Microfiltration

Microfiltration is a filtration process which removes contaminants from a fluid (liquid & gas) by passage through a microporous membrane. A typical microfiltration membrane pore size range is 0.1 to 10 micrometers (µm). This process requires feed rates of very high velocities at low pressures. Each microfiltration module requires a 30 GPM cross flow with a feed pressure from 30 to 40 PSI. (GPM is gallons per minute, a unit for flow rate while PSI is the unit for pressure in United States, EES unit. 1PSI=1 lb/in2)Microfiltration is not fundamentally different from reverse osmosis, ultrafiltration or Nanofiltration, except in terms of the size of the molecules it retains.
In microfiltration, low pressure membranes were selected to remove turbidity spikes and pathogens without chemical conditioning. As low pressure membranes get more and more accepted by people, this technology begins to used to apply on waters with more solids and higher levels of dissolved organics. Some of these waters required chemical pretreatment, including pre-chlorination. These shifts in water quality triggered change in low pressure membrane technology. Improvised processes were introduced to deal with higher solids and chemical compatibility.


Basic Principles
Membranes are semi-permeable thin barrier sheets. Synthetic membranes are used to remove different solutions and particles in the water treatment process.
There are five types of membrane processes (see table below).





Different Pressure Processes

Reverse osmosis and microfiltration as well as ultrafiltration are often described as being pressure processes. Actually, they are very different from each other :
• Mircofiltration is a direct continuation of conventional filtration that makes it possible to remove particles smaller than a micron such as colloids and bacteria.
• Ultrafiltration are even better in removing particles. With this process, viruses and heavy molecular organic compounds can be removed.
These two processes use a straining technique and therefore separation depends on the size of the pores and which species are chosen.
How Microfiltration Works

When the untreated water is pumped into the filters and forced through the holes in the sides of the straws, the particulate matter will accumulate on the outer wall of the straws. Then, the filtered water flows through the straws and out of the array, then into the dstribution and storage system. During this process, chemicals are added for various purposes. Flouride is added for healthy teeth; polyphosphate for homeowners with lead piping and a small amount of chloride to continually disinfect the distribution system.

Through microfiltration, we can eliminate the use of chemicals in the treatment process and decreases the use of chlorine for disinfection up to 50%.

Purity of NEWater

By comparing with different types of water, we will get a conclusion on how pure is the water from NEWater.

Distilled water

During the process of distillation, the water is boiled, followed by collecting of steam. After that, it is condensed. Through this process, many harmful bacteria and substances will be removed. However, the natural minerals in the water will not be there anymore.

Mineral water

On the other hand, mineral water contains dissolved minerals that are either naturally or artificially prepared. This water has been filtered, so there will no be any harmful substances in the water.


NEWater

In the NEWater process, water has already gone through microfiltration and reverse osmosis before the process of UV disinfection. The UV light will be absorbed by the bacteria and viruses, rearranging the genetic material. Thus, the bacteria and viruses can no longer reproduce, can be considered as dead.

In reverse osmosis, bacteria and viruses with smaller particles than water particles will still be able to pass through. Moreover, the mineral will also be removed from water. However, wit UV distillation, even those small viruses can be removed.



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This should be the last part on introduction of NEWater. I will put up my part later :D

Introduction of NEWater

NEWater is reclaimed water which has gone through treatment in NEWater Pants that consists of four processes: Microfiltration, Reverse Osmosis, water Conditioning and Ultraviolet Disinfection. After these four processes, the pure water can be used for both protable and non-portable purposes.

The below are the basic steps for the four processes with brief explanation. We will be researching more on the individual process to find out more about the Physics principle behind it.
In the first step of NEWater, water will go through microfiltration. It consists of tiny fibers which traps the solid (mostly bacteria and harmful micro-organisms) in the tubes. Besides, it can ensure a good stream of steady flowing water to prevent blockage and clogging up.

Later in the process of reverse osmosis, water will be applied pressure that would allow the water to flow from the concentrated side to the less concentrated side through a partially permeable membrane. In this process, viruses and dirty content like nitrate, chloride, sulphate etc will be removed.

For safety precaution, a back up process Ultraviolet rays is added in to wipe out harmful particles in one zap.

Lastly, the cleansed water is mixed with reservoir water to give it a “water taste” and is ready to be drunk.

History of NEWater

There are many reasons of why NEWater is invented. One of the reason is that Singapore’s daily water consumption keeps increasing daily. As the population in Singapore and the growth of economy, more water is needed to maintain our daily life. Besides, as water is easily accessible, more and more people are taking it for granted. They waste water and use water uncontrollably, without putting any thought to it.

