Preliminary design for



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Water treatment plant for UI.City, UI.Country

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PRELIMINARY DESIGN FOR UI.City UI.State, UI.Country

UI.Name.First UI.Name.Last

UI.Organization


May 3, 2017 at 3:48:53 a5/p5

Copyright © 2010 Cornell University

Table of Contents



Disclaimer 4

Permission and Licensing Information 4

Introduction to AguaClara 5

The Technology 5

Determination of the hydraulic design 5

Plant Components 10

Coagulant Tanks 10

Entrance Tank/Pre-sedimentation 11

Chemical Dose Controller 14

Calibrating the doser 15

Rapid Mix 15

Flocculation 16

!Syntax Error, .. 17

General Flocculator Design 18

Inlet Channel 18

Sedimentation Tanks 19

Assigning dimensions to the sedimentation tank 20

Inlet Manifolds 21

Sludge drain 23

Tolvas 23

Plate settlers 23

Launders 24

Canal de salida 25

Chlorine Disinfection 25

Manejo de lodos 26

Stacked Rapid Sand Filtration: SRSF 26

Materials List 29

Entrance Tank 29

Flocculation Tank 29

Sedimentation Tank 30

SRSF 30




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http://aguaclara.cee.cornell.edu/

Dr. Monroe Weber-Shirk, Director


This preliminary design was requested by UI.Name.First UI.Name.Last on behalf of UI.Organization. The design was created on May 3, 2017 at 3:48:53 a5/p5 by the AguaClara Design Server at Cornell University. The design is for UI.City UI.State, UI.Country and has a design flow rate of Q.Plant. The design was created with MathCAD code version SVN.Version.

This design is the result of over 20,000 hours of undergraduate, graduate, and faculty labor. The design incorporates advanced fluid dynamics analysis for the hydraulic design to minimize floc breakup between the flocculator and the sedimentation tank. The chemical feed system is based on a series of inventions by the AguaClara team that make it possible to directly set the desired chemical dose and to maintain that dose automatically even as the flow rate through the plant varies. The high rate, shallow sedimentation tank design is optimized for high performance, low cost of construction, and ease of maintenance. The fabrication techniques that make it possible for a single operator to completely disassemble a sedimentation tank while keeping the rest of the plant in operation were developed by the AguaClara team at Cornell and by our partners in Honduras.

The economic value of this design is approximately 10,000 USD. This estimate is based on the amount of time that would be required to create this design if an environmental engineering firm used the AguaClara design algorithms, but not the automated design tool, to create this design. The AguaClara team is committed to continue providing this design service because we want to encourage new implementation partners to explore the use of this technology. We also recognize that high design costs would prevent this technology from being available to small communities. However, we do require funding to maintain our design team and to continue to integrate improvements into our designs. We recommend that implementation partners include a design fee for the AguaClara design service in the project budget. The recommended nominal fee (not its true value!) for use of this design service is 100 USD per L/s of plant capacity. You are welcome to create multiple designs for each facility that you intend to construct to obtain an optimal plant conFiguretion. This recommended fee can be paid to AguaClara by check or online to Cornell University. This fee will likely be between 1% and 2% of the overall project cost for a water treatment plant. Thank you for your support.

Donate by Check

Make the check to Cornell University

Write AguaClara in the memo field

Mail to: AguaClara, 220 Hollister Hall, Cornell University, Ithaca, NY 14853    

Disclaimer


This document is a DRAFT. It has not been reviewed for official release. It is included with the design files to show what we plan to deliver in the near future.

This design, including the files accompanying this document, is only a draft and must be reviewed and approved by a licensed engineer prior to construction. If you have questions about this design please contact the AguaClara design team at Cornell University at CUAguaClara@gmail.com.


Permission and Licensing Information


Copyright © 2010 Cornell University

Authors: The AguaClara team at Cornell University under the supervision of Dr. Monroe Weber-Shirk

This design was created using the open source engineering services of the AguaClara program at Cornell University. It is subject to the Creative Commons Attribution-ShareAlike 3.0 United States license. If you alter, transform, or build upon this work, you may distribute the resulting work only under the same, similar or a compatible license.

Permission to use this AguaClara Design Tool along with the subsequent AutoCAD renderings and supporting files for design specifications provided by Cornell based on your input parameters (collectively "WORK") and their associated copyrights without a written agreement is hereby granted. Any water treatment plants built using this WORK shall be designed and supervised by a licensed civil engineer.

IN NO EVENT SHALL CCTEC, CORNELL UNIVERSITY, OR THEIR EMPLOYEES BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF WORK AND ITS ASSOCIATED COPYRIGHTS, EVEN IF CCTEC OR CORNELL MAY HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE WORK PROVIDED HEREIN IS ON AN "AS IS" BASIS, AND CCTEC, CORNELL, AND THEIR EMPLOYEES HAVE NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. CCTEC, CORNELL, AND THEIR EMPLOYEES MAKE NO REPRESENTATIONS AND EXTEND NO WARRANTIES OF ANY KIND, EITHER IMPLIED OR EXPRESSED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, OR THAT THE USE OF WORK AND ITS ASSOCIATED COPYRIGHTS WILL NOT INFRINGE ANY PATENT, TRADEMARK OR OTHER RIGHTS.

