the feasibility of ozone for purification of hatchery waters

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The Feasibility Of Ozone ForPurification of Hatchery WatersDarrell W. Monroe & William Phillip KeyPublished online: 23 Jul 2008.

To cite this article: Darrell W. Monroe & William Phillip Key (1980) The Feasibility OfOzone For Purification of Hatchery Waters, Ozone: Science & Engineering: The Journal ofthe International Ozone Association, 2:3, 203-224, DOI: 10.1080/01919518008550883

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OZONE: SCIENCE AND ENGINEERING 0191-9512/80/030203-22$02.00/0Vol. 2, pp. 203-224, 1980 International Ozone AssociationPergamon Press Ltd Copyright (c) 1981Printed in the USA

THE FEASIBILITY OF OZONEFOR PURIFICATION OF HATCHERY WATERS

Darrell W. Monroe and William Phillip Key

Environmental Process Analysts and Advisors, Inc.Lakewood, Colorado

Abstract

Ozone is feasible as a disinfectant of nursery tank makeup waterin a planned recycle system at the Dworshak National Fish Hatchery.A dosage of 3 mg/L ozone to the makeup water should prevent diseasecarrying organisms and algae from entering the nursery tank systemby way of the makeup water which is taken from the North Fork of theClearwater River.

In December of 1977, the consulting engineering firm, EnvironmentalProcess Analysts and Advisors, Inc. of Lakewood, Colorado, was contracted bythe Hatchery Study Group, U.S. Army Corps of Engineers, Walla Walla District,Walla Walla, Washington to study the feasibility of using ozone to purifywaters used in fish hatcheries. The study was confined to investigationof the use of ozone at the Dworshak National Fish Hatchery on the North Forkof the Clearwater River in Idaho. The information contained in this reportis the direct result of the findings of this feasibility study.

The Dworshak National Fish Hatchery was built to perpetuate the anadro-mous steelhead trout run blocked by construction of the Dworshak Dam on theNorth Fork of the Clearwater River. The hatchery and dam were constructed bythe Army Corps of Engineers and the hatchery is operated by the Fish andWildlife Service, Department of the Interior.

This facility is the largest steelhead hatchery in the world, releasingover three million steelhead smolts each year. The first smolts were releasedin 1970 and adult spawners from that age group and subsequent smolt releaseshave returned to the hatchery.

The hatchery is a unique facility, responsible for maintenance of avaluable resource and faces special problems. The species of steelheadinhabiting the North Fork of the Clearwater is noted for its size, strength,and excellence as a game fish. The specie has not completely adapted to thehatchery environment and exhibits sensitivities to stress not associated withmore domesticated hatchery strains of trout.

The hatchery is of the re-use type with biofilters installed forammonia, nitrogen, and BOD5 removal and a nominal 10% freshwater makeup. Thewater chemistry characteristics of the makeup water from the North Fork ofthe Clearwater River lend a further complexity to the successful operation ofthe facility. This river water has been compared to distilled water and isvery low in hardness and alkalinity.

A general description of the flow scheme of the three existing systemswould show rearing pond water flowing by gravity to filter beds for treatmentand then into a sump. The treated water is pumped from the sump to an aerationtower and returned to the rearing ponds by gravity. Ten percent of the treatedwater is wasted to the river before aeration. Makeup water is added to thetreated flow just prior to the flow entering the aeration towers for System Iand after the aeration towers for Systems II and III. The makeup water is

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204 D.W. Monroe and W.P. Key-

prepared for use in the system first by contact with electric grids, then sandfiltration, and finally by ultraviolet light for disinfection.

The makeup water also serves to heat or cool the main water flow. Thethree existing systems are described in Table I.

TABLE I. EXISTING SYSTEM DESCRIPTION

Ponds Flowrate1Biofilter Filter Loading""System Rearing Nursery (GPM) Type Media (GPK/FT2)

I 25 64 15,000 Dovmflow Oyster Shell 1& crushedrock

II 25 ~ 15,000 Upflow Norton Rings2 23-1/2 inch

III 34 — 22,500 Upflow Norton Rings 23-1/2 inch

Notes: 1) Make-up water comprises ten percent of total flow.2) System II filters are being converted to granular

media (Sept.-Dec, 1977).3) Design value.

Each of the existing systems have faced the same problem during facilityoperation. Neither of the two original filter bed designs has ever been ableto achieve the design loading value. Ammonia and nitrite values from thefilter beds often approach toxic levels and at times exceed those levels.This has led to forced reduction from the design value in the number of fishheld in the rearing ponds. While the reduced water quality of the recycleflow may make the fish population more sensitive to infection from disease,the lack of minerals in the water is probably of more importance in thisregard.

