Changes

=='''Introduction'''==

=='''Introduction'''==

Conventional flat roofs on industrial, commercial, and institutional buildings are designed to quickly remove rainwater from their surfaces. The passive control strategy of these conventional roof assemblies provides no opportunity for rainwater reuse and contributes to downstream erosion and the potential for flooding. Credit Valley Conservation’s Smart Blue Roof (SBR) flips this idea on its head and uses an active control strategy to capture rainwater for reuse. This emerging technology has the capacity to effectively manage runoff, capture rainwater for non-potable reuse, and conserve energy through evaporative cooling. What makes the SBR cutting edge is that it is the first blue roof system to be compliant with the Canadian Standards Association’s new Rainwater Harvesting Standard (CSA B805-18). Compliance with this standard is essential, because it is anticipated to be incorporated into the Ontario Building Code (OBC) in the near future. The key objective of this pilot project is to explore the potential of this new technology and pave the way for others to adopt active stormwater controls.

Conventional flat roofs on industrial, commercial, and institutional buildings are designed to quickly remove rainwater from their surfaces. The passive control strategy of these conventional roof assemblies provides no opportunity for rainwater reuse and contributes to downstream erosion and the potential for flooding. Credit Valley Conservation’s Smart Blue Roof (SBR) flips this idea on its head and uses an active control strategy to capture rainwater for reuse. This emerging technology has the capacity to effectively manage runoff, capture rainwater for non-potable reuse, and conserve energy through evaporative cooling. What makes the SBR cutting-edge is that it is the first blue roof system to be compliant with the Canadian Standards Association’s new Rainwater Harvesting Standard (CSA B805-18). Compliance with this standard is essential, because it is anticipated to be incorporated into the Ontario Building Code (OBC) in the near future. The key objective of this pilot project is to explore the potential of this new technology and pave the way for others to adopt active stormwater controls.

=='''Station 1 – Roof Surface'''==

=='''Station 1 – Roof Surface'''==

To demonstrate that the roof could safely support more than a maximum of 150 mm of water, a structural load assessment was conducted by WSP Canada. This assessment concluded that ponding an average of 130 mm across CVC’s sloped roof applied a very similar force and torque distribution profile as ponding 130 mm across a completely flat roof. As such, it was considered safe to pond water at a depth of 75 mm at the parapet (roof edge) and 250 mm at the roof drains (lowest point) by the City of Mississauga, and an exemption was granted.

To demonstrate that the roof could safely support more than a maximum of 150 mm of water, a structural load assessment was conducted by WSP Canada. This assessment concluded that ponding an average of 130 mm across CVC’s sloped roof applied a very similar force and torque distribution profile as ponding 130 mm across a completely flat roof. As such, it was considered safe to pond water at a depth of 75 mm at the parapet (roof edge) and 250 mm at the roof drains (lowest point) by the City of Mississauga, and an exemption was granted.

The OBC specifies a maximum rooftop retention time of 24 hours because standing water can lead to the proliferation of algae, bacteria, and mosquitoes. To avoid the rise of water quality issues, the City of Mississauga required that CVC install a separate CSA-compliant water recirculation system on the third floor (see Figure 2). This system draws rooftop rainwater through the recirculation line that is immediately upstream of the east modulating control valve. The following are the main treatment components found on the third floor:

The OBC specifies a maximum rooftop retention time of 24 hours because standing water can lead to the proliferation of algae, bacteria, and mosquitoes. To avoid the rise of water quality issues, the City of Mississauga required that CVC install a separate CSA-compliant water recirculation system on the third floor. This system draws rooftop rainwater through the recirculation line that is immediately upstream of the east modulating control valve. The following are the main treatment components found on the third floor:

*'''Micron Filters:''' Remove any fine debris from the rainwater. This filtration is important for removing impurities, eliminating odours, and ensuring debris does not impede the efficacy of the ultra-violet treatment (UV) unit by blocking light. Two (2) filters are present, the first with a filter pore size of 20 μm and the second with a filter pore size of 5 μm – A pore size of 5 μm is required for CSA compliance.

*'''Micron Filters:''' Remove any fine debris from the rainwater. This filtration is important for removing impurities, eliminating odours, and ensuring debris does not impede the efficacy of the ultra-violet (UV) treatment unit by blocking light. Two (2) filters are present, the first with a filter pore size of 20 μm and the second with a filter pore size of 5 μm – A pore size of 5 μm is required for CSA compliance.

