MATCHING WATER QUALITY TO TASK:
City of Guelph Transit Bus Wash Rainwater Harvesting Project
Guelph Transit is a municipally owned transit utility established by Council resolution on December 1, 1994. This utility provides people with mobility and access to employment, community resources, medical care, and recreational opportunities across Guelph with service continuing around the clock on a daily basis to meet the needs of the Guelph community. In 2013 Guelph Transit provided conventional and mobility services with over 6.9 million passenger boardings. Performance benchmarking has shown that Guelph carries more passengers per capita than most Canadian municipalities of similar size. These services are currently facilitated by Guelph Transit’s fleet of 73 low–floor conventional buses and 10 mobility vans.
The Guelph Transit Operations Centre is located at 170 Watson Road South, Guelph Ontario. With the last expansion of the Guelph Transit facility in the late 1980s, a bus wash system was built including a simple rinse water reuse system that captured final rinse water from each bus wash for use during the first rinse (requiring water of lesser quality) of subsequent buses.
However, due to continued odour and discolouration issues stemming from the limited treatment of reclaimed wastewater, this system was decommissioned in 2007 after efforts to remediate the problems were unsuccessful. From that period forward, buses have been washed through one–time use of potable water from the municipal supply without any water reclamation.
The City of Guelph strives to be a leader in water conservation and efficiency. As one of Canada’s largest communities reliant on a finite groundwater supply, our ability to reclaim precious water capacity through conservation initiatives offers the benefits of:
- reducing the environmental impact on our water resources;
- lessening water utility operational and capital investments while meeting the water needs of our growing community; and
- best positioning our community’s resiliency with respect to potential future impacts from climate change.
In an effort to reduce water usage associated with its municipal operations, the City of Guelph’s Water Services Department initiated a series of civic facility water use audits in 2009. These audits showed great potential for reducing water use associated with bus washing at the Guelph Transit facility through the implementation of a new bus wash water reclamation system. In the fall of 2010, Water Services retained Enviro-Stewards (engineering consultants) to evaluate the feasibility of this project and to perform detailed end–use monitoring of the existing bus wash process in an effort to combine an assessment of current water demands and the evaluation of technical solutions to reduce water and energy intensity at the Guelph Transit facility.
The objective of this Project was to reduce potable water consumption and wash chemical requirements at the current Guelph Transit facility through the integration of a Rain Water Harvesting System within its current bus wash process to supplement wash water needs. Furthermore this project endeavored to provide an innovative technological water conservation solution which could be replicated by other transit utilities in small/medium sized municipalities by best matching of water quality to water use task.
Key challenges of this project included:
- assessing storm water quality and quantity available for capture based on operations building physical attributes;
- defining optimal rainwater storage tank sizing based on natural precipitation yield, process water needs and the cost to implement storage options;
- design of raw rainwater treatment to address source water characteristics, manage history with workplace health and safety process concerns and reduce operational and maintenance costs experienced by end operator; and
- project affordability and maintaining a return on investment that would promote adoption of amongst other Ontario municipalities.
Based on the results of the on-site investigation and subsequent modelling carried out by Enviro-Stewards a water conservation program—including the installation of wash process spray nozzle retrofits and a complementary rainwater harvesting system to reduce the amount of municipal water currently used for bus washing—was implemented at the Guelph Transit Operations Centre. Rationale supporting the use of rainwater harvesting at this facility included:
- A large roof area for rainwater collection;
- Large floor space available for rainwater harvesting system infrastructure;
- Easy accessibility to the existing roof drainage piping;
- Opportunity to reduce bus wash chemical consumption; and
- An immediately available opportunity for rainwater use as final rinse water.
This rainwater harvesting system included the implementation of 13,500 litres of storage tank capacity for stormwater capture, and the employment of made in Ontario technology to automate the integration of rainwater captured into the current wash process.
Preliminary results of the Guelph Transit Bus Wash Rainwater Harvesting System include:
- 120,000 litres of rainwater captured over the first four months of operation, offsetting about one third of the municipal water normally required for the final rinse. Extrapolating this over one year, and using historical weather data as a guide, an estimated 480,000 litres of rainwater is expected to be used in place of municipal water annually.
- Replacement of nozzles with new, more efficient models has proven to be a simple, relatively low cost solution for water savings. Based on the data collected to date, the new nozzles have reduced overall bus wash water consumption by an estimated 25 per cent (1.9 million litres a year worth about $6,225 annually).
- Onsite capture of as much as 13,500 litres of stormwater per rain event, reducing stormwater surges to local infrastructure and reducing associated quantity and quality impacts to the environment and downstream water users.
Application for Ontario Municipalities
Ontario communities can benefit from the following lessons of this project:
- Small changes can make a big difference. By installing more efficient spray nozzles the bus wash process reduced water use by 25 per cent (or 1.9 million litres a year) with less than a year payback. Always seek to conserve first.
- Run-off can be a useful resource. With a changing climate, more frequent and intense rain events are anticipated to occur. By viewing stormwater as a resource, communities can come to assess opportunities for capture and use of this water source. By matching water quality to task it is possible to cost effectively reduce operational costs and impacts to the environment.
- Rain water can perform better than city water in certain applications. Rainwater is naturally soft and its use for final rinsing reduces the amount of spot remover used when buses are washed with municipal water (naturally hard).
- Site–based containment yields community benefit. Surge protection provided by onside storage tanks can reduce loadings on localized stormwater infrastructure during storm events. Beyond rainwater harvesting, the employment of site–based containment can provide benefit to areas of routine flooding in communities or other applications seeking to reduce servicing constraints on stormwater infrastructure.
- Size rainwater storage tank capacity correctly. By increasing rainwater storage you may be able to capture more rainwater during severe rain events but this excess storage will not see use all the time. It is important that modelling of precipitation, storm event yield, process water needs and tank cost be completed as part of rainwater system design to understand routine storage needs and the diminishing returns of storage which might only see use a few days a year.
Download Project (PDF file 2Mb) Bus Wash Rainwater Harvesting Project
Acknowledgements Project consultant: Enviro-Stewards Inc. Government partners: Ontario Ministry of the Environment and Climate Change, Walkerton Clean Water Centre. This project has received funding support from the Government of Ontario. Such support does not indicate endorsement by the Government of Ontario of the contents of this material.