drinking water
Application - Drinking Water
Produce Quality Drinking Water In Sufficient Quantities
Water is declared drinkable and can be distributed to consumers only when it meets well-defined quality parameters. It is, moreover, one of the most stringently controlled food products. It is subject to extreme vigilance at every stage of its journey, from collection to distribution.
The production of drinking water thus requires expertise in multiple technologies and processes as well as the ability to anticipate requirements, which involves precise knowledge of water resources. Available reserves of natural water include groundwater (water tables), standing or running surface water (lakes, rivers, etc.), and seawater. The implementation of a treatment system to produce water that is suitable for drinking depends on the quantity of water available, its quality (taking into account the possible variations), economic costs and environmental constraints.
To deliver quality drinking water pure enough for human consumption, from public networks to private taps, it needs treatment and distribution technologies. Tap water is not naturally drinkable, unlike commercially available mineral and spring water. It only becomes drinkable thanks to extensive physical and chemical treatments.
General Process To Address Dranking Water
Eliminate Unwanted Elements From Water
We use specific treatments that allow for extracting a certain number of elements from water:
Suspended solids and dissolved organic matter.
Certain minerals (iron, manganese, arsenic, sulphates, etc.).
Make Salt Water Drinkable
Desalination is another way of meeting the growing needs for both drinking and fresh water. It is also a responsible means of managing water resources:
Benefit from reverse osmosis technology for high quality desalinated water.
Keep investment and operating costs under control.
Limit the environmental impact of producing drinking water through the use of renewable energies for the power supply of water treatment plants, as well as internal energy recovery and the dispersal of saline concentrates (brine) to protect flora and fauna.
Disinfect Water Prior To Distribution
Disinfection is the final stage of water treatment for the production of drinking water. It is critical because it:
Removes all pathogenic microorganisms from the water.
Guarantees the bacteriological quality of the water for the consumer thanks to the residual effect of the disinfection process.
Choose the most appropriate disinfection system: chlorination, ozonation or UV radiation.
Overview Of Drinking Water Treatment Technologies
There are a list of mature technolgoies to treat a water source into potable water, including:
Clarification and purification
Granular activated carbon
Ion exchange
Biological treatment
Reverse osmosis/nanofiltration
Adsorptive Media
Ultraviolet Photolysis and Advanced Oxidation Processes
Disinfection
Checking below for more information about these technologies.
Clarification And Purification
Water drawn from the natural environment is loaded with:
Suspended solids.
Mineral substances.
Organic substances.
Depending on the concentration levels of these substances in the water, there are different water clarification operations that can be performed to render it safe to drink.
The decantation and flocculation / coagulation techniques put in place by Veolia Water Technologies guarantee the best solution at the best price for our customers.
Granular Activated Carbon
Granular activated carbon (GAC) is a porous adsorption media with extremely high internal surface area. GACs are manufactured from a variety of raw materials with porous structures
GAC is useful for the removal of taste- and odor-producing compounds, natural organic matter, volatile organic compounds (VOCs), synthetic organic compounds and disinfection byproduct precursors. Organic compounds with high molecular weights are readily adsorbable.
Treatment capacities for different contaminants vary depending on the properties of the different GACs, which in turn vary widely depending on the raw materials and manufacturing processes used.
Ion Exchange
Cation Exchange - In a cation exchange treatment process, water passes through a bed of synthetic resin. Positively charged contaminants in the water are exchanged with more innocuous positively charged ions, typically sodium, on the resin’s surface.
Cation exchange is useful for water softening by removing hardness ions such as calcium and magnesium. It can also remove other positively charged contaminants including barium, radium and strontium.
Treatment capacities for different contaminants vary depending on the properties of the resin used and characteristics of the influent water. A number of vendors manufacture different resins, including those designed to selectively remove specific contaminant ions.
Anion Exchange - In an anion exchange treatment process, water passes through a bed of synthetic resin. Negatively charged contaminants in the water are exchanged with more innocuous negatively charged ions, typically chloride, on the resin’s surface.
Anion exchange is useful for the removal of negatively charged contaminants including arsenic, chromium-6, cyanide, nitrate, perchlorate, per- and polyfluoroalkyl substances (PFAS), sulfate, and uranium.
Treatment capacities for different contaminants vary depending on the properties of the resin used and characteristics of the influent water. Several of vendors manufacture different resins, including those designed to selectively remove specific contaminant ions.
> Read more about Ion Exchange
Biological Treatment
Biological treatment of drinking water uses indigenous bacteria to remove contaminants. The process has a vessel or basin called a bioreactor that contains the bacteria in a media bed. As contaminated water flows through the bed, the bacteria, in combination with an electron donor and nutrients, react with contaminants to produce biomass and other non-toxic by-products. In this way, the biological treatment chemically “reduces” the contaminant in the water.