Users of WORK shall indemnify, hold harmless and defend Cornell, its officers, employees, agents, and the sponsors of the research that let to WORK against any and all claims, suits, losses, damage, costs, fees, and expenses resulting from or arising out of use of WORK. This indemnification shall include, but not be limited to, any product liability. Users of WORK, at their sole cost and expense, shall sufficiently insure their activities in connection with the WORK and obtain, keep in force, and maintain insurance or an equivalent program of self insurance. Cornell shall notify users of WORK in writing of any claim or suit brought against Cornell in respect of which Cornell intends to invoke the provisions of this paragraph. Users of WORK shall keep Cornell informed on a current basis of its defense of any claims under this paragraph.

Introduction to AguaClara



Aguaclara is a program in the School of Civil and Environmental Engineering at Cornell University that aims to design robust technologies for municipal level water treatment. The plants are sustainable because they are built using locally available materials, and treatment and chemical dosing processes are designed to use gravity power, thus eliminating the need for electricity.

Plants remove suspended particles, sediments and pathogens to produce clean water. The removal process begins with the addition of a coagulant through a semi-automatic chemical dosing system. The addition of coagulant is essential because it promotes the aggregation of suspended particles. The coagulant is mixed with water in a rapid mixer. The mix of incoming water and chemical coagulant then passes through a flocculation tank, which is effectively a long channel containing staggered baffles around which the water mixture flows. Here, particles collide to form flocs, which eventually grow large enough to be sedimented.

The flocculated water then enters the sedimentation tank. The top of the tank has a several plates (known as lamella) to "capture" the flocs and force them to fall to the bottom of the tank, thus removing debris from the water. Floc-free water exits through launder pipes located at the top of the tank, and the sludge is drained from the tank bottom.

The final process is filtration. Aguaclara has designed a stacked rapid sand filter, which further reduces the turbidity of the water, but whose design is simple and easy to maintain. Prior to distribution, clean water is disinfected with chlorine to kill any harmful microorganisms. This last step is performed after filtration because it is easier to disinfect clean water.



This document provides a summary of Aguaclara, processes with regard to the design of closed facilities. This means that all calculated values (eg, number of flocculation tanks, the distance between the centers of the orifices, etc..) are specific to this plant design, and do not necessarily apply to other Aguaclara plants.

In the Aguaclara Design Tool (ADT), you enter basic design parameters (eg flow rate, wall thickness, number of wanted sedimentation tanks, the dimensions of purchased lamella material, etc.). The software uses these parameters as variables in a series of hydraulic and geometric algorithms that define the dimensions of the plant reactors and their accessories. The software product is a three-dimensional drawing in AutoCAD of each reactor that is to be given to the designer. The designer completes the design based on the ADT output by adding the final treatment components as well as the plant building.

The Technology

Determination of the hydraulic design


Included is the design for a plant for UI.City having a máximum flow rate of Q.Plant base don user inputs to the ADT. The goal of the plant with respect to water quality is to reduce the turbidity of the wáter as much as posible and to have it meet international wáter quality standards (<5 NTU), maintain the color within norms (15 Unidades de Color – UC), disinfect the wáter with chlorine, and maintain a residual chlorine concentration throughout distribution between 0.3 and 1.0 mg/L. The plant treats water without using electricity, utilizing pre-sedimentation, coagulation, flow control, rapid mix, flocculation, hydraulic upflow sedimentation, filtration, and chlorination.


The ADT allows the user to manipulate some basic plant parameters. The software uses these parameters as variables in a series of hydraulic and geometric calculations that define the dimensions of the various plant components.
For the plant design of UI.City, the following variables have been requested:
Maximum flow rate: Q.Plant

Thickness of the plant walls: T.PlantWall

Minimum concrete thickness: T.ConcreteMin

Coagulant stock concentration: C.CoagStock

Turnover time for the coagulant stock: Ti.CoagStock

Number of sedimentation tanks: N.SedTanks

Number of sedimentation bays: N.SedBaysEst

Width of the lamella used for sedimentation plates: W.SedPlate

Length of the lamella used for sedimentation plates: L.SedPlateSheet

Thickness of the lamella used for sedimentation plates: T.SedPlate

Thickness of the weirs in the sedimentation tanks: T.SedWeir


Inlet channel

Flocculation tank

Coagulant tanks

Entrance tank

Sedimentation tanks

Exit channel

Chemical dose controller

Figure : 3D AutoCAD drawing of the water treatment plant as given by the AguaClara Design Tool.