Singapore has been buying water from Malaysia since 1920. Currently, there are two agreements between Singapore and Malaysia that will end in 2011 and 2061. As 2011 draws near, Malaysia and Singapore are still not able to agree on terms for another water treaty. If this continues, Singapore will be in a situation of shortage of water. Hence, other sources of water needed to be created and the government has come up with the idea of NEWater to serve the purpose of being the fourth national tap to fulfill the growing water consumption.

It seems like I've forgotten to post the most basic part: the part about the NEWater. So I will post them up now :D

Second meeting today (;

Hello all,

Today will be the review of the meeting we had this morning about the physics poster which we are to hand in on Friday. The meeting was about 20 minutes and we came up with another job allocation to do our project, so please take note if any of you had missed out anything during the meeting! :)

We discussed the things we want to put in the poster:

1) The process of making Newater which involves physics, mainly the four processes we have researched before - Ultraviolet Disinfection, reverse osmosis, water conditioning and microfiltration.

2) Advantages and disadvantages of Newater

3) Pictures

4) Interesting facts about Newater

5) Singapore's reliance on Newater and how it is going to affect us in future

Regarding the job allocation, it goes like this, because of different CCA timing and time constraint okay:

Sijia + Amanda will do on Wednesday after school in class. We will probably do half of the poster first, then on Thursday after school, Huiyan + Zheng Liang will finish the poster. Hopefully, everything can be done by then and we do not need to rush on Friday :D

We can do it everybody!

Reverse Osmosis

REVERSE OSMOSIS :D

Reverse osmosis is utilize in the second stage of the NEWater production process and it is also the thrid barrier after the conventional wastewater treatment process and microfiltration or ultra filtration.

Osmosis is the movement of water from a region of HIGH concentration to a region of LOW concentration through a PARTIALLY PERMEABLE MEMBRANE. From the word REVERSE osmosis, it suggests that this process is the opposite of osmosis. Osmotic pressure is the basis of reverse osmosis. In reverse osmosis, water particles move from a region of LOW water potential to a region of HIGH water potential through a PARTIALLY PERMEABLE MEMBRANE. In this process, the membrane filters out undesirable materials such as bacteria, viruses, heavy metal, nitrate, chloride, sulphate, disinfection by-products, aromatic hydrocarbons and pesticides as these materals are to large to pass through the membrane and only water particles are able to pass through it.

Water Conditioning (:
Basically, water conditioning is process whereby it restores the pH balance of the water. To neutralize the acidity, an alkaline is added in. The process of NEWater goes like this: first, the water will go through the micro filtration whereby suspended solids, bacteria and viruses are removed. Next, it undergo reverse osmosis the other impurities such as nitrate and chlorine are being removed. To ensure the purity of the water, the water is further purified by Ultra Violet Rays whereby it will disinfect the water. After all these processes, the water becomes slightly acidic (pH5) and is completely devoid of everything. There is no presence of any minerals at all in these waters. These waters are then transported to factories for industrial use whereas the rest of the water is sent for water conditioning. Here, to neutralize the acidic pH of the water, Sodium Hydroxide is added into the water. After this, the water is released into the nation’s reservoir where it is mix with other water that contains minerals.

PS, i took like 4hours to get all these info D:
as in i was not able to get detailed information
so i'll try to look for more though it's kind of hard :(

here's a little video on the making of NEWater
it's super cute :D
http://schools.moe.edu.sg/rgps/html/process.htm

Meeting

Hi all,

This is the review of our meeting conducted on monday, 23rd June 2008, in class after school, so i am posting here just in case we forget our individual job allocation of the various tasks.

We discussed about the job allocation for the research of our project - How physics is applied in the process of producing Newater. To have a complete and detailed research of how physcis is applied in the manufacturing of Newater, we have to research on these four aspects of the process: water conditioning, reverse osmosis, ultraviolet disinfection, micro filtration. Therefore, Huiyan, our group leader, assigned each of us to research on each of the aspect:

Amanda Lee -> Water Conditioning
Zhengliang -> Reverse Osmosis
Sijia -> Ultraviolet Disinfection
Huiyan -> Micro Filtration

A note from Huiyan: Please edit and paraphrase your work before posting up on the blog, to avoid plagarism and the dateline of this research is up to this week. As for the poster which is to be handed in next week, we will conduct another meeting on Monday morning, 7am at classroom, to discuss. Please do not be late! :D

Ultraviolet Disinfection

hi all, below is my sharing of ultraviolet disinfection, which is part of the process of making Newater. Sijia, this is.

