Recycling Treated Municipal Wastewater for Industrial Water Use

Water Quality Overview
The total coliform
limits and
treatment process
requirements
imposed by the
Title 22
regulations are the
only regulatory
criteria that must
be met for all
Minnesota
Section 3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
There are two water quality drivers that affect the treatment requirements for a specific recycled
wastewater supply:
Regulatory requirements: typically for the protection of public health and the environment, with a
focus on microbiological parameters.
User-specific requirements: specific water supply uses, which in the case of industries is a very
specific set of water quality criteria for a given facility.
Recycled wastewater for industrial use in Minnesota is currently required to meet regulatory limits based
on the California Water Recycling Criteria, Title 22 California Code of Regulations (Title 22). The
complete list of criteria is included in Appendix A. The criteria specific to industrial applications
(excluding any irrigation uses) are listed in Table 3.1. The MPCA handles permitting recycled wastewater
as part of the NPDES permit process. The MPCA establishes recycled wastewater water quality criteria
on a case-by-case basis and bases its assessment on the Title 22 criteria. Therefore, the Title 22 criteria
will serve as the
basis for selection
of treatment
technologies to
meet regulatory
requirements in
this study.
Table 3.1. California Water Recycling Criteria (Industrial Uses)
Type of Use
Cooling water where no mist created
Process water with no worker contact
Boiler feed
Mixing concrete
Cooling water where mist created 2
Process water where worker contact likely
Total Coliform
Limits
≤ 23/100 ml 1
≤ 240/100 ml
(max in any 30day
period)
≤ 2.2/100 ml 1
≤ 23/100 ml
(max in any 30day
period)
Treatment
Required
Secondary
Disinfection
Source: Adapted from State of California [2000].
1
Based on running 7-day median; daily sampling is required.
2
Drift eliminator required; chlorine or other biocide required to treat cooling water to control
Legionella and other microorganisms.
3
Not required under certain conditions.
Secondary
Coagulation 3
Filtration
Disinfection
industrial recycled wastewater uses. The other water quality criteria that will drive the treatment process
selection will vary with the specific use of the water. These use-specific criteria do not need to meet a
regulatory permit limit, but would likely be listed as concentration requirements in an agreement between
a municipality and industry for supply of recycled wastewater. Generalized water quality limits for
various industrial uses are provided in Table 3.2 and several constituents are discussed below.
Metropolitan Council Environmental Services 39