Basic parameters for plant design UI.City UI.State, UI.Country

Maximum plant flow rate:

Q.Plant

Treatment process:

Semi-automatic coagulant (Alum or PAC) doser, rapid mix, horizontal/vertical hydraulic flocculation, upflow sedimentation with lamella, chlorination

Approximate head loss:

HL.PlantTotal

Number of chemical dosers:

1

Number of coagulant tanks:

2

Type of coagulant doser


Laminar flow gravity doser

Coagulant stock concentration:

C.CoagStock

Type of rapid mix:

Turbulent flow in a ND.RMPipe pipe

Number of flocculation tanks:

1

Number of channels in a flocculation tank:

N.FlocChannels

Dimensions of each flocculation tank:

W.FlocChannel in width

L.FlocTank in length

H.Floc in depth


Hydraulic residence time in the flocculator for the maximum design flow rate

Ti.Floc

Number of baffles in the flocculation tank:

N.FlocBaffles

Material of the baffles in the flocculation tank:



Dimensions of the inlet channel to the sedimentation tank:

L.SedChannel in length

W.SedInletChannel in width

H.SedInletChannel in depth


Number of sedimentation tanks:

N.SedTanks

Number of sedimentation bays per sedimentation tank:

N.SedBays

Dimensions of the sedimentation tank:

W.Sed in width

L.Sed in length

H.Sed in depth


Hydraulic residence time in the sedimentation tanks for the maximum design flow rate:

Ti.Sed

Total number of sedimentation plates:

N.SedPlatesTotal

Angle of the sedimentation plates:

AN.SedPlate

Length of the sedimentation plates:

L.SedPlate

Perpendicular space between sedimentation plates:

S.SedPlate

Upflow velocity in the sedimentation tanks at the maximum design flow rate:

V.SedUpBod

Capture velocity of the sedimentation tanks at the maximum design flow rate:

V.SedCBod

Number of chlorine storage tanks:

2

Type of chlorine doser:

Laminar flow gravity doser

Table : Basic parameters of the plant design UI.City UI.State, UI.Country.

We have designed the treatment processes according to the maximum flow rate using the algorithms of the ADT. The hydraulic processes of the plant include pre-sedimentation, coagulation, flow control, rapid mix, horizontal/vertical hydraulic flocculation, hydraulic upflow sedimentation, filtration, and chlorination.

Plant Components

Coagulant Tanks

The design of the coagulant storage tanks is based on the tank sizes available for purchase through Rotoplast for Latin America. AguaClara has created a database of available dimensions for each tank available from the provider. For plants that need tank dimensions that are slightly different from the set dimensions, the ADT automatically rounds down to the nearest desired volume to make the size as optimal as possible.

The volume of the tanks is determined by the plant flow rate and coagulant concentration. The maximum coagulant flow rate is first calculated based on user inputs according to the relationship between the flow rate of the plant and the flow rate of the coagulant:


Once you have calculated the maximum coagulant flow rate, the volume of the tank can be computed using the following formula:

Figure : Dimensions of the coagulant tanks

Figure : The plumbing used to deliver the coagulant to the rapid mix system

Entrance Tank/Pre-sedimentation

The main functions of the entrance tank are to remove solids from the water through sedimentation, control the flow through the plant, and to provide a place where the quality of the raw water can be observed.


The first function of the entrance tank is pre-sedimentation (sand trap) to remove solids such as sand, silt, and clay from the water before applying the coagulant to the influent. It is designed for a capture velocity of W.EtCapture to remove these particulates. A length of L.Et is assigned to the entrance tank to correspond to the sedimentation tank length plus enough space to fit the float of the chemical dose controller and the rapid mix pipes. The width, W.Et, is then assigned to ensure the minimum desired capture velocity is met while still allowing enough space for a person to fit inside and construct the tank. The depth of the tank is then determined such that the velocity in the upper rectangular portion of the tank does not exceed the velocity in the flocculator, V.Floc, while ensuring the depth is sufficiently small that the drains are easy to access. In this case, the tank has a height of H.Et.

Figure . The entrance tank and rapid mix pipes. Water enters the first hopper, flows through the trash racks, enters the rapid mix pipes, and exits into the bottom of the flocculator.
To allow for easy maintenance, N.EtHoppers hoppers must be built into the entrance tank, at an angle of AN.EtSlope, forcing sediments to slide to the bottom where the ND.EtDrain drains are located. When too much sediment has accumulated, the upper drain pipes must be removed until the sludge is flushed out. Directly below the entrance tank, there is a drain channel to collect the waste.

Figure . Side view of the entrance tank. The leftmost pipes make up the rapid mix system, which transports water from the entrance tank to the flocculator. The upper pipe of the rapid mix system has a series of orifices that approximate the shape of a sutro weir, linearizing the relationship between height of water in the entrance tank and the plant flow rate.


Figure . Front view of the entrance tank. The vertical pipes centered on each hopper are removed to flush out sludge. The rightmost vertical pipe drains the overflow channel. The drain valve is used to control flow rate through the plant.

The second function of the entrance tank is to control plant flow rate. Flow in excess of the maximum spills into a channel that runs the length of the entrance tank on the uphill side. The water in this channel is wasted using an overflow channel that empties into a drain channel perpendicular to the entrance tank. This channel is sized to handle the entire plant flow, and requires a width of W.EtOverflowChannel. Based on a maximum acceptable headloss of HL.ChannelMax and H.PlantFreeboard freeboard, the depth of the channel must be H.EtOverflowChannel. There is another drain system at the bottom of the first hopper of the entrance tank which consists of a ND.EtFlowControl valve that the operator can use to further control the flow rate through the plant. This drain can also handle the whole plant flow and empties into the perpendicular drain channel.

