here and here).

"Right now those articles are being used as references and have opened doors in other countries where this technology is starting to be implemented as well," says researcher Urbina. 

BAP system in tannery effluent. Credit: Researcher's courtesy.

Results 

"We were able to implement the two systems, and they were evaluated within an experimental design to find out which variables affected the process. In the case of the BAP system, the variables most involved were temperature and pH, as well as the concentration of bicarbonate and peroxide. And, for the case of photolysis, they were lamp potential, pH and temperature. The latter is perhaps one of the variables that most controls advanced oxidation processes," says the researcher. 

Within these two systems, a three-stage analysis was carried out. In the first stage, four strains of microorganisms were cultured, two of microalgae (Scenedesmus sp and Chlorella sp) and two of cyanobacteria (Hapalosiphon sp and Oscillatoria sp), in order to determine their growth capacity and their biomass characteristics. This analysis translated, in turn, into a contribution to the academy, since there were no reports in scientific literature on the growth of this type of microorganisms in real wastewater of the type studied in this doctoral research. 

After this procedure, the photolysis system and the BAP were implemented, which would treat water from both dyeing and tanning activities. The purpose of this double process was to evaluate which was the most suitable for each case. For this evaluation, a response surface experimental design with Desing expert was used, where the concentration of the wastewater and the light/dark cycle were optimized in the biomass production of these microorganisms.   

The third step consisted of evaluating which microorganism had the highest growth rates in the post-BAP and UV/Peroxide effluents, and which had the highest biomass production. The results showed that the microalgae Chlorella sp had the best results in tannery wastewater where the BAP system was used, while the cyanobacterium Hapalosiphon sp had the best results in dyehouse wastewater where the photolysis system was used. After obtaining these results, the research was scaled up in sample size: from 300 milliliter photobioreactors to volumes of 5 and even 10 liters. 

Photobioreactors with microalgae and cyanobacteria in BAP and UV/Peroxide effluents. Credit: researcher's courtesy.

After this, the cultured microorganisms were dried and the metabolites produced were evaluated: how many proteins, lipids, pigments, carotenoids, phycocyanins and phytohormones were generated, both in the case of cyanobacteria and microalgae, in order to deduce the potential use of this biomass.  

"We found that, with the advanced oxidation process, we achieved removals of up to 45% or 50% of pollutant loads. And, once the system was coupled with the cultivation of microalgae and cyanobacteria for the two types of wastewater, we achieved removals of around 95% of BOD (biological oxygen demand). Almost 100% of nitrogen compounds were removed, in addition to about 94% of heavy metals. In other words, the removal of the pollutant load of each of the parameters evaluated was in the order of 87% to 96%, which showed perfectly how we mitigated to a great extent the pollutant load of these wastewaters", explains the researcher Néstor Andrés Urbina Suárez, and adds that, as regards the findings in the biomass, it was found that one was produced that enhanced the accumulation of lipids and carbohydrates of the microorganisms. 

Final efficiency with BAP system coupled to microalgae cultivation. Credit: researcher's courtesy.

Research with international projection. Contributions to scientific and academic development 

According to researcher Urbina Suárez, the finding brought about by the production of biomass in the wastewater studied is quite important, since it allows thinking about the future use of such biomass as a source of carbon in the production of biofuels such as biodiesel and bioethanol, to give an example. "The research, apart from generating a new technology for the treatment of complex waters such as these, also generated a biomass with a very large potential use of valorization, since it can be used by the industry and reincorporated again to the productive process", says the researcher Urbina.  

Other aspects that could benefit from the results of this research have to do with obtaining energy, production of alternative fertilizers that contribute to reduce the impact of other materials on the environment, all within a bet that has prioritized the reduction of costs of raw materials used, which increases the likelihood that this bet could be taken up and scaled by industries in the sector.  

Regarding the scientific field and the development of this type of technologies, throughout his research, which has taken about 7 years of research, the researcher Néstor Andrés Urbina Suárez has been publishing his findings, as a way to document and share with the scientific and academic community the results of his doctoral bet. This process has resulted in 9 scientific articles and 10 international papers, which shows the impact that his project has caused both nationally and in other countries where similar technologies are being developed for the treatment and use of complex wastewater.  

In addition to this, last September, in the framework of the "International Meeting on Engineering Education ACOFI 2024", one of the most important events in engineering worldwide, his doctoral bet was awarded the distinction of best thesis laureate among the participants. About this recognition, the researcher thinks that this was the result of having bet on a research that sought to evaluate a method that until now had no parallel. For him, the visibility that this recognition translates into is the most important thing, as it will allow him to continue disseminating his findings in other communities:  

"Many times one is left with the results in a document, but I think that something we achieved within the working group is to be able to transfer knowledge through scientific papers and articles, and to make the scientific community aware that in our country we also do quality research and that we respond to real needs that help mitigate the impact currently generated by wastewater." 

If interested in being in touch with the researcher or any further information about the investigation, please write the Faculty of Engineering Communications Office: comunicaingenieria@correounivalle.edu.co.