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The
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AguaClara
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Technology
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A
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Brief
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Overview
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of
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the Technology
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Technology {float:right|border=2px solid black|width=300px} [!Ojojona Photos^0015_08_094.jpg|width=300px!|Ojojona Photos] {float} |
The
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AguaClara
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technology
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is
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an
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innovative
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form
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of
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flocculation
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-sedimentation
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that
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has
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been
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adapted
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at
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Cornell
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University
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to
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operate
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without
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electrical
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input.
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Unlike
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conventional
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flocculators,
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which
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rely
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on
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large
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motor-driven
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stirring
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devices,
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ours
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create
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mixing
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solely
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with
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gravitational
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forcing
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through
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turning
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channels.
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The
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chemical
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dosing
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for
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the
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plants
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is
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all
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accomplished
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by
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using
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simple float
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valve-regulated
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constant
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head
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devices,
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and
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the
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plant
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flow
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rates
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are
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measured and controlled using riser pipes with calculated patterns of holes drilled through.
Sites for AguaClara plants are selected based on the presence of a distribution system and the apparent commitment of the town to the project. Candidate sites must have a distribution system in place that will be able to deliver the treated water to homes. AguaClara is responsible for the research, design, capacity building, and training going into each plant, but construction is supervised by a partner organization and plant operations and maintenance are the responsibility of the municipality or local water board.
A Detailed Plant Tour
The entrance tank to the rapid mix
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using a linear orifice meter. Sites for AguaClara plants are selected based on the presence of a distribution system, and the apparent commitment of the town to the project. Candidate sites must have a distribution system in place that will be able to deliver the treated water to homes. AguaClara is responsible for the research and design going into each plant, construction is supervised by a partner organization, and plant operations and maintenance is the responsibility of the municipality or local water board. h2. A Detailed Plant Tour h4. The entrance tank to the rapid mix {float:left|border=2px solid black|width=300px} [!Tamara Report Photos^Grit Chamber Figure 6.jpg|width=300px!|Tamara Report Photos] {float} |
Source
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water
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flows
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via
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the
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pre-existing transmission line to the entrance tank for an AguaClara plant. This entrance tank contains riser pipes with orifices of calculated size and spacing to obtain a linear relationship between the depth of water in the entrance tank and flow rate of water through the plant. This design mimics the shape and function of a Sutro Weir. The water leaving the entrance tank is mixed with alum, a coagulant, en route to the flocculator.
When alum is added to water it decreases the net charge on suspended dirt particles in the flow. When particles collide in an un-coagulated stream (one not treated with alum), they tend to repel one another. Conversely, particles in a coagulated stream are more likely to actually stick together and form larger conglomerates. These larger clumps of particles are referred to as flocs.
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distribution system to the entrance tank for the AguaClara plants. This entrance tank contains riser pipes with orifices of calculated size and spacing, which restricts the flow rate of water actually being treated to a specified amount. The water leaving the entrance tank is mixed with alum, a coagulant, en route to the flocculator. \\ {float:right|border=2px solid black|width=300px} [!Ojojona Photos^0015_08_130.jpg|width=300px!|Ojojona Photos] {float} Alum is dosed using a flow control module (FCM) developed by AguaClara. The FCM is a bottle fitted with a plastic float valve on the inlet, and a set length of tubing on the outlet. The float valve ensures a nearly constant head, while the elevation of the discharge of the exit tubing determines the head loss and hence flow rate. Plant operators adjust the alum dosing necessary for plant operation by adjusting the height at which the exit tubing drips into the raw water stream. The operators have a chart that relates influent turbidity to required alum dose, and required alum dose to the required tubing height . The dose delivered by the FCM is therefore a function of the (constant) head in the bottle, the (constant) length |
Alum and chlorine are dosed using a flow controller (FC) developed by AguaClara. The FC is a small jar fitted with a plastic float valve on the inlet, and a calculated length of tubing on the outlet. The float valve ensures a nearly constant head, while the elevation of the discharge of the exit tubing determines the total head loss, and hence flow rate.
Plant operators adjust the alum dosing by adjusting the height at which the exit tubing discharges into the raw water stream. The operators have a chart that relates influent turbidity to required alum dose, and required alum dose to the required tubing exit height. Chlorine is dosed similarly, except that the chlorine FC exit tube discharges into the plant exit stream. The dose delivered by the FC is therefore a function of the (constant) head in the bottle, the (constant) length and diameter of the outflow tubing, and the elevation at which the tubing discharges.