In the last hopper of the entrance tank, water flows through the orifices drilled into the exit pipe, which serves as a linear flow orifice meter (LFOM). The arrangement of the orifices (similar to a sutro weir) approximates a linear relationship between plant flow rate and the water height above the bottom row of orifices. When there is no flow through the plant, the water level will be below the bottom of the bottommost orifices, while at maximum flow the water level will be at the top of the topmost orifices. The orifices span a total vertical height of HL.Lfom, the maximum height over which a linear relationship is valid. The top of the topmost orifices is aligned with the top of the overflow weir, so that water in excess of the maximum flow is wasted. After flowing through the orifices, the water continues through ND.RMPipe rapid mix piping, where coagulant is applied.
Figure . Front view of a linear flow orifice meter. As seen in the figure on the left, the water level is at the bottom row of orifices at minimum flow conditions. On the other hand, at maximum flow conditions, the water height is at the top row of orifices.


Length

L.Et

Width

W.Et

Height

H.Et

Height of the hoppers

H.EtHopper

Length of a hopper

L.EtHopper

Table . Dimensions of the entrance tank


Chemical Dose Controller

Coagulation involves the precise dosing of chemical coagulant to the plant influent to neutralize the forces that keep colloids in suspension, thus permitting flocculation. To administer the dose without pumps, AguaClara plants utilize a dosing system that consists of tanks to store the coagulant solution, a platform to maintain the needed elevation, a constant head tank with a float valve, a scale, and a dosing tube.


The coagulant solution must be stored in stank tanks on an elevated platform. The chemical solution must flow from the stock tanks to a bottle equipped with a float valve. The float valve is used to maintain a constant head in the bottle, ensure the chemical flows based on a constant hydraulic potential. The solution flows from the contant head tank through a flexible tube mounted on a scale. The inclination of the scale is based on the elevation of a float attachment that sits in the entrance tank, which is related to the plant flow rate. A slider is used to adjust the position of the flexible tube alone the scale, thus determining the dose of coagulant. The doser is calibrated such that when there is no flow in the plant, the scale sits horizontally, preventing coagulant flow. When the plant is operating, the float rises in proportion to the plant flow, tilting the scale and providing the necessary head to deliver the specified dose. The further away from the float the slider is set, the higher the dose administered.
The coagulant will automatically stop flowing when there is no flow through the plant, and it will automatically administer the specified dose based on the water level in the entrance tank, which is proportional to the plant flow rate as a result of the LFOM.
Figure Front view of the chemical dose controller with the scale in the “off” position (with no-flow in the plant).
Figure . Front view of the chemical dose controller with the scale in operating position. The figure illustrates that the scale must be inclined to provide the hydraulic head required to deliver the corresponding coagulant dose.

The chemical dose controller is mounted on the outside of the entrance tank, and is fed from a valve in the stock tank at Z.CoagTankOutlet from the plant floor. The chemical tank platform must be Z.CoagTank above the plant floor to provide enough hydraulic head (H.CdcMax) between the coagulant tank exit and the constant head tank to make up for losses through the float valve. From the float valve, the solution flows through N.CdcTubes tubes having an inner diameter of D.CdcTube and a length of L.CoagCdcTube to the dosing device, the fulcrum of which is mounted at the top edge of the entrance tank. The length and diameter of the tubes are designed to relate the needed range of coagulant flow rate, 0 to C.CoagDoseMax, to to the maximum flow rate of the plant, while always maintaining laminar flow. The length of the scale from the fulcrum to the float is L.CdcFloatArm in length, and the length of the scale from the fulcrum to the opposite side is L.CdcScaleArm. After passing through the tube, the solution falls freely through a PVC pipe into the tee outside of the entrance tank. There will be sufficient venting to allow air to mix with the water, reducing chances of foam forming in the first channel of the flocculator.


Calibrating the doser

For the doser to function optimally, it is crucial for each component to be installed correctly, and the initial calibration of the doser must be carried out according to the following steps.


Once the doser is installed, the scale needs to be set at the zero level. To do this, empty the entrance tank until there is no flow through the plant. At this point, the water level is just below the bottom orifices of the simulated sutro weir. Then, with the scale perfectly horizontal, adjust the length of the rope attached to the float.
With the scale in the horizontal position, mount the constant head tank such that its water level is at the same elevation as the dosing tube.
Then, fill the entrance tank until the water height corresponds to the maximum flow rate (where the topmost orifices of the LFOM are just submerged). The scale should be set nearly to the maximum height (approximately HL.Lfom)
Position the slider to an intermediate dose. It is important to calibrate the doser at an intermediate dose because this method leaves extreme flow rates less susceptible to calibration errors.
At the intermédiate dosing position, measure the flow of coagulant and compare it to the desired (theoretical) flow rate. If the flow rate is greater than the theoretical, cut the tube and repeat the test until the theoretical value matches the measured value. If the flow rate is less than the theoretical, you need to obtain a larger tube and start the process over. Once the theoretical and measured values match, the doser is ready for use.
It is important to periodically clean each part of the doser. Also, air bubbles, which cause dosing errors, must not be present in the tubes. If bubbles are present, remove the tube from the dosing system and force the bubbles out.

