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Table of Contents
Introduction
Acknowledgements
Executive
Summary
Local
Context
Ecological
Wastewater Overview
Ecological
Treatment in Cantarrana
Concept Plan
Appendices
Bibliography
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The
Cantarrana Prototype
Concept
Plan for an Incremental, Ecological Wastewater Treatment
In order to maximize
some of the benefits of Cantarrana’s physical, socio-political,
cultural and economic characteristics, we propose a system that
is low-cost, resource-efficient and low-maintenance while improving
water quality and human health. The system will also provide open
space and educational opportunities while potentially generating
jobs and economic revenues. Furthermore, the proposed system will
attempt to both integrate community concerns and provide a tangible
overall benefit to local residents. Finally, it will utilize existing
and potential financial and technical resources, both within and
outside Cuba. We refer to this incremental, ecological system as
the Cantarrana Prototype. This incremental, ecological system
emphasizes the inherent flexibility of ecological wastewater treatment
systems; the Cantarrana Prototype is designed to evolve over an
extended time period, providing greater levels of treatment as the
overall water quality of the Almendares watershed improves and the
community gains experience with the system.
The Cantarrana Prototype
is a phased, low-cost, adaptable ecological wastewater system for
Cantarrana and similar communities. The system features phased treatment
plans, both chronologically and geographically, in order to achieve
increasing levels of water quality as funding and resources become
available. Chronologically, the system evolves from constructed
wetlands to an improved sanitary sewer system to aquaculture, each
phase improving water quality on its own but most effectively when
applied together. Geographically, the system can provide treatment
to just one city block in order to demonstrate effectiveness, work
out design issues, or obtain funding before serving the rest of
the neighborhood. The phased development includes:
Phase
1: Santoyo Constructed Wetland
Phase
2: Addition of Settling Tanks
Phase
3: Direct Connection of Domestic Wastewater to Wetland
Phase
4: Outdoor Solar Aquatic System
Phase
5: Solar Aquatic System Integrated with Horticulture
Each phase is designed
to be expanded into the other phases with no or little retrofitting,
and can be developed as funding and time permits yet still provide
some improvements in water quality from the beginning. The proposed
project is adaptable enough so that site-specific choices may be
made in order to incorporate different designs or technologies if
applicable. Although we have designed this system for Cantarrana,
this incremental, ecological approach to wastewater treatment is
highly replicable in communities that share conditions found in
Cantarrana, including: unsewered, low to moderate density urban
settings, proximity to a river of creek and sufficient open space
along a creek or river.
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1: Santoyo Constructed Wetland
In the first phase of
the Cantarrana Prototype, all residential and industrial outfalls
remain the same as they are today, while a portion of water from
the Santoyo is diverted and treated by a series of channels and
ponds near the mouth of the creek (see Figure
27). The treatment system is a constructed wetland system using
ponds and dams to combine free water surface and horizontal subsurface
treatment types. Effluent flows through channels and ponds separated
by planted gravel dams, which filter out organic matter, BOD and
COD. Plants provide an aesthetic and functional amenity. Conveyance
channels follow the natural contours of the water channel, minimizing
regrading. The first phase of the Cantarrana Prototype provides
primary to secondary level treatment to both industrial and residential
waters flowing through the Santoyo. However, since diverting the
entire stream flow through the constructed wetland would probably
overload the system, the Cantarrana Prototype treats only a part
of the Santoyo’s flow. Periodic sampling of soils, plant material
and influent and effluent quality will provide valuable data on
the success of this system design and efficiency over time. Monitoring
will also help establish appropriate times for replacement of filter
media or harvesting of plants.
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| Benefits |
Limitations |
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Treatment of both
residential and industrial waste
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Follows natural grading
of water channel
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No energy requirements
beyond construction
- Little standing water
for mosquito breeding
- Lowest cost and resource
needs for implementation
- Minor maintenance
requirements: plants and gravel filters must be replaced every
10-20 years.
- Potential to integrate
public trails into the open space near the system
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- Probably not possible
to divert the entire stream flow through the constructed wetland,
so does not treat all the Santoyo’s water.
- Would occupy the
majority of open space within the community
- Initial labor requirements
— digging the channels and ponds, some regrading, etc.
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Phase
2: Addition of Settling Tanks
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The second phase adds settling
tanks at the end of the residential blocks along the Santoyo in conjunction
with the existing storm and sanitary system. Depending on existing
infrastructure and construction/maintenance preferences, one tank
could be situated at the end of each block nearest the creek, or several
smaller tanks could be distributed along each block (see
Section A-A in page 49). Implementation of this step can occur
in conjunction with Phase 1, or it can take place as a separate phase,
but it is absolutely necessary to have in place before moving forward
to any of the later phases.