*'''UV Lamp:''' Disinfects rainwater by sterilizing bacteria and viruses with UV radiation. Note that UV disinfection does not have any residual effect that can be harmful to humans or aquatic life. A dosage of 40 mJ/cm2 is administered – This dosage is required for CSA-compliance.

*'''UV Lamp:''' Disinfects rainwater by sterilizing bacteria and viruses with UV radiation. Note that UV disinfection does not have any residual effect that can be harmful to humans or aquatic life. A dosage of 40 mJ/cm^2 is administered – This dosage is required for CSA-compliance.

*'''Chlorine Pump:''' Provides a chlorine residual of 0.5 mg/L that can ensure that rainwater on the roof surface is protected from recontamination.

*'''Chlorine Pump:''' Provides a chlorine residual of 0.5 mg/L that can ensure that rainwater on the roof surface is protected from recontamination.

It is important to note that chlorination only occurs when the roof water’s chlorine residual drops below 0.5 mg/L, at which water is passed through a chlorination unit and directed back to the filters. This recirculation system was not included in the original SBR design, but its inclusion will ensure that the ponding of water on the roof does not present any water quality and human health concerns. CVC has engaged Toronto Metropolitan University (TMU) to research the water quality of the SBR (among other research areas). Hopefully, this research will demonstrate that rooftop treatment is not required and that treatment before final distribution is sufficient.

It is important to note that chlorination only occurs when the roof water’s chlorine residual drops below 0.5 mg/L, at which water is passed through a chlorination unit and directed back to the filters. This recirculation system was not included in the original SBR design, but its inclusion will ensure that the ponding of water on the roof does not present any water quality and human health concerns.

=='''Station 4 – Basement Cistern and Treatment System'''==

=='''Station 4 – Basement Cistern and Treatment System'''==

*'''Settling Tanks:''' Allow any sediment that is suspended in the rainwater drained from the roof to settle out before rainwater enters the cistern. Three (3) settling tanks are present.

*'''Settling Tanks:''' Allow any sediment that is suspended in the rainwater drained from the roof to settle out before rainwater enters the cistern. Three (3) settling tanks are present.

*'''Rainwater Cistern:''' Has capacity for up to 5,000 L of rainwater. This cistern holds water that will then be pumped through the CSA-compliant treatment system. After treatment, rainwater is used in Building A’s toilets.

*'''Rainwater Cistern:''' Has capacity for up to 5,000 L of rainwater. This cistern holds water that will then be pumped through the CSA-compliant treatment system. After treatment, rainwater is used in Building A’s toilets.

*'''Micron Filter:''' Removes any fine debris from the rainwater that was not settled out in the settling tanks. This filtration is important for removing impurities, eliminating odours, and ensuring debris does not impeded the efficacy of the UV treatment unit by blocking light. A filter pore size of 5 μm is used.

*'''Micron Filter:''' Removes any fine debris from the rainwater that was not settled out in the settling tanks. This filtration is important for removing impurities, eliminating odours, and ensuring debris does not impede the efficacy of the UV treatment unit by blocking light. Filter pore sizes of 100 μm and 5 μm are used.

*'''UV Lamp:''' Disinfects rainwater by sterilizing bacteria and viruses with UV radiation. Note that UV disinfection does not have any residual effect that can be harmful to humans or aquatic life. A dosage of 40 mJ/cm2 is administered.

*'''UV Lamp:''' Disinfects rainwater by sterilizing bacteria and viruses with UV radiation. Note that UV disinfection does not have any residual effect that can be harmful to humans or aquatic life. A dosage of 40 mJ/cm^2 is administered.

*'''Chlorine Pump:''' Provides a chlorine residual of 0.5 mg/L that can ensure that rainwater is protected from recontamination in the distribution line or when supplied to the toilets. Chlorination is not required for CSA compliance, but it was added for good measure.

*'''Chlorine Pump:''' Provides a chlorine residual of 0.5 mg/L that can ensure that rainwater is protected from recontamination in the distribution line or when supplied to the toilets. Chlorination is not required for CSA compliance, but it was added for good measure.

*'''Agitator:''' Mixes the newly introduced chlorine solution into the treated rainwater. This ensures that water is sufficiently mixed prior to being added to the greywater line.

