Feedwater Pretreatment in the Bottled Water Business
Feedwater used for bottling water must be treated effectively to eliminate a variety of contaminants. Treatments, contaminants found and the final processing of water can vary, depending on the source of the water.
Bottled water plants must comply with a variety of specific regulations from the U.S. Food and Drug Administration (FDA) and the bottled water industry that guarantee the safety and quality of the product. These standards protect consumers, of course, and adherence to these tests will help avoid contaminated water, costly product recalls and loss of customer trust that would follow.
Bottlers are mandated by law to test feedwater. The first tests are required at the time the bottler enters the business. It is imperative that the selected source of feedwater be tested upfront to determine the types of treatment systems that will be required to prepare the water for bottling. Every feedwater source has different contaminants and mineral composition.
Once in operation, a bottling plant must follow a strict testing regimen prescribed by the FDA and the bottled water industry. Some of these tests include:
- A full water analysis at the time of plant start-up and annually thereafter.
- Monthly tests for bacteria.
- A pH level check every hour the plant is operating and once daily if not operating.
- An ozone check at start-up of every product bottling run, plus twice per product per day.
- Periodic testing of source and bottled water for bromide and bromate levels.
Treatment varies by water source. Water from each source tends to contain certain contaminants and must be identified in the bottler’s supply.
The industry generally recognizes these four primary types of water for bottling:
Spring water. Spring water is defined as water that is derived from an underground formation from which water flows naturally to the earth’s surface. Sometimes this water is referred to as mineral water.
Well water. Well water (or bore hole) water is defined as water derived from a hole bored or drilled, which taps the water of an aquifer.
RO-processed water. Reverse osmosis (RO)-processed water is defined as purified water that is produced by the RO process and meets the definition of purified water in the U.S. Pharmacopoeia.
Distillation-processed water. Distillation-processed water is defined as water that has been vaporized and condensed and meets the definition of purified water in the U.S. Pharmacopoeia.
Some bottled water operations use municipal water supplies as their feedwater. Typically, these bottlers use either the RO or the distillation method to treat municipal water before bottling.
Treatment varies by water source. Water from each source tends to contain certain contaminants and must be identified in the water bottler’s supply so it can be treated properly. Here, we will address typical problems and contaminants found in the source waters for the types of water to be bottled.
Contaminants typically found in spring water include nitrates, total dissolved solids (TDS), bromide/bromate, bacteria, iron or manganese, and general sediments and particles that make the water cloudy (turbidity).
A typical treatment method usually prescribed for spring water includes multimedia filtration down to 15 microns followed by filtration to 5 microns, ultraviolet (UV) systems and depth filtration down to 1 micron absolute.
If the bottler plans to ozonate the water, other pretreatment may be needed to remove any iron or manganese that may be present. In some cases heavy bacterial contamination occurs on a steady basis, and chlorination followed by chlorine removal through carbon filtration will be necessary.
A main concern today is the presence of bromide/bromate in spring water. Levels of bromate must be below 10 mg/L in water to be bottled. This can be a problem with ozonating the water to be bottled, due to conversion of naturally occurring bromide to bromate. Contact the International Bottled Water Association (IBWA) concerning the testing for bromide and bromate and methods to alleviate this problem.
Well water often contains such contaminants as nitrates, TDS, iron or manganese, bacteria and bromides. It also typically shows pH balance problems.
Pretreatment methods usually include multimedia filtration, aeration, depth filtration (down to 1 micron) and UV application.
Well water, along with spring water, may require additional pretreatment to remove iron or manganese from the feedwater. Additionally, chlorination of the well and carbon filtration may be required if there is reoccurring heavy bacterial contamination.
If bromide levels are high, ozonation of the water may not be possible. In these cases, UV units followed by 1-micron absolute filtration will be required.
Some correction of pH levels may be required if very low pH values are noted. Such low values often are a result of carbon dioxide gas in the water. Aeration will drive the CO2 out of the water. In some cases, sacrificial calcium carbonate filters will help raise pH values as well.
Typical contaminants to be aware of when using an RO system include bacteria, silica, hardness, turbidity, iron and manganese, chlorine, and the chlorinated hydrocarbons found in the municipal water supplies from which feedwater is often drawn.
Turbidity can be reduced by multimedia filtration, followed by 5-micron filtration. Softening the incoming feedwater typically reduces hardness. A twin alternating automatic regenerating system is preferred to prevent any hardness passing to the RO unit. Anti-scalant chemicals can also be used to keep hardness minerals in suspension and prevent scaling of membranes.
Silica is a problem if it is more than 20 ppm in feedwater. If levels are high, the recovery rate of RO systems can be changed or the incoming feedwater pH lowered by acid injection.
The preferred method is to inject an anti-scalant solution into the feedwater to keep the silica in solution until it goes out of the system in the reject drain water stream. In this case, a good product flush system should also be installed in an RO system.
Iron and manganese are removed from the feedwater by pretreatment methods such as aeration, chlorination and softening. They can also be kept in solution with the use of anti-scalants.
The chlorine must be removed from the feedwater before it reaches the RO system. This is accomplished by using carbon filtration or sodium bisulfite injection. Chlorine will attack the membranes, causing loss of product quality.
Chlorinated hydrocarbons such as trihalomethanes (THMs) are produced in some waters that have been heavily chlorinated. Carbon filtration will reduce THMs prior to the water entering the RO system. This treatment will help reduce the quantity of contaminants in the final product water. If not reduced, these contaminants may exceed recommended levels in the product water and may affect final ozonation of the product water.
Contaminants to be aware of when using distillation include chlorine, high TDS, hardness, silica and high chloride levels.
Pretreatment includes using carbon filtration to remove the chlorine before it enters the distillation equipment; otherwise, the chlorine will attack internal parts of the distiller made of stainless steel.
Very high levels of TDS will dictate the need for either an RO unit before distillation or a special seawater-type distillation system.
A twin alternating automatic regeneration softener is recommended to remove hardness before feedwater enters the distiller because the hardness may cause scaling problems.
Silica levels may need to be tested for large-size distiller units. High silica levels may result in silicate formations inside the distiller.
FDA and bottled water industry standards require the proper testing and treatment of all water to be bottled and marketed. Bottled water plants must comply for obvious reasons, not the least of which is to maintain consumer confidence in safe and healthy bottled water products.