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In a joint project of the
Municipality of Lo Barnechea and the International Development Research
Centre of Canada, the Faculty of Physical Sciences and Mathematics of the
University of Chile conducted the Technical and Economic
Pre-feasibility Study for Treatment and Reuse of Wastewater in the Eastern
Sector of Santiago for Irrigation.
The need to recover water
for irrigation was caused by the damage affecting the community during the
drought period in that area, which became even worse in the summer of
1997. The study compiled press releases revealing the impact of the
drought and the deep concern at different levels of the community.
The system took into
consideration the irrigation of 700 hectares in the highlands of Lo
Barnechea that require irrigation during the summer (0.5
L/second/hectare) equivalent to an average daily load of 350 L/s. The
quality of the water for gardens and school yards was adopted according to
the California State standard of 2,2 Coliformes/100 mL, with an absent
ecotoxicity evaluated for grass and ornamental plants. This water
quality guarantees –from the point of view of human and plant
health—that irrigation of gardens and fields will be safe. The private
economic evaluation of investments and operation costs resulted in an investment
of $2.656 million for a flat rate of $73/m3 and economic
results obtained guarantee its sustainability. The rate of $73/m3 is
favourably compared with the alternative of watering with potable water.
The design foresaw roofed
process units that could be set up in harmony with the urban areas of Lo
Barnechea and open air facilities that could be used for sports or
other recreational activities. At the same time, an enclosed facility will
not produce offensive odours to the community in case of operational
failures.
Two commercial treatment
technologies that use reduced space were analysed and investment and
operation costs were determined. After a private economic evaluation, the MSBR
System proved more convenient.
The investment of the treatment
plant using the chosen technology for a load of 350 L/s is of $2.348
million. This allows the activity to be performed with attractive
economic parameters for a rate over $68/m3. The treatment plant
will be located on the bank of the Mapocho River, at present occupied by
sports fields.
The legal report of
the study concluded that the irrigation system should operate through a private,
non-profit corporation that has the authorisation to distribute
irrigation water or by a private enterprise that becomes in charge
through a legal tender. The Municipality would provide the
necessary land through agreement for the installations required.
Therefore, the Municipality must participate as an active member as it
also requires irrigation water to maintain its green areas.
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