Rapid Mix


Once it has been dosed with coagulant, the water passes through the rapid mix system. Rapid mix serves to uniformly distribute the coagulant through the raw water. In this plant, the rapid mix occurs as turbulent flow through a L.RMPipe long pipe, with an inner diameter of ND.RMPipe. This pipe brings water from the point at which coagulant is dosed to the entrance of the flocculator.

Flocculation


The flocculator encourages the particulates in the water, now neutralized with coagulant, to collide and stick together. As these particulates, or flocs, collide and stick together, they grow heavy enough to settle out by the time they reach the sedimentation tank. Since the particles collide more easily in turbulent flow, turbulence is created by a series of staggered baffles that force the water to make 180 degree turns. The baffles are spread throughout several consecutive channels to maintain a compact design and minimize cost of construction by sharing channel walls. To allow the two tanks to share a wall, the flocculator length is set to that of the sedimentation tank, L.Sed. There are a total of N.FlocChannels channels in the flocculator, each channel having an inner width (excluding wall thickness) of W.FlocChannel.

The flocs need to collide enough times that they grow large enough to settle out in the sedimentation tank, but not so large that they settle out in the flocculator. The required collision potential (the possibility of colliding in the flocculator) is CP.Floc, while the actual collision potential is CP.FlocTotal. Note that the value of the actual collision potential may be significantly higher than the required since the number of floc channels must be an integer.


The height of the flocculator was calculated by summing the head losses within the flocculator, the water height in the sedimentation tank, and a freeboard height of H.PlantFreeboard, giving a total height of H.Floc (excluding floor thickness). The total width (perpendicular to the channels) of the flocculator, including all walls except for the one shared with the sedimentation tank, is W.FlocWithWalls. The total length of the floc tank, including wall thickness, is L.FlocWithWalls. The floor of the flocculator, above the floor thickness, is elevated Z.FlocTank from the sedimentation tank floor, also above the floor thickness. These dimensions together give a residence time in the flocculator of Ti.Floc. The average velocity in the flocculator is V.Floc.

Figure : Top view of a vertical flocculator



!Syntax Error, ..



General Flocculator Design


Gate valves at the bottom of alternate channels in the flocculator allow for draining. The nominal diameter of the flocculator drain pipes is ND.FlocValve, calculated to ensure the tank can drain in less than Ti.FlocDrain. Since each valve is draining the water from at least two channels, this design requires N.FlocValves valves. Elbows connected at the end of the drain piping redirect the flow of water into the drain channel, minimizing splashing.

Since the center of the valve is aligned with the floor (above the floor thickness), slopes need to be built in to allow efficient draining. The width of the slope is the inner diameter of the drain piping, while the depth of it is the inner radius. The length is given to make the slope 30 degrees. In the even that a 30 degree slope causes a slope longer than the space between baffles, the end of the slope is simply set to 5 cm away from the nearest baffle.


Inlet Channel


The influent to the sedimentation tank passes through a channel that distributes the water to the individual bays within each tank. This channel is designed to ensure that the flocs can be transferred to the bottom of the sedimentation tanks without being broken. Other restrictions on the dimensions include: sufficient width to accommodate the inlet manifolds that deliver water to the bottom of tank, tiene que tener suficiente profundidad para apoyar los tubos recolectores de salida de los tanques de sedimentación, tiene que ser poco profundo para permitir fácil acceso al fondo, y tiene W.SedInletchannelPreweir de espacio libre.


Length

L.Channel

Width

W.InletChannel

Height

H.InletChannel

Water height

HW.InletChannel

Table . Dimensions of the inlet channel

El canal distribuidor también tiene un vertedero de H.SedWeirInlet de altura sobre el nivel del fondo y un tubo de 4 pulgadas de diámetro fundido en el final del canal. Este tubo se mantiene tapado excepto cuando se quiere botar agua floculada al canal de limpieza para que no ingrese a los tanques de sedimentación. Cuando se desborda agua del canal, el vertedero mantiene el canal y el tanque de floculación llenos de agua para evitar cambios abruptos en el nivel de agua que pueden perjudicar el tratamiento.





Type of weir

Perpendicular

Length

W.SedWeirInlet

Height

H.SedWeirInlet

Head loss

HL.SedWeirInlet

Table . Dimensions of the inlet channel weir

Sedimentation Tanks


The objective of the sedimentation tanks is to remove, by gravity, the flocs that have been formed in the flocculator. Los tanques de sedimentación de flujo ascendente tienen cinco partes: los tubos distribuidores, los canales de drenaje, las tolvas, las placas sedimentadoras, y los tubos recolectores del agua decantada.

