09-05-2014, 03:03 PM
New Technologies for Water and Wastewater Treatment: A Survey of Recent Patents
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Abstract:
The concern over increasing needs for drinking water and awareness for development of systems to improve
water quality both for drinking purposes and for effluents from wastewater treatment and industrial facilities have
provided incentives to develop new technologies and improve performance of existing technologies. In this paper, the
patents on treatment of water and wastewater approved during the period from 1999 to 2007 were reviewed. The patents
surveyed were classified into two groups as technologies for water purification systems for drinking water, and
technologies for treatment of wastewater. An assessment of the current and future outlook for development of new
technologies, methods of treatment, equipment and instruments which can be used for water and wastewater treatment
applications are presented.
INTRODUCTION
Water is an essential substance for living systems as it
allows the transport of nutrients and waste products in living
systems. Research shows a clear correlation between
diseases and the amount and types of fluids consumed,
health-promoting properties of nutrients which can be added
to water, optimal intake levels, and consumption patterns.
Although three quarters of the Earth’s surface is covered
with water, most of that water is not suitable for human
consumption. Today, hundreds of millions of people in vast
regions of the world do not have access to water to meet
their basic needs. Natural disasters also create conditions
which limit the availability of water that is suitable for
human consumption. Industrial processes use significant
amounts of water which require treatment before discharging
to surface water systems. Municipal wastewater treatment
systems discharge their effluents which often impact the
aquatic organisms. This paper provides a survey of new
developments and innovations relative to water treatment for
drinking purposes and wastewater treatment during the
period from 1999 to 2007. For drinking water treatment, the
recent technological advancements relate to primarily
filtration (media filtration and membrane systems), disin-
fection processes, ion exchange, and carbon adsorption
processes. For wastewater treatment, a significant majority
of recent developments relate to biological processes and
advanced treatment technologies such as adsorption. A
review of the recent patents show innovative designs for
treatment units, efficient approaches for water quality, as
well as nanotechnology applications for removing impurities
and disinfection purposes.
WATER TREATMENT SYSTEMS FOR DRINKING
WATER
The general treatment of drinking water takes place in
several steps to remove dissolved and suspended solids. The
treatment processes may include processes such as floccu-
lation, sedimentation, and media filtration to remove colloi-
dal and suspended solids; ion exchange, carbon adsorption,
and membrane processes to remove dissolved solids; and a
disinfection step often achieved by chlorination, ozonation,
and ultraviolet radiation (UV). Drinking water is obtained
either from surface water or ground water aquifers. Figure 1
presents the general schematics of conventional treatment
processes for drinking water treatment depending on the
source water characteristics. The main concerns with surface
water aquifers are the suspended solids and organic matter
which may be present due to storm water runoff. Therefore,
presedimentation, coagulation or coarse filtration processes
are generally used for water treatment followed by
disinfection. The main concern with the ground water
aquifers which are used as drinking water sources are the
presence of dissolved contaminants such as salts, organics,
or gasses.
Media Filtration
Media filters remove suspended solids from water. Media
filters are often constructed using one or more layers of sand,
gravel, anthracite, and other inert media. As the water moves
through filter media, suspended particles are trapped within
the filter. The top layer removes organic compounds, which
contribute to taste and odor. Most particles pass through
surface layers but are trapped in the pore spaces and/or
adhere to particle surfaces within the media.
Figure 2 present the compact treatment system developed
by Wang [1]. The mineral filtering apparatus removes solids,
chemicals, and pesticide residues, and adds nourishing
elements to the water. The process includes multiple filtering
steps, such as a gravity filter, ion exchange, sterilization unit,
deodorizing segment, and a section for releasing minerals to
water. As the raw water flows from top to bottom, it is
treated by each step by filtration, deodoriziation, ions
exchange, sterilizing, and magnetizing processes which
improve the water quality suitable for drinking. The treated
water contains minerals as nutrients for human consumption.
Hybrid Filtration Systems
Technologies which combine coarse filtration with
membrane filtration processes offer ease of operation and
optimize the benefits of both types of filtration systems.
Rhee [8] invented a water purifier which enables a used filter
to be replaced with ease. It also allows replacing the used
filter without having to shut off the water inlet port. Aalto et
al. [9] disclosed improvements for the filtration unit of an
earlier water treatment system. The system includes two
compartments (i.e., a primary and a secondary unit) in a
built-in manner in the same frame. The water moves by
gravity from the primary chamber to the secondary unit
where a thin film (filter) made of plastic is located. The main
characteristic of this system is that underneath the primary
space there is an accessory space that has an essentially
smaller cross-section to keep the filter surrounded by
unclean water.
WASTEWATER TREATMENT SYSTEMS
Municipal wastewater treatment processes involve pri-
mary treatment processes which include physical-chemical
processes such as sedimentation, secondary treatment
processes which include biological units such as activated
sludge or trickling filters. Fig. (5) presents the treatment
scheme for wastewater treatment. The treated water is
disinfected before it is discharge to a receiving body. The
sludge produced is typically dewatered for land application.
The wastewater treatment for industrial applications may
involve treatment processes specifically designed to remove
contaminants that are present in the industrial effluents.
Examples of typical industrial wastewater treatment proces-
ses include sorption, membrane filtration, precipitation and
pH adjustment.