The nitrifiers in the biofilters are further hampered at times byalgae growth on the filter media. Algal blooms also occur in the rearingponds. The known inefficiency of ultraviolet light for destroying algae in themakeup water plus the probability that some disease-causing organisms weresurviving the ultraviolet light system led to the investigation of ozone as asterilant.

These investigations were funded by The Office of Water Research andTechnology, Department of the Interior, The Water Resources Research Institute,University of Idaho, and, in part, by the Walla Walla District Corps of Engi-neers .

General conclusions contained in these studies can be summarized asfollows:

1. Ozone can be expected to do a significantly better job of watermakeup sterilization than ultraviolet light.

2. Side benefits to the use of the ozone as a makeup water sterilantwill probably enhance operation of other parts of the system andlessen stress on the fish. For example:a. Destruction of incoming algae would improve biofilter operations.b. Decreased ammonia, increased nitrate, and decreased total

organic nitrogen concentrations can be expected.c. A more uniform BODc concentration can be expected in the reuse

water.d. Reduction of suspended organic material.

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Ozone Purification of Hatchery Waters 205

3. High ozone residuals remaining in the water in contact with thefish could adversely affect the population. However, exposureconcentrations of 0.1 mg/L for a period of two days and two over-dose accidents during the studies caused no fish mortalities.

4. Ozone treatment appeared to be more expensive on both a capitalcost and annual cost basis than ultraviolet treatment.

The purpose of this study is to address in a preliminary design reportthe economic and technical design feasibility of applying ozone for disinfectionof the makeup water for a fourth system under consideration at the DworshakNational Fish Hatchery.

Design Conditions

The following conditions were used for design purposes and were stipulatedin the contract Statement of Work (SOW), derived from previous studies atDworshak, or are drawn from engineering knowledge of previous ozone applicationsfor water disinfection. The SOW describes the fourth system as a new rearingsystem to be added to the facility. The biological filter beds for System IVare to be installed in existing concrete vessels at the site but a newmechanical building and aeration towers are to be constructed. The newmechanical building design will incorporate water filtration equipment, waterheating and cooling equipment, pumps, electrical switchgear and the ozoneequipment.

The makeup water to be disinfected is to be used for the purpose ofsupplementing recycle flow to nursery tanks holding the fish fresh from theincubators. The nursery tanks are existing vessels and will be repiped fromSystem I to the new System IV. System IV will be comprised of four separateand independent flow subsystems with any combination of the four subsystemsin operation at any given time.

The water to be disinfected is taken from the North Fork of the Clear-water River immediately adjacent to the Hatchery. Flowrates for makeup waterof System IV are defined as varying from 100 gpm to 1000 gpm. This water Is100% saturated with dissolved oxygen and nitrogen gas with super saturationconcentrations of at least 120% possible for each gas on an extended basis.The raw water temperature ranges from 34° to 70° F and 10 feet of head isavailable as the water enters the new mechanical building.

The recycle water flowrates in System IV are defined as 2000 gpm per sub-system or a total of 8000 gpm. The characteristics of this recycle waterare obviously difficult to predict and for the purposes of this preliminaryreport the recycle water quality of System IV is assumed to have approximatelyone-half the Chemical Oxygen Demand (COD) of that found during normal operationin existing systems I,II, and III. The characteristics for recycle water fromthe existing systems were derived from data sheets prepared by Fish and Wild-life personnel operating the facility.

The test work Is severely limited in its use for design purposes in thatvery few tables or graphs list the actual ozone dosage applied or the ozonegenerator efficiency (% ozone by weight of feed gas) used for that particulartest. Ozone dosage values are critical since in engineering design practicethese 'values are used to size normal and maximum operating supply capabilitiesof the systems. Significant capital cost and measurable operating costsavings can be achieved with accurate knowledge of ozone dosage requirements.

The values used for ozone generator efficiency output are just ascritical. The driving force for transferring ozone from a gaseous form intothe liquid being treated is closely related to the concentration of ozone inthe feed gas applied to the liquid. The Importance of understanding therelationship between disinfection efficiency of ozone and the ozone generatoroutput efficiency is that the power required for the ozone generator forozone production can be optimized only over a very narrow range of outputefficiencies. In the absence of clearly defined ozone dosage and generatorefficiency information, values of 3 mg/L as a maximum dosage and 1% ozone by

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206 D.W. Monroe and W.P. Key

weight of air for generator output will be used for design purposes.

