— HOME & GARDEN
Where does our water go?

FOR MOST of us, once we flush a toilet, drain our dish-
washer or hose our car down in the driveway, whatever
happens to the water is pretty much a mystery.

Sewage, after all, isn’t generally
a subject that families cluster
together to discuss over the dinner
table.

But a few summers ago, Vic-
toria hit the cover of the New
York Times because of the outcry
over its raw sewage outfall into
the ocean and staff with the
Greater Vancouver Regional
District’s (GVRD) sewerage and
drainage system say the number of
public inquiries received at the of-
fice have risen dramatically.

The treatinent of our household
“wastewater has become a topic of
concern on the public’s en-
vironmental agenda, and people
want to Know what happens to
their water and how they, indi-
vidually, can help protect our
waterways.

This concern is relatively new,
even at the government level.
While Vancouver's first sewers
were built in the 1880s, it wasn’t
until the late ’50s and ’60s that
plants were built to actually treat
the wastes that were being spewed
into our surrounding water
bodies.

Today, however, the Lower
Mainland’s sewerage and drainage
system has four large treatment
facilities and one small one (a

. secondary wastewater facility in
Langley), serves 1.6 million resi-
dents with the help of 35 pumping
stations and 435 kilograms of
trunk interceptcr sewers, and
treats over 380 billion litres of
wastewater each year. |

From the largest to the smallest,
the four wastewater treatment
plants are the Iona Island plant
(opened in 1963), the Annacis

“Island plant (1975), the Lions
Gate plant at the north ead of the
Lions Gate Bridge (1959), and the
Lulu Island plant (1973).

These facilities accept waste

- from each of their ‘‘sewerage
areas’’ for treatment and disposal.

How your sewage
is treated

While the Annacis and Lulu
stand treatment plants are cur-
rently being upgraded to more en-
vironmentally sound secondary

By Peggy Trendell-Whittaker
Contributing Writer

treatment facilities — a $500 mil-
lion project that is part of a
seven-year, $1 billion sewerage
upgrading and expansion program
— all four main plants presently
offer primary treatment only.

The piants are ail located on the
lowest available ground to take
advantage of gravity in the collec-
tion of the raw sewage. As a
result, once the raw sewage has
been screened and cut into small
particles, it must be raised a
number of metres to the ‘‘in-
fluent’’ channel that will transport
it to pre-aeration tanks.

In the pre-aeration tanks, air is
introduced to replenish the oxygen
that the water has lost through the

naturally occurring biochernical.

reactions taking place.

In a primary treatment facility,
the oxygen demand of raw sewage
is reduced by about 35%, while
the upgraded secondary facilities
are expected to return the effluent
to a state almost approaching that
of river-water composition,

The manner in which the air is
injected into the pre-aeration tank
creates a rolling action that settles
“‘grit.”? such as sand and coffee
grounds, from the rest of the
sewage. The grit is removed from
the aeration tanks and buried.

**Scum,’” consisting of
floatables such as plastic bags and
household grease, is aiso removed
and similarly disposed of.

The remaining organic sludge is
then settled out in sedimentation
tanks, thickened and sent to
digesters where it is Processed,
destroying disease-causing
bacteria, reducing the sludge vol-
ume by about 50%, and produc-
ing methane gas.

This methane gas, believe it or
not, saves taxpayers hundreds of
thousands of dollars each year, as
it is used extensively to generate
electrical and mechanical power at
three of the plants.

What happens to the sludge

next depends on the trestment fa-"

cility.

At Lions Gate, sludge is
pumped into the ocean on the
outgoing tides from Burrard Inlet.
This plant, however, is currently
undergoing an upgrade that will
enable it to remove the water
from the sludge, which can then
be used as soii conditioner.

At Lulu Island, sludge and the
“scum’’ from the sedimentation
tanks are incinerated, and the
resulting ash is buried on site.

At the Iona and Annacis Island
facilities, slidge is pumped to
lagoons near the plants. Each day,
about 15 truckloads of sludge —
60 tonnes of dry weight solids —
are produced in the Lower
Mainland, and engineers are
working hard to find practical
applications for the high-nutrient,
nitrogen-rich substance.

In 1989, the University of Brit-
ish Columbia’s (UBC) Forest
Sciences Department teamed up
with the GVRD to research the

use of sewage sludge as an organic ©

forest fertilizer.

Similar experiments throughout
the world have produced dramatic
tree growth, and the UBC project
at the Malcolm Knapp Research
Forest in Maple Ridge is also hav-
ing good results.

‘‘Nutrifor’’ sewage-sludge fer-
tilizer is expected to enhance the
forest industry in B.C., as well as
provide an excellent organic addi-
tion to municipal landscaping,
golf courses, landfills and other
areas where fast-growing cover is
desirable.

The Malcolm Knapp Research
Forest is open to the public from
8 a.m. to 4 p.m. year-round:

Meanwhile, back at the treat-
ment plants, there is still the re-
maining effluent to be pumped in-
to the Burrard Iniet in the case of
the Lions Gate plant, the Georgia
Strait if it’s coming from the Iona
plant, or the Fraser River in the
case of the Lulu and Annacis
Island facilities.

Over the summer months, the

effluent is treated with chlorine to
ensure coliform or other
pathogenic bacteria are destroyed.
This helps keep waterways safe
for swimmers.
An excerpt from In Our
Backyard: A Vancouver En-
vironmental Guide by Peggy
Trendeil-Whittaker, published by
Whitecap Books, $8.95.

NOVEMBER 11-15

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Piease ask your children to send us their
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