Recycling Treated Municipal Wastewater for Industrial Water Use

Craddock Consulting Engineers 1
In Association with CDM & James Crook
TM4-WWTP Eff Quality_0707.doc
1.0 Introduction
This technical memorandum is the fourth in a series of memoranda developed under
a Metropolitan Council (Council) project titled “Recycling Treated Municipal
Wastewater for Industrial Water Use.” Funding for this project was recommended by
the Legislative Commission on Minnesota Resources (LCMR) from the Minnesota
Environment and Natural Resources Trust Fund. The Met Council is providing
additional funding for the project through in-kind contributions of staff time. Other
state agencies are participating via stakeholder meetings and technical review and
input.
Objective
This memorandum summarizes the effluent quality of wastewater treatment plants
(WWTPs) in Minnesota. The purpose of the WWTP effluent quality analysis is to
assess the applicability of WWTP effluent as a water source for industries in
Minnesota. The constituents evaluated serve as indicators of the level of treatment
provided by a WWTP and depending on the industrial use of the water, as specific
water quality parameters of concern.
Constituents of Concern
The analysis focuses on the following constituents: 5-day carbonaceous biochemical
oxygen demand (CBOD5), total suspended solids (TSS), ammonia (NH3), total
phosphorous (TP), and fecal coliforms. Table 1 lists the constituents evaluated and
reasons for concern in industrial water reuse. These constituents are routinely
measured in WWTP effluent as part of the National Pollutant Discharge Elimination
System (NPDES) Permit requirements.
Table 1. Water Quality Concerns for Industrial Applications
Constituent Reason for Concern
CBOD5 (indicator of organic content) Biological fouling, foaming, imparts color or odor,
interference with disinfection
TSS Deposition, clogging, interference with disinfection
Ammonia Corrosion, interference with disinfection
Phosphorous Scaling, microbial growth
Fecal Coliforms (indicator organism) Infectious disease
The water quality constituents listed in Table 1 are only a subset of the constituents
industries evaluate to select a water source and possibly treat as part of their routine
facility operations. Technical Memoranda 1, 2, and 3 produced for this project provide
additional information on the water quality parameters of concern for industrial
water use. These five constituents are evaluated in detail because they provide a
general indicator of the level of treatment at individual WWTPs and there is a well
documented database with a high level of quality control and assurance associated
with the database.