Changes

[[File:Treatmenttrain TRCA.JPG|thumb|600px|Example of a generalization of utilizing a “Treatment Train Approach” illustrated here. Using [[permeable pavement]] as a source control/lot control on your business/residential property, effluent then flows into conveyance control such as an [[Exfiltration trench|exfiltration system]], used in conjunction with the minor stormwater system as shown above. and then flowing into a stormwater management pond (wet pond) for additional erosion and flood control (TRCA, n.d. Understand - Stormwater Management. Accessed: https://trca.ca/conservation/stormwater-management/understand/</ref>]]

[[File:Treatmenttrain TRCA.JPG|thumb|600px|Example of a generalization of utilizing a “Treatment Train Approach” illustrated here. Using [[permeable pavement]] as a source control/lot control on your business/residential property, effluent then flows into conveyance control such as an [[Exfiltration trench|exfiltration system]], used in conjunction with the minor stormwater system as shown above. and then flowing into a stormwater management pond (wet pond) for additional erosion and flood control (TRCA, n.d. Understand - Stormwater Management. Accessed: https://trca.ca/conservation/stormwater-management/understand/</ref>]]

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==Overview==

==Overview==

A treatment train uses a combination of lot-level or source (LID), conveyance and/or end-of-pipe practices to meet water quality, water quantity, water balance, and erosion design criteria for the site.  These may be implemented to reduce the burden of facility maintenance, address a broader range of design criteria, increase overall treatment system performance, and/or control the rate of flow through downstream facilities.

A treatment train uses a combination of lot-level or source (LID), conveyance and/or end-of-pipe practices to meet water quality, water quantity, water balance, and erosion design criteria for the site.  These may be implemented to reduce the burden of facility maintenance, address a broader range of design criteria, increase overall treatment system performance, and/or control the rate of flow through downstream facilities.

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'''Performance calculation''': If the downstream facility provides filtration, such as [[bioretention]] or [[Infiltration trenches|stone filled trenches]], the overall water quality performance of this facility would not increase with [[pretreatment]] because the coarse sediment and debris captured by the pretreatment device would be removed by the downstream facility even in the absence of pretreatment.  The purpose of adding pre-treatment is to prevent clogging or filling and thereby reduce the cost and effort of long term [[Inspections and maintenance|maintenance]] and delay requirements for major facility [[Maintenance, Rehabilitation and Repair|rehabilitation or replacement]].

'''Performance calculation''': If the downstream facility provides filtration, such as [[bioretention]] or [[Infiltration trenches|stone filled trenches]], the overall water quality performance of this facility would not increase with [[pretreatment]] because the coarse sediment and debris captured by the pretreatment device would be removed by the downstream facility even in the absence of pretreatment.  The purpose of adding pre-treatment is to prevent clogging or filling and thereby reduce the cost and effort of long term [[Inspections and maintenance|maintenance]] and delay requirements for major facility [[Maintenance, Rehabilitation and Repair|rehabilitation or replacement]].

===2. Treatment trains designed to address one or more design criteria===  

===2. Treatment trains designed to address one or more design criteria===  

These types of treatment trains combine practices that address different [[Screening LID options|design criteria]], in recognition that most individual stormwater facility types do not meet all design criteria as stand-alone facilities.  For instance, [[SWM ponds|stormwater wet ponds]] may provide [[water quality]], erosion and flood control but not water balance control (i.e. [[Runoff volume control targets|runoff volume control]]).  [[Bioretention]] provides good water quality and water balance control but are rarely designed for flood control.   

These types of treatment trains combine practices that address different [[Screening LID options|design criteria]], in recognition that most individual stormwater facility types do not meet all design criteria as stand-alone facilities.  For instance, [[SWM ponds|stormwater wet ponds]] may provide [[water quality]], erosion and flood control but not water balance control (i.e. [[Runoff volume control targets|runoff volume control]]).  [[Bioretention]] provides good water quality and water balance control but are rarely designed for flood control.   

'''Example''': [[Pretreatment#Concentrated underground flow|Proprietary filtration treatment device]] (providing water quality) draining to an underground [[infiltration trench]] or [[Infiltration chambers|chamber system]] (providing water balance control).  Overflows from the trench or chamber system could drain to a [[dry pond]] or other flood control facility to provide water quantity and erosion control).  Another example may be to direct low flows from a stormwater management pond [[outlet]] to an infiltration practice.   

'''Example''': [[Pretreatment#Concentrated underground flow|Proprietary filtration treatment device]] (providing water quality) draining to an underground [[infiltration trench]] or [[Infiltration chambers|chamber system]] (providing water balance control).  Overflows from the trench or chamber system could drain to a [[dry pond]] or other flood control facility to provide water quantity and erosion control).  Another example may be to direct low flows from a stormwater management pond [[Overflow|outlet]] to an infiltration practice.   

