Stream N: Water and Wastewater Residuals Management


14.1 Biosolids beneficial use – The greening of old gravel pits

14.2 Innovative use of biological phytoremediation systems for treatment of landfill leachate

14.3 Improved, energy efficient sludge digestion at the Greater Nanaimo pollution control centre



14.1 Biosolids beneficial use – The greening of old gravel pits

Presented By: Rene-Carl Dionne, SYLVIS Environmental Inc.
Time: Tuesday, 2:00 - 2:30 PM

The British Columbia (BC) Ministry of Transportation and Infrastructure (MoTI) operates aggregate pits located throughout the province. These pits provide materials used for road construction and maintenance activities. Many of these pits are no longer being used and require reclamation. In many cases, traditional methods have failed to maintain vegetation cover resulting in sub-standard reclamation outcomes.

These sites are well suited for biosolids, as applications provide a large influx of organic matter and nutrients released over several years, stimulating soil development, which will enable a sustainable reclamation.These pits offer multiple operational advantages for biosolids reclamation, particularly with respect to accessibility, and distance from sensitive features.

In December 2010, the first load of Regional District of Central Okanagan biosolids was delivered to Bob's Lake pit. Deliveries continued until applications, which started in October 2011, before being diverted to Pennask Pit. Since then, over 22,000 bulk tonnes of biosolids originating from six different plants have been delivered to four different pits in the BC Interior. These pits generally offer a flat and bare ground surface ideal for applications; however, operational modifications are made in consideration of site-specific characteristics.

Building on the success of this program, other MoTI pits are being considered for reclamation using biosolids. Each new site has specific operational and logistical challenges based on location and current usage of the sites, which are often different from the original land use purpose.

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14.2 Innovative use of biological phytoremediation systems for treatment of landfill leachate

Presented By: Denis Matiichine, SYLVIS Environmental Inc.
Time: Tuesday, 2:30 - 3:00 PM

Landfill leachate is generated when precipitation percolates through the landfill and takes up the organic and inorganic constituents stored within. The resulting leachate contains elevated concentrations of constituents such as ammonia nitrogen and suspended solids that may potentially be deleterious if released to the environment. Leachate is generated during both the active phase of landfill operations and following closure, necessitating an ongoing, long-term leachate management strategy. SYLVIS has been working with Ecowaste on managing the leachate produced at the site through an innovative soil-plant phytoremediation system and a subsurface constructed wetland.

The soil-plant system consists of vegetated treatment plots that have been established deployed across closed cells of the landfill and irrigated with leachate. The fabricated soil, comprised of biosolids, sand and woodchips serves as a growing medium and retains chemical constituents, while the vegetation consisting of hybrid poplars, coppice willows and forage grasses assimilates nutrients and reduces the volume of leachate through evapotranspiration.

The primary function of the subsurface constructed wetland at Ecowaste is to reduce the concentrations of ammonia nitrogen and suspended solids in the leachate. The wetland consists of a vegetated pond, which utilizes wetland plants species for nutrient uptake, and a denitrification bed that utilizes a carbon source to support microbial denitrification processes.

For over eight years the soil-plant system has successfully treated the leachate at Ecowaste reducing the concentrations of key leachate constituents specified in the landfill's Operational Certificate to below discharge limits.

pdf icon Presentation PDF


14.3 Improved, energy efficient sludge digestion at the Greater Nanaimo pollution control centre

Presented By: David Lycon, AECOM.
Time: Tuesday, 3:00 - 3:30 PM

The Regional District of Nanaimo operates the Greater Nanaimo Pollution Control Centre, which provides chemically enhanced primary treatment for an average annual flow of approximately 35 ML/d. Their original sludge digestion process was comprised of two 1,840 cubic meter, gas mixed, floating roof, mesophilic digesters that were operated in series. Due to sludge stabilization capacity limitations, a new digester has been constructed.

The new digester is a 3,900 cubic meter, fixed roof, mesophilic digester that utilizes a linear motion mixing system. The LMM system is designed to mix the digester contents with a much reduced input of energy, relative to more conventional mixing systems. The new digester acts as the primary digester, with the two existing digesters performing as a secondary digester (flow through vessel) and sludge storage tank, respectively. The mixing system for the new digester is comprised of three individual linear motion mixers that have been designed to operate in series, using a "waffle" tank bottom design.

Since put into operation in the spring of 2013, the digestion process has worked well, with a noticeable increase in volatile solids destruction, relative to the pre-existing configuration. In an effort to establish the effectiveness of the mixing system, a lithium tracer study was conducted. This type of analysis is utilized to determine the active volume of the digester and to identify the presence of short circuiting. In addition to the lithium tracer analysis, computational fluid dynamic modeling was also undertaken to analyze the performance of the new mixing system.




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