Biodiesel is created through a transesterification reaction, a process in which vegetable oil is reacted in excess of methyl alcohol in the presence of an alkaline catalyst.
Based near Rome, there is an Italian company that produces a large quantity of biodiesel made from frying oils collected in Italy, France, Spain and Holland. In addition to biodiesel, they also make distilled fatty acids, glycerin and vegetable olein, which, for the most part, are all byproducts of the biodiesel process. They are also able to create electricity from biogas generated by their waste treatment processes and distillation bottoms (pitch).
This company's original wastewater treatment system included physical-chemical processes, activated sludge (oxygen-based) and granular activated carbon (GAC). As the business grew, their wastewater treatment facilities became too small to facilitate their new treatment objectives.
The primary issue was higher recalcitrant chemical oxygen demand (COD) after the biological stage, with a significant increase in GAC consumption. The discharge COD target was set at 250 ppm. The company investigated multiple technologies, including ultrafiltration (UF), but membranes maintenance caused by fouling of the membranes was not acceptable. They then wondered if advanced oxidation using ozone might be a more economical option to reduce the GAC consumption and De Nora Water Treatment (Capital Controls® Ozone Group) was immediately contacted.
DeNora’s Capital Controls® group is one of the oldest continuously operating ozone companies in the world, with significant experience in industrial and municipal ozone water treatment. As this group recommended pilot testing of ozone-based processes, tests were performed onsite in a batch process using a 30 gÌh ozone generator fed with LOX.
Experiments were then performed using both ozone and an ozone/peroxide mix. The ozone peroxide was done with a correction in pH to 9 with NaOH and,H2O2 injection with a 1:1 ratio with 03. The results showed that ozone/peroxide was a faster treatment option than ozone alone. This result was expected since molecular ozone is a slower reacting agent than the hydroxyl radical formed in the ozone/peroxide reaction.
The final design of the system required a 17 Kg/h ozone generator as a containerized package (shown below to the left) and a complete water treatment solution (show on the right). The ozone water mixing is done with a double-stage, side-stream pump injection system. A small amount of the ozone, about 0.5 Kg/h, is used for sludge reduction and control of filamentous bacteria. Thanks to DeNora’s Capital Controls® group, the system has been in successful operation since 2014.
Source: Ozone News: Vol 47, No 2; Tony Sacco, 4/2019
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