Recycling Treated Municipal Wastewater for Industrial Water Use

TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
its full potential for overall quality and costs. UV treatment in this part of the process
train adds only slightly to the cost. UV costs an additional $0.15/1000 gallons to the
membrane softening treatment costs.
Advanced
Secondary
Effluent
Microfiltration
Cartridge
Filtration
Ultraviolet Radiation*
*UV can also follow RO
Reverse Osmosis
Disinfection
for residual
Figure 13. Tertiary 4 – Membrane Softening with UV
5.6.6 Treatment Cost Summary
The cost to treat WWTP effluent water beyond the advanced secondary treatment
processes is expected to be $1.25 - $5/1000 gallons for a 0.5 mgd supply, $1.00 -
$3.50/1000 gallons for a 1 mgd supply, and in the range of $0.50 - $2.50/1000 gallons
for a 30 mgd supply. Figure 14 and Table 17 summarize the costs for flows from 0.1 to
30 mgd for each of the tertiary reclaimed water classifications. These costs are for
treatment in addition to the base system treatment, transmission, and other system
costs.
An accurate comparison of costs for the higher quality water must include the
industry’s onsite treatment cost and cannot be compared soley to the incoming water
supply cost. Most industries requiring Tertiary 4 reclaimed water have their own
onsite treatment systems to provide this water quality. In many cases, the industry
provides this additional treatment to potable supplies. Some industries also have
treatment processes to provide water of similar quality to Tertiary 1-3 reclaimed
water. Water conservation practices have promoted cooling systems with higher
levels of recirculation. However, this requires a higher quality of incoming water so
that the concentrations of the recycle do not cause corrosion or scaling problems.
In comparing conventional treatment to membrane systems to soften the water and
remove dissolved solids, the membrane process is more expensive except when
treating smaller supplies. However, additional credit in microbial removal with
membranes could offset disinfection costs. Blended supplies and treatment streams
could also be considered to optimize treatment costs and meet multiple water supply
needs. The costs of conventional treatment for larger supplies may be low since it is
assumed that there is adequate capacity to handle the solids and for reasonably
inexpensive disposal practices, such as land application of lime sludge. This may not
be an option for some municipalities or industries.
40 Craddock Consulting Engineers
In Association with CDM & James Crook
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