Recycling Treated Municipal Wastewater for Industrial Water Use

Section 2
Implementation Considerations
Craddock Consulting Engineers
In Association with CDM & James Crook 2-27
TM1-Sec2_0707.doc
Table 2.12. Wastewater Reuse Facilities in Minnesota
Facility Type of Reuse
Flow,
mgd
Treatment Type
Hennepin County Public Toilet Flush 0.0056 Activated sludge, activated
Works
Water
carbon, membrane filtration
(Zenon, Inc.)
Lake Allie Golf course 0.0056 Activated sludge, activated
irrigation
carbon, membrane filtration
(Zenon, Inc.)
Turtle Run South Golf course
irrigation
0.0168 Recirculating gravel filter
Izaty’s Golf and Yacht Golf course and 0.086 Recirculating gravel filter, sand
Club
alfalfa field
irrigation
filter
City of Nisswa Golf course 0.038 Aerated stabilization ponds, dual
irrigation and
other uses
media filter
City of Montgomery Golf course
irrigation
0.1 Aerated ponds, sand filter
City of Mankato Industrial
6.2 Disinfected tertiary recycled
(cooling water for
power plant)
water
Sources: Communications with MPCA and City of Mankato [April 2006]
Cooling Water
There are more than 20 steam electric generating plants in the U.S. that use municipal
wastewater, primarily as cooling water. A variety of treatment processes are used and
are dependent on the water characteristics, treatment facility location (at the WWTP
or the power plant) and site specific requirements. Typically the process train consists
of oxidation, coagulation, filtration, and disinfection. Some examples illustrate the
different treatment processes and variety of power facility applications for reuse.
One of the first industrial reuse applications in Minnesota is the Mankato Energy
Center (MEC), with construction completion scheduled by the end of 2006.
Wastewater plant effluent from the Mankato WWTP (maximum 6.2 mgd) will be
pumped to the MEC and MEC cooling water discharge will be returned to the plant
as a permitted industrial user and commingled with treated effluent prior to
dechlorination. The MEC uses an evaporative cooling process with an average loss of
75%. The MEC will initially produce 365 megawatts with an ultimate capacity of 630
megawatts.
New facilities constructed at the Mankato WWTP include: high-rate clarification for
tertiary phosphorus removal with ferric chloride and polymer (Kruger Actiflo units),
cloth media disk filtration, expanded chlorination using sodium hypochlorite, transfer
pumping, and ancillary structures and equipment. Tertiary phosphorus removal is
required to provide a supply with total phosphorus concentrations less than the
permitted limit of 1 mg/L to the MEC. Chemicals containing phosphorus are added