Recycling Treated Municipal Wastewater for Industrial Water Use

3.2 Water Reuse Treatment Technologies
3.2.1 Overview
TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
Treatment requirements for specific industrial reuse applications are based on
multiple factors including: the quality of the source water used by a community,
chemicals discharged to the WWTP, the WWTP’s existing process train, water reuse
regulations, the intended use of the water by the industry, and the quantity of water
reclaimed at an individual facility. The treatment technology selected will depend in
part on whether treatment is incorporated at the centralized WWTP, onsite at the
industry, or at a satellite facility along the distribution line. If storage is required,
additional treatment may be required for algae growth and by-products and for
residual disinfection. With all these variables, the treatment process and transmission
system selected is a site and case-specific one.
Treatment process requirements for reclaimed water beyond standard secondary
treatment processes can be categorized by the target parameter (adapted from Metcalf
& Eddy, 2007):
Enhanced suspended and dissolved solids removal (chemical addition/softening)
Residual suspended solids removal (filtration)
Residual colloidal solids removal (membrane filtration)
Residual dissolved solids removal (demineralization/softening)
Residual and specific trace constituent removal (multiple processes)
Disinfection (microorganim removal/inactivation)
The relationship of various treatment technologies that can be used to achieve a
desired reclaimed water quality is depicted in Figure 3. The treatment process
schematic assumes a WWTP secondary effluent as the beginning point of the
treatment train. The schematic shows the potential use of one or more of the
processes targeting a specific parameter. A treatment train would consist of several of
the processes shown, but would not include all processes shown.
The effluent quality of various treatment trains is compared in Table 3 to provide a
perspective on the additional removals obtained with different levels of treatment.
Secondary effluent from an activated sludge facility with and without nutrient
removal are listed in the first two columns of the table and represent a quality for
non-contact industrial activities without concern for hardness and dissolved solids.
An example industrial water use application for secondary treatment water is sand
and gravel washing operations or site dust control. Advanced secondary treatment
water, which has reduced levels of phosphorus and ammonia, could be used for
cooling water purposes if the hardness and dissolved salt concentrations are not too
high or an industry provides their own additional onsite treatment. For these process
Craddock Consulting Engineers 7
In Association with CDM & James Crook
TM3-Component&Costs_0707