Figure :Top view of the sedimentation tank


Assigning dimensions to the sedimentation tank


Se dimensionan los tanques de sedimentación en base a los criterios de diseño de las varias partes descritas anteriormente así como las dimensiones estándares del material de las láminas usadas para las placas sedimentadoras. Láminas de policarbonato, un buen material para placas sedimentadoras por su resistencia y lisura, son comerciales en dimensiones de 3.66 de largo por 1.08 m de ancho por 0.02 m de espesor. Para hacer el uso más eficiente de este material, el algoritmo de dimensionamiento de los tanques de sedimentación de la herramienta de diseño de AguaClara fija el ancho de cada tanque al ancho de la lámina, en 1.08 m, y usa un algoritmo de optimización para escoger un solo largo de todas las placas de tal manera que el diseño requiere la compra de un mínimo número de láminas. Utilizando este constante además de los constantes Vascendente, Vc, α, el ángulo de inclinación de las tolvas, el número de tanques de sedimentación deseados, y el caudal máximo de la planta, se calculan las dimensiones de los tanques de sedimentación.



Number of sedimentation tanks

N.SedTanks

Number of sedimentation bays per sedimentation tank

N.SedBays

Width of each bay

W.SedBay

Length of each bay and tank

L.Sed

Altura de las paredes inclinadas

H.SedBayDivider

Ancho de las paredes inclinadas

W.SedSlope

Angulo de inclinación de las paredes

AN.SedSlope

Table . Dimensions of the sedimentation tank

Figure : Cámaras sedimentadoras y tolvas del tanque de sedimentación


Inlet Manifolds


The objective of the inlet manifolds is to transport the flocs into the bottom of the sedimentation tank without breaking them. El diseño de los tubos distribuidores también depende del factor de la tasa de disipación de energía máxima, εmax, la idea siempre siendo pasar los flóculos formados a los tanques de sedimentación sin romperlos por demasiada turbulencia. Se determina el diámetro de los tubos de entrada fijando εmax = 6 mW/kg en el lugar donde hay el mayor potencial de romper flóculos: la entrada a los tubos en el fondo del canal distribuidor.

Figure : Tuberías del tanque de sedimentación

Each one of the N.SedBays bays in each sedimentation tank has a maximum flow rate of Q.SedBay, which, according to this equation, requires a ND.SedManifold inlet manifold pipe to prevent floc breakup. The length of each inlet manifold pipe is L.SedManifoldPipe, and the pipes have an elevation of Z.SedManifoldLift from the sedimentation tank floor.

The inlet manifolds distribute water along the length of the sedimentation tank through orifices along the bottom of the pipe. The total cross-sectional area of the jets coming out of the manifold must equal the approximate inner diameter of the pipe itself, given by the maximum energy dissipation constraint. La suma de las áreas de los chorros de estos agujeros tiene que ser aproximadamente igual al diámetro del tubo para preservar la tasa de disipación de energía máxima que se toma como criterio para dimensionar el tubo, tomando en cuenta las restricciones de tamaños estándares de brocas para perforar los agujeros. Cada tubo distribuidor tiene N.SedManifolPorts de D.SedManifoldPort de diámetro espaciados a S.SedManifoldBetween centro a centro a lo largo del tubo.

Adjuntos a los agujeros, y en posición perpendicular al tubo de distribución, se encuentran tubitos de longitud L.Diffuser y diámetro D.Diffuser. El propósito de estos tubos verticales es evitar la creación de corrientes circulares en el fondo del tanque de sedimentación y la creación de zonas muertas, donde los sedimentos pueden ser acumulados.



Nominal diameter

ND.SedManifold

Diameter of the orifices

D.SedManifoldPort

Number of orifices

N.SedManifoldPorts

Center-to-center distance between orifices

B.SedManifoldPort

Length

L.SedManifoldPipe

Elevation from the sed tank floor

Z.SedManifold

Espacio entre el centro de la tubería y la cubierta

S.SedManifoldBetween

Table . Dimensions of the inlet manifold


Sludge drain


El en fondo de cada tanque de sedimentación hay un canal de drenaje para purgar los lodos acumulados en el proceso de sedimentación. El canal es un hueco de W.SedSludge ancho por H.SedSludge de alto que recorre todo el largo del fondo del tanque. En un lado del tanque, el canal da a una válvula de bronce de D.SedSludgeValve de diámetro que controla el nivel de lodo en el tanque. Encima del canal de cada tanque se colocan placas de ferrocemento perforados con N.SedsludgeOrifices de D.SedsludgeOrifice espaciados a B.SedSludgeOrifices de centro a centro. Estos agujeros están distribuidos uniformemente a lo largo del canal para lograr purgar los lodos de todas las partes del tanque uniformemente. Los diámetros de los agujeros en el canal y el diámetro de la válvula están diseñados para vaciar un tanque en Ti.SedDrain .



Width

W.SedSludge

Height

H.SedSludge

Ancho de la tapadera

W.SedDrainCover

Grosor de la tapadera

T.SedSludge

Diameter of the sludge orifices

D.SedSludgeOrifice

Center-to-center distance between the sludge orifices

B.SedSludgeOrifices

Número de orificios

N.SedSludgeOrifices

Table . Dimensions of the sludge drain

Tolvas


Cada tanque tiene una tolva de AN.SedSlope de inclinación y una elevación de Z.SedSlopes. Esta geometría crea mayores velocidades en el fondo del tanque que en la parte superior de la tolva, lo cual sirve para mantener los flóculos sedimentados en suspensión, maximizando el potencial de floculación y retención de partículas en un manto de lodo. La velocidad ascendente del agua en la parte superior de la tolva se fija en Vascendente = 69 m/día (8 mm/s) en la herramienta de diseño de AguaClara.