Biological treatment is useful for the removal of contaminants including nitrate and perchlorate. Following a startup period, the bacterial population in the water will adapt to consume the target contaminants as long as favorable conditions, such as water temperature and electron donor and nutrient concentrations, are maintained.
Biological treatment can achieve high removals (greater than 90 percent) of nitrate and perchlorate. The process destroys contaminants, as opposed to removing them, and, therefore, does not produce contaminant-laden waste streams. Biological treatment remains effective even in the presence of certain co-occurring contaminants.
Reverse Osmosis/Nanofiltration
Reverse osmosis (RO) and nanofiltration (NF) are membrane separation processes that physically remove contaminants from water. These processes force water at high pressure through semi-permeable membranes that prevent the passage of various substances depending on their molecular weight. Treated water, also known as permeate or product water, is the portion of flow that passes through the membrane along with lower molecular weight substances. Water that does not pass through the membrane is known as concentrate or reject and retains the higher molecular weight substances, including many undesirable contaminants.
RO and NF are useful for the removal a wide range of contaminants. RO can remove contaminants including many inorganics, dissolved solids, radionuclides and synthetic organic chemicals. RO can also be used for removing salts from brackish water or sea water. NF is useful for removal of hardness, color and odor compounds, synthetic organic chemicals and some disinfection byproduct precursors.
RO and NF are proven technologies that can achieve high removals of a broad range contaminants at once. They do not selectively target individual contaminants and remain effective for water that contains mixtures of contaminants. The processes do not usually require adjustment based on the specific trace contaminants present.
> Read more about Membranes
Adsorptive Media
Adsorptive water treatment technologies involve passing contaminated water through a media bed. The contaminants in the water adsorb to empty pore spaces on the surface of the adsorptive media as the water passes through. Granular activated carbon (GAC), described above, is one type of adsorptive media, but other types exist, including aluminum-based, iron-based, titanium-based, zirconium-based and other types of media.
Adsorptive media treatment is useful for removal of inorganic contaminants including antimony, arsenic, beryllium, fluoride, selenium, thallium, and uranium. The capacity of the media to adsorb different contaminants depends on the specific type of media used, the water chemistry (e.g., pH), and contaminant valence.
Adsorptive media is a proven technology with high removal efficiencies for certain inorganic contaminants (e.g., up to greater than 99% for arsenic, up to 99% or more for fluoride). When the appropriate media is used in combination with the appropriate water quality conditions (e.g., pH), the process can remove selected target contaminants to concentrations below relevant regulatory limits. Another advantage is that some types of adsorptive media can be regenerated in place after their capacity is exhausted. The regeneration process typically uses an acid wash, followed by a caustic wash.
Ultraviolet Photolysis And Advanced Oxidation Processes
Ultraviolet (UV) light can be used on its own (in photolysis), or in combination with chemical addition (in UV advanced oxidation), to reduce the concentration of organic contaminants. In UVAOP drinking water treatment, water passes through a reactor vessel equipped with lamps that emit UV light. In photolysis, the contaminants are degraded by the photons emitted by the UV lamps. Advanced oxidation adds chemicals such as hydrogen peroxide (H2O2) or chlorine. These chemicals react with the UV light to generate radicals (such as hydroxyl) that in turn oxidize the contaminants.
UVAOP is useful to reduce the concentration of organic micropollutants that may be difficult to address with other technologies including 1,4-dioxane, N-nitrosodimethylamine (NDMA), and methyl tert-butyl ether (MTBE). The process can also be useful for treatment of taste and odor issues. The effectiveness of the process depends on the UV dose, chemical dose (in advanced oxidation), contact time, concentration of the target contaminants, and other water quality parameters (e.g., UV transmittance, presence of radical scavengers).
UVAOP can achieve high removal efficiencies for 1,4-dioxane (up to greater than 99%) and MTBE (greater than 90%). The process destroys contaminants, as opposed to removing them, and therefore, does not produce contaminant-laden waste streams.
Disinfection
Disinfection is the final stage in drinking water treatment before its distribution. Disinfection is used to remove pathogenic micro-organisms from the water. However, it should be noted that disinfection is not the same as sterilisation (sterilisation = destruction of all germs present in a medium) and therefore a few common germs may remain in the water following disinfection
Disinfection consists in rendering inactive pathogenic organisms carried in water such as bacteria, viruses or parasites. Disinfection differs from sterilisation which aims at the total elimination of all germs. The germicidal action of disinfectants is based on oxidation reduction mechanisms. Thus, the effectiveness of a chemical disinfectant will be directly related to its oxidising capacity which is itself linked to temperature and pH.
Disinfection can be attained by means of physical or chemical disinfectants. The agents also remove organic contaminants from water, which serve as nutrients or shelters for microorganisms. Disinfectants should not only kill microorganisms. Disinfectants must also have a residual effect, which means that they remain active in the water after disinfection. A disinfectant should prevent pathogenic microorganisms from growing in the plumbing after disinfection, causing the water te be recontaminated.