Optimization of the water treatment process in an Italian winery: A case study

Water is an essential ingredient in wine production. The winery plant considered in this study, located in the Langhe area (Piedmont, NW Italy), used approx.100,000 m(3) per year of high quality water for cleaning and sanitation operations. Water was collected from the local shallow aquifer and contained high concentrations of dissolved iron (Fe(II), 800-3500 mu g/L) and manganese (Mn(II), 300-700 mu g/L). The water treatment plant (WTP) owned by the winery included a series of treatment processes (air sparging and sodium hypochlorite injection, settling, filtration on a quartzite - pyrolusite filter, removal of excess chlorine with an activated carbon filter and, finally, microfiltration and reverse osmosis, RO) that were deemed to be adequate to make the groundwater compliant with potable uses. However, a survey carried out by the authors revealed the presence of two critical issues in the WTP's management, concerning the Fe(II) and Mn(II) oxidation and removal, and the backwashing of the dual media filter. Firstly, the results of pilot tests demonstrated that the process of air sparging was sufficient for the oxidation of iron and that NaClO was not necessary for that operation. The present concentration of pure oxidant, of 21.5 mg NaClO/L, could be reduced by at least 75 %, without altering the capacity of the WTP in the removal of the two metals. Secondly, a new combination of water fluxes could improve the efficiency of the dual media filter backwashing, thus allowing to simultaneously avoid the use of the RO corrosive concentrate and to minimize the use of high quality water.In the end, a very basic cost model was used to compare the unit cost for water treatment in the current scenario and after the introduction of the two proposed solutions. Specifically, that model considered three cost items: operating costs (that included four sub-items: mortgage, maintenance, consulting and cost for nonamortizable raw materials and consumable), the costs for the purchase of the chemicals necessary for the water treatment process, and the energy costs. The results coming from the application of the cost model demonstrated that the introduction of the proposed solutions into the WTP, at no additional costs, had an undeniable positive impact on the final unit cost of the treated water, that was reduced by 20 %.