Recycling Treated Municipal Wastewater for Industrial Water Use

Section 3: Recycled Wastewater System Components and Costs
Recycling Treated Municipal Wastewater for Industrial Water Use
As more restrictions are being placed on loadings to our waterways, the removal of the nutrients, nitrogen
and phosphorus, will be implemented at more WWTPs and limits could be lowered for those already
removing nutrients. New facilities and major expansions permitted in the state are anticipated to have
nutrient limits that would dictate the use of an advanced secondary treatment process train. In addition,
because one of the largest and most likely industrial uses of recycled wastewater 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 these facilities would require additional treatment
processes to meet the water quality requirements of a specific industry and the regulatory requirements.
Recycled Wastewater Classifications
Five types of recycled wastewater, listed in Table 3.4, are used to categorize the recycled wastewater
options available for specific industrial water supply requirements. The classification is based on a train
of treatment technologies to meet a set of water quality goals. All classifications provide a safe supply
from a public health perspective – the different water quality goals relate to the specific requirements for
the industrial water use. All classifications assume an initial WWTP effluent quality typical of a
secondary activated sludge system with ammonia and phosphorus removal, defined as the “base” supply.
Additional treatment processes following secondary treatment are required to produce the other four
classes of recycled wastewater. The term ‘tertiary’ is used to define these classifications because the
treatment process generally follows the secondary treatment process at a WWTP.
Table 3.4. Recycled Wastewater Classifications
Classification Characteristics
Base
For non-contact industrial uses with low concern for hardness and dissolved solids
Advanced Base WWTP process train – a secondary treatment system with ammonia and phosphorus
Secondary removal
Tertiary 1 For industrial uses with human contact potential and/or industries that require partial hardness
Conventional
or phosphorus removal
Requires a coagulation/flocculation/sedimentation process with filtration; chemical used
depends on target constituent
Removes hardness (with lime) and some dissolved salts; provides some soluble organic
removal and color removal
Tertiary 2 For industrial uses with human contact potential and/or industries that can use hard/high salt
Membrane
water
Filtration Provides soluble organic removal and color removal
Provides pathogen removal and reduces disinfection requirements
Tertiary 3
Membrane
Softening
Tertiary 4
Advanced
Processes
For industries requiring low dissolved salts
Requires Tertiary 2 water followed by softening with reverse osmosis (RO) or electrodialysis
(ED) depending on the target constituents
For industries requiring low dissolved salts and removal of trace constituents
Requires Tertiary 3 water with RO and either ion exchange, carbon adsorption or advanced
oxidation processes, depending on the target constituent.
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