Distillation is probably the oldest method of water purification. Water is first heated to boiling. Then the water vapor rises to a condenser where cooling water lowers the temperature so the vapor is condensed, collected and stored. Most contaminants stay behind in the liquid phase vessel. However there can sometimes be what is called carry-overs found in thedistilled water. Organics such asherbicidesandpesticides, with boiling points lower than 100°C, cannot be removed efficiently and can actually become concentrated in the product water. Another disadvantage of distillation is cost. Distillation requires large amounts of energy and water and is very slow to produce clean water.
Distilled water can also be veryacidic(low pH), thus it should be contained in glass. Since there is not much left after distillation, distilled water is often called "hungry" water. It lacks oxygen and minerals and has a flat taste, which is why it is mostly used in industrial processes.
Table 1. Distillation
Removes a broad range of contaminants
Some contaminants can be carried into the condensate
Requires careful maintenance to ensure purity
Consumes large amounts of energy
System usually takes a large space on counter
Ion Exchange The ion exchange process percolates water through bead-like spherical resin materials (ion-exchange resins). Ions in the water are exchanged for other ions fixed to the beads. The two most common ion-exchange methods aresofteninganddeionization.
Softening is used primarily as a pretreatment method to reduce waterhardnessprior toreverse osmosis (RO)processing. The softeners contain beads that exchange two sodium ions for every calcium or magnesium ion removed from the "softened" water.
Deionization (DI) beads exchange either hydrogen ions for cations or hydroxyl ions for anions. The cation exchange resins, made of styrene and divinylbenzene containing sulfonic acid groups, will exchange a hydrogen ion for any cations they encounter (e.g., Na+, Ca++, Al+++). Similarly, the anion exchange resins, made of styrene and containing quaternary ammonium groups, will exchange a hydroxyl ion for any anions (e.g., Cl-). The hydrogen ion from the cation exchanger unites with the hydroxyl ion of the anion exchanger to form pure water.
These resins may be packaged in separate bed exchangers with separate units for the cation and anion exchange beds. Or, they may be packed in mixed bed exchangers containing a mixture of both types of resins. In either case, the resin must be "regenerated" once it has exchanged all its hydrogen and/or hydroxyl ions for charged contaminants in the water. This regeneration reverses the purification process, replacing the contaminants bound to the DI resins with hydrogen and hydroxyl ions.
Deionization can be an important component of a total water purification system when used in combination with other methods discussed in this primer such as RO filtration and carbon adsorption. DI systems effectively remove ions, but they do not effectively remove most organics or microorganisms. Microorganisms can attach to the resins, providing a culture media for rapid bacterial growth and subsequent pyrogen generation. The advantages and disadvantages of this technology are summarized below.
Table 2. Deionization
Removes dissolved inorganics effectively.
Regenerable (service deionization).
Relatively inexpensive initial capital investment
Does not effectively remove particles, pyrogens or bacteria.
DI beds can generate resin particles and culture bacteria.
High operating costs over long-term.
Carbon absorption is a widely used method of home water filter treatment because of its ability to improve water by removing disagreeable tastes and odors, including objectionablechlorine. Activated carbon effectively removes many chemicals and gases, and in some cases it can be effective against microorganisms. However, generally it will not affecttotal dissolved solids, hardness, or heavy metals. Only a few carbon filter systems have been certified for the removal oflead,asbestos,cysts, andcoliform. There are two types of carbon filter systems, each with advantages and disadvantages: granular activated carbon, and solid block carbon. These two methods can also work along with a reverse osmosis system, which can be read about below.
Activated carbon is created from a variety of carbon-based materials in a high-temperature process that creates a matrix of millions of microscopic pores and crevices. One pound of activated carbon provides anywhere from 60 to 150 acres of surface area. The pores trap microscopic particles and large organic molecules, while the activated surface areas cling to, or adsorb, small organic molecules.
The ability of an activated carbon filter to remove certain microorganisms and certain organic chemicals, especially pesticides, THMs (the chlorine by-product), trichloroethylene (TCE), and PCBs, depends upon several factors, such as the type of carbon and the amount used, the design of the filter and the rate of water flow, how long the filter has been in use, and the types of impurities the filter has previously removed.
The carbon adsorption process is controlled by the diameter of the pores in the carbon filter and by the diffusion rate of organic molecules through the pores. The rate of adsorption is a function of the molecular weight and the molecular size of the organics. Certain granular carbons effectively remove chloramines. Carbon also removes free chlorine and protects other purification media in the system that may be sensitive to an oxidant such as chlorine.
