WATER in the DISTILLERY
Part II – Water Treatment
W
ater is rarely available exactly at the specifications required for its various duties in a distillery. Therefore, it is common to treat water sources to adjust the composition of the solutes present. Of course there should be no physical particles present and, if so, they need to be removed, using technology appropriate to the dimensions of the particles. During the treatment of city water, it is first passed through screens to remove large items of debris, such as leaves and twigs. Next a flocculant such as aluminum sulfate may be added. This has the ability to induce small particles to aggregate into larger particles. Subsequent aeration causes these flocs to float so they can then be skimmed off the water surface. Flocculation tends to be most effective at slightly acidic to neutral or slightly alkaline pH (5.5 – 7.5). Under more alkaline conditions aluminum sulfate can hydrolyze to form gelat-
WRITTEN BY PAUL HUGHES, PH.D.
inous aluminum hydroxide. Given that the efficacy of aluminum sulfate is pH dependent, it is prudent to perform labscale tests to determine the appropriate dosing levels. This approach offers a cost-effective way of providing an initial clean source of water. Any remaining particles can be effectively removed by filtration through deep sand bed filters, and the water may be further filtered through activated carbon, which is effective at removing organic compounds and chlorine. A final sterilizing step is typically applied, either by the addition of chlorine, chlorine dioxide or ozone, or, alternatively, it can be treated with UV light or sterile filtered. No one method is perfect, with each method having its own advantages and disadvantages (Table 1). Bromination can also be applied when legionella is a potential issue. There are also specific methods for removing water hardness, either by boiling, treatment with lime (calcium hydroxide), or by
Water is rarely available exactly at the specifications required for its various duties in a distillery. Therefore, it is common to treat water sources to adjust the composition of the solutes present.
TABLE 1. Water sterilization options Safety in use Method of use Automation Reliability Ease of control Effect under dose Effect over dose 110
Chlorine Safe Dosing Yes Good Simple Not sterile Flavor taint
Chlorine Dioxide Safe Dosing Yes Good Simple Not sterile None
Ozone Safe Dosing Yes Good Simple Not sterile Oxygen hazard
UV Radiation Safe In line Bulb check Variable Simple Not sterile None
Sterile Filter Safe In line Integrity test Good Fair Not applicable None WWW.ART ISANSPI RI TMAG.CO M