New: Greater Vancouver Covid-19 Virus in Wastewater:
Lulu Isld:
Dec 20: 47,219
Jan 5: 803,923 (17x)
Iona:
Dec 20: 40,060
Jan 5: 332,835 (8x)
Lions Gate:
Dec 20: 27,064
Jan 5: 304,426 (11x)
Annacis:
Dec 20: 37,117
Jan 5: 694,718 (19x)
metrovancouver.org/services/liqui…
@vb_jens #Covid19BC
Not sure of factors that can influence wastewater Covid-19 virus concentration (eg freezing vs snowmelt conditions?)
Map of wastewater treatment plants in Greater Vancouver
Now correlate with BCCDC Reported Cases for Vancouver Coastal health ..
in 16 days wastewater Covid virus concentration increased up to 19x in greater Vancouver. doubling time ∼4 days. (uncertain impact of regional precipitation / snowmelt pattern).
During same period VCH reported case # unchanged/declined. One can estimate degree of under-reporting
Add Langley
Dec 20: 31,334
Jan 5: 300,700 (10x)
In city of Vancouver, parts of the city still have combined sewer system, where stormwater is combined in single pipe with wastewater from homes etc, carried to sewage treatment plant.
vancouver.ca/home-property-…
Also in Burnaby, parts of city still have legacy combined sewer system, where rain water also gets treated (and thus diluting Covid-19 virus concentration) burnaby.ca/services-and-p…
Between Jan 5-7:
Increasing mean temp to above freezing (melting snow)
Large increase in Total precipitation including rain.
Combined sewer system draining rainwater into sewage treatment plants -> Diluting virus concentration. climate.weather.gc.ca/climate_data/d…
Quick answer: Warming to > 0C + significant rainfall Jan 5-7 may have contributed to dilution of Covid-19 virus concentration in wastewater treatment plants in Greater Vancouver where there are still Combined Sewage system treating Home + Rain water.
Good on BCCDC to point out the snowmelt run-off in the situation report released today.
but we should predict the snowmelt run-off affects results in a "underestimation" kind of way. bccdc.ca/Health-Info-Si… #Covid19BC
Don't know why BCCDC bother putting the "daily cases" line in the graph knowing the % positivity rate was 30%+ and PCR testing was signficantly reduced since Dec 23 (VCH) and Dec 30 (FH).
One don't use known under-reported case trend to try to reach a narrative with waste water data.
One use wastewater data to try to understand how much undertesting there was.
Eg Iona island, cases 'dropped' ~Dec 20, coinciding with VCH switching away from PCR on Dec 23.
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