8.4.9 Membrane Processes for Point-of-Use Applications
Reverse osmosis water purification systems are easily available in the market across
most of the countries which can be fixed in individual apartments for providing
point-of-use safe water. Only concern in such plants is the very low recovery which
results in wastage of water. Ultrafiltration is used as a final treatment step for the
production of ultrapure water for electronic, pharmaceutical, and potable water
applications. In places where salinity levels are acceptable, ultrafiltration membranes
can be used for obtaining safe water without microbial contaminants. Further
ultrafiltration-assisted devices have been developed (Bindal et al. 2011) for the
remediation of groundwater contaminants such as arsenic, fluoride, iron, and so on.
8.5 Future Outlook and Prospects
As the society moves toward environmental conservation, membrane processes have
more important role to play, particularly in recovering and recycling every component present in the waste stream. Most of waste streams contain value materials but
normally not recoverable at an acceptable cost and effort. The availability of a
variety of membrane processes and membranes offers plenty of opportunities to
realize wealth from waste.
The general practice in waste management is to mix all the spent streams
(effluents) and treat them as a single batch. Naturally, the whole system becomes
complex and complicated, and other than water not much is recoverable.
Membrane processes are modular in nature and the capacity is flexible. Accordingly, small-capacity units can be installed without the requirement of much foot print.
In this context, it is possible to decentralize the water treatment operation both in
industries and residences. Spent streams emanating from different processes can be
isolated and processed which will be easier, and many times value can be recovered.
Consequently, each stream will have only one type of contaminant which can be easily
separated. The contaminant may be a valuable raw material or product or an intermediate. This is possible even in domestic waste where gray water can be isolated from
black water. Water can be recovered from gray water using ultrafiltration and reverse
osmosis, while the black water can be bioprocessed to generate energy.
Forward osmosis being a passive process can be used to link the wastewater–
resource loop. This would help in recovering water from waste without using
energy. Membrane distillation also has a bright prospect if it could be used for
recovering water from return cooling water of industries or power plants. If the
cooling circuit uses less water, the temperature of the cooling water would be higher
to provide better yield of a desalinated water which could be a win–win situation.
Recovery of values particularly heavy metal species such as in mine discharges and
electroplating industries through size-enhanced ultrafiltration looks promising after
recovery of acid through diffusion dialysis. It is expected the membranes would have
a larger role to play in water treatment in the years to come.
8 Role of Membranes in Wastewater Treatment
275
Reverse osmosis water purification systems are easily available in the market across
most of the countries which can be fixed in individual apartments for providing
point-of-use safe water. Only concern in such plants is the very low recovery which
results in wastage of water. Ultrafiltration is used as a final treatment step for the
production of ultrapure water for electronic, pharmaceutical, and potable water
applications. In places where salinity levels are acceptable, ultrafiltration membranes
can be used for obtaining safe water without microbial contaminants. Further
ultrafiltration-assisted devices have been developed (Bindal et al. 2011) for the
remediation of groundwater contaminants such as arsenic, fluoride, iron, and so on.
8.5 Future Outlook and Prospects
As the society moves toward environmental conservation, membrane processes have
more important role to play, particularly in recovering and recycling every component present in the waste stream. Most of waste streams contain value materials but
normally not recoverable at an acceptable cost and effort. The availability of a
variety of membrane processes and membranes offers plenty of opportunities to
realize wealth from waste.
The general practice in waste management is to mix all the spent streams
(effluents) and treat them as a single batch. Naturally, the whole system becomes
complex and complicated, and other than water not much is recoverable.
Membrane processes are modular in nature and the capacity is flexible. Accordingly, small-capacity units can be installed without the requirement of much foot print.
In this context, it is possible to decentralize the water treatment operation both in
industries and residences. Spent streams emanating from different processes can be
isolated and processed which will be easier, and many times value can be recovered.
Consequently, each stream will have only one type of contaminant which can be easily
separated. The contaminant may be a valuable raw material or product or an intermediate. This is possible even in domestic waste where gray water can be isolated from
black water. Water can be recovered from gray water using ultrafiltration and reverse
osmosis, while the black water can be bioprocessed to generate energy.
Forward osmosis being a passive process can be used to link the wastewater–
resource loop. This would help in recovering water from waste without using
energy. Membrane distillation also has a bright prospect if it could be used for
recovering water from return cooling water of industries or power plants. If the
cooling circuit uses less water, the temperature of the cooling water would be higher
to provide better yield of a desalinated water which could be a win–win situation.
Recovery of values particularly heavy metal species such as in mine discharges and
electroplating industries through size-enhanced ultrafiltration looks promising after
recovery of acid through diffusion dialysis. It is expected the membranes would have
a larger role to play in water treatment in the years to come.
8 Role of Membranes in Wastewater Treatment
275