Recycling Treated Municipal Wastewater for Industrial Water Use

TM3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
Heavy Metals Removal: Industrial processes have historically used ion exchange
to recover heavy metals. A variety of natural an synthetic resins are available with
selectivity for specific metals.
Total Dissolved Solids Removal: Anionic and cationic exchange units used in a
series can be used to remove TDS or demineralize the water.
Reduction of Organics: Ion exchange can be used to remove the highly ionized
organics in the water. Specifically prepared resins have been used to reduce TOC
levels by 50 percent.
Advanced Oxidation Processes (AOPs)
Advanced oxidation processes destroy trace constituents that are not completely
oxidized by conventional oxidation processes. There are a host of processes and
groupings of processes that have been used, principally in the drinking water
industry and research stages, to handle specific contaminants and the emerging
contaminants of concern. These processes are all applicable to treatment of water for
reuse.
The primary AOPs that have application to water reuse systems include:
Hydrogen Peroxide/Ultraviolet Light (H2O2/UV)
Hydrogen Peroxide/Ozone (H2O2/Ozone)
Ozone/Ultraviolet Light (Ozone/UV)
The UV processes are the most promising for Minnesota application, where UV
radiation is becoming amore common form of disinfection. UV facilities could be
retrofitted or planned for new construction to handle any specific removal of trace
constituents.
The use of AOPs will be a very site-specific application or is a consideration for future
management of trace constituents. The technology is identified in this study to
emphasize that applications do exist and research is ongoing to prepare for handling
the treatment of these constituents.
3.2.6 Disinfection (Microorganism Removal/Inactivation)
Most Minnesota WWTPs disinfect with chlorine or UV. The main compounds used
for chlorination are gaseous chlorine (Cl2) and liquid sodium hypochlorite (NaOCl).
Because of safety concerns and regulatory requirements, many WWTPs have moved
from chlorine gas to sodium hypochlorite. Other disinfectants (not emphasized in this
study) include ozone, chlorine dioxide, and calcium hypochlorite (for smaller
WWTPs). Membranes also provide a barrier to microorganisms and reduce or can
potentially remove the need for chemical or UV disinfection.
Given the elevated potential for human contact, disinfection is an essential part of the
process train in treating water for reuse. Disinfection requirements for reuse under the
Title 22 criteria are greater than for discharge to the receiving stream under most
Minnesota NPDES permits. Specific needs for Minnesota’s wastewater treatment
Craddock Consulting Engineers 17
In Association with CDM & James Crook
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