Western Canada Water magazine - Spring 2015

WESTERN CANADA

WATER

T H E O F F I C I A L M A G A Z I N E O F WAT E R P R O F E S S I O N A L S A C R O S S W E S T E R N C A N A D A SPRING 2015 | Volume 67 | Issue No. 1

Treatment Plant UPGRADING

PM 40065075 Return undeliverable Canadian addresses to: lauren@kelman.ca

Cover Photo: Iqaluit’s Wastewater Treatment Plant

TREATMENT PLANT UPGRADING

50 years of wastewater management and improvements in Iqaluit GLENN PROSKO, AND KEN JOHNSON, STANTEC CONSULTING, EDMONTON

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.

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 led 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 what was a regional centre, and is now a capital city.

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 a macerator system at the head of Koojesse Inlet. The macerator technology was constructed at six 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

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.

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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 ‘90s 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.

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

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

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 waterproof.

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

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

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 Iqaluit, a remedial work plan was developed to utilize a conventional wastewater treatment process technology, and abandon the application of MBR technology.

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. Phase 1 of the design

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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.

Phase 2 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 of 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 wastewater and 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 still accounts for about one-third 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.

Spring 2015

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TREATMENT PLANT UPGRADING

The wastewater treatment facility currently provides primary treatment, which discharges at the head of Koojesse Inlet. Work is proceeding to complete a secondary sewage treatment improvement to the facility.

TREATMENT PLANT UPGRADING

CRYOFRONT – News, Views and Muse from the Far North

Whitehorse’s LTECF – a showcase project KEN JOHNSON, STANTEC

Lagoons are the most common type of sewage treatment in Canada, and are often the treatment process of choice for small and medium sized communities because of their very low operating costs, and proven capability to achieve high quality effluent. This is particularly true for high latitudes where the costs and operational challenges of mechanical systems are magnified several times.

The City of Whitehorse used a four cell primary sewage lagoon system for many years, which provided appropriate technology for this community located at 60° 34’ North latitude and 135° 04’ West longitude in the Yukon Territory.

A new $20 million lagoon system, referred to as the Livingstone Trail Environmental Control Facility (LTECF), was constructed in 1996, which upgraded the sewage discharge to a secondary treatment quality (See Figure).

The most recent work on LTECF system was completed in 2009, with a $5.6 million improvement that created a surface discharge into the Yukon River. This was the first major work on this facility since work was completed on it in 1996.

The origins of the facility began in the late 1980s when regulatory demands for a higher quality effluent prompted the City to investigate options for achieving a secondary quality or better effluent.

A number of studies were completed in the late ‘80s and early ‘90s considering mechanical and lagoon systems. In the end, the terrain of an area to the north of the City, near what is called the Livingstone Trail, was able to accommodate a large lagoon system.

In 1994, the City of Whitehorse retained an engineering team led by the Stanley Consulting Group (now Stantec) that included D. Nairne and Associates and EBA Engineering, to complete the engineering work to serve the 18,000 people living in Whitehorse.

The LTECF includes two 115,000 cubic metre primary lagoons; four 290,000 cubic metre secondary lagoons following the contour of the area; and one 5.8 million cubic metre Long-Term Storage (LTS) lake, with a one-year retention time. The long-term storage

Lagoons are the most common type of sewage treatment in Canada, and are often the treatment process of choice for small and medium sized communities.

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area, a retention lake 3 km long and 2 km wide, can fill to a depth of six metres.

The facilities were constructed over a two-year period. The work also included clearing and extension of a forcemain from the old Whitehorse primary lagoons to the LTECF, and upgrading of the other facilities associated with the collection system. The completion of the work in 1996, allowed the City of Whitehorse to end the direct discharge of primary treated sewage effluent into the Yukon River. The total capital cost of the LTECF was approximately $20 million ($1996), which was a cost of about $1,100 per resident.

The initial design of the facility included a discharge structure from the

LTS for a seasonal discharge into the Yukon River. However with such a high quality effluent anticipated from the LTS, the City started considering an opportunity that would accommodate no direct discharge to the Yukon River. Adjacent to the LTS is a glacial pothole lake formation that lies 16 metres below the level of the surrounding lakes and less than a decimetre above the level of the Yukon River itself. The materials in between the pothole lake and the river are sands and gravels.

The City applied to the Yukon Territory Water Board to obtain an additional Class A water licence for a trial discharge of up to two million cubic metres of fully treated effluent into the pothole lake.

The discharge would gradually seep into the groundwater, along with other water from the lake, and very slowly make its way to the river. The trial discharge into Pothole Lake (PHL) was a success, and from the fall of 1998 to 2009, treated effluent was discharged from the LTS pond into the lake.

The utility of the PHL discharge diminished with time, and in 2008 the City tendered a design/build project for the construction of a direct discharge into the Yukon River from the LTS pond. One of the problems with the PHL discharge was the short time period, dictated by the water licence, when the City could discharge effluent into the lake.

This period was only 90 days from August and October. Even though approximately 3.5 million cubic metres of treated sewage was released into

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TREATMENT PLANT UPGRADING

PHL lake each year, this isn’t enough to completely empty the LTS pond.

As well, the exfiltration capacity of PHL was diminishing with time. This situation made the direct effluent discharge into the Yukon River an essential facility addition for the City of Whitehorse.

Mother Nature does most of the work in the lagoon system. In a typical July, the City receives approximately 256 hours of bright sunshine and has an average daily temperature of 14°C. During summer months the wind stirs the holding cells and puts oxygen into the system, helping microbes and natural chemical processes to break down the sewage contaminants in the warm summer temperatures. The only addition to the system is biological enzyme that enhances biodegradation.

The City is generally pleased with the operation of the facility. The effluent quality standard is 45 mg/L for BOD5 and 60 mg/L for suspended solids, and the effluent measurements from the LTS have been recorded to be less than the detection limits for the tests.

Fecal coliform levels in effluent from the

system may not exceed 2000 counts per 100 millilitres, and tests of the system have found fecal coliform counts ranging from less than 3 per 100 millilitres to a high of 240 per 100 millitres. The old system would discharge over 100,000 counts per 100 millilitres.

Almost 20 years after it was built, the Livingstone Trail Environmental Control Facility remains a showcase project, demonstrating the opportunity for a sewage lagoon system to produce a very high quality sewage effluent at high latitudes in Canada.

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Spring 2015

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