Scientists to CRD: petition the feds for reclassification
By Jay Cullen, Chris Garrett, Jack Littlepage, Rob Macdonald, Tim Parsons, Tom Pedersen, Vera Pospelova, Rick Thomson, Diana Varela, Michael Whiticar, December 2015
Marine scientists plead for an evidence-based approach to developing sewage treatment for Victoria.
We thank Focus reader Rick Weatherill for joining the discussion of the marine impacts of Victoria’s wastewater discharges, particularly for raising the important issues of “non-biodegradable plastics, heavy metals, pharmaceuticals, and other chemicals such as sunblock.” [See Weatherill’s letter in Focus, November 2015.]
Before discussing these specific wastewater components, we would like to stress that, as marine scientists who also enjoy local waters for recreation and appreciate their value to local commerce, we certainly would not wish society to continue on with practices that can harm the marine environment.
We are not necessarily against land-based sewage treatment, but would like to see a rigorous and quantitative evaluation of real or potential problems. That evaluation should consider targeted and cost-effective remedies, where advisable, in preference to expensive and elaborate schemes that might not even address the problems and would also create significant impacts on land. An overall cost-benefit analysis of proposed schemes is clearly needed. However, our main point is that, even if all we care about is protecting the marine environment, regardless of cost or impacts elsewhere, the marine impacts of the present system are small enough that land-based treatment is a low priority for marine environmental protection in the greater Victoria region.
Most readers are probably aware that the discharges at Clover Point and Macaulay Point pass through 6mm screens that remove anything larger than a pea (below left). In addition, most of the remaining oil, grease and other floatables then rise to the surface of a settling tank and are skimmed off (below middle). The resulting wastewater, which really resembles a thin grey soup, is pumped down a pipe over 1 km long at each location and discharged in water of 60m or 65m depth via a number of ports that ensure rapid mixing with the seawater (below right).
The effects on the marine environment within a few hundred metres of the outfalls are described in the annual reports published by the CRD (www.crd.bc.ca/about/document-library/documents/annual-reports/environmen...). The sea floor is affected within a couple of hundred metres of each outfall, but the ecosystems there are still rich and thriving even if different from those farther away, in much the same way that a home gardener’s compost pile differs from the rest of the garden. While much of the suspended organic matter settles out near the outfalls, particularly at the Macaulay Point outfall, some is carried away by the strong currents and may be deposited elsewhere, but at a rate that is estimated to be no more than a few percent of the downward rain of organic matter from natural marine processes. All this organic matter is rapidly incorporated into the ecosystem and supports a large and varied population of marine organisms.
The inputs of organic matter and nutrients can lead to low oxygen levels and dead zones in more confined waters and are a main reason for land-based treatment in such places. These inputs are not an issue here, however, due to powerful currents that rapidly disperse the effluent and generate turbulence that maintains the high oxygen levels in the water. Moreover, the local waters are already rich in nutrients due to the deep inflow of offshore Pacific water into the Salish Sea and the mixing of this water up into the sunlit zone, fuelling our wonderfully rich ecosystem.
The federally-mandated secondary treatment would, in large part, remove organic material that is of little consequence locally. To be sure, such treatment would also remove some contaminants of possible concern that are attached to the organic material, but the removal efficiency varies greatly from one contaminant to another. Many contaminants would still be discharged to a considerable extent through new and existing outfalls with effects that require further evaluation. The reader is right to be concerned about the items he lists, whether we have secondary treatment or not.
As many readers are probably aware, the impact of plastics on the oceans has become a matter of major concern. “Microplastics” and “nanoplastics” present a particular problem. Some of these come from the breakdown of larger pieces of plastic that cannot come from our wastewater discharges. But there is also global concern about very small plastic particles that originate as “microbeads” in various cosmetic and other products and in the form of “microfibers” from washing clothes made of synthetic material. Many of these very small pieces of non-biodegradable material would pass straight through the secondary sewage treatment mandated by the federal government. They could perhaps be removed by appropriate tertiary treatment, but could be controlled very much more cheaply and effectively by banning the use of microbeads in consumer products and by developing appropriate filters for washing machines. Source control, as adopted by the CRD in recent decades for many other substances, is very effective in reducing or eliminating potential environmental impact and avoiding the need for heavy-handed and expensive treatments that may not even address real issues.
