Recycling Treated Municipal Wastewater for Industrial Water Use

TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
This study assumed the need for carbon regeneration every 90 days, which is a
conservative rate.
The use of GAC following RO increases the treatment cost, expressed as cost of
service, above the base system cost to $3.70/1000 gallons for a 1 mgd supply. At 30
mgd, the cost is approximately $2.30/1000 gallons. This process train provides the
highest costs of the six treatment trains evaluated. Without RO, the treatment costs
would drop by approximately $1.30/1000 gallons for a 1 mgd system, assuming that
microfiltration is still required.
Tertiary – 4 With Ion Exchange
Ion exchange units are commonly used at many industries that require very low
levels of dissolved minerals. Similar to GAC, the ion exchange reactors would follow
reverse osmosis (Figure 12).
Advanced
Secondary
Effluent
Microfiltration
Cartridge
Filtration Ion Exchange
Reverse Osmosis
Disinfection
Figure 12. Tertiary 4 – Membrane Softening with Ion Exchange
Ion exchange annual costs are highly variable depending on the resin type and target
constituent. The estimated cost, expressed as cost of service, for ion exchange
following reverse osmosis is $3.30/1000 gallons for a 1 mgd supply and $3/1000
gallons for a 5 mgd supply. It is unlikely that larger volumes of this quality of water
will be required; plus the annual costs would drive process requirements to use other
technologies.
Tertiary – 4 With Ultraviolet Radiation
Additional treatment with ultraviolet radiation was included because some laboratory
grade water quality is used by industry and UV provides additional pathogen
protection. It can also be combined with hydrogen peroxide and other oxidants to
remove persistent chemicals. In some cases, the UV and hydrogen peroxide can be
used instead of reverse osmosis to target certain constituents rather than remove all
constituents. UV can be pre or post-reverse osmosis, as shown in Figure 13.
Disinfection prior to the membrane RO is used to minimize biofouling of the
membrane. However, there could be constituents in the water that affect the
transmittance and result in less economical performance of pathogen kill. Pilot
testing is often performed to optimize the process train and use each unit process to
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