Settling tanks, even
if put in place with no other treatment, could have a dramatic effect
on water quality by simply removing solids from the wastewater stream.
If at all possible, Cantarrana Prototype designers should add a
separate domestic wastewater system in conjunction with the construction
of settling tanks, rather than integrating them into the current
stormwater system. Otherwise, in periods of heavy rainfall, the
combined sewer system will overflow with little or no settling having
taken place. Also, depending on the quality of solids and tank system,
this system enables composting of solids for use as fertilizer,
or conversion to biogas through a high-tech reactor.
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| Benefits |
Limitations |
- Improved positive
impact on water quality
- Possibility for use
of biosolids for compost/biogas
- Removal of solids
will decrease odor within and nearby the wetland system
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- Requires substantial
additional capital investment in materials and labor, especially
if designers include a separate sewer pipe system.
- Operators will need
to pump tanks periodically, depending on the size and loading
of solids. This adds to maintenance requirements.
- Installation of tanks
and trenching for pipes will possibly inconvenience residents
/ factories
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Phase
3: Direct Connection of Domestic Wastewater to Wetland
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At this point, the settled
residential wastewater is directly linked to the wetland channel
that extends along the eastern bank of the Santoyo, up to the bridge
at Avenue 63. Simultaneously, phase 3 redirects the water originally
diverted from the Santoyo, back to its original channel, eliminating
the industrial inflow to the Cantarrana Prototype (see Section
D-D). This phase extends the sewer pipes that currently flow
directly into the river, so that they cross the Santoyo and connect
with the channel.
By directly connecting
the wetland system with the residential sewage pipes, this phase
further improves the quality of effluent. After separation of solids,
the Cantarrana Prototype system treats household wastewater much
more efficiently if it is piped directly into the wetland system
rather than diluted and mixed with the industrial and solid waste
contamination carried from further upstream. This addition to the
system would be cost-efficient, requiring little additional money
or labor for increased improvements in water quality over stages
1 or 2.
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Phase
4: Outdoor Solar Aquatic System
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This phase involves the
construction of a series of impermeable tanks or ponds that would
support a constructed food chain. Wastewater flows through the tanks
for primary settling, through the conveyance channel for minor settling
and aeration, then into the aquaculture tanks. Phase 4 integrates
tanks with the channels and existing ponds at the mouth of the Santoyo.
The food chain promotes the production of plants to be used as compost,
animal fodder, or crafts. Depending on community acceptance of such
nutrient recycling, hydroponic channels may be integrated in the
later stages to grow vegetables.
Although solar aquatic
systems are more expensive and complex to construct and maintain,
they offer maximum nutrient recycling potential, as well as opportunities
to generate food and revenue. However, artificial food chains are
delicate, and could be sensitive to the industrial contaminants
in the water, as well as to toxic household substances improperly
disposed of by the system’s users. A high amount of community
involvement, awareness and participation is therefore required —
not just in maintaining and operating the system, but to keep it
in working order. This is not necessarily a limitation, but an opportunity
to involve the whole community in wastewater treatment and develop
a system that is well integrated within the neighborhood.
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| Benefits |
Limitations |
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Significant labor
requirements
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Complex to construct
and maintain
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Sensitive to any
toxic substances often used in households
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Phase
5: Solar Aquatic System Integrated with Horticulture
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The final phase of the
Cantarrana Prototype utilizes the wastewater nutrients and byproducts
generated by the solar aquatic system to sustain and benefit the
community. The intensive production of ornamental or edible plants
can either be used directly by the community members, sold to generate
revenue, used in the production of goods (furniture or crafts) or
used for horticultural projects within the community, the PMH, or
the wider city. Plants are germinated and grown on site, with the
use of semi-treated wastewater as a natural fertilizer. Biosolids
and compost are used as fertilizer for plants on-site or sold for
off-site use.
This phase requires that
additional land be devoted to the system, either by the tire factory
or in conjunction with the decommissioning of the CO2
factory in 2001. Either site would likely involve the cleanup and
decontamination of adjacent land, which would be both time consuming
and expensive. Similar to the artificial food chain in phase 4,
adding horticultural production would require a high degree of community
participation and cooperation to keep the system productive. However,
it is also an excellent way to stimulate community participation
and involvement, especially with the additional opportunities for
creating jobs and generating revenue.
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| Benefits |
Limitations |
- Generation of "green
jobs"
- Provides a focus for
the community
- High degree of educational/research
potential
- Economically sustainable
with proper management
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Additional
Nonbuilt Strategies for Water Quality Improvement
In addition to the phased
ecological wastewater system recommendations, there are non-built
strategies that can substantially improve water quality in the Almendares
and Santoyo waterways. These include programs geared to promote
changes in wastewater management at the household level. Successful
educational programs help to reinforce a sense of responsibility
and accountability in environmental protection and can contribute
positively to long-term benefits. Small-scale changes, even on a
household level, can have a significant cumulative impact in conserving
water and reducing the quantities of toxins entering the river or
groundwater.
