Organic Residuals,
Energy & Resource Recovery
Sludge & Biosolids Management
Wastewater sludge is an organic resource. Even sludge can play a part in resource recovery during the wastewater treatment process, helping to lower our greenhouse gas emissions and bring wastewater treatment closer to carbon neutral operations.
How is wastewater sludge treated?
The sludge we collect from primary and secondary treatment will contain a great deal of wastewater macro-contaminants. This sludge can be treated using a number of anaerobic processes. Such processes generate methane as a by-product, and with gas cleaning, this methane, then called biogas, can be sold to Terasen Gas or used for power generation as well as space and wastewater process heating.
Sludge produced by wastewater plants must be treated to Class A quality (free of pathogens), after which it will require proper disposal or reuse. Treated and dewatered sludge is called biosolids.
What could the CRD do with biosolids?
Our current plan for biosolids calls for a Biosolids Management Facility at either a site in the Upper Victoria Harbour or at Hartland Landfill. Any facility would incorporate processes to recover biogas, heat energy and electrical power. It would also produce biosolids suitable for further energy recovery in a waste-to-energy process.
2009 Results of our Evaluation
It's important to consider the management of biosolids and organic residuals with wastewater treatment and overall wastewater management. Potential exists to co-manage solid waste organics (food wastes) with wastewater biosolids, as these materials share a fundamental characteristic--they are both comprised primarily of the element carbon. Over the past months the CRD has developed and evaluated a variety of biosolids management strategies that consider various levels of solid waste management integration with wastewater management.
How were biosolids/organic residuals evaluated?
Biosolids and organic residuals strategies were looked at in light of energy recovery (e.g. to produce biomethane), as a beneficial reuse product (e.g. compost, coal substitute) or using some combination of these approaches. Integration of the wastewater and solid waste programs was another considered and the consulting team does not recommend the full integration of biosolids and solid waste. Four broad strategies were developed and evaluated, including:
- Strategy 1 - Maximum beneficial reuse
- Strategy 2 - Maximum integration and maximum energy recovery
- Strategy 3 - Separate digestion and balanced energy recovery / beneficial reuse
- Strategy 4 - No digestion and balanced energy recovery / beneficial reuse
Within these broad strategies a number of sub-strategies were developed to allow further investigation of specific elements within the strategies. In the end, a total of eight sub-strategies reflecting the four broad strategies were developed and evaluated.
Read the Household Organics Management Report (PDF 
), published in July 2010, which drafts a plan for organics management and collection in the Capital Region.
What was learned?
Evaluation of the strategies included:
- Carbon footprint analysis (CFA)
- Life-cycle analysis (LCA)
- Capital costs, operations and maintenance costs
- Revenue generated from saleable products
- Greenhouse gas emission costs/credits
The CFA and LCA findings were considering using the CRD's triple bottom line methodology, which takes into consideration the environmental, social, economic impacts of wastewater treatment.
What biosolids management strategy is the CRD considering?
Recommendations in the November 2009 Biosolids Management Report include the following.
- From 50-90% of biosolids product should be initially directed to a cement kiln as fuel
- Investigation into additional disposal methods, such as cement manufacturers, topsoil product blending, dried fertilizer product and mine reclamation.
- Partnership with academic institutions to explore and develop pilot programs, such as a biocell program, codigestion with food waste and gas recovery.