Softening Tank.
Water Softening Tank
The open trough carrying lime water leads into to a pipe which
ends in a circular weir directly above the large bell-mouth pipe through which
the raw water from underground entered the softening tank. This arrangement
gave a very fast and thorough mixing of the lime water and hard water. The
combined waters then had to flow through arched openings at the bottom of a
baffle wall which partitioned off the water mixing part of the softening tank,
into the main part of the tank.
The water slowly passed through the tank and
over the wall at the far end into a flill depth compartment adjacent to the
filters. From this compartment, water flowed to the filters through pipes and
valves so that the supply to any filter could be controlled. It was in the
main part of the tank that the actual softening of the water took place. Some
of the particles settled to the bottom of the large tank as sludge but most
were carried over to the filters and removed there.
It was necessary occasionally to remove the 'sludge' in the bottom of the softening
tank, which had to be done quickly as pumping from underground had to stop
while it was done. After making sure that the service reservoirs were full,
the water was let out of the softening tank, and staff with shovels, brooms
and hoses went in and swept the sludge out through the sludge drain to the
clarifying tanks on the north side of Hazeley Road.
Sludge Disposal.
To complete the story of water softening, there is the part of
the waterworks north of Hazeley Road. It was here that the sludge from the
cleaning of the softening tank and the filter tanks was dealt with.
The sludge,
which looked like a white slurry, was led into two clarifier tanks, only one
of which is now visible. The tanks allowed sludge to settle to the bottom of
the tank and the now clear water on top emptied into the drains, the thickened
sludge was pumped to a settlement area by a pump housed in the existing small
wooden hut.
There the sludge was directed into shallow lagoons to dry out, the banks of
the lagoons were built up as the dried sludge filled them, so that the area
was continuously rising.
The settlement area is now the high bank behind the
clarifier tank and sludge pump house, which since lime softening ceased, has
become overgrown with trees. Some commercial use was found for the sludge,
for some time a firm purchased some of it as a base for toothpaste.
Some was
also used in agriculture for land treatment. Although the same substance (calcium
carbonate) as chalk, the sludge was never successfuly recycled,