The elevation of the Dworshak National Fish Hatchery was taken to beapproximately 1000 feet above sea level and appropriate ambient air temperatureand other meterological data were derived from the ASHRAE Handbook ofFundamentals, 1972 Edition.

Process Definition

Process considerations

The basic objectives of an ozone system installed at Dworshak will beto provide disinfection of the raw water makeup flow to the nursery tanksystem. Such disinfection should be sufficient to preclude entrance into thenursery tanks of disease causing bacteria and virus by means of the makeupwater.

Attaining this goal in an economical design requires consideration of anumber of factors influencing ozone generation and dissolution. The rawwater influent to the treatment system will exert some ozone demand due tosuspended solids and COD in the form of organic and inorganic compounds. Re-duction of this ozone demand usually results in reducing the amount of ozoneneeded to attain a given level of disinfection. The electric grid devicesused in the other three systems at Dworshak should be installed in System IVto remove higher order organisms from the influent raw water. The grids shouldbe followed by sand filtration to remove suspended solids which can alsoexert an ozone demand.

Given that the ozone demand has been reduced to a low value by practicaltreatment methods, design consideration can be focused on the method forcontacting ozone with the water to be treated. Various studies have demonstratedthat disinfection by ozone in water occurs due to two basic causes. Onecause of disinfection is actual contact of the microorganisms with ozonated gasin the bubble formed by the diffusers and thus destruction of the organism.However, most researchers feel this method of contact is of lesser importanceto disinfection than a second cause of microorganism destruction which istransfer of the ozone to the dissolved form in the liquid and subsequentdestruction of the microorganism.

There are essentially three different types of contact devices usedfor dissolving ozone in water; the porous dlffuser type, injector type andsubmerged turbine type. Porous diffuser systems are mounted at or near thebottom of a tank and bubble ozone (2-3mm bubbles) into the liquid. Eithertank depth or water flow counter to the flow of the oxygen gas is used toattain dissolution of ozone from the gaseous to the dissolved form. Advantagesto this contactor include minimal loss of hydraulic head, the energy of theair compressors used to supply the ozone generators is conserved to bubble thegas into the liquid,diffuser materials are compatible with ozone and there isat least some operational data on the use of the contactor for disinfection.

Both the injector type and submerged turbines have the claimed advantageof being highly efficient. Both systems attain that efficiency by expenditureof energy; the injector type due to the high pressure head that must besupplied to the water, and the submerged turbine due to the need for an addition-al compressor and a gear reducer to drive the turbine. While these systemsmay be feasible for larger disinfection or industrial applications, it isfelt that the simplicity of design and operation and the economics of theporous diffuser system warrant its selection for dissolution of ozone atDworshak.

Efficient dissolution of ozone into a liquid by a porous diffuser is theresult of a set of complex interactions. These interactions include thewater depth in the contact tank, the bubble size produced by the diffusers,temperature of the water, flow velocity and direction of the water, ozoneresidual in the water, barometric pressure due to elevation and concentrationof the ozone in the carrier or feed gas.

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The relationship of the various interactions is described mathematically in

the equation for mass transfer of a gas (ozone) to a liquid (water) per unit time:

dcs - KDA (Cs - Cw)

dt

Where K = a constant

D = ozone diffusion coefficient

A = total surface area of the ozonated air bubbles

Cs= ozone concentration at the saturation point for the liquid

Cw= residual ozone concentration in the water

The K and D factors are constant for a given application and cannot be changedto effect more efficient transfer. The remaining three variables, A, Cs, and Cw

can be controlled either by design considerations or operative manipulationand are therefore of interest to the designer. The A factor is a function ofthe volume of ozonated air applied to the diffusers and the diameter of thebubbles generated by the diffusers. An equation for this relationship showsthat the total surface area of the ozonated air bubbles are directly proportionalto six (6) times the volume of ozonated air piped to the diffusers (v) andinversely proportional to the diameter of the ozonated air bubbles (d), as isshown mathematically in the following equation:

ATotal = 6 x v

Thus, A can be increased either by increasing the volume of ozonated air orby decreasing the bubble diameter formed.

Porous media diffusers composed of aluminum oxide have been chosen formany ozone disinfection systems in this country. The diffuser can be purchasedin various porosities capable of producing 2-3mm bubbles over a wide range ofgas flow rates. This flexibility maintains the smallest practical bubblesize while allowing significant changes in gas volume flow to meet changingdosage requirements.