Ultraviolet radiation

Ultraviolet light is electromagnetic radiation in the spectrum with a wave length between 100 and 400 nanometers (nm). The ultraviolet spectrum can be divided into three bands: UV-A 320 to 400 nm, UV-B 280 to 320 nm, UV-C 100 to 280 nm.
The UV-C band contains the wavelengths (250-270nm) which have been found to be very effective in destroying many microorganisms (optimum wavelength is 265nm).

UV Dosage

Through research, biologists have determined the amount of UV required to destroy different kinds of microorganisms, termed as the dosage, and is a function of a certain intensity of UV (expressed in power or microwatts), delivered for a given period of time (seconds), over a given area (square centimeters). Below is formulae:

Power X Time X Area or microwatt-sec/cm2 (µW-s/cm2)

A short exposure time at high intensity can be as effective as a long exposure time at lower intensity, as long as the product of power multiplied by time is the same. The UV reactor design is critical to obtaining proper UV dosage of water. The water entering the UV chamber must be sufficiently free of suspended solids and the flow-rate of the water must match the power of the lamp so that the microorganism has time to absorb the UV radiation and be destroyed.

How is Physics applied in the manufacturing of Newater?

Sea Water Desalination Reverse Osmosis Units

The laws of physics require approximately 1 psi driving force for each 100 mg/l of solids dissolved in the water to be treated. Seawater has about 35,000 mg/l of dissolved solids so to obtain the first drop of permeate water a pressure of 350 psi is required. Reverse osmosis units on the other hand normally treat water where the dissolved solids content is in the area of 6,000 mg/l or less, thus, the required pressure is 60 psi. To insure an adequate flow of water from the respective devices, seawater units usually operate in the area of 1,000 psi and RO units in a range of 150 to 250 psi.

Reverse Osmosis

When two water (or other solvent) volumes are separated by a semi-permeable membrane, water will flow from the volume of low solute concentration, to the volume of high solute concentration. Whenever a solute movement is blocked by the membrane it will transfer momentum to it and, therefore, generate pressure on it. Since the velocity is the same as that of a free molecule, the pressure will be the same as the pressure of an ideal gas of the same molecular concentration. Hence, the osmotic pressure p, is given by van't Hoff formula , which is identical to the pressure formula of an ideal gas:
p = cRT
where c is the molar solute concentration, R is the gas constant, and T is the absolute temperature. The osmotic pressure depends only on its molar concentration, as the formula states.

Figure-1 shows connected vessels separated by a semi-permeable membrane. If there is only water in the device, the level will be the same at both arms. When solute molecules are added to one arm, water will start to flow into it, so that its level will go up at this arm, and down at the other arm. The system will stabilize when the osmotic pressure is balanced by the hydrostatic pressure generated by the difference h in the water levels.

cRT = rh, where r is the water specific gravity.

The conservation laws of energy and momentum require that whenever particles collide with a moving wall, they will change direction and increase or decrease their speed. Thus, they transfer both momentum and energy to the wall .

The conservation law of momentum requires that solute molecules, that generate osmotic pressure on the semi-permeable membrane, must generate, via the volume of the solution, the same osmotic pressure on all the solution boundaries, including its free surface. In this respect the osmotic pressure acts according to Pascal law. Pascal's law states that for all points at the same absolute height in a connected body of an incompressible fluid at rest, the fluid pressure is the same, even if additional pressure is applied on the fluid at some place.



This is Sijia sharing, hope it helps.

REVERSE OSMOSIS and OSMOTIC PRESSURE

Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied. The membrane here is semipermeable, meaning it allows the passage of solvent but not of solute.
The membranes used for reverse osmosis have a dense barrier layer in the polymer matrix where most separation occurs. In most cases the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes (such as salt ions). This process requires that a high pressure be exerted on the high concentration side of the membrane, usually 2–17 bar (30–250 psi) for fresh and brackish water, and 40–70 bar (600–1000 psi) for seawater, which has around 24 bar (350 psi) natural osmotic pressure which must be overcome. (wikipedia)
Since pressure is also needed, can we also research on osmotic pressure?
zhengliang

Reply for the second letter

Here's the reply for the second letter which I received on Saturday, May 31, 2008 12:06:16 PM.

Dear Hui Yan

Apologies for the delay.

I believe our colleagues will revert back soon. Please give us some time.

Please feel free to contact us if you have any enquiries. Many thanks andhave a nice day!

Best Regards,
Jennifer TAN (Ms)
Assistant Gallery Manager, NEWater Visitor Centre
Tel 6546 7874 / 6541 0511