Recycling Treated Municipal Wastewater for Industrial Water Use

TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
facilities to achieve microbial limits to protect public health are discussed under
Section 3.3.
3.3 Municipal WWTP Processes and Water Quality
3.3.1 Overview
Assumptions were made to define a starting point for treatment requirements to meet
regulatory and industrial specific uses of a reclaimed water supply. For this project, it
is assumed that the WWTP is supplying an effluent from a secondary treatment
system. The secondary system is an activated sludge system with nitrification and
phosphorus removal, defined for this project as ‘advanced secondary treatment’.
While some Minnesota municipal facilities may have total nitrogen removal or the
capability, the majority do not. Hence, in this study only ammonia nitrogen removal
is assumed under the term ‘advanced secondary treatment’ or when the term nutrient
removal is used.
The majority of Minnesota’s larger WWTPs have an advanced secondary treatment
process or will have this capability as Total Maximum Daily Loads (TMDLs) are
developed across the state. New facilities and major expansions permitted in the state
are anticipated to have nutrient limits that would dictate this assumed process train.
In addition, because one of the largest and most likely industrial uses of reclaimed
water is for cooling water, which requires minimal levels of phosphorus and
ammonia – use of an advanced secondary treatment system effluent is an optimum
starting point. This assumption does not exclude consideration of other types of
wastewater treatment facilities for water reclamation, such as fixed film systems
(trickling filters and rotating biological contactors), stabilization ponds,
chemical/physical package systems, or natural systems (wetland treatment).
However, it is likely that additional processes would need to be added to meet the
water quality requirements of a specific industry and the regulatory requirements.
3.3.2 Base WWTP Definition and Effluent Quality
A “base level” water quality produced by a “base WWTP” was assumed for purposes
of estimating costs of service for a municipality to supply an industry with reclaimed
water. The base level reclaimed water quality is defined for this study as a hard water
that meets regulatory standards for non-contact industrial water uses. The base level
water quality is assumed to have the constituent concentrations listed in Table 6, as
typical of an advanced secondary wastewater facility effluent. This list includes
constituents in most Minnesota NPDES permits (for discharge to a receiving water),
those required by the California Title 22 regulations, and others that relate to specific
industrial water uses, such as total dissolved solids (TDS).
If a facility has advanced secondary treatment, the first seven constituents listed in
Table 6 (through fecal coliform) are expected to be included in the facility’s NPDES
permit, with the exception of nitrate. The concentrations listed for these seven
parameters are considered “typical” effluent concentrations, based on a review of
Minnesota WWTP discharge reports and typical operations of similar secondary
WWTPs across the U.S. The BOD and TSS concentrations listed are typically less than
18 Craddock Consulting Engineers
In Association with CDM & James Crook
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