Recycling Treated Municipal Wastewater for Industrial Water Use

Section 3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
Section 3: Recycled Wastewater System Components and
Costs
This section presents the third area of inquiry into the feasibility of Minnesota’s industries using recycled
wastewater by addressing the question: Is wastewater recycling an economical practice? The answer
begins with identification of the system components which include treatment facilities for a range of
treatment requirements and potential facilities to meet those requirements. After establishing a basis for
the system components, a system of cost curves was developed for varying system sizes and transmission
distances. Costs are presented by industry category as cost of service, on a dollar per gallon basis, to
compare a recycled wastewater supply to traditional supplies. Appendix II-3 provides background
information and more detail on the treatment requirements, treatment technologies, and cost assumptions
used in the analysis.
3.1 Recycled Wastewater System Overview
Recycled wastewater systems can be configured in many ways. Commonly used components are shown
in Figure 3.1 and are described below. This study assumed certain components, identified as (1) through
(7) and attributes for those components to develop costs. These assumptions are also described below.
Treatment of WWTP Effluent (1)
— Additional processes to those currently used by an existing WWTP, if needed.
— New WWTP processes to replace existing processes during a plant upgrade, such as membrane
filtration to replace clarification.
Additional Disinfection (2)
— A residual disinfectant is often used in the transmission system to minimize bacterial growth.
Liquid chlorine (sodium hypochlorite) is assumed for this study.
— Additional disinfection is required for year-round disinfection and more stringent pathogen limits.
The existing facilities may be able to achieve this, but it is assumed new equipment is required.
Storage (3)
— In some instances, storage will be required to balance the diurnal or other WWTP flow variations,
with the requirements of a specific industrial demand for different peak hour, weekly or other
dominant demand patterns.
— Storage will likely be required for WWTPs that reclaim over 50 percent of their flow. Smaller
facilities, with less equalization capacity, are more likely to need storage.
— The cost curves developed assume no storage requirements. Appendix II-3 provides storage
system cost information.
Pump Station (4)
— A pump station located onsite at the WWTP.
— For cost development purposes, this study assumes delivery of supply to industry at a pressure of
40 pounds per square inch (psi) and the same elevation as the WWTP.
Recycled Wastewater Transmission System (5)
— Transmission main and branch transmission lines supplying water to industries.
— Variable flows and distances. This study evaluated flows of 0 to 30 mgd and distances of 1 to 10
miles.
Booster Pumps (6)
— Some industries may require booster pumps depending on their location and delivery pressure
requirements.
— Industries A-D shown on the schematic represent potential configurations for pumping and
treatment facilities not located on the WWTP site (either at the industry or in the transmission
system).
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