Plate settlers


Plate settlers, used to remove small particulates that cannot settle in the bottom of the tank, sit above the slopes in the sedimentation tank. The plate settlers are set an an angle of AN.SedPlate to ensure efficient sedimentation. Los algoritmos de diseño de la AguaClara Design Tool utilizan el constante de la velocidad de captura Vc = 9.0 m/día (0.104 mm/s) que garantiza una velocidad conservadora para un alta remoción de sólidos.

Cada canal del tanque de sedimentación de la planta tiene un total de N.SedPlates placas sedimentadoras organizadas en N.SedModules módulos de N.SedModulePlates placas. Los módulos descansan en un marco de tubería de PVC colocado en la parte superior de las tolvas.



Width of the plate settlers

W.SedPlate

Length of the plate settlers

L.SedPlate

Center-to-center spacing of the plate settlers

B.SedPlate

Number of plate settlers

N.SedPlates

Number of plate settler modules

N.SedModules

Number of plate settlers in each module

N.SedModulePlates

Table . Dimensions of the plate settlers

Launders


En el tanque de sedimentación el agua pasa por el tubo distribuidor en el fondo, la tolva, y las placas sedimentadoras. Al salir de las placas el agua ya está decantada o aclarada. Sale del tanque por un tubo recolector perforado ubicado inmediatamente sobre la parte superior de las placas. El tubo recolector está diseñado para proporcionar significativamente más pérdida de carga hidráulica en las pérdidas menores de los orificios perforados que en las pérdidas mayores ocasionadas por el flujo turbulento dentro del tubo, de tal manera que el flujo que entra el tubo recolector por los orificios es uniforme a lo largo del tanque. Por esta razón cada tubo recolector de ND.SedLaunder de diámetro lleva N.SedLaunderOrifices agujeros de D.SedLaunderOrifice de diámetro espaciados a B.sedLaunderOrifices de centro a centro en N.SedLaunderOrificesRow filas en la parte superior del tubo. Este diseño tiene el beneficio de crear un sobrenadante sobre el tubo recolector que evita que material flotante en la superficie del agua salga del tanque de sedimentación.

Figure : The launder in a sedimentation bay




Number of orifices in the launder

N.SedLaunderOrifices.

Nominal diameter of the launder

ND.SedLaunder.

Elevation of the launder

Z.SedLaunder.

Total number of launders in the plant

N.Launders.

Length of each launder

L.SedLaunder.

Table . Launder dimensions


Canal de salida


El agua decantada sale de los tubos recolectores a un canal recolector de salida que lleva el agua al proceso de desinfección. Este canal tiene dimensiones de H.ExitChannel de profundidad, W.ExitChannel de ancho, y L.ExitChannel de largo. Un vertedero longitudinal de cresta aguda de H.SedExitChannelWeir de elevación en medio del canal garantiza que los tanques de sedimentación se mantienen llenos de agua con un mínimo de pérdida ocasionada por el vertedero.

Chlorine Disinfection


Se dosifica una solución de hipoclorito de calcio al agua decantada en la caja distribuidora al final del canal de salida. El sistema de dosificación de cloro es parecido al del coagulante y consiste en: tambos para almacenar la solución de cloro, una mesa para elevar los tambos, y un dosificador sencillo gravitacional.

Se monta el dosificador sencillo en el borde de la caja distribuidora de tal manera que las gotas de cloro caen al efluente de la planta, donde se mezclan con el agua. El operador de la planta maneja la manguera dosificadora de este dispositivo para escoger la dosis apropiada de cloro para el caudal que se trata. Hay suficiente tiempo de contacto en las líneas de conducción y los tanques de abastecimiento para lograr la desinfección. La válvula flotadora del dosificador sencilla se posiciona sobre el borde de la solera superior del canal de salida. La mesa para los tambos de cloro debe ser diseñada con una elevación suficiente para proporcionar la carga hidráulica necesaria para que la solución de cloro pueda llegar a la botella con flotador, superando las pérdidas ocasionadas por la válvula flotadora y la manguera de suministro. Se almacenan las soluciones de cloro en dos tambos colocados encima de la mesa.



Figure : Diagrama de un dosificador de cloro



Figure : Fotografía de un dosificador de cloro en una de las plantas existentes de AguaClara


Manejo de lodos


Cada proceso de la planta produce residuos. El tanque de entrada produce sólidos sedimentables, los tambos de coagulante residuos de impurezas de la solución química, los tanques de floculación y sedimentación lodos de flóculos, y los tambos de cloro residuos químicos. Hay dos salidas de lodos principales. La primera salida es el canal de lodos del tanque de entrada, que tiene un ancho de W.EtDC, un largo de L.EtDC, y una altura de H.EtDC. La segunda salida recoge los residuos de los procesos de floculación y sedimentación y conduce los residuos a un canal de limpieza ubicado a lo largo de la pared posterior de la planta. El acceso a las válvulas manuales de floculación y sedimentación es a través de tapaderas en el pasillo que cubre el canal de limpieza. Este pasillo queda debajo del piso del resto de la planta para permitir acceso manual a las válvulas. Esta salida tiene una altura de H.DC, una longitud de L.DC, y un ancho de W.DC.

