Impact of some herbicides on the biomass activity in biological treatment plants and biodegradability enhancement by a photo-Fenton process

Abstract

In recent years, the use of agrochemicals has increased because they are essential for profitable agricultural production. Herbicides are heavily demanded compounds and among these, the most marketed are 2,4-D, atrazine and acetochlor. They have characteristics that can cause problems to humans and the environment. Therefore, it is necessary to design systems that can reduce these compounds to harmless molecules. This work aims at evaluating the possibility of incorporating these herbicides into degradable effluents in a biological treatment system, without reducing its efficiency. For this purpose, studies of organic matter degradability in the presence of these agrochemicals were performed. A synthetic effluent based on glucose and mineral salts was inoculated with microorganisms. Glucose consumption and biomass concentration were assessed. Subsequently, preliminary studies were performed to test the viability of degradation of the most harmful compound with an advanced oxidation process (AOP). The results showed that the incorporation of these herbicides into degradable effluents in a biological treatment system has a negative impact on microorganisms. Therefore, the application of an AOP, such as the Fenton or photo-Fenton processes, prior to a biological treatment was found to degrade these substances to simpler and less toxic molecules.

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU

“…Atrazine removal by Fenton and photo-Fenton processes was already tested as single compound, in a mixture with fenitro-thion (Rizzo et al, 2009), and spiked in a synthetic effluent (Benzaquen et al, 2013). In these reports atrazine degradation was effective with UV radiation enhancing the performance of the Fenton process.…”

“…Atrazine is an herbicide known to induce the inhibition of the biological activity of the aerobic biomass normally found in the activated sludge of WWTPs. Thus, it is also important to assess the feasibility of its degradation by AOPs to remove it before entering into biological treatment processes or even into the environment (Benzaquen et al, 2013). Table S2 shows that atrazine is easily degraded by using Fenton-based processes, typically studied at concentrations of 0.1-100 mg L −1 , with H2O2 and iron concentrations of 5-50 mg L −1 and 1-55 mg L −1 , respectively.…”

Acid‐treated Bentonite as filler in the development of novel composite PVA hydrogels

“…Methylene blue (MB), Congo red, Crystal violet, and Safranin T are some of the synthetic dyes removed by some nanoclays and their composite derivatives. Those studies were boosted by the knowledge of dangerous undesired risks associated with dyes exposition: kidney, liver, brain, skin, central nervous, reproductive, and endocrine systems damages, among many other ones . In addition, carcinogenic and mutagenic effects have also been reported …”

Combined chemical oxidation and biological processes for herbicide degradation

“…The biological treatment of wastewater is often the most cost‐effective alternative of all treatment options. However, some industrial wastewaters containing certain toxic and/or biorecalcitrant organic compounds cannot be treated with this conventional process . Consequently, it is necessary to explore other alternatives to treat these wastewaters.…”

“…Atrazine is a possible carcinogen and a known endocrine disruptor in amphibians of the aquatic biota . Interestingly, atrazine is hardly degradable by biological treatments . Some studies have focused on the biodegradation of atrazine in wastewater .…”