Caroni Arena Reservoir

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ENEN110D EnvironmentalEngineering

Individual Assignment

Anson Ryan 57807

Caroni Arena Reservoir


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Table of Contents Caroni Arena Reservoir _________________________________________ 1

Water Treatment Theory _________________________________ 3History of the Caroni Arena Reservoir ____________________________________ 3

Water Treatment Units ___________________________________ 4Conclusion ________________________________________________________ 9

References ____________________________________________ 10
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Water Treatment Theory

Water treatment is the process which makes water purifies water for various usessuch as drinking, industrial or medical. This process removes existing contaminants

or reduce the level of contaminants present and improve the water quality. Water inits raw state is unlikely to be free of contaminants and may go through several typesof water treatment depending on its characteristics and required water qualitystandards. Bacteria, algae, viruses, fungi, suspended solids, and minerals such as ironand manganese, are among the substances that are removed throughout watertreatment. Successful treatment should ensure the elimination of all disease-causingorganisms and so reduce the likelihood of the happening of waterborne disease.

(Hygiene and Environmental Health HEAT Module, 2011)

History of the Caroni Arena Reservoir

The Caron Arena is the largest dam ever built in Trinidad and Tobago. Reaching up to134 feet. Completed in 1981, the Reservoir can hold approximately 45.5 million m 3 ofwater. Before its creation, the site located between the El Pillar and Los Bajosfaults, was covered with thick virgin forest. This naturally faulting area allows forsteep elevations and low valleys which provides 1,700 acres of water storage. Twomajor water ways supplies the reservoir one being the Arena River and the TumpunaRiver.

Although the beautiful forest has been lost the site has gained a new attraction withplay parks, picnic tables and shady huts with cooking facilities.

(WASA, Arena Reservoir , 2008)


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Water Treatment Units

Raw Water Intake

The Raw Water Intake located along the north bank of the Caroni River is the firstpart of water treatment where trash racks and travelling band screens removes largedebris such as wood leaves and other forms of debris before the water enters theplants pumps. Eight Raw Water Pumps draw the water from the river and pump itacross to Headworks. (WASA, Waste Water Treatment, 2008)

In Theory this process is called Screening and is separated into two categories.

Coarse Screens which remove large solids and man-made materials and debris and

are typically 6mm or larger. These screens can be manually and mechanicallycleaned. Types of course screens are bar screens and trash racks as used by CaroniArena.

Fine screens are used to remove small material which may cause problems later on inthe treatment process. The openings in the screens are typically 1.5 to 6mm. andvery fine screens are 0.2 to 1.5 mm.


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Headworks This is the first stage for coagulation to occur. Where Aluminum Sulphate (acoagulant), a liquid polymer and chlorine are added to the water.

The design of the headworks ensure rapid mixing and uniform

distribution of the chemicals with the raw water. The alum reactsrapidly with the waters alkalinity to produce a gelatinous (jelly -like

precipitate) of Aluminum Hydroxide called microfloc that entraps andabsorbs impurities. The liquid polymer aids in coagulation by enlargingthe floc particles through bridging. Chlorine is sometimes added at the

headworks to prevent algae growth on the walls of the flocculationand sedimentation basins. (WASA, Waste Water Treatment, 2008)

In theory this process is referred to as flash mixing. These mixers are often expensiveto maintain.

Flocculation-Sedimentation Basins

The Flocculation basin allows the constant mixing of microfloc formed duringcoagulation. This allows for larger, heavier floc to form. After the water leaves theflocculation basins, it enters the sedimentation basins where solids are removedfrom water via gravity settling. A 1-2 hour period is enough for the floc to settle.(WASA, Waste Water Treatment, 2008)

The flocculation basin often has a number of compartments with decreasing mixingspeeds as the water advances through the basin. This compartmentalized chamberallows increasingly bulky floc to form without being broken apart by the mixingblades.

The sedimentation basin is designed to remove suspended organic solids from thewater. These solids are said to be heavier than water and settles slowly at 1.0 to2.5m/h. There are various types of sedimentation basins some are:

1) Circular basin center feed, 2) circular basin rim feed and 3) the long rectangularbasin. These are also referred to as clarifiers.


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Sludge Lagoon

This area is designated to store the sludge generated from the flocculation-sedimentation process. The sludge flows by gravity to the lagoons. The recoverypump located at the end of the north and south lagoon sections returns the clearwater from the lagoons to the headworks. (WASA, Waste Water Treatment, 2008)

Lagoons are classified by the amount of mechanical mixing necessary. For Aerobiclagoons enough energy is provided to keep the entire contents aerated. Facultativelagoons are supplied with only enough energy to mix the liquid portion of the lagoonand the solids that have sunk to the bottom undergo anaerobic degradation .

Filtration

Filtration allows the final and complete removal of any finely separated matter, andany remaining floc after the coagulation and sedimentation process.

