Contaminant of Concern (CEC) in Potable Reuse Concentrate
What potential environmental and ecological impact do these CEC's pose in evaporation ponds, wetlands and other
means by which concentrate is disposed?
What are the the major contaminants of emerging concern (CECs) that are found in RO concentrate?
How efficiently do RO processes remove common CECs from tertiary wastewater?
What other treatment mechanisms and/or processes such as oxidation, adsorption, and biological treatments aid in
What are existing water analytical methods used to analyze water containing CECs?
Potable reuse and treatment of it via reverse osmosis is gaining popularity especially since intake and discharge
permitting and regulation in California are making coastal desalination increasingly more difficult. Also from
thermodynamic stand point, desalination of ocean water is much more energy intense than RO processing a tertiary
treated wastewater stream. Therefore, there is a need to study the effect of CECs in RO concentrate streams and to
increase the water supply portfolio across the west.
It is vital to develop a more comprehensive understanding of CECs found in the concentrate streams when utilizing
RO to produce water for direct and indirect potable reuse. RO concentrate streams generated from potable reuse
feed streams are highly concentrated in CECs. Research has been done on CECs for wastewater effluents and reuse
in product water. However studies related to concentrate streams from RO that treat reuse waters are lacking. This
will further guide this research. The goal is to find the best way to manage and dispose of concentrate streams
containing high levels of emerging contaminants with the least impact to the environment.
Need and Benefit
Recycled water projects are becoming more and more common in water industry. They are being built to help
alleviate water shortages throughout the world by allowing the reuse of available water. The ability to use reclaimed
water to supplement water sources in either indirect or direct potable reuse situations hinges on implementing
effective, high-level treatment processes. This research on methods to treat CECs in RO concentrate streams will
create an essential database of knowledge. Currently, to the best of PIs knowledge, there is no comprehensive
databasethat includes information regarding CECs removal and treatment in membrane process applied for
direct/indirect reuse cases. In addition, there is no inclusive manual or guidelinefor monitoring and treatment of
membrane process concentrate streams for CECs. Generally, there is a large information gap on this topic which
will allow the knowledge gathered to be applied to current systems to help improve public and environmental
health. It will also serve as a solid groundwork for future research. The issue is only going to become more
problematic as more advanced water treatment plants are constructed so progress towards a solution needs to be
started as soon as possible.
Reuse of low saline concentrate from wastewater treatment plants is desirable to expand existing water supplies if
the (contaminants of concern) CECs can be removed properly and cost effectively. Wastewater reuse is desirable
due to lower energy requirement of treating it with reverse osmosis (RO) since it lacks the total dissolved solids of
typical brackish and seawater used for RO, thereby decreasing the operations cost by up to 1/3 of typical RO.
Additional benefits of utilization of this concentrate stream is the capture of additional water captured in the typical
concentrate stream along with reduction of the volume of concentrate that require disposal. RO treated wastewater
concentrate needs to be studied for proper CEC removal for direct and indirect potable reuse.
RO concentrate streams from direct and indirect membrane treatment will require disposal. Limited options are
available when it comes to inland concentrate disposal and they include deep well injection, surface water injection,
wetland treatment, evaporation ponds and others. These concentrate streams contain high concentrations of CECs
since membrane treatment does a great job of rejecting most of the CECs, therefore, the majority of CECs end up in
the concentrate streams. Long term effects of highly concentrated CEC that are being disposed inland have not
been studied much and therefore require more attention as direct and indirect potable reuse are employed more.
CECs consist of a wide variety of contaminants including pharmaceuticals, personal care products (PPCP),
alkylpheonls, flame retardants, hormones, steroids, and pesticides (USEPA, 2010). RO is able to reject a majority of
CECs found in drinking water, including pharmaceuticals and organic compounds. However, the concentrate is not
of a quality that can be used for reuse projects due to the high concentration of remaining CECs and therefore
requires additional treatment for their removal.
CECs can pose a great risk toward reuse projects because of their effect on the environment and human health and
are carefully being observed. CECs are beginning to be monitored by USEPA and countries such as Singapore are
leading efforts in reuse, therefore the removal and treatment of CEC rich concentrate streams is needed.
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