The Cs factor is a function of Henry's Law, which states that the sol-ubility of a gas is directly proportional to its partial pressure and that ina mixture of gases each will dissolve independently of the other and in directproportion to its partial pressure. Assuming a contact tank depth of twenty(20) feet, elevation of 1000 feet above sea level, and water at 50° F (10°C), thesaturation value for ozone in water is approximately 6.8 ng/L. This value isalso related to an ozone concentration In the feed gas (air) or 1% by weight.

The water depth of twenty feet is chosen from experience that indicatesa 2-3 mm air bubble containing ozone will dissolve approximately 90% of thatozone in the liquid before the bubble reaches the surface. The concentration of1% ozone in the feed gas is chosen because this is typically the most economicaloperating point for ozone generators using air as a feed source.

The C factor directly affects ozone transfer. The critical aspect ofC is that it be high enough to uniformly cause disinfection and yet lowenough to maintain efficient ozone usage. Proper monitoring of (!„ in theholding tank with feedback to logic affecting the ozone generator output is anecessary design feature.

Almost all ozone disinfection systems in this country are designed withsufficient volume in the ozone contact tank or tanks immediately downstreamto create an effective holding volume. There is considerable debate in theozone applicatinn community concerning how rapidly disinfection with ozone

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occurs, and where, with respect to the diffuser, does microorganism inactivationoccur. It is felt that with the type diffuser and contact tank proposed inthis study an additional holding tank volume is necessary.

For the application at Dworshak, the holding tank provides anotherfeature compatible with the unique characteristics of the facility. Sinceozone degrades to oxygen in water with respect to time, the holding tank servesnot only to offer additional opportunity for disinfection but also for signifi-cant natural reduction of the ozone to oxygen well before any possibilityof contact with the fish.

Previous studies at Dworshak indicate that the half-life of ozone in theraw water can be as low as eight (8) minutes due to the rate of ozone decomposi-tion being increased by the presence in the water of inorganics exhibiting anozone demand. With knowledge of the fragile nature of the fish population, aholding tank with approximately fifteen (15) minutes detention time is recom-mended. A more detailed discussion of ozone decomposition and concentrationdownstream from the contact tank is presented in the Dosage Calculation sectionof this report.

Since the ozone dissolution system is expected to dissolve at least 90%of the ozone fed to the liquid, provisions must be made to destroy the remaining10% ozone contained in the gas collected in the sealed ullage space above thecontact and holding tanks. The requirement to destroy the remaining ozonebefore venting to the atmosphere stems from the fact that ozone at the concen-tration to be found in the vent stream, approximately 1000 ppm, is highlyobjectionable to humans, can harm nearby plant life, and causes destructionof certain organic compounds, notably rubber.

Early ozone destruct devices used high temperature to decompose ozone,converting it to oxygen before venting any gas. Typically these units operatedat 610° F (320°C) to decompose the ozone. In the last few years, ozone destructunits have been developed that operate efficiently at much lower temperatures(-hence, significantly less power). These units pass the vent gas over a pre-heated material that causes a catalytic decomposition of the ozone to oxygen.These units are available from a number of suppliers, require minimal mainten-ance or changing of the catalytic bed and are presently being operated orinstalled in a number of locations in this country.

An alternative concept for off-gas ozone destruction would be consideredduring the design phase of this project. This concept would use a blower toforce the off-gas from the contact ullage space through gas piping to thewater pipe used to waste water from the biofliters to the river. It ishighly probable that the ozone demand in this water (the 10% of all recycleflow wasted to the river), would reduce the ozone content in the gas effectivelyto zero. Capital cost savings of between $5,000 - $10,000 could be realized bydeletion of the ozone destruct device.

A final process consideration for design is the heat generation by theozone generators and the auxiliary equipment in the system. Ozone generatorsproduce substantial amounts of heat that must be removed by either coolingwater or forced air convection. The air compressors supplying the ozonegenerators also require cooling water flow. The ozone destruct unit can beconfigured to reclaim heat that would normally be vented to the atmosphere.

Heat reclamation or dissipation is a process consideration since thedisinfected makeup water usually needs to be heated to match the temperatureof the recycle water in the nursery tanks. The feasibility of using excessheat from the ozone generation system to pre-heat the raw water and thematerials compatibility questions associated with the heat exchangers arediscussed later in this report.

