From Waste To Resource

August 20, 2009

Waste To Resource

Over the last few decades, when the words “Victoria” and “sewage” have been used together, it has usually been in reference to the debate on why one of Canada’s last major urban centres continues to discharge untreated wastewater into the marine environment.

This debate has been heated and emotional, on both sides of the issue. Ironically, the delay in moving to wastewater treatment may have been a blessing in disguise.

As planning now moves ahead, the region has the opportunity to look at wastewater management from a different point of view — not as a waste to dispose of, but as a resource to use.

In 2006 the Capital Regional District (CRD) embarked on a program to develop a wastewater management strategy for the Victoria area.

Associated Engineering, with CH2M Hill and Kerr Wood Leidal, developed a report entitled, “The Path Forward.” The team is now working on developing the CRD’s $1.2 billion wastewater management program.

Environmental factors have driven the change to viewing wastewater as a resource: earth’s resources are limited, so there is a need to reuse and recover them when possible. There is also the need for energy efficiency and reducing our carbon footprint.

Currently, sewage from the region is fine screened and then released into the open ocean at the Juan de Fuca Strait.

The opportunities for using wastewater as a recoverable resource fall into four main areas — energy from organic solids, wastewater heat energy, water reuse, and nutrient recovery.

Looking at wastewater management from a resource recovery approach can be coupled with how we look at overall urban water planning.

Traditional thinking in urban areas is to configure the wastewater management system as a centralized system, where wastewater is conveyed to a single large treatment plant, then the effluent is disposed of.

While some elements of resource recovery benefit from a larger scale, such as recovering energy from organic solids, other elements such as heat recovery or water reuse can be better achieved on a local basis.

Combining the benefits of both a centralized approach with decentralized elements can thus lead to a distributed or hybrid approach to wastewater management.

An example of this is to use an existing wastewater trunk system as the system’s “backbone.”

The decentralized plants can perform local heat recovery or water reuse, but then can be developed in the sewerage area with the “central” plant at the end of the sewerage system focused on wet weather flow management and energy recovery from the organic solids.

All of these opportunities have been influenced by technology changes in the wastewater industry. One major change has been the development of membrane based separation.

In this approach, the traditional secondary clarifier, which separates the solids from the treated liquid portion by gravity, is replaced by a membrane process.

Membrane separation allows not only an increase in treatment performance, but also a much smaller plant footprint.

Additionally, there have been significant improvements in technologies aimed at recovering energy from organic solids. And in the long term, there are promising developments in microbiological fuel cell technologies that perhaps will lead to the generation of hydrogen fuel from wastewater.

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