Grey water re-use growing
- by Bruce Nagy
It is probably wise to be skeptical about the next big thing. But sometimes it is just common sense; like the coming move toward more grey water recycling, especially in cities.
The news is that there is little doubt that purple (grey water) piping will continue to grow as a source of revenue. The technology is pretty straightforward and reliable. Selling it or adding it should be easy during the next few years. Canadian mechanical contractors are reporting increasing requests for grey water-ready rough-ins or complete grey water recycling systems.
"Water bills are going up fast and a lot of builders are interested," reported Andrew Atchison of Atchison Plumbing & Heating Ltd. in London, Ontario.
Grey water systems for toilet flushing and below grade irrigation are being added to building codes across the country along with rainwater. Municipalities are taking a great interest in anything that controls potable water demand and sewage treatment volumes. Builder and TV personality John Bell talks about the addition of grey water systems to some 50,000 Ontario homes over the next eight years, as well as seven schools, which have recently incorporated the technology.
Water use was dramatically reduced at St. Cecilia Elementary School with a grey water recycling system.
The United Nations says fresh water per capita is in steep decline worldwide. In Canada we might think fresh water is abundant, but we are the fastest growing G8 country and we increasingly live in cities where crumbling infrastructure costs big money. Water is no longer 'free.'
According to the Alberta Water Research Institute our urban water infrastructure is generally more than 100 years old, leakage is about 25 percent, and repair budgets are far from keeping up. Cities have been forced to implement unpopular water rate increases as high as 10 percent per year. This is expected to continue for some time and still fall short of paying for needed upgrades. As our municipalities grow, they will need $31 billion to repair existing infrastructure and $57 billion to build more according to a report from the Federation of Canadian Municipalities. In addition, hydro companies are studying ways to reduce pumping costs.
Even in rural areas, weeping beds are not allowed in some places, according to Mike Tiffe, President of TAB Mechanical Inc. in Tyendinaga Mohawk Territory, Ontario. He recently worked on a cottage being converted to a permanent residence where a grey water recycling system helped alleviate holding tank pump-out concerns.
There are two pumping stations in the St. Cecilia system. The one of the left handles grey water and the other is for rainwater.
An elementary school application
The Brac water recovery system at St. Cecilia Elementary School in Vaughan (north Toronto) is an integration of two separate grey water recycling and rain water harvesting systems, which together supply toilet flushing and irrigation. Each system stores 6,600 litres.
Grey water guru Chris Thompson from Project Innovations Inc. in Barrie, Ont. explains that grey water is collected from hand sinks and water fountains and rainwater from the main roof section of the building. Wastewater from sinks and fountains travels below the floor in the boiler room to a lift station. Dual pumps move the water through pressure filters, then to a grey water storage tank buried outside. If the tank is full, the water is diverted to the sanitary sewer through an actuated three-way valve.
The controller uses pressure along with sensors in the tank to monitor water levels and determine required chlorination. A chlorination pump draws water through a foot valve in the tank and through a strainer on the pump station. This water is circulated through the chlorinator and then directed in sequence to two separate locations. First, the lift station receives freshly chlorinated water to maintain any new sitting water in the lift station and also to disinfect the pressure filters. Then, freshly chlorinated water is sent directly back to the tank to disinfect the stored water in the tank.
When one of the connected toilets is flushed, the drop in pressure triggers the main pump, which draws water through the foot valve, through the strainer and then sends it to the toilets until the demand has been met. A pressure tank, when charged, buffers the pump and reduces the amount of “pump starts” required to meet demand. This results in an energy saving because most of the power drawn by a pump occurs in the first few seconds of operation.
A dye dispenser injects incoming water with food grade blue dye to provide a visual indication that the water sent to the toilets is not suitable for drinking. It also provides visibility throughout the school when the source of available grey water is depleted. The system then calls for make-up rainwater to restore the tank to the preset level.
The level will be monitored and adjusted over the first year to determine the most efficient level, depending on usage and supply patterns. If the system reaches a low level or in the case of equipment or power failure, a spring return valve activates to provide city water to the toilets in bypass mode.
The rain water system is also used for irrigation during summer months. Rainwater enters the boiler room, travels through a strainer and filter then flows out to the storage tanks outside. As with the grey water system, a float switch triggers when the tank is full and closes an actuator valve, pushing surplus rainwater to the storm drain. Chlorine is used with rainwater, but blue dye is not. Water counters are also installed on both systems for water in and out, so total water savings can be monitored.