Vol.:(0123456789) 1 3 International Journal of Environmental Science and Technology https://doi.org/10.1007/s13762-020-02711-2 ORIGINAL PAPER Tertiary treatability of molasses secondary efuents for color and organics: performance and limits of ozonation and adsorption C. Fall 1  · L. M. Barrón‑Hernández 1  · M. T. Olguín‑Gutierrez 2  · K. M. Bâ 1  · M. Esparza‑Soto 1  · M. Lucero‑Chávez 1 Received: 16 October 2019 / Revised: 19 February 2020 / Accepted: 10 March 2020 © Islamic Azad University (IAU) 2020 Abstract Molasses wastewaters (MWWs) such as baker’s yeast and distilleries efuents are usually pretreated by anaerobic, followed by aerobic biodegradation. This removes almost all the BOD, enough for meeting the current discharge standards in many low- and middle-income countries. However, as shown in the present work, the biotreated efuent still contains high levels of recalcitrant COD, color (melanoidins) and inorganic salts that end up in rivers (approx. 1000 mg/L COD, 2850 Pt–Co color units, 5000 mg/L TDS and 5400 μS/cm conductivity). To address this global problematics, and given the lack of proven cost-efective advanced treatment trains for MWW, this study assessed the performance and limits of ozonation and activated carbon (AC) adsorption (contrasting with O 3 applications on raw MWW). The applied versus the reacted O 3 doses were quantifed, allowing also to estimate the ozone uptake rate as a new tool for characterizing the reactivity of the wastewaters. The efects of the treatments on diferent key parameters were studied: COD, color, aromaticity (UV 254 nm ), toxicity (Micro- tox) and biodegradability (by respirometry). O 3 reduced the color (> 95%), but causing low COD mineralization (< 35%) and biodegradability enhancement (only 8% more). Meanwhile, adsorption was efcient on both COD and color (97–91%), but needing high AC dosage. In consequence, a more sustainable treatment train was suggested, i.e., upgrading the activated sludge with aerobic granular sludge technology and transforming the granules into AC. Keywords Activated sludge · Bakery yeast · Melanoidins · Ozone · Sorption · Vinasse Introduction Molasses, a sugar industry by-product generated in large quantities, is widely used as feedstock by fermentation industries, such as for baker’s yeast and for bioethanol pro- duction. So, molasses containing wastewater (MWW) results from different industrial processes, mainly sugar mills (e.g., cane-based), ethanol distilleries (industrial grade or biofuels) and baker’s yeast manufactures, being the latter of most interest in the present study. A great increase in MWW generation is expected with the foreseeable increase in bioethanol production in the world. Regardless of the specifc source, raw MWW is a high-strength efuent char- acterized by an elevated soluble organic load, mostly bio- degradable, but with considerable amounts of recalcitrant chemical oxygen demand (COD) very difcult to remove. It also has a persistent dark brown color attributable to the pigments of melanoidins (Hoarau et al. 2018; Zhang et al. 2019) and great quantities of total dissolved solids (TDS) and inorganic salts. Vinasse residuals from the fabrication of diferent beverages (Robles-González et al. 2018) bear similar characteristics; so, the problematic wastewater cor- responds to a large volume of heavily contaminated efuents throughout the world. Meanwhile, nowadays treatment tech- nologies and agricultural management practices of MWWs are very defcient, causing serious pollution threat to many surface waters and soils, more specially in low- and medium- income countries. Raw wastewater rejected by molasses-fed yeast ferment- ers contains high COD levels that are easily reduced from Editorial responsibility: M. Abbaspour. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13762-020-02711-2) contains supplementary material, which is available to authorized users. * C. Fall c-fa-ll@hotmail.com 1 UAEM, IITCA (ex CIRA), Universidad Autónoma del Estado de México, col. Centro, C.P. 50000 Toluca, Mexico 2 Dep. de Química, Instituto Nacional de Investigaciones Nucleares (ININ), Ocoyoacac, Mexico