Recycling Treated Municipal Wastewater for Industrial Water Use

Section 2: Recycled Wastewater Demand & Supply
Recycling Treated Municipal Wastewater for Industrial Water Use
of recycled wastewater from Empire by Flint Hills Resources was not pursued because of water quality
issues, notably high chlorides in the Empire WWTP effluent, it is possible that potential future Flint Hills
Resources expansions could consider this source. Also, the industrial areas along the outfall could benefit
from this potential 24 mgd source of recycled wastewater.
Factors Influencing Potential for Industrial Use of Recycled Wastewater – Lower
Mississippi River Watershed
The majority of the Lower Mississippi River watershed has a good water supply from bedrock that most
communities rely on as their primary water source. Most of the watershed is in Ground Water Area 3 of
the state, with eastern regions in Area 2 and the northern reaches in Area 1 (refer to Figure 2.8). All three
areas have a reliable and productive bedrock aquifer.
Area 3 has extensive near-surface karst areas that result in its aquifers being vulnerable to contamination.
There is wide-spread nitrate contamination in near-surface aquifers as well as occurrences of pesticides
and other contaminants. The susceptibility to contamination index places this watershed in the medium to
highest range (refer to Figure 2.9). Area 2 on the western edge of the watershed has a more productive
buried sand aquifer, but still limited surficial sand aquifers. The northern watershed, in Area 1, has a
reliable supply for all three general aquifer levels.
Portions of the Lower Mississippi River watershed will be affected by the TMDL for Lake Pepin. The
planning process for this TMDL has established preliminary targets of phosphorus and solids loading
reductions of one-half into Lake Pepin. While nonpoint sources are significant contributions to this load,
it is likely that loading reductions for most point sources will be considered.
2.3 Twin Cities Metro Area Inventory
The industrial inventory for the Twin Cities metro area indicates a diversity of industries and a prevalence
of potential recycled wastewater customers along the river corridors. The industry inventory in the Twin
Cities metro area was based on the same MDNR database as for the state and watershed analysis plus
those industries discharging to the Met Council’s sewer system for treatment at one of eight WWTPs.
Figure 2.13 presents the industries with water permits (MDNR appropriation permits) and Figure 2.14
locates a larger set of industries in the Twin Cities metro area, based on Met Council’s Industrial
Dischargers permit program (Met Council, 2005).
The Met Council database provides for a more detailed categorization of the industries, as shown in the
legend of Figure 2.14. These industry categories are documented with subcategories in Appendix II-1
(Appendix E). Figure 2.14 also identifies if the industry obtains its water from a municipal (potable)
source or another source, which typically would be through a MDNR appropriations permit. The other
source could be ground water (well), surface water or a combination of both. The municipal designation
was rolled up to include any industry that uses a municipal supply.
The Met Council (specifically, the Environmental Services division or MCES) Industrial Dischargers
Permit database includes any discharger to the Met Council’s sewer system. It does not include all
industries in the area, because some have their own treatment systems and discharge permits. Some
dischargers use little water, such as landfill leachate systems, and mainly collect and treat water for
discharge. These industries were excluded from the evaluation.
The industries in the Twin Cities metro area discharging to the sewer system, as shown in Figure 2.15,
had a combined water demand of 65 mgd in 2005. The largest water users were food industries, at 15
mgd, followed by the metal products industries at 10 mgd. Water used in the electronic products and
paper/packaging industries and for power/steam/air conditioning and health care facilities, all had
category totals over 5 mgd.
24 Metropolitan Council Environmental Services