**5. Conclusion**

In this type of seasonal industry, the treatment system must be able to treat the wastewater produced in all labour period. A vertical reactor coupled with highly efficient Venturi injector and multiplier nozzles was used for winery wastewater treatment. Regarding mass transfer parameters, the estimation of OTR could be interesting for studying the influence of operational conditions on volumetric mass transfer coefficient. The results showed a decrease in the kLa value during the treatment period. This decrease in kLa value may evidence that some of the existing compounds in wastewater optimize the oxygen mass transfer during the initial phase of treatment.

The SOUR measurements throughout the wastewater treatment showed high values, which could indicate a high organic load to the existing suspended solids in the mixed liquor. This high SOUR rate is due to the high activity of the microbial population to oxidise substrates, in the begging of the treatment.

The implemented strategy, where an aerobic step alternated with an anoxic one was adopted, showed to be a good approach to minimize the sludge production and to reduce energetic.

However, further studies should be conducted in order to better understand the effect of winery wastewater composition in mass transfer coefficients. The use of two consecutive stages of treatment might improve the performance of this technology because it allows higher flexibility. The result of feast / famine treatment in sludge should also be exploited, as it is of interest in this type of seasonal industries.

Moreover, the treated wastewater revealed its suitability to be integrated in the irrigation systems as confirmed by direct toxicity bioassays. This study is expected to contribute to the implementation of an efficient wastewater treatment, intending the preservation of the water resource, the reduction of the wastewater sludge production and the energy safe.