Carbon is usually used in combination with other treatment processes. The placement of carbon in relation to other components is an important consideration in the design of a water purification system.
Table 3. Carbon Adsorption
Removes dissolved organics and chlorine effectively.
Long life (high capacity).
Can generate carbon fines.
Microporous Basic Filtration
There are three types of microporous filtration: depth, screen and surface. Depth filters are matted fibers or materials compressed to form a matrix that retains particles by random adsorption or entrapment. Screen filters are inherently uniform structures which, like a sieve, retain all particles larger than the precisely controlled pore size on their surface. Surface filters are made from multiple layers of media. When fluid passes through the filter, particles larger than the spaces within the filter matrix are retained, accumulating primarily on the surface of the filter.
The distinction between filters is important because the three serve very different functions. Depth filters are usually used as prefilters because they are an economical way to remove 98% of suspended solids and protect elements downstream from fouling or clogging.
Ultrafilters are available in several selective ranges. In all cases, the membranes will retain most, but not necessarily all, molecules above their rated size
Table 5. Ultrafiltration
Effectively removes most particles, pyrogens, microorganisms, and colloids above their rated size.
Produces highest quality water for least amount of energy.
Will not remove dissolved inorganics.
Reverse osmosis (RO) is the most economical method of removing 90% to 99% of all contaminants. The pore structure of RO membranes is much tighter than UF membranes. RO membranes are capable of rejecting practically all particles, bacteria and organics >300 daltons molecular weight (including pyrogens). In fact, reverse osmosis technology is used by most leading water bottling plants. Natural osmosis occurs when solutions with two different concentrations are separated by a semi-permeable membrane. Osmotic pressure drives water through the membrane; the water dilutes the more concentrated solution; and the end result is an equilibrium.
In water purification systems, hydraulic pressure is applied to the concentrated solution to counteract the osmotic pressure. Pure water is driven from the concentrated solution and collected downstream of the membrane.
Because RO membranes are very restrictive, they yield slow flow rates. Storage tanks are required to produce an adequate volume in a reasonable amount of time.
RO also involves an ionic exclusion process. Only solvent is allowed to pass through the semi-permeable RO membrane, while virtually all ions and dissolved molecules are retained (including salts and sugars). The semi-permeable membrane rejects salts (ions) by a charge phenomena action: the greater the charge, the greater the rejection. Therefore, the membrane rejects nearly all (>99%) strongly ionized polyvalent ions but only 95% of the weakly ionized monovalent ions like sodium.
Reverse osmosis is highly effective in removing several impurities from water such as total dissolved solids (TDS),turbidity, asbestos, lead and other toxic heavy metals,radium, and many dissolved organics. The process will also remove chlorinated pesticides and most heavier-weight VOCs. Reverse osmosis and activated carbon filtration are complementary processes. Combining them results in the most effective treatment against the broadest range of water impurities and contaminants.
RO is the most economical and efficient method for purifying tap water if the system is properly designed for thefeed waterconditions and the intended use of the product water. RO is also the optimum pretreatment for reagent-grade water polishing systems.
In addition, Reverse osmosis treatment is an insurance policy against nuclear radiation such as radioactive plutonium or strontium in the drinking water. If one lives near a nuclear power plant, this is a key way to ensure the household is drinking the best water for their health.
Table 6. Reverse Osmosis
Effectively removes all types of contaminants to some extent (particles, pyrogens, microorganisms, colloids and dissolved inorganics)
Requires minimal maintenance.
Flow rates are usually limited to a certain gallons/day rating.
Ultraviolet (UV) Radiation
Ultraviolet radiation has widely been used as agermicidaltreatment for water. Mercury low pressure lamps generating 254 nm UV light are an effective means of sanitizing water. The adsorption of UV light by the DNA and proteins in the microbial cell results in the inactivation of the microorganism.
Recent advances in UV lamp technology have resulted in the production of special lamps which generate both 185 nm and 254 nm UV light. This combination of wavelengths is necessary for the photooxidation of organic compounds. With these special lamps, Total Organic Carbon (TOC) levels in high purity water can be reduced to 5 ppb.
Table 7. Ultraviolet Radiation
Effective sanitizing treatment
Oxidation of organic compounds (185 nm and 254 nm) to < 5 ppb TOC
Will not remove particles, colloids, or ions
Pulling It All Together
Water Purification Systems
Because each purification technology removes a specific type of contaminant, none can be relied upon to remove all contaminants to the levels required for critical applications. A well-designed water purification system uses a combination of purification technologies to achieve final water quality.
Each of the purification technologies must be used in an appropriate sequence to optimize their particular removal capabilities. The schematic below shows a central laboratory water purification system designed to produce water for critical applications.