Stacked Rapid Sand Filtration: SRSF

Las plantas de AguaClara cuentan con un sistema de filtración no convencional. Comúnmente, solamente plantas de grandes caudales pueden permitirse la incorporación de un filtro de arena. Los filtros de arena convencionales usan grandes cantidades de agua limpia para el retrolavado, electricidad, y son de construcción y mantenimiento complejo, incluyendo varias válvulas y piezas que se rompen con facilidad y son difíciles de reponer.

Por estas razones, el equipo de AguaClara ha diseñado un filtro con unas restricciones de diseño que no use electricidad, evite el uso de válvulas y piezas caras y de difícil obtención, que use poca agua, que cada parte del filtro sea visible y accesible para el operador, y que sea de fácil manejo.
Usando los principios de perdida de cabeza y aprovechando las diferencias de altura del agua, el equipo de AguaClara creo un diseño de tres filtros de arena en uno (FRAMCa). Este diseño reduce la cantidad de agua que se necesita, y gracias a su tamaño compacto y sencillo, una planta de relativamente poco flujo puede contar con tres filtros de arena.
Filtration begins once the settled water leaves the sedimentation tank. To ensure the filter functions optimally, the water must be sufficiently treated at the start of the process to a low turbidity. The filter must be washed regularly to liberate particulates trapped in the void space of the filter media. Once the water leaves the filter, it is sent to a distribution tank where chlorine is applied to destroy the last of the particulates.

Figure . ( Left) Top view of the sedimentation tank and a single filter below it. (Right) Isometric view of the filtration unit and sedimentation tank.

The SRSF has eight components:an entrance channel, an entrance box, a filter box, a distribution tank, caja de salida, caja de rebose, a backwash channel, a backwash box, and a siphon.
Figure and Error: Reference source not found show the layout of the filter. Water from the sedimentation tank enters the entrance channel then into the entrance box over a weir, flowing into the inlet manifold pipes. During filtration, all four pipes are utilized to distribute flow evenly to each of the six sand layers in the filter box and flow exits through the exit manifold into the exit box. Once in the exit box, the filtered water flows over a weir and is then piped to a distribution tank.

Figure Error: Reference source not found more clearly shows the parts of the filter associated with backwash. For backwash operation, all water in the entrance channel will only flow through the bottom inlet manifold pipe. The dirty backwash water will then flow through the siphon into the backwash box. The backwash weir makes up one wall of the backwash box and controls the height of water throughout the filtration system. The dirty water flows over the weir from the backwash box into the backwash overflow box, then down a pipe to the drain channel.


Figure . Top view of the filter labeled for filtration flow.



The siphon must be large enough to allow for draining all the water in the filter in a reasonable amount of time, set to be 3 minutes as well as have less than 10 cm of head loss at steady state.

Materials List

Esta seccion describe parametros utiles y estimaciones de los materials necesarios para la construccion de esta planta. Las dimensiones y materials descritas aqui estan divididas acorde a la unidad operacional de la planta a la que pertenecen.


Entrance Tank


  • El volumen de concreto necesario para construir el tanque de entrada es Vol.EntranceTank.

  • El suelo del tanque de entrada tiene un area de A.EtFloor.

Flocculation Tank


  • El volume de concreto necesario para construir los suelos del tanque de floculacion es Vol.FlocFloor y Vol.FlocWallsn par alas paredes del tanque.

  • Este suelo tiene un area de A.FlocFloor.

  • Hay N.FlocValves valvulas en el tanque de floculacion , cada una con un día metro nominal de ND.FlocValve.


Sedimentation Tank


  • Los volumenes de concreto necesario para construir el tanque de sedimentación son:

Vol.SedSlopes

Para las tolvas del tanque

Vol.SedWalls

Para las paredes del tanque

Vol.SedFloor

Para el suelo del tanque

  • El area de la superficie del tanque de sedimentación es A.SedFloor.

  • Hay N.Launders tuberias de salida de agua limpia, cada una de longitude L.SedLaunder length y ND.SedLaunder de día metro. Cada tuberia de salida tiene dos filas de orificios con un total de N.SedLaunderOrifices orificios, cada uno de día metro D.SedLaunderOrifice.

  • Cada una de las tuberias distribuidoras tiene longitud de L.SedManifoldPipe, con un día metro nominal de ND.SedManifold. Hay N.SedBays tuberias distribuidoras.

  • Hay un total de N.SedPlatesTotal placas sedimentadoras, cada una de longitud L.SedPlate y W.SedPlate de ancho.

  • Hay N.Valves valvulas, cada una de ND.SedSludgeValve día metro nominal.



SRSF





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