The rapid mix through the flocculator
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and diameter of the outflow tubing, and the elevation at which the tubing drips. \\ h4. The gentle mix through the flocculator {float:left|border=2px solid black|width=300px} [!Tamara Report Photos^Flocculation Tank Figure 7.jpg|width=300px!|Tamara Report Photos] {float} |
Alum
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and
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raw
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water
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flow
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through
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a
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short
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series
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of
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pipe
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elbows
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acting
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as
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a
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rapid
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mix.
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This
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disperses
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the
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alum
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throughout
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the
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raw
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water
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stream,
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ideally
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coating
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a
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significant
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number of
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the
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suspended
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particles.
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This
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mixed
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solution
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then
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enters
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the
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vertical
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flow hydraulic flocculator.
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The
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vertical
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flocculator
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for
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treatment of small
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flow
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rates
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was
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also
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developed
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by the team at
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Cornell
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University
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.
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The
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flocculator
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is
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comprised
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of
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a
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series
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of
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channels
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with
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alternating
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up
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and
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down
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baffles.
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The
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baffles
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force
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water
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to
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change
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direction
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through
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an
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amount
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of
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space
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that
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is
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calculated
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to
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provide
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target
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mixing.
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This
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mixing
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is
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vital
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to
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the
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water
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treatment
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process
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because
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it
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is
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the
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engine
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that
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drives
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floc
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formation.
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At
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the
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beginning
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of
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flocculation
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the
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suspended particles
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are
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small.
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The
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vertical
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flocculator
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has
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many
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more
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tight
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turns
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in
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the
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early
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sections
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of
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the
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tank
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as
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compared
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with
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the
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later
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sections.
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As
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the
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stream
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mixes
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and
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larger
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flocs
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form,
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the
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number
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of
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baffles
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per
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unit
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length
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of
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the
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tank
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decreases
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to
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reduce
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the
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strain
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on
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the
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flocs.
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The
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exact
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values
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for
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mixing
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parameters
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at
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various
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stages
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of
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floc
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formation
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are currently
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a
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central
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focus
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for
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the
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AguaClara
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laboratory
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research
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team.
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Earlier
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AguaClara
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plant
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designs
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employed
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the
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use
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of
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a
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horizontal
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flocculator
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instead
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of
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the
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vertical
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model
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now
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in
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use.
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The
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horizontal
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model
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is
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similar
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to
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the
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vertical
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one,
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except
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that
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the
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stream
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is
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forced
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to
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side-wind
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from
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left
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to
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right
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through
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the
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channels,
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instead
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of
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up
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to
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down.
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The
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vertical
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flocculator
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has
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a
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smaller
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footprint
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than
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its
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horizontal
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counterpart,
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which
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decreases
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the
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overall
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cost
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of
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construction.
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The
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vertical
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model
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also
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is
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less
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prone
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to
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premature
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sedimentation
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throughout
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the
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tank,
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which
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is
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another
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main
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reason
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why
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the
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team
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has
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shifted
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focus
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to
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vertical
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flocculation.
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The
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sedimentation
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tanks
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to
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the customers
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customers {float:right|border=2px solid black|width=300px} [!Tamara Report Photos^Flocculation to Sedimentation Channel Figure 9.jpg|width=300px!|Tamara Report Photos] {float} |
The
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stream
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leaves
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the
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flocculator
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and
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travels
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to
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the
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sedimentation
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tanks
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via
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a
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channel.
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The
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tanks
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have
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bottom-level
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entrance
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manifolds to
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distribute
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water
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evenly
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across
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the
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floor
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of
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each
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tank,
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and
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an
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effluent
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launder
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pipe
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collects
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water
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from
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the
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top
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of
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each
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tank.
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Tanks
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are
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fitted
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with
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arrays
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of
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lamella
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that
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are
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angled
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60º
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from
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the
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tank
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floor.
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The
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heavy
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flocs
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settle
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out
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of
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the
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slowly
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rising
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water
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and
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onto
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the
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lamella.
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The
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size
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of
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the
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tanks
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and
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the
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positioning
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of
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the
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lamella
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are engineered
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to
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allow
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the
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water
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to
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rise
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up
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through
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the
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tank
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at
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a
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slower
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speed than
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the
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flocs
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take to fall
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out
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onto
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the
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lamella.