The first step is pretreatment equipment specifically designed to remove contaminants in the feed water. Pretreatment removes contaminants that may affect purification equipment located downstream, especially reverse osmosis (RO) systems. Examples of pretreatment are: carbon filters (or tanks) for chlorine removal, particulate filters for sediment/silt/particulate removal, and softening agents to removemineralsthat cause "hard" water.
The next purification step is Reverse Osmosis (RO). RO removes 90 to 99% of all the contaminants found in water. It is the heart of any well designed water purification system because it effectively removes a broad range of contaminants.
However, the tight porosity of the RO membrane limits its flow rate. Therefore, a storage container is used to collect water from the system and distribute it to other points-of-use such as polishing systems.
Polishing systems purify pretreated water, such as RO water, by removing trace levels of any residual contaminants. Polishing elevates the quality of pretreated water to "Type I" or "ultrapure" water.
A polishing system is designed to remove residual traces of impurities from water already pretreated by some other means (such as reverse osmosis or deionization). Treating raw tap water using such a system would quickly exhaust its capacity and affect final quality.
A typical polishing system may consist of activated carbon, mixed-bed deionization, organic scavenging mixtures and 0.22 µm final filtration. Systems can also be enhanced with ultrafiltration, ultraviolet oxidation or other features for use in specific applications.
This combination of purification technologies, combined with proper pretreatment, will produce water that is virtually free of ionic, organic and microbial contamination. Read Next:Top 20 Harmful Water Contaminants
Maybank truly created a the best credit card to be used at Malaysia that can collect 5x points and max rebate RM50 per month when use on weekend. Below is the places that can used. Happy shopping :)
Places that accepts AMEX [Klang Valley] Airlines :
Cathay Pacific Airways
Chocolates shops in KLIA
KLIA Airport Limo
Lcct Eraman duty free
LCCT Taxi Voucher Merchant Solutions
KTM Intercity (over the counter)
Automotive Service Centre:
Ah Man Tyre Centre - Belakong
BMW Auto Bavaria-Glenmarie
BMW Auto Bavaria-Segambut
CARs International - Car Polish & Waxing
Federal Auto (Volvo)
Honda The Millennium Auto & Carriage(Jalan Damansara)
KS Tyre (Ampang) Sdn. Bhd
Lim Tayar (or CKL) @ all outlets. refer - www.limtayar.com.my/html/our_outlets.html
Perodua Service Center Balakong (min RM50)
Perodua Service Center Puchong - Bandar Bukit Puchong
Proton Centre Of Service Excellence …
Is RON97 Really Better Than RON95? – Tried And Tested!
For the first time in history, petrol kiosks in Malaysia are experiencing a shortage of RON97 petrol, after demand for the fuel surged following a reduction in its price on Dec 1.
The high demand came after the Government scrapped subsidies for RON95 and diesel and implemented a managed float system, which resulted in a very low difference between the price of RON95 (RM2.26 per litre) and RON97 (RM2.46 per litre).
The price of RON97, which incidentally fell nine sen from RM2.55 to RM2.46 per litre in December 2014, saw some petrol kiosks double their sales of the fuel from an average of 500 litres to 1,000 litres in a day.
In February 2015, retail prices of RON95 and RON97 fell further to RM1.70 per litre and RM2.00 per litre, respectively.
However, prices of RON95 and RON97 went up by 20.5% and 22.5% in August to RM2.05 per litre and RM2.45 a litre respectively.
Here is a comparison of RON95 and RON97 prices from Dec 2014 to Ja…
Just want to list down all the places that can use AMEX to maximise the point that can be claimed by Maybank Amex since have 5x points and 5% rebate on weekends capped at RM50
whoohoo just saw my card in Maybank2U. will get it soon :)
2/4/11-first swipe at Shell!
1/6/2011-just in 2 months have over 15k+ points, wow! really easy to earn points with this card, happy spending
21/7/2011-redeem 75k points at Maybank Treatpoints Fair. Thanks MBB. Really enjoyed using the card :)
23/8/2011-getting in big trouble overusing the credit card. Check out my ugly experience and hopefully you'll be a wise guy and don't have to go through the same thing. How I owe credit card again! 11/11/2011- please check all latest update HEREkeep up good work ronnie :) Places that USE AMEX at Malaysia AMEX Selects 2013 (PDF) Airlines : AirAsia Cathay Pacific Airways Dragonair EVA Air Emirates Airline Singapore Airlines Chocolates shops in KLIA Firefly JetAirWays KLIA Airport Limo KLIA Express …