Park officials, community
leaders, and local residents may implement the following options
for small-scale water quality improvement efforts on a neighborhood,
household or individual basis. These are not meant to be recommendations
or alternatives for the overall wastewater system; instead, they
are to be viewed as suggestions for a more personalized approach
to water conservation and management in general. These efforts,
applied individually or in combination, are an effective component
of the phased concept plan for ecological wastewater treatment in
Cantarrana.
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Examples
of nonbuilt strategies
- Pursue water conservation
while cleaning, bathing and cooking.
- Simple roof collectors
are in common use throughout Cuba. They can be as simple as a
55-gallon drum placed under the roof to collect rainwater. After
the solids have settled out, use the runoff for showering, washing
clothes, or other household uses.
- Given Cuba’s
economic situation, soaps and detergents are likely to be used
sparingly. Judicious use of soap in cleaning and bathing limits
the amount of nutrients that enter the river. If possible, use
phosphate-free soaps.
- Separate greywater
(from cleaning, bathing and cooking), store it and reuse it for
irrigation; the high nutrient content in these waters is an effective
fertilizer.
- Place mechanical
or bio-filters in outfall pipes and replace regularly to separate
solids before wastewater enters the river.
- Manure from animals
raised along the water channels should be contained and disposed
of in an approved site away from the river.
- Small-scale compost
systems (for each household or street, for example) cut down on
food wastes and are an effective fertilizer.
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Conclusion
The Cantarrana Prototype is
low-cost, small scale, energy efficient, and integrated with surrounding
environments; it may consist of a single type of alternative wastewater
system or a combination of alternative wastewater systems. Many characteristics
illustrate the system’s significant contributions to local, national
and international interests. First, the Cantarrana Prototype offers Cantarrana
residents an effective wastewater treatment system, designed to evolve
to meet changing conditions. Second, it integrates local input by addressing
and responding to their concerns about feasibility, overall effectiveness
and environmental credibility. Third, it helps establish a connection
between Havana’s GDIC and the University of Washington, a relationship
that will continue to foster educational and cultural exchanges through
future collaboration. Finally, this plan provides a model for implementation
of similar systems in other Havana neighborhoods, other areas throughout
Cuba and around the world.
On an immediate, local level
the Cantarrana Prototype will diminish the risk of water- or fecal borne
disease, decrease odor, and provide numerous possibilities for raising
the awareness of residents, and others interested in replicating the project,
such as planners and engineers. For this reason, transparency of such
a system — making its workings apparent to the neighborhood —
is crucial. The Cantarrana Prototype be located in spaces that are currently
vacant and underutilized, providing the community with a new point of
reference to the river and revealing the processes that are taking place
within it.
The ecological wastewater treatment
system will serve as a model for others in the watershed, serving as an
example of how such technology can be applied on a neighborhood-by-neighborhood
basis. Due to its scale, the system provides marginal improvements to
the overall water quality of the Almendares. However, the treated water
is likely to be cleaner than the river itself, and as other neighborhoods
in the watershed duplicate this process, significant improvements to overall
water quality can be expected.
Nonbuilt alternatives can also
substantially improve water quality. Positive behavioral changes at an
individual, household or neighborhood level, such as conservation of water
and detergent, may be achieved through successful educational programs.
Park officials, community leaders, and local residents may combine nonbuilt
alternatives and the Cantarrana Prototype wastewater treatment system.
As experts explained, the national
and local resources for a large-scale conventional treatment plant that
would meet the needs of Cantarrana and similar communities along the Almendares
are not available now and are unlikely to become available in the foreseeable
future. The high capital costs, expensive maintenance and intensive use
of energy and chemicals exceed the thresholds of what most communities
can invest. In the meantime, these poor communities lack basic sanitary
services and have greater exposures and incidences of water-borne diseases.
By employing ecological alternatives, residents and community groups can
manage their own wastewater systems at a much lower cost with substantial
additional benefits. With increased reliance on ecological systems to
meet community needs, as well as increased collaboration between localities
and international stakeholders, the UW team believes that the implementation
of the Cantarrana Prototype will set a positive example for Cantarrana
residents, Havana planners and engineers, and international interests.
Moreover, a wastewater system
for Cantarrana and other communities within the PMH needs to be compatible
with the open space and recreational objectives of the PMH. A large-scale
conventional system sited within the PMH would counter these objectives
while the Cantarrana Prototype we present in this report could become
an important element in the plans for park restoration.
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