Vinasse processing by electrodialysis combined with nanofiltration: emphasis on process optimization and environmental sustainability.

Vinasse, due to its high organic load, low pH, high corrosivity, and high potassium levels, can cause salinization, acidification, loss of fertility, and leaching of constituents when applied to agricultural soils. In this context, electrodialysis (ED) was used to remove potassium from this effluent, to concentrate it in the cathode concentrate compartment. The cathode concentrate was subjected to nanofiltration (NF), allowing the electrolyte to be reconditioned and simultaneously generating a solution rich in potassium, making it an input for the fertilizer industry. The conditions of NF were optimized by the design of experiments. The optimal conditions obtained were 6 bar pressure, 1.8 L min-1 flow, and 1.6× feed dilution factor. Although the reconditioned electrolyte has been feasible, the raw vinasse (pre-ultrafiltered) was compared and proved to be a sustainable option. The NF permeate had a potassium concentration of 90% and magnesium of 84%, in addition to the annual reduction in magnesium sulfate demand (139,450,988 kg) and distilled water (5,019 m3). It was also possible to obtain an increase of approximately 400% in the rate of the application of vinasse in fertigation without compromising the needs of the plantation, the quality of the soil, and groundwater.

A survey on experiences in leachate treatment: Common practices, differences worldwide and future perspectives.

The necessity for landfill leachate treatment is a requisite to reduce the environmental impact related to municipal solid waste landfills and different aspects must be considered while deciding for an appropriate treatment process. For example, it was demonstrated that the landfill leachate stabilization in tropical regions is achieved right after its first year of operation, requiring technologies capable of treating leachates of a higher recalcitrant character if compared to those leachates from temperate regions and same landfill age. In view of its complexity and variability, stand-alone processes (either biological or physicochemical) are often ineffective in attaining the threshold values for its discharge in receiving bodies. Due to that fact, full-scale facilities have adopted integrated routes, harvesting the benefits of both biological and physicochemical processes. The implementation of membrane bioreactors followed by polishing membrane separation process (nanofiltration and reverse osmosis) seems to be a trend in leachate treatment by full-scale treatment plants. This technology is widely employed in China, European countries, and tropical countries as Brazil, generally with a treatment cost lower than the costs related to its disposal in domestic effluent collection systems. From the technologies already employed by full-scale facilities, four integrated routes were proposed for a sensitive analysis considering the treatment of a landfill leachate of different physicochemical characteristics. From all routes, those employing the membrane separation process as a polishing step had a better efficacy in attaining the threshold values for leachate disposal, being that an interesting alternative for leachate polishing by full-scale facilities.

Influence of COD/SO42- ratio on vinasse treatment performance by two-stage anaerobic membrane bioreactor.

Vinasse is sulfate-rich wastewater due to sulfuric acid dosage in some ethanol production steps. The vinasse sulfate concentration is subject to seasonal variations. A two-stage anaerobic membrane bioreactor (2S-AnMBR) was operated to evaluate the influence of COD/SO42- ratio on vinasse treatment performance by using a real vinasse sample under natural seasonal COD/SO42- variation. This ratio directly affects the sulfidogenesis efficiency, which is responsible for different forms of inhibition in the anaerobic treatment of sulfate-rich wastewater. The bioreactor presented a stable performance at the highest COD/SO42- ratios (50-94), with high removal of chemical oxygen demand (COD) (97.5 ± 0.4%) and volatile fatty acids (VFA) (98.0 ± 0.6%), but low removal of sulfate (69.9 ± 9.5%), indicating lower sulfate reducing bacteria (SRB) activity. In the lowest COD/SO42- ratios (9-20), a deterioration in the removal of organic matter (87.0 ± 1.3%) and VFA (69.8 ± 15.5%) was observed, accompanied by sulfate removal increase (92.9 ± 2.6%). A significant correlation between COD fractions removed via methanogenesis and sulfidogenesis and the COD/SO42- ratio was found, indicating that the increase of this ratio is beneficial to the methanogenic archaea activity. The occurrence of sulfidogenesis, favored by the lower COD/SO42- ratios, induced the microbial soluble products (SMP) and extracellular polymeric substances (EPS) release and protein/carbohydrate ratio increase in the mixed liquor, contributing to the filtration resistance increase.