Recycling Treated Municipal Wastewater for Industrial Water Use

Section 3
Inventory of Major WWTPs and Potential Industrial Reuse Demands
WWTPs
There are two municipal WWTPs in this watershed with design capacities greater
than 1 mgd: Chisago Lakes Joint STC and Metro Council’s St. Croix Valley WWTP.
Table 3.16b summarizes the design capacity and historic flows for the plant. These
WWTPs discharged 3.9 mgd in 2005. There are also smaller WWTPs that discharge to
surface waters with a combined design capacity of 5.2 mgd.
Table 3.16b. WWTPs in the St. Croix River Watershed
Facility Name
Design
Capacity,
mgd
2005 Ann
Avg Flow,
mgd
Flow as % of
Design
Capacity
Chisago Lakes Joint STC
Met Council - St Croix Valley
1.26 0.756 60.0%
WWTP 4.5 3.126 69.5%
Total
Source: MPCA, 2005
5.76 3.882 67.4%
Industries and Proximity to WWTPs
Figure 3.16c presents the location of the industries and WWTPs in the St. Croix River
watershed. Table 3.16c lists the various industries and their distance from the closer of
the two WWTPs. The sand and gravel companies are all located a considerable
distance from a WWTP, the closest is 5 miles away. Andersen Corporation, which
used approximately 0.6 mgd of ground water in 2004, is within 1 mile of the Met
Council St. Croix Valley WWTP. The Xcel Energy facility is also within 1 mile of this
WWTP.
Factors Influencing Potential for Industrial Reuse
This watershed resides in Ground Water Area 1 of the state, which has a good
bedrock aquifer supply and moderate bearing surficial sand and buried sand aquifers.
As development continues around the metro area, supply pressures will be placed on
ground water resources in the metro area and fringe areas to the north. Water quality
has not been an issue, in general, for this area. The St. Croix supply as a surface water
is superior to other major waterways of the area. Low-level contamination of upper
aquifers has occurred from spills and general effects of urbanization. Areas
developing with private individual sewage treatment systems (ISTSs) or clustered
systems have the increased risk of nitrate and pathogen contamination.
Rapid population growth and accompanying land-use changes have affected the
water resources of the St. Croix River Basin. The St. Croix Basin Water Resources
Planning Team (St. Croix Basin Team), working with recently completed nutrient and
sediment research, has recommended a 20-percent reduction in total phosphorus
loading within the St. Croix Basin. This is based on a 39-percent projected population
growth in the St. Croix Basin by the year 2020. The St. Croix basin will also be part of
the Lake Pepin TMDL which is projected to require a 50% reduction in solids and
phosphorus loads from upstream sources.
3-36 Craddock Consulting Engineers
In Association with CDM & James Crook
WWReuseTM1_Sec 3_final.doc