[box type=”shadow” ]Mohamed Salah, P.Eng., Joint General Manager, Water Technologist, Larsen & Turbo Ltd, explains about membrane technology and its application in waste water in a conference session held during the Waste Technology India Expo 2018[/box]
Membrane technology is a comprehensive term for many different and very idiosyncratic separation processes. There is a thin layer between immaculate and murky water which is called as membrane.
The major reasons for using membrane technology in waste water treatment are its high quality, low BOD content, turbidity and most importantly, the log removal of pathogens. Another reason is the construction time that is less compared to other technologies used for rehash. As a result, installation becomes easy as you get a pre-packed and pre-designed system. The reuse which comes after the membranes are used for irrigation, surface as well as process water.
MBR
Membrane Bio Reactor (MBR) is the mother of all reuse. It combines both secondary as well as tertiary treatment. MBR is an alternative for convention modus operandi. On the other hand, if there is already an existing treatment plant to reuse water, there are different types of filtration methods that can be used.
Advantages
- Membranes are submerged which are made of hollow fibre or flat sheet
- Quality is far better than conventional
- MLSS (mixed liquor suspended solids) is used
- People prefer using high MLSS because there won’t be a need for secondary clarifier down the stream of the treatment plant
Drawback
It requires an air scouring system and high recirculation rate to keep the water flowing through the membrane systems. The MBR tank sucks the clean water from the mixed water hence building a layer of cake around it. Hence, it requires removal of cake with air scouring and have a circulation to dilute the cake effect in the membrane.
Alternate
Having an ordinary treatment plant whether conventional activator system or MBBR (Moving bed biofilm reactor), other option for reuse is to have a pressurized ultra-filtration system which will deliver the same quality as that of MBR. It will carry all the weight of membranes. The thin layer is also made of hollow fibre and the material of construction is same. The only difference is in the flux rate which is higher. The footprint is good. The quality procured will be better in terms of sun and disk filter. Still if one is not satisfied and wants to get a high-quality water after the ultra-filtration, Reverse osmosis (RO) method will come in place. RO will give a treated water having very little TDS (total dissolved solids), which is very important when it comes to boiler feed water and sulphur.
Future
- High demand in the Chinese market
- Customer acceptance, increased demand
- Increase of vendor pool and application pool
- Decrease in manufacturing cost
- Various options of membrane materials
- Improved operating cost
- Reduced replacement cost
- Decrease in chemical consumption
- Optimization in backwash and air scouring
- Improved life cycle cost
- Better trained operators
