Recycling Treated Municipal Wastewater for Industrial Water Use

Appendix B
Status of Water Reuse Regulations and Guidelines
human contact with the water, such as flushing sanitary sewers or making concrete.
Conversely, uses such as snowmaking and vehicle washing are likely to result in contact
with the reclaimed water, and tertiary treatment with a high level of disinfection is
usually required.
Treatment, Water Quality, and Other Requirements
Treatment Process Requirements
With few exceptions, state water reuse regulations prescribe treatment unit process
requirements. Where expected exposure is incidental or not likely, a low level of
wastewater treatment is usually acceptable and undisinfected or disinfected secondary
treated effluent may be allowed dependent on the type of use. In most states, the
definition of secondary treatment means that neither the BOD (total BOD) nor TSS
exceed 30 mg/L. A few states use the term “oxidized wastewater” to define secondary
treated wastewater, where oxidized wastewater is defined as wastewater in which the
organic matter has been stabilized, is nonputrescible, and contains dissolved oxygen.
Most state regulations do not require a specific type of secondary treatment; e.g.,
conventional activated sludge, extended aeration activated sludge, lagoon systems, and
other types of secondary treatment may be acceptable. Where public exposure to
reclaimed water used for nonpotable applications is expected to occur, tertiary treatment
usually is required. Different types of acceptable tertiary treatment may include sand
filtration, multi-media filtration, membranes, or other methods shown to be effective in
reducing particulate and organic matter.
BOD, TSS, and Turbidity Requirements
Most states specify wastewater treatment processes and reclaimed water quality limits
for TSS and/or turbidity, total or fecal coliforms, and disinfection. States that have
regulations for potable reuse also include limits on chemical constituents that include,
but are not limited to, the U.S. EPA drinking water standards. For uses of reclaimed
water that require a high quality product water, BOD and TSS limits as low as 5 mg/L
are specified in some states. These limits are applicable where filtration or other tertiary
treatment processes are used to remove some objectionable constituents and prepare the
water for disinfection. Daily sampling for BOD and TSS, using composite samples is
usually required, although less frequent sampling is allowed in some states. Not all
states include limits for BOD and TSS, and several states specify turbidity requirements
in lieu of TSS. Turbidity limits generally are required only for tertiary treated reclaimed
water where human contact is expected or likely. Where required, most states require
that turbidity be continuously monitored. The compliance point for turbidity usually is
just prior to disinfection.
Where specified, limits on turbidity in reclaimed water after filtration range from 1 to 10
nephelometric turbidity units (NTU), with 2 NTU being a common requirement.
California specifies different turbidity requirements depending on type of tertiary
treatment. Where media filtration is the tertiary treatment process, turbidity after
filtration cannot exceed an average of 2 NTU within any 24-hour period, cannot exceed 5
NTU more than 5 percent of the time within a 24-hour period, and cannot exceed 10
Craddock Consulting Engineers B-9
In Association with CDM & James Crook
WWReuse Tm1_Appendix B_Regulatory.doc