'''Performance calculation''':  Treatment trains designed to address multiple design criteria may improve overall water quality performance by, for example, reducing water quality concentrations in the first facility and reducing water quality loads (through infiltration/evapotranspiration) in a second facility.  Even if the effluent concentration from facility one and facility two are the same, the overall load reduction of the treatment train may be greater than provided by any one of the facilities alone.

'''Performance calculation''':  Treatment trains designed to address multiple design criteria may improve overall water quality performance by, for example, reducing water quality concentrations in the first facility and reducing water quality loads (through infiltration/evapotranspiration) in a second facility.  Even if the effluent concentration from facility one and facility two are the same, the overall load reduction of the treatment train may be greater than provided by any one of the facilities alone.

The design intent of these treatment trains is to enhance overall system performance.  The previous category of treatment train may enhance performance, but the objective may not always be to address a broader range of stormwater criteria.   

The design intent of these treatment trains is to enhance overall system performance.  The previous category of treatment train may enhance performance, but the objective may not always be to address a broader range of stormwater criteria.   

'''Performance calculation''':  In the example above, the [[bioretention]] facility would provide water quality load reductions through filtration (water quality concentration reductions) and infiltration (volume reductions).  Since the second facility would receive effluent from the [[underdrain]] of the bioretention, no further reduction in TSS concentrations would be expected (ie. the TSS concentration would already be at the ‘irreducible’ level) (Schueler, 2000)<ref>Schueler, T.  2000.  Irreducible Pollutant Concentration Discharged from Stormwater Practices.  Technical Note #75, In Watershed Protection Techniques. 2(2), 369-372, Centre for Watershed Protection. Accessed: https://owl.cwp.org/mdocs-posts/elc_pwp65/</ref>.  The TSS water quality load would be reduced in the second facility only by further reductions in volumes through infiltration.  If the parameter of interest was total [[phosphorus]] (TP) rather than TSS, there is the potential that the second facility may further reduce TP through filtration/adsorption, especially if the second facility contained [[Sorbtive media|reactive media]] designed to remove phosphorus.

'''Performance calculation''':  In the example above, the [[bioretention]] facility would provide water quality load reductions through filtration (water quality concentration reductions) and infiltration (volume reductions).  Since the second facility would receive effluent from the [[underdrain]] of the bioretention, no further reduction in TSS concentrations would be expected (ie. the TSS concentration would already be at the ‘irreducible’ level) (Schueler, 2000)<ref>Schueler, T.  2000.  Irreducible Pollutant Concentration Discharged from Stormwater Practices.  Technical Note #75, In Watershed Protection Techniques. 2(2), 369-372, Centre for Watershed Protection. Accessed: https://owl.cwp.org/mdocs-posts/elc_pwp65/</ref>.  The TSS water quality load would be reduced in the second facility only by further reductions in volumes through infiltration.  If the parameter of interest was total [[phosphorus]] (TP) rather than TSS, there is the potential that the second facility may further reduce TP through filtration/adsorption, especially if the second facility contained [[Sorbtive media|reactive media]] designed to remove phosphorus.

===4. Treatment trains designed to optimize treatment facility sizing through flow control===

===4. Treatment trains designed to optimize treatment facility sizing through flow control===

==Treatment trains with runoff volume reduction facilities==

==Treatment trains with runoff volume reduction facilities==

These types of treatment trains are becoming more common because they can achieve multiple [[Runoff volume control targets|stormwater control]] and [[water quality|treatment objectives]].  Since wet ponds alone do not achieve stormwater water balance criteria, they must be supplemented with facilities providing runoff volume reductions to meet regulatory requirements. If site water balance objectives require control of the 90th percentile event (roughly 25 – 30 mm in most jurisdictions), the same infiltration facilities may also be used to treat the water quality storm (typically 25 mm), allowing for a [[dry pond]] or similar temporary detention facility to be used at the end-of-pipe to meet flood and erosion control criteria.

These types of treatment trains are becoming more common because they can achieve multiple [[Runoff volume control targets|stormwater control]] and [[water quality|treatment objectives]].  Since wet ponds alone do not achieve stormwater water balance criteria, they must be supplemented with facilities providing runoff volume reductions to meet regulatory requirements. If site water balance objectives require control of the 90th percentile event (roughly 25 – 30 mm in most jurisdictions), the same infiltration facilities may also be used to treat the water quality storm (typically 25 mm), allowing for a [[dry pond]] or similar temporary detention facility to be used at the end-of-pipe to meet flood and erosion control criteria.