Iqaluit wastewater management and improvements

50 YEARS OF WASTEWATER MANAGEMENT AND IMPROVEMENTS IN IQALUIT, NUNAVUT Ken Johnson Glenn Prosko Stantec Consulting

In 1964, a water treatment plant was constructed beside Lake Geraldine above the community of Frobisher Bay. This facility set the stage for "modern" water and sanitation facilities in the community, and what has become an infrastructure quandary for the community of Frobisher Bay, now the City of Iqaluit.

The wastewater treatment facility in Iqaluit is situated at the head of Koojesse, Inlet, beside a primary sewage lagoon that was used for many years.

Directly to the Ocean At the discharge end of the water system in 1964, the sanitary sewer outfall consisted of a five pipe system that discharged raw sewage directly from a gravity collection system into the salt water of Koojesse Inlet. The community has lead the way in many circumstances with innovation and leadership in advancing "standards and criteria" for water and sanitation systems in the far north. At the same time, the community has been at the mercy of a variety of circumstances that have placed the community many steps behind in elements of the infrastructure expectations for a regional centre, now the capital city of Nunavut.

The shoreline discharge of raw sewage was maintained for the next dozen years

until the construction of several lift stations provided the means to pump the sewage to macerator system at the head of Koojesse Inlet. The macerator technology was constructed at 6 sites across the Northwest Territories (NWT and Nunavut), and ultimately the technology failed at all of the locations.

The formal explanation for the failure was "vortexing problems with the bagged sewage in the hopper", and the informal explanation was that the honey bags (plastic bags containing the sewage) were too strong and ultimately jammed the macerator.

The macerator experiment was probably the first experience that the communities of the north with "inappropriate" large scale water and sanitation technology.

Successful Lagoon Operation

Concurrent with the construction of the macerator station in Iqaluit was the construction of a holding pond built on the tidal plain at the head of Koojesse Inlet. The lagoon was created by the construction of two berms which connected the existing shoreline to an island.

This facility operated successfully for several decades, although several overflow and breaching events demanded improvements in the earth structures, and the perimeter drainage to the facility. The lagoon performed well as a primary treatment facility, with a continuous discharge, providing 10 to 15 days of detention time. The effluent quality from the lagoon systems varied significantly over the course of the year because the only process at work in the winter months was sedimentation, with biodegradation enhancing the process performance during the summer months.

Great Expectations Expectations for improvements in the primary treatment system prompted Iqaluit in the early 90's to retain a consultant to complete an engineering feasibility study for improving the wastewater treatment system. The initial scope of work included only the consideration of improving the sewage detention capabilities, with the expectation that this would improve upon the overall quality of the primary effluent.

This scope of work was expanded to include options for a mechanical treatment system; these options included a rotating biological contactor (RBC), an extended aeration system (EA) and a sequencing batch reactor (SBR). These options were evaluated against nine lagoon options, that included relocating the lagoon facility to other areas on the perimeter of the community. The highest rated scenario from a decision analysis evaluation was the construction of a new facility, consisting of a detention lagoon (primary treatment) west of the community, and the construction of an outfall into the deeper water of Koojesse Inlet; the capital cost of this option was estimated to be $5.7 million (1994 dollars). None of these options advanced beyond the feasibility stage.

A Design-Build Experience Regulatory pressure was placed upon Iqaluit to advance a system capable of producing secondary treatment effluent quality. Based upon a decision in 1997, a design build request for proposals was issued, and a proponent was selected to build a secondary sewage treatment facility. A designbuild contract was awarded in 1998, and the contractor selected a membrane bioreactor (MBR) process applying the Zeeweed membrane technology.

This facility operated successfully for several decades ‌

The inexperience of the design builder in northern wastewater treatment became evident by mid 1999.

Significant problems began to arise concerning the placement of concrete within the water retaining aeration basins. Upon filling the basins, major leakage was observed, in addition to deflections in the walls of the basins due to insufficient structural strength.

To effectively deal with the problem, Iqaluit suspended all construction activities, and retained the services of a third party structural engineer to complete the necessary structural investigations and make recommendations for remedial work.

Remedial work was completed, and the water retaining aeration basins were determined to be structurally sound and retain water.

At this point, the design builder effectively abandoned the project.

Iqaluit subsequently became aware of additional design and construction problems with the facility.

Evaluation of an Un-commissioned Facility An evaluation of the un-commissioned sewage treatment plant was completed in 2002, and included an accounting of all the electrical, instrumentation, mechanical, structural, and architectural equipment or features found within the plant, and comparing this to

the equipment and features presented in the design documents. This accounting identified significant deficiencies in both the design and construction.

These deficiencies were generally associated with the hydraulic capacity; process efficiency; overall durability against extreme cold weather conditions, and a corrosive plant environment. As well, the deficiencies were associated with the ability of plant personnel to operate and maintain a complex and highly automated facility in a safe, efficient, and practical manner.

The evaluation presented recommendations to replace, or modify, electrical, instrumentation, mechanical, and structural elements of the existing facility. In consultation with the Iqaluit, the remedial work was designed to utilize a conventional wastewater treatment process technology, and abandon the application of MBR technology.

Construction in 2005 provided preliminary and primary treatment to an MBR facility that was abandoned by a design build contractor.

Moving Forward with Secondary Treatment The move forward with remedial work was presented in a phased approach recognizing that the financial capacity of Iqaluit may dictate an incremental approach. As well, a phased approach recognized the efficiency of expanding the facility with the population increase in the community.

The design of the remedial work incorporated the existing structure and process equipment as much as possible, which was a hallmark feature of the work. A Phase 1 of the design proceeded to construction to complete a primary treatment system for a design population of 12,000. The treatment processes consisted of an auger screen from the original facility, and a primary screen (Salsnes Filter) housed in an addition to the original building envelope. This addition also provided a building envelope for the sewage lift station associated with the original work.

A Phase 2 of the work would include the design and construction of a secondary clarifier to match the hydraulic capacity of the aeration basins to be converted from the MBR process. The completion of new secondary clarifiers would provide for a fully functional secondary treatment plant capable handling the flow for a population of 8,000.

A future Phase 3 for the facility would include the design and construction of additional aeration basins with the hydraulic capacity for a population of 12,000. However, the available funding for the project accommodated only the completion of Phase 1, and Phase 2 was shelved for implementation in the future.

Eight years after completion of the Phase 1 work, the project is proceeding and the City of Iqaluit has retained Stantec to provide the cold regions engineering expertise for the completion of the feasibility phase of a secondary sewage treatment facility.

An important consideration for the facility is the influence of septage (trucked sewage) on the facility performance, which is still accounts for about 1/3 of the flow into the facility.

The feasibility stage of the project will make sure that “no stone is left unturned� regarding treatment alternatives, as the community embarks on the final chapter in a process that has been "in the works" for 20 years.

Septage (trucked) sewage) is currently dumped into the sewer system immediately upstream of the waste water treatment facility.