Water supply and wastewater system: brief history

June 15th, 2007

Long time ago, probably up to present, public water facilities were part of civil engineer’s project. Water supply and wastewater drainage were among the job whose civil engineers do to preserve environment and protect human health. Read the rest of this entry »

Why TiO2 is most often used photocatalyst

June 15th, 2007

This post is dedicated to answer several questions raised why TiO2 being a popular photocatalyst and thus often being used for photocatalysis and photodegradation any unwanted compounds or chemicals including microorganism, organic particles.

I just found in a paper of Weimin Xi (2001), he stated that TiO2 is having considerable photocatalytic activity. Honestly I do not know what does that mean by photocatalytic activity. It has high stability, non-environmental impact and low cost. Despite that not all those factors I know, but I ever read somewhere in journals, probably by Katsofidou, that the presence of TiO2 of course coupled with ultraviolet (UV) irradiation has produced non hazardous stream of product water as a result of transformation of organics treated by photocatalysis.

Fouling as membrane shortcomings

June 15th, 2007

I do not care if this post will contain only a couple hundred words. I just found an interesting definition of cake formation on the membrane surface. As you probably aware, this cake formation along with pore blockage, concentration polarization have caused fouling, sort of clogging in conventional filter, which increase negative value of membrane operation, lower water produced, higher production cost etc.

What I would like to mention in this post is about particle cake layer formation on the membrane surface. It is said by Weimin Xi (2001) that particle cake will eventually reach steady state thickness when the particle convection to the membrane surface is balanced by the back-transport of the particles away from the membrane surface. I will tell the truth, I do not know much about back-transport of membrane, but it certainly connect with the resistance of the membrane.

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June 14th, 2007

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Civil Engineering-civilization

June 13th, 2007

Civilization is the most important keword of this post. Through western civilization settled agriculture and the development of agricultural skills created a cooperative social fabric and spawned the growth of communities, as well as changed the face of the earth with its overriding impact on the natural environment. Civilization had contributed to the change of our natural landscape to more “artificial” one. Thus it produced both positive and negative impact to the natural habitat. Read the rest of this entry »

Does TiO2 coating form denser pore size?

June 10th, 2007

Interesting question is raised because that result that what I have got. Interesting, in one side it is known that the coating of TiO2 has caused higher affinity of membrane surface. In my opinion higher affinity, more or less, means higher permeability, higher chance that more water passes the pore of membrane. But my experiment shows the opposite. I just did a simple permeability though, but I think despite of its simplicity, it offers a very powerful tool to gain some insight about what is going on after coating in terms of its ability to allow water pass through the membrane. This post is dedicated to find out is it really true that the coating of TiO2 affect the pore size of membrane surface and make it denser. Read the rest of this entry »

About ultrafiltration: introduction

June 7th, 2007

Combine with microfiltration, ultrafiltration (UF) is a low pressure membrane. UF is usually used for potable water treatment, biological wastewater treatment and also for ultrapure water production. The latter is common method for metal or electronic industries. UF typically operates within 40-1000 kPa (5.8-145 psi) (0.4-10 bar) having molecular weight cut off (MWCO) ranging from 1 kDa to 100 kDa (kilo Dalton).

MWCO is a term used to define 90% of molecular weight of a compound can be retained by the UF. Since UF have higher pore size or MWCO than reverse osmosis (RO), it usually produce higher flux. However, since RO has denser pore size, thus the rejection is become more excellent, even a virus may be filtered out to result a high ultrapure water. Read the rest of this entry »

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