The filtration system is a monotype constant rate gravity filtersystem. The filter media consist of six feet of sand. Periodic

backwashing of the filters is required to remove any accumulatedsuspended materials. - (WASA, Waste Water Treatment, 2008)

Normal sand filter systems are separated into two: types Slow Sand Filter Systemsand Rapid Sand Filter systems. Slow sand filter systems uses a cleaning systems whichdoes not require backwashing but rather scrapping and removing of the top layer.Rapid Sand Filters should be cleaned regularly. It is recommended that they arecleaned before each run. These filters are not as deep as the WASA type as the slowrapid system ranges from 30-75cm while the rapid sand filter system ranges from 60to 90cm. WASAs fi ltration system is referred to as a Tertiary Filtration System.


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DisinfectionFollowing filtration the water flows to the clear-well where it is disinfected andstored. Chlorine is added to the water to remove and destroy bacteria or virusespresent in the water. (WASA, Waste Water Treatment, 2008)

Disinfection refers to the elimination of pathogenic microorganisms. This reduces thepossibility of waterborne diseases occurring.

pH Adjustment

In order to maintain a pH level of 7 lime is added to the filtered water. Anappropriating agent is added to the water before distribution to control scaling andcorrosion. (WASA, Waste Water Treatment, 2008)

High Head Pump StationsThese pumps pump the filtered, chlorinated water from the clearwell into thepipeline distrubtion system. They then discharge into the common header pip that isconnected to the north and south transmission lines leaving the plant. (WASA, WasteWater Treatment, 2008)

Health and SafetyThese are the health and safety chemical guidelines according to (Health and Safetyat the Water and Sewerage Authority, 2008)

One of the main chemicals used in the water treatment process is chlorine gas. Thisgas, while being one of the most effective disinfectants for public water supplies, is

extremely dangerous to humans and other living species at high concentrations.Chlorine gas is supplied in 150 lbs. and one ton pressurized cylinders. In the event ofaccidental leakage, it is important for this situation to be arrested as early aspossible to prevent widespread injury. Our well-trained operators know how to usechlorine and contain a chlorine leak.


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Lime and alum are two other common chemicals used in water treatment. Lime(calcium oxide, is highly caustic and can cause blisters and severe irritation ifexposed to bare skin. Alum, aluminium sulphate, is corrosive and care must be takento avoid skin contact or inhalation. It will even damage the soles of strong shoes!

One of the most recently introduced chemicals is polyaluminium chloride (PAC). It isused to enhance flocculation and sedimentation in the water treatment process andmust still be handled with extreme care.

On water treatment plants our operators and chemical mixers, those most at risk ofcoming into contact with chemicals, are provided with a range of PPE speciallyselected to suit the type the hazard they face.

In addition, Material Safety Data Sheets (MSDS) are provided wherever chemicals areused. These provide critical information on each chemical, its characteristics, whatwould be considered safe limits for exposure, guidelines for transportation,instructions on how to handle spillage and emergency measures in the event ofcontact.

WASA also require the following PPE:

1. Head Protection: Hard hats class E2. Face Protection: Face visors

3. Eye Protection: Safety glasses, safety goggles

4. Ear Protection: Earmuffs and earplugs

5. Respiratory System Protection: Full-face respirators, half face respirators with

variable filters, dust masks, self-contained breathing apparatus

6. Hand Protection: Gloves specially designed to protect against cuts, heat and

abrasions

7. Foot protection: Steel tipped boots

8. Whole Body protection: Fabric and plastic coveralls, Hazmat suits, reflective

vest and safety harnesses.


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Conclusion

According to (Sharda Surujdeo-Maharaj, 2007 )the Water and Sewerage Authorityindicated that 92% of the population of this country have access to drinking waterand sanitation and state that their drinking water supply meets stringent WorldHealth Organization standards.


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References(EPA), U. S. (June 2003). Wastewater Technology Fact Sheet: Screening and Grit Removal. Office of Water.

Hygiene and Environmental Health HEAT Module . (2011). Retrieved from LabSpace:http://labspace.open.ac.uk/mod/oucontent/view.php?id=453412&section=1.4

Ragsdale and Associates Training Specialists, LLC. (n.d.). Tertiary Treatment. In F. Ragsdale, WASTEWATER

SYSTEM OPERATORS MANUAL. Albuquerque: Ragsdale and Associates Training Specialists.

Sharda Surujdeo-Maharaj, M. A.-K. (2007 ). CHEMICAL WATER QUALITY OF RIVERS . St Augustine: TheUniversity of the West Indies .

WASA. ( 2008). Arena Reservoir . Retrieved from WASA:http://www.wasa.gov.tt/WASA_Education_water_Reservoir_Arena.html

WASA. (2008). Waste Water Treatment . Retrieved from Water Sewerage Authority Trinidad and Tobago:http://www.wasa.gov.tt/WASA_Education_water_WaterTreatment.html

WASA. (2012). Wastewater & Re-use Student Study Manual.

WASA, W. S. (2008). Health and Safety at the Water and Sewerage Authority . Retrieved from WaterSewerage Authority Trinidad and Tobago: http://www.wasa.gov.tt/