Process Description

Figure I describes the basic treatment process for the makeup water inSystem IV derived from the process considerations discussed above. The raw

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water passes first through an electric grid device and then through sandfilters. Filtered water flows to the ozone contact tank where ozone dis-solution occurs and then to a holding tank with approximately fifteen (15)minutes detention time. The disinfected makeup water then passes throughheat exchangers that heat or cool the water as necessary to match the recycleflow temperature. The heat exchangers are similar to those used in existingSystems I through III.

Make-LpRaw V.atpr100 - 1C00 GPM, 3W0°F

03 ResidualDiversionTo waste

101 continuouswaste ^

25 -250 GPM eact

AerationTowers200-2000 GrM each

Eio-Filters200 - 2000 CPH each

FIG. I. Nursery Tank System Water Flow Schematic.

It is worth re-emphasizing the critical nature for proper functioningof this disinfection system. The fish in the nursery tanks comprise a fullyear's production and cannot be replaced. With this concern in mind, thedisinfection system must have a control system that will consistently performtwo basic functions:

1. Maintain a high level of makeup water disinfection and quicklynotify operators of the existence of anomaly situations that would

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affect this function.2. Preclude an occurnnce such that residual ozone is introduced into

the nursery tanks.

Figure 2 describes a control system capable of performing the abovefunctions. Air is compressed to a pressure of 15 psig and delivered to theozone generator at a temperature of 80°F . A 100% standby compressor shallbe supplied. The compressed air is delivered to a reciprocating heatless-type drier. The separate beds of the drier are automatically regeneratedand provide dry air at a dew point of -60°F to the ozone generator.

A particulate filter is located downstream from the drier assemblyto prevent "dusting" (particulate matter) from the drier reaching theozone generator. Between the filter and the ozone generator the air flowis regulated to the proper pressure. The dewpoint of the air flow is alsomonitored between the drier and the ozone generator.

The dry air flowrate to the ozone generator is established by a manualset point. Since the water flow rate in the nursery tanks at Dworshak isessentially constant for long periods of time, the manual method can be usedfor establishing an air flow set point which represents a "constant" waterflow.

The residual ozone analyzer at the outlet of the ozone holding tankmonitors the residual ozone concentration in the disinfected makeup water.This residual analyzer converts the ozone concentration reading (0-lppm)to a proportional 4-20 ma DC signal that is sent through proper buffer devicesto a control module and also to the control systems annunciator subsystem.The control module compares the residual analyzer signal with a manuallyestablished setpoint from an analyzer-indicating-controller (AIC). Thecomparison results in a 4-20 ma DC control signal being sent to an ozonegenerator controller that automatically adjusts power to the generator tomaintain the ozone residual concentration between pre-set values. The controlmodule will include two mode control (proportional, reset) so that theresidual analyzer signal will be compared at sufficient lengths of time sothat the ozone generator is not being forced to continually "hunt" a propersetting. Again, the uniform water flows at Dworshak complement this typecontrol method.

The signal from the ozone analyzer to tha annunciator subsystem isautomatically monitored on a continuous basis. If the signal indicates theresidual concentration stays below the residual setpoint for a predeterminedtime, both visual and audible alarms will alert the operator. A recorderdescribing the residual concentration history will assist the operator indetermining whether to reset the generator setpoint. If necessary, the airflow setpoint can be adjusted upward as well.

If the residual analyzer signal stays between 10 and 20% above the set-point for a predetermined time, visual and audible alarms will require theoperator to verify analyzer accuracy and determine whether to change therespective setpoint values for ozone dosage and airflow. A residual analyzersignal indicating residual ozone concentrations 25% greater than the setpointvalue will cause makeup water from the holding tank to be wasted to theriver until the problem is corrected. The concentration of ozone in theullage space is compared to a setpoint value ( actually a range due to thecomplexity of mass transfer) and if higher than the allowable an appropriatesignal is made to the operator. A higher than allowed ozone concentrationin the ullage space off gas could indicate either a diffuser failure or aleak at a joint in the supply piping. Ozone concentration in the buildingatmosphere is also monitored and an out-of-tolerance condition causes analarm situation for the operator. Table II lists anomaly situations,appropriate alarms, and operator actions.

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airHaVe-up l n t a V ' e

water supply.cooling tater

Interlock

air flow setpoint (annual)

air ozoneanalyzer

- dewpolnt

airflow- air tenp

- Inter--J lock

[ tratlon

X. __Air/Ozone

I (—| Coolins water -IJ Interlock -I

.Jr i,

OzoneGenerator

DU.tt o'f- / a _ fl f= 1gas blover / V !J

i l=5n I—

• Main circuit breaker. Kaln po^er control

Rerotc start

- Surge protectionSystw interlockLa=p testAnalog inout

. Residual ozone recorder

Control signil to DJke-upv.HPr waste valves

FIG. 2. Controls and Instrumentation Schematic

TABLE II. CO'iTPOL SYSTEM FL-VCTTONS

1. toss of power to ozonegenerator main systemcircuit breaker.

