Water Conditioning

Water Conditioning & PurificationJ U L Y 2 0 0 4

Summary: Distillation is one of the most natu-ral and efficient technologies available for pu-rifying water supplies for use in the bottledwater industry. Previously, cost was an over-riding issue working against it, but with newdesigns also has come a more cost-efficientoption for dealers.

Distillation technology replicatesthe hydrological cycle found innature, using the simple evapo-

ration-condensation-precipitation model.Historically more expensive than the re-verse osmosis (RO) process because ofhigher initial investment in equipmentand the electrical power required to boilwater, the latest distillation technologyhas closed the operational cost gap withRO.

In practice, many bottled water op-erators use a combination of methodsto remove impurities from their sourcewater prior to introducing it into thebottle-filling process. That’s because noone method can remove all impurities.Available methods include distillation,RO, activated carbon filtration, ultravio-let and ozone disinfection and ion ex-change.

The most common single methodof removing contaminants from source/feed water with the bottled water in-dustry is RO with about 40 percent ofU.S. bottlers using this process vs. anestimated 15 percent that use distillation.

The other 45 percent of bottlers eitherdon’t remove contaminants becausethey produce and market spring wateror mineral water, or they use other tech-nologies.

A matter of dollars and centsExpense is likely the single most im-

portant reason that only about one inseven bottlers use distillation. The ma-jor cost factor is equipment. Operatorscan invest more than $100,000 in settingup a first-class distillation system whileRO systems are about a tenth of thattotal. The cost of energy required to heatthe water to boiling in the distillationprocess has historically made even thecost of producing a gallon of distilledwater much more expensive than RO.New distillation technology has an-swered that challenge, as we shall see.

Yet, in the long run, distillation canbe quite economical. For one thing,while RO typically creates one gallon ofreject water for every gallon of productwater produced, distillation produces upto six gallons of product water for ev-ery gallon of reject water it produces.

Distillation is broadly viewed as thesingle most effective method of purify-ing water. High quality water can beproduced by distillation from virtuallyany municipal supplies, wells (boreholes) springs, lakes and rivers. Becauseof the extended boiling process, any mi-

crobiological contaminants, includingCryptosporidium, are killed.

While there are different types ofdistillers, they all operate on nature’s ba-sic principles:

• Water is heated to boiling, chang-ing it to a gas (steam), leaving impuri-ties behind.

• As the steam cools, it condensesback to water.

• Condensation is collected as dis-tilled water.

Two types of systemsTwo basic types of distillation sys-

tems are multiple effect (ME) and vaporcompression (VC). VC distillers operateon the principle of heat exchange to re-cycle heat generated to boil the water,thus conserving energy (see FYI).

ME distillers are more simply de-signed. With no moving parts, there’snothing really to wear out. Distillers withmore than one boiler (effect) are de-signed to recycle the heat energy, whichcreates the steam in the first boiler toheat the water in the second boiler. Atwo-boiler unit produces twice the dis-tilled water as a single-boiler unit for thesame cost. A four-boiler unit producesfour times the water, and a six-boiler unitwill produce six gallons of water for theapproximate cost of distilling one gal-lon of water.

Technical advances, as seen in the

The Use ofDistillation Technology

in theBottledWater

Industry

By Bruce Kucera

The Planet Earth storefront emphasizesthe use of distilled water in its bottledwater products.

A purification unit used by Planet Earth todistill its water for bottling purposes.

J U L Y 2 0 0 4Water Conditioning & Purification

latest VC systems, allow many oftoday’s better commercial distillationsystems to produce water to 1 part permillion (ppm) total dissolved solids(TDS) at a fraction of the cost of earlierdistillers. In fact, bottled water compa-nies can offer very competitive priceson their products often equal to—oreven less than—companies using ROsystems.

“Initial investment is certainlyhigher for distillation equipment thanfor RO,” says Troy Krause, manager ofPlanet Earth, the leading bottled watercompany in Lincoln, Neb. “But the ac-tual costs of producing a gallon of waterusing the newest vapor compression-style distillers is now about equal with agallon produced by RO.” Distillationproduces water at one cent per gallon.RO produces water at slightly less. Lo-cally, Krause says, Planet Earth competeson an even field with its RO competi-tors: “In fact, our prices are often a littlelower than theirs.”

