Keep it simple on sewage

Re: “New argument over sewage,” editorial, Jan. 16.

I have been involved for more than 20 years in the water- and wastewatertreatment industry for a multinational corporation examining innovative technologies, including technologies for managing biosolids. There is a well-established, simple way of maximizing the value of the biosolids.

The integrated resource management concept appears to be a desirable green approach to the biosolids problem. After all, generating electricity from biogas produces revenue. But it is not that simple.

The anaerobic digesters can be difficult to operate, and the biogas needs to have hydrogen sulfide and siloxanes removed to have trouble-free power generation. The investment costs are high. The operating costs will most likely exceed the value of the power generated.

In addition, a substantial quantity of biosolids will remain after the digestion process. At this point, the nitrogen and phosphorus nutrients have not been recovered.

The incineration of the biosolids is not environmentally friendly, since it produces CO2 and probably polluting gases such as nitrogen oxides and sulfur dioxide. The residual ash would have to be landfilled.

A better approach would be to avoid anaerobic digestion and to de-water the biosolids at the treatment plant. The Capital Regional District should find a composting site away from residential development for composting these biosolids along with food scraps and possibly yard waste. This site could be leased to a composting firm. In this way, the nutrients are largely captured and CO2 production is minimized.

William de Waal, PhD North Saanich