*'''Agitator:''' Mixes the newly introduced chlorine solution into the treated rainwater. This ensures that water is sufficiently mixed prior to being added to the greywater line.

*'''Rooftop temperature Sensors:''' Measures the temperatures above the building and on the inside of the roof assembly (below the concrete roof slab). These sensors compare the heat gradient across the roof assembly where the SBR is located and where a conventional roof system remains. By doing so, the cooling benefit and energy savings of the SBR can be calculated.  

*'''Rooftop temperature Sensors:''' Measures the temperatures above the building and on the inside of the roof assembly (below the concrete roof slab). These sensors compare the heat gradient across the roof assembly where the SBR is located and where a conventional roof system remains. By doing so, the cooling benefit and energy savings of the SBR can be calculated.  

The data collected from these sensors is used to optimize rainwater use and quantify the SBR’s performance. An example of this optimization is the decision to prioritize treatment and distribution or the evaporative cooling benefits of the SBR. This decision is based on the atmospheric temperature outside of Building A. These are the details of the two (2) temperature scenarios:

The data collected from these sensors is used to optimize rainwater use and quantify the SBR’s performance. An example of a possible optimization scenario is the decision to prioritize treatment and distribution or the evaporative cooling benefits of the SBR based on atmospheric temperature. This decision is based on the atmospheric temperature outside of Building A. These are the details of the two (2) temperature scenarios:

*'''External Temperature Below 20°C:''' Priority is placed on ensuring the cistern is filled with enough rainwater to supply toilets. Roof surface readily drains roof water to the basement.  

*'''External Temperature Below 20°C:''' Priority is placed on ensuring the cistern is filled with enough rainwater to supply toilets. Roof surface readily drains roof water to the basement.  

*'''External Temperature Above 20°C:''' Priority is placed on maximizing evaporative cooling benefits. Rainwater depth on the roof is maximized and rainwater is not drained to the basement cistern. If the basement cistern is empty, municipal water is used in the toilets.

*'''External Temperature Above 20°C:''' Priority is placed on maximizing evaporative cooling benefits. Rainwater depth on the roof is maximized and rainwater is not drained to the basement cistern. If the basement cistern is empty, municipal water is used in the toilets.

 

Data is transmitted to the PLC from the various sensors, and these data streams are uploaded to CVC’s existing WISKI database to calculate key performance indicators (KPI’s). Some of the KPI’s for the SBR include the following:

Data is transmitted to the PLC from the various sensors, and these data streams are uploaded to CVC’s existing WISKI database to calculate key performance indicators (KPI’s). Some of the KPI’s for the SBR include the following:

*'''Total Volume of Stormwater Managed:''' Calculated as the amount of rainwater that is supplied to toilets or evaporated. Managed stormwater does not have the opportunity to contribute to flooding or erosion.

*'''Total Volume of Stormwater Managed:''' Calculated as the amount of rainwater that is supplied to toilets or evaporated. Managed stormwater does not have the opportunity to contribute to flooding or erosion.

*'''Net Energy Savings:''' The sum of energy savings through evaporative cooling and energy savings from avoiding the need to treat and distribute water from Lake Ontario for use in Building A. This amount considers the energy demands of the in-house treatment systems.

*'''Net Energy Savings:''' The sum of energy savings through evaporative cooling and energy savings from avoiding the need to treat and distribute water from Lake Ontario for use in Building A. This amount considers the energy demands of the in-house treatment systems.

*'''Emissions Prevented by Reduced Potable Water Demand:''' Greenhouse gas emission reductions due to a lowered need for electricity in the City of Mississauga’s water treatment system.  

*'''Emissions Prevented by Reduced Potable Water Demand:''' Greenhouse gas emission reductions due to a lowered need for electricity in the Region of Peel’s water treatment system.  

These KPI’s, and others, will be important metrics for quantifying the benefits of CVC’s SBR. With the information gained from this implementation study, the potential of this emerging technology can be understood by others. Through knowledge dissemination, CVC aims to showcase SBR technology as an effective and feasible stormwater management and water conservation solution.

These KPI’s, and others, will be important metrics for quantifying the benefits of CVC’s SBR. With the information gained from this implementation study, the potential of this emerging technology can be understood by others. Through knowledge dissemination, CVC aims to showcase SBR technology as an effective and feasible stormwater management and water conservation solution.