While Krause thinks that, to the av-erage customer, “bottled water is bottledwater,” he adds, “there’s still perceivedvalue of the product in the customer’seye if they know it’s distilled. And, ofcourse, some of our customers demanddistilled for such uses as in scientific labo-ratories.

“Distillation gives us product differ-entiation,” Krause says. “All our com-petition uses RO so we can talk aboutthe benefits of distilled water.”

Part of customer awarenessHis salespeople are trained to em-

phasize that product differentiation,Krause says: “We tell them the benefitsof distilled water include a better taste, amore consistent product, and distillationremoves more impurities than RO... An-other advantage to distilled water is pri-marily for ourselves. That we sell onlydistilled water assures us that we’re pro-viding our customers with the best wa-ter possible.”

Krause says Planet Earth, like mostother bottlers using distillation, first soft-ens its feed water with an ion exchangetreatment system before water entersthe distiller. “This treatment removes alot of the minerals that can create scal-ing and other corrosion within the dis-tillers themselves,” he says. “We wantto remove as much of such minerals andnitrates as we can up front, so we don’thave to deal with them in the distillers.”

Planet Earth also uses an activatedcarbon filtration system to “put a polishon our finished product to make it thehighest quality water we can produce,”Krause says. “If our product water

The boiling process begins withboth heating elements turned on. Asthe water in the boiling chamberreaches near-boiling temperatures, thecompressor turns on, engaging thenon-contacted liquid ring seal. Whenthe operating boiling temperature isreached, the No. 2 heating elementturns off and the No. 1 heating ele-ment cycles on and off, maintainingthe boiling at just the right tempera-ture. This step minimizes the amountof energy required to heat the water,achieving maximum efficiency.

The steam from the boiling waterflows through a baffling system andthen into the compressor. In the com-pressor, the steam is pressurized,which raises the steam’s temperaturebefore routed through a special heatexchanger located inside the boilingchamber. The pressurized steam is at a highertemperature than the feed water inside the boil-ing chamber. The pressurized steam gives offits heat to the feed water inside the boiling

Figure 1. Flow diagram of vapor compressionmethod of water distillation

FYI: Vapor Compression Technology

chamber, causing this water to boil and creat-ing more steam.

While the pressurized steam is giving ofits latent heat, the steam condenses. One of the

heating elements will cycle on and offperiodically as needed to provide any“make-up” heat that’s required to keepthe system operating at optimum tem-perature for maximum efficiency. At thisstage, the condensed steam is consid-ered distilled water, but is still very hot—only slightly cooler than boiling tem-perature. This outgoing hot distilledwater preheats the incoming new feedwater that will soon be distilled.

As the incoming water is preheated,the outgoing distilled water cools towithin 20°F (11°C) of the incomingfeedwater temperature. This exchangehelps to pre-heat the incoming feed wa-ter to within a few degrees of the boil-ing temperature, saving even more en-ergy. High-quality vapor compressiondistillers recycle nearly 98 percent ofenergy required. It uses about 0.12 kilo-

watts per hour (kWh) of electrical power toproduce one gallon (3.78 liters) of distilledwater. Depending on local electricity rates, powercosts could be as little as one cent per gallon.

doesn’t test out at 1 ppm TDS, then wedon’t bottle it.” By comparison, munici-pal water guidelines are a maximum of500 ppm TDS.

ConclusionDistillation is nature’s way of re-

moving impurities from water. While in-vestment in equipment remains higherfor distillation systems, the latest tech-nology has lowered the actual cost ofproducing a gallon to about one pennyper gallon. The answer is in the designof today’s energy-conserving distillationequipment.

About the author Bruce Kucera is vice

president of Norland In-ternational Inc., of Lin-coln, Neb., a company thatsupplies complete bottledwater operations to com-panies around the world.The company’s productsrange from turnkey bot-tling plants to a variety of components for thebottled water industry including distillers,bottle washers, fillers and cappers, blowmolders and packaging equipment. Kuceracan be reached at (402) 441-3737, (402) 441-3736 (fax) or email: [email protected]

Reprinted with permission of Water Conditioning & Purification Magazine ©2004