Recycling Treated Municipal Wastewater for Industrial Water Use

TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
smaller WWTPs where the diurnal flows could drop below the required demand of
an industry or group of industries. Weekly demand patterns of industry could also
change and should be accounted for when establishing storage requirements.
This study does not consider any seasonal storage requirements for a reclaimed
supply. Seasonal storage would be required for WWTPs that incorporate reuse
practices to reduce their discharges to waterways and supply seasonal customers.
These facilities would need to store effluent during periods when the seasonal reuse
customers do not use water. These are cases where the WWTP’s NPDES permit limits
are more stringent in the warmer months and rather than upgrade treatment facilities
to meet the lower seasonal mass limits, a portion of the plant effluent is reused and
not discharged to the receiving stream. Seasonal storage may also be required to meet
a seasonal water demand, where peak demands cannot be consistently matched by
the WWTP flow. The majority of Minnesota’s industries have year-round water
demands, with the exclusion of agricultural processing industries that may depend on
seasonal crops, industries that use reclaimed water for landscape irrigation, and some
cooling water applications. Seasonal storage facilities are more commonly used in
water reuse systems for irrigation practices.
Reclaimed water storage can also provide system reliability with a short-term supply
if there is a process disruption, as well as additional contact time for chlorine
disinfection.
4.3 Pumping
The model for this study assumes a pump station is located on the WWTP site and is
owned by the municipality. The pump station will include redundancy and reliability
features consistent with state water supply requirements. The pump station is sized
for peak flow and a residual pressure at the end of the pipe line of 40 psi, assuming
delivery at the same elevation as the WWTP.
4.4 Transmission Pipelines
The majority of reclaimed transmission piping is polyvinyl chloride pipe (PVC) or
ductile iron pipe (DIP) meeting specific industry standards. For this study, the
transmission system is assumed to be all forcemain: pipe with a diameter of 24 inches
or less is PVC, DR 18, Class 150. Greater than 24 inch diameter pipe is assumed to be
DIP, Class 51 with push-on joints. Pipelines are sized to carry the peak hour demand
(peaking factor of 3) of a given industry at a target velocity of 5 to 7 fps.
5.0 Costs
5.1 Overview
This section presents the estimated cost of service for a municipal water reuse system
to serve a “base level” water quality and “alternative” water quality supplies to
industries. The base level quality is defined as a hard water that meets regulatory
standards for non-contact industrial water uses. The processes needed to produce the
base level water quality define a “base WWTP” for water reuse to which other
28 Craddock Consulting Engineers
In Association with CDM & James Crook
TM3-Component&Costs_0707