The reader’s second concern was with metals. Scientists at the CRD monitor the concentration in sediments near the outfalls of metals such as lead, copper and mercury. The levels of some metals are indeed higher within 100 metres or so of the outfalls than at reference stations farther away. However, much of the metal is in chemical forms that are not available for biological uptake. Although the sediment contamination is an indication of potential effects, the abundance of marine organisms near the outfalls suggests that the actual effects are small. The mercury may be a residue of discharges from dentists’ offices, now reduced by source control. Some of the lead may have come from historical use of leaded gasoline and some of the lead, copper and zinc from past mining activities within the Strait of Georgia. Some copper and lead may still enter the sewage system from leaching of old domestic water pipes. Sewage treatment does not destroy metals. Many metals will be concentrated in the sludge. If this is disposed of on land, these metals may be remobilized into soluble chemical forms and contaminate surface and ground water.
Numerous pharmaceutical compounds are present in sewage, with some discussion in CRD studies as well as in the 2006 SETAC report. These compounds require discussion one by one, to determine which are likely to present problems in the marine environment and which would be removed or degraded in secondary treatment. One of the pharmaceuticals of greatest concern at present is 17alpha-ethinyl estradiol (EE2), a synthetic estrogen used in contraceptive pills and hormone replacement therapy. Concentrations in undiluted or even treated wastewater, while only a few parts per trillion, appear to be high enough to cause problems in larval fish, at least in freshwater. The huge dilution with our present system, by many hundredfold for dissolved substances, followed by gradual degradation, make it very unlikely that EE2 is of concern locally or that we are contributing to global contamination. The same is generally true of most other soluble compounds, though we should remain alert to possible problems and be prepared to address them appropriately. Insoluble compounds may become attached to organic particles and be deposited on the sea floor to degrade there or be buried.
For toxic compounds that are soluble, the much-criticized saying that “dilution is the solution to pollution” is valid, if the substance of concern becomes diluted below toxic thresholds and then degrades. The substances that do matter are the persistent organic pollutants (POPs) that degrade very slowly and so gradually accumulate in the environment and may even build up in the marine food chain. PCBs were an example of this sort of chemical. Their use was prohibited in the 1970s but they continue to circulate in the global environment, with concentrations in marine mammals, for example, only slowly declining. In light of the experience with PCBs, governments were unwise to allow the use of various polybrominated biphenyl ethers (PBDEs) as flame retardants in furnishings and other products. Their use is also now being banned, but concentrations may continue to increase for a while. Wastewater is presently an important route to the ocean but sewage treatment is only partly effective, and transferring PBDEs in more concentrated form to sludge might have more serious impacts.
The reader also expresses concern over sunblock. Some types of sunblock have been found to affect corals in areas where swimmers have applied the material liberally before visiting the coral reefs, but we do not have similar situations locally. If components of sunblock do enter local waters, either from recreational activities or in the wastewater, the extreme dilution by strong currents and subsequent degradation make it unlikely that these components will pose a problem for the marine environment, though it might need attention in our lakes.
Let us, by all means, devote more resources to marine environmental protection. But first, let’s identify what matters most. Land based sewage treatment for the Victoria region is not time-critical and is low on our shopping list. At the very least, we urge the CRD to petition the federal government to reclassify Victoria’s discharges as medium or low risk, with treatment deadlines of 2030 and 2040 respectively, rather than (as is now the case) high risk requiring treatment by 2020. That way we would have time for the rational, quantitative, evaluation of potential problems and their solution if necessary, rather than rushing into expensive treatment systems that would largely address non-problems. Many of the investigations that would clarify the nature of potential problems, small though these problems are likely to be, could have been carried out for a small fraction of the cost of failed proposals and the associated public relations campaigns.
We also urge concerned members of the public to read the annual reports published by the CRD based on the excellent monitoring and analysis programmes of CRD scientists, and perhaps even request a visit to the easily accessible pumping station at Clover Point.
Jay Cullen, Chris Garrett, Jack Littlepage, Rob Macdonald, Tim Parsons, Tom Pedersen, Vera Pospelova, Rick Thomson, Diana Varela, Michael Whiticar. The above are all current, former, or adjunct professors of marine science, Tim Parsons at UBC and the rest at UVic.