Fall 2009 CRYOFRONT Column

Page 1

Cryofront: News and Views from the Far North

The continuing opportunity for on-site wastewater recycling in the far north By Ken Johnson, NTWWA Director

At the turn of the millennium,

land development. Development cost charges per lot, including roads and drainage, in the City of Yellowknife, may exceed $90,000 using traditional buried water and sewer services with freeze protection. The use of on-site wastewater treatment is not new in its application, and has provided a means for cost effective development in a rural southern context for many decades. However, innovations with on-site wastewater treatment in the late 1990s extended the application of this technology into an urban setting, and into the specialized application of on-site wastewater recycling. Wastewater

wastewater recycling was a hot topic in the land of the cold. For a variety of reasons, the interest in the technology dropped off. However a renewed interest in wastewater recycling is developing with the involvement of municipal and federal governments. Within the City of Yellowknife and elsewhere in the Canadian North, the climate, surficial bedrock, permafrost and soil conditions pose special problems for land development. The use of conventional water and sewer servicing technology with freeze protection adds significantly to the cost of

Potable water use (includes: bathtub faucet, kitchen sink faucet, bathroom faucet & shower head)

Potable Water Supply

Non potable water use (includes: toilet & washing machine) Control valve normally open to septic tank

Potable Water Storage

Septic Tank

Sewage Tank

Treatment Units

Residuals from treatment process

28 | Western Canada Water | Fall 2009

Non Potable Water Storage

Excess non potable water (removal or seasonal outside use)

recycling may reuse approximately 55% of the wastewater stream for non-potable water uses such as toilets and laundry. On-site wastewater recycling still appears to be an emerging technology even in a warm region context, with only a limited number of systems having actually been applied in a full scale application. Based upon a study undertaken by the City of Yellowknife a decade ago, systems were identified that have potential application to on-site wastewater recycling in the Canadian North. The top rated systems at the time had already been applied to on-site wastewater recycling; however, the systems had not achieved an approved operational status for a residential application. One system was progressing toward an approved operational status through trial operations in N’Dilo, NWT (near Yellowknife), however this system did not advance beyond a pilot scale. The application of an on-site wastewater recycling system to a new development offers the opportunity to incorporate the plumbing requirements, space requirements, structural requirements, electrical requirements, and operation and maintenance requirements as an integral part of the building design for a single unit. The most critical part of the single unit is the plumbing, which must ensure a separation of the potable and non-potable water supply systems, and provide no opportunity for cross-connection between the systems. The most significant part of the incorporation of the system is the space requirement, which would be expected to be in the range of 10 square metres (4 metres X 2.5 metres) for a single unit within a household. Large scale and universal application of on-site wastewater recycling technology may not influence the typical subdivision design. However, without the need to consider the

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installation of a sewage collection system and a water distribution system, there is a greater potential for innovation in site planning and development phasing. New regulations will be required to implement on-site wastewater recycling in the north. The practical responsibilities for on-site wastewater recycling should remain with the homeowner in regard to compliance with regulations, and with the Territorial Government for establishing and maintaining the regulations to compliment the Territorial Public Health Act. Based upon preliminary cost estimates in the Yellowknife study, an on-site wastewater recycling system may offer a significant cost saving in an application to a typical residential development. A life cycle cost estimate (20 years – 4% net interest) suggests that the cost savings in comparison to a piped system may be approaching 40%; however, these numbers must be tempered with the fact that they reflect the potential production scale cost of the technology, and not the experimental scale of the technology. Although the system may prove to be cost effective and technically appropriate in the future, the implementation will require a marketing effort to gain public acceptance.

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Ken Johnson is a consulting engineer and planner, a jazz enthusiast, and a “cool guy” by virtue of the fact that he has been working in the far north for over 20 years. He may be reached at ken.johnson@cryofront.com.

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Fall 2009 | Western Canada Water | 29


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