2. Lou air flow to theozone generator.

3. High air temperature

4. Low cooling water flow to

5. Ozone generator failure.

6. Ozone low output.

?, Ozone analyzer failure*

8. High Ozone concentrationIn bulldlog*

9. High ozone concentrationin ullage space.

10. High devpolnt tempera-ture In air flow to gen-erator.

11. High ozone residual Inholding tank effluent.

ALARM

visualaudible

Raw water flow automaticallystopped until disinfectionsystem can be rc-started.

Automatic switching toback-up subsystea.

Automatic switching toback-up subsystem.

Switch to back-up vaterflow; if condition persists,•witch ozone generator sub-systems .

Automatic switching to back-up generator aubsysten.

Automatic switching to back-

Kone until failure verifiedby operator.

Purge system activated inbuilding.None until condition verified.

Autocratic switching to back-

Bypass valves activated towaste nakcup water until con-dition corrected.

Manual action by operatorto restart disinfectionsystem.

System action verified byoperator; troubleshootcompressor.

System action verified byoperator; troubleshootconprenor.

Operator verifies actionand troubleshoots system.

Operator verification andtroubleshoots generator.

Operator verification andtroubleshoots generator.

Manual action by operatorto establish an ozone out-put to nalntaln disinfection.

Operator verification.

Operator verifies condi-tion before shutting downsystem.

System action verified byoperator; troubleshootssubsystem.

Operator verifies action andtroubleshoots systea.

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Dosage Calculations

Estimating a dosage supply capability for an ozone disinfection processis normally a fairly straight-forward, simple effort. The application atDworshak, however, presents special problems. Little previous work is ofuse in predicting either the normal operating dosage value or the maximum supplydosage to be provided. This situation has led to the selection of 3 mg/L as amaximum supply dosage for the reasons outlined in the Design Conditions Section.The calculation for ozone dosage for any row water flow rate is then:pounds ozone/day=(mg/L ozone)(gpm flowrate)(1440mln)(8.34Pound)10~6

day 8ai

Therefore, for a maximum flowrate of 1000 gpm and a maximum ozonedosage of 3 mg/L, 36 pounds/day of ozone supply capacity is required.

It is not known at this time whether a full 3 mg/L ozone dosage will berequired to attain disinfection of the raw makeup water. An engineeringjudgement based on the purity of the makeup water, the uniformity of liquidflow, and the uniform low ozone demand in the makeup flow suggests the normaloperating dosage will be less than 3 mg/L. The system design will thenobviously have to accomodate lower dosage rates without affecting disinfectionefficiency or operational economy.

This requirement to accomodate gas flows below the design value takeson increased significance when one considers that the minimum makeup flowrate is 100 gpm. This liquid flow rate requires an ozone supply of only 3.6pounds/day for a 3 mg/L dosage. Therefore, from maximum water flow to minimumwater flow a 10:1 turndown capability is required of all components of thesystem while maintaining disinfection efficiency. Consider now the operationalcondition facing the disinfection system if treatment can be attained duringperiods of operation at 1 mg/L and if these low dosage requirements coincidewith the minimum water flow periods (100 gpm). This operational conditionwould call for an ozone supply of only 1.2 pounds ozone/day and a 30:1 turndowncapability in the entire system.

This requirement for such a broad range of system supply capabilitydoes not rule out ozone as a potential candidate for disinfection. Therequirement does lead to a set of specific recommendations pertinent to thedesign phase of this project:

1. Operational personnel should determine whether or not makeup waterflowrates will actually vary from 100 gpm to 1000 gpm in thenursery tank system.

2. With respect to the conclusion in the analysis in (1) the specifica-tion for bid should be as clear as possible in defining for equipmentsuppliers the supply range over which the system must operate.

3. Provide sufficient design time and funding to address in necessarydetail the functional integration of all system and subsystem com-ponents. Although analysis to date indicates the 30:1 turndownrange is feasible for all components, there are questions of airsupply, valve sizing, diffuser flow maintenance, and controlintegration that must be further studied.

This section of Dosage Calculation will also be used to address thesafety aspect associated with using ozone around the young, fragile fishpopulation. The context of this task in the SOW is that an