WCW Conference & Trade Show ▪ Winnipeg ▪ September 20 - 23 ▪ 2009
Sewage Composting in Iqaluit, Nunavut – Black Gold Ken Johnson Cortney McCracken AECOM ABSTRACT In the Canadian north, municipal sewage sludge has been virtually ignored because of the predominance of lagoon wastewater treatment systems. The application of mechanical sewage treatment systems in Nunavut, and an increased regulatory scrutiny over the past 15 years have created a demand for sewage sludge handling, treatment, and disposal. The City of Iqaluit, Nunavut has been working toward the implementation of a secondary sewage treatment system since 1998, and with it the need for sludge management. This is an ambitious goal for the community considering the inherent challenges to the design, construction and operation of facilities in the harsh arctic environment. Conventional municipal sewage treatment uses physical, chemical, and biological processes to separate solids and biological contaminants from municipal wastewater. Solids in the sludge are typically processed in a digester system, in which biodegradable materials are “digested” into stable organic matter. Sewage sludge may be further treated through dewatering, heat drying, alkaline (lime) stabilization, composting, or other processes. Freezing and thawing, as an efficient method of sewage sludge conditioning, has been used for many years in cold climates. The final separation is achieved when the “released” water drains away from the solids after thawing, leaving a porous sludge with solids content of 20 to 30%. Following this dewatering and drying process, composting may provide stabilization and destruction of pathogens. The composting process requires the addition of bulking materials such as wood chips and cardboard pieces. The City of Iqaluit landfill facility has been able to divert sewage biosolids from the first phase of the wastewater treatment plant. The process for the biosolids is to dry the solids throughout the long winter making use of Iqaluit’s cold dry weather, and compost the dried solids during the short warm summers to produce a cover material for the landfill. This process is attractive because the finished material is non-hazardous, and will reduce the use of precious granular material at the landfill - granular material may cost over $40 per cubic metre in Iqaluit. Managing sewage sludge through freeze-thaw-composting is not without its challenges, but the City of Iqaluit has successfully completed a pilot program. Where other municipalities take for granted the technologies available to them, the arctic must re-engineer the process to suit the environment.
WCW iqaluit paper KJohnson CMcCracken 090630 Page 1 of 11