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Sludge,
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made
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up
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of
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settled-out
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flocs,
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collects
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at
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the
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bottom
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of
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the
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sedimentation
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tanks
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and
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can create
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a
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diffuse
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filter
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for
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incoming
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water.
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Having
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some
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degree
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of
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sludge
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build-up
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is
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therefore
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desirable,
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but
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excess
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sludge
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will
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begin
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to
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rise
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through
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the
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tank
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if
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it
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builds
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up
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too
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much.
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The
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AguaClara
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team
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has
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recently
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begun
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to design weirs into the sedimentation tanks to control sludge levels to create a beneficial sludge blanket. In earlier designs plant operators isolated each sedimentation tank and opened a bottom drain to wash the sludge out. Current designs incorporate a system of sludge hoppers that remove the sludge only to a specific level in the tank, leaving some to act as a filter. Most of the initial turbidity is removed from the water by the time it exits the sedimentation tanks either way, but the sludge blanket filtering effect may help us achieve even better standards for effluent water.
From the launder at the top of the sedimentation tanks, clear water flows to a distribution tank. Chlorine is dripped into the stream of water entering the distribution tank to kill any bacteria that weren't eliminated by removing sediment. The chlorine is dosed using the same type of flow controller used for alum. Clean, disinfected water then flows from the distribution tank into people's homes along a series of municipal pipes.
The Case for Treatment Before Chlorination
Influent water straight from the source contains dirt, organics, and potential pathogens. Although chlorine is used as a broad-spectrum disinfectant worldwide, it is not necessarily an easy solution. Chlorine reacts with organics present in the water, forming carcinogenic compounds. This has the dual effect of not achieving disinfection because the chlorine is "used up" on the dead matter, while also creating a new health hazard. Flocculation is essentially the process of sticking solids in raw water together, while sedimentation is the process of letting those heavy solids sink out. The resulting water is clear of most solids, which allows us to add chlorine to kill remaining pathogens without producing excessive byproducts.
The Social and Cultural Side
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assess potential design modifications to control the sludge level in a sedimentation tank. Currently plant operators can isolate each sedimentation tank and open a bottom drain to wash the sludge out. Future designs may incorporate some system of sludge hoppers that would remove the sludge only to a specific level in the tank, leaving some to act as a filter. Most of the initial turbidity is currently removed from the water by the time it exits the sedimentation tanks, but the sludge blanket filtering effect may help us achieve even better standards for effluent water. From the launder at the top of the sedimentation tanks, clear water flows to a plant exit tank. A weir in the plant exit tank controls the water level in the plant. Sedimentation tanks can be hydraulically isolated from the plant by inserting pipe nipples into the Chlorine is dripped into the weir in the exit tank. The chlorine is dosed using the same type of flow controller used in alum dosing. Clean, disinfected water then flows from the distribution tank into people's homes. h2. The Case for Treatment Before Chlorination Influent water straight from the source contains dirt, organics, and potential pathogens. Although chlorine is used as a broad-spectrum disinfectant worldwide, it is not necessarily an easy solution. Chlorine reacts with organics present in the water, forming carcinogenic compounds. This has the dual effect of not achieving disinfection because the chlorine is "used up" on the dead matter, while also creating a new health hazard. Flocculation is simply the process of sticking all the solids in raw water together, while sedimentation is the process of letting those heavy solids sink out. The resulting water is clear of most solids, which allows us to add chlorine to kill remaining pathogens without producing excessive byproducts. h2. The Social and Cultural Side {float:right|border=2px solid black|width=300px200px} [!Tamara visit^IMG_5748.jpg|width=200px!|Tamara visit] {float} |
Social
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sustainability
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is
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of
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key
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importance
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to
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the
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AguaClara
...
team.
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The
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first
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concern
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for
...
plant
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design
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features
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is
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that
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they
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be
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practical
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for
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the
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communities
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using
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them.
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All
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AguaClara
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plants
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are
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built
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by
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locals
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through
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construction
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projects
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supervised
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by
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the
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Honduran
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NGO
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Agua
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Para
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el
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Pueblo
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(APP).
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Two
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Cornell
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graduates
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apply to spend a year as employees of APP while assisting with plant operator training and data collection. Groups from the Cornell team visit the sites of AguaClara plants several times each year, interviewing customers and plant operators to gain an understanding of how to better suit our research and design to the local needs.