Winery and olive mill wastewaters treatment using nitrilotriacetic acid/ UV-C/Fenton process: Batch and semi-continuous mode

In this work, both red and white winery wastewaters (WW) and olive mill wastewater (OMW) were submitted to a treatment by Fenton-based processes (FBPs). The main aim was to evaluate the most efficient and economic process. Initial tests, resorting to a batch reactor, demonstrated that UV-C/Fenton (lambda = 254 nm) was the most effective process. Operational conditions such as pH, H2O2 and Fe2+ concentrations revealed to have a superior influence within dissolved organic carbon (DOC) removal as well as regarding the reactor's energy consumption. As a means to prevent iron precipitation, the addition of nitrilotriacetic acid (NTA) was tested. With experimental conditions pH = 3.0, [H2O2] = 194 mM, [Fe2+] = 1.0 mM, [NTA] = 1.0 mM, radiation UV-C (254 nm), time = 240 min, the kinetic rate related with DOC removal showed a k(red) (WW) = 0.0128 min(-1) > k(OMW) = 0.0124 min(-1) > k(white) (WW) = 0.0104 min(-1) and both the WW and OMW achieved the Portuguese legal limit values for wastewater discharge. Furthermore, comparative experiments were performed in a semi-continuous reactor, being that the results put in evidence that the concentration of H2O2 added and the flow rate of reagents' addition (F) had a significant effect on the efficiency of the reactor. Under an optimum experimental procedure pH = 3.0, [H2O2] = 97 mM, [Fe2+] = 1.0 mM, [NTA] = 1.0 mM, radiation UV-C (254 nm), F = 1 mL min(-1), time = 240 min, there were observed higher DOC removal kinetic rates (k(OMW) = 15.20 x 10(-3) min(-1) > k(red) (WW) = 11.64 x 10(-3) min(-1) > k(white) (WW) = 11.57 x 10(-3) min(-1)) and a cost ranging between 0.0402 and 0.0419 /g.DOC. These results showed that semi-continuous reactors have the potential to be applied to large scale treatments, with low reagents consumption and reduced energy requirements.

Automated summary

In this study, the treatment of red and white winery wastewaters and olive mill wastewater using Fenton-based processes was investigated. The results showed that UV-C/Fenton was the most effective process, and operational conditions such as pH, H2O2 and Fe2+ concentrations played a significant role in dissolved organic carbon (DOC) removal and the energy consumption of the reactor. Addition of nitrilotriacetic acid (NTA) was tested to prevent iron precipitation. Comparative experiments in a semi-continuous reactor demonstrated the potential application of this process on a large scale, with low reagents consumption and reduced energy requirements.