Recycling Treated Municipal Wastewater for Industrial Water Use

Section 3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
The cost analysis indicates that there are economically viable applications to provide treated wastewater
effluent as a water supply to industries. The technology is available and as competition increases in the
membrane market, more economical solutions can be anticipated to meet the specific water quality needs
for a spectrum of industries in Minnesota. Treatment costs were estimated to range from $0.50/1000
gallons for larger supplies (30 mgd) with water quality suitable for cooling water to over $7.00/1000
gallons for smaller supplies (0.1 mgd) treated to meet stringent industrial water requirements.
Total System Costs
To provide a comparison of total system costs to treatment costs, a 5-mile transmission system was
evaluated as shown in Figure 3.6. The cost to deliver a base supply, inclusive of transmission costs,
disinfection system costs (assumed
as part of the base system) and
administrative/laboratory costs
ranged from $0.40/1000 gallons
for 30 mgd to $8.88/1000 gallons
for a 0.1 mgd supply. For
membrane softening, the costs
range from $2.20/1000 gallons to
$13.73/1000 gallons. Both
transmission and treatment system
costs on a per gallon basis become
more economical as the system
capacity exceeds 1 mgd.
Figure 3.6. Comparison of Base and Membrane Softening System
Costs for 5-Mile Transmission
Cost of Service, $/1000 gallons
8.00
7.00
6.00
5.00
4.00
3.00
2.00
$8.88 - Base
$13.73 - Tertiary 3
Base Tertiary 3 - Membrane Softening
$2/1000 gallons
Typical Potable Water Supply Cost
The evaluation of a 1 mgd
1.00
recycled wastewater supply
transmitted 5 miles was estimated
0.00
0.1 0.5 1 1.5 2 3 4 5 10 15 30
to have a cost of service ranging
Recycled Wastewater Flow/Demand, mgd
from $1.35/1000 gallons to
$3.75/1000 gallons, depending on the water quality delivered. As summarized in Table 3.9, industrial
water uses that are non-contact and have little concern with higher salts and hard water (base supply) are
very competitive, at $1.35/1000 gallons, with potable water supplies assumed at a typical cost of
$2.00/1000 gallons. For industries that may have similar water quality requirements to the base supply,
but may have human contact with the supply water, the cost is $2.45/1000 gallons. Cooling water and
process water requirements for many industries will likely require softened water and removal of
dissolved solids, as provided by Tertiary 3 treatment processes, which is estimated to cost $3.75/1000
gallons. The treatment requirements for Tertiary 3 processes place these system costs above typical
potable supply costs, but it is not out of the range of some rural system water utility costs. While system
costs for ground water supplies would likely be less than this, for areas with water shortages or watershed
discharge limitations, recycled wastewater could be a cost-effective water supply.
Table 3.9. Estimated Costs for a 1 mgd Recycled Wastewater System*
Water Quality Classification Characteristics
System Cost of
Service, $/1000
gallons
Base Non-contact uses
No concern for hardness or high dissolved solids 1.35
Tertiary 2 – Membrane Filtration Potential contact uses
No concern for hardness or high dissolved solids 2.45
Tertiary 3 – Membrane Softening Potential contact uses
*
Based on a 5-mile transmission system
Require soft water with lower dissolved solids 3.75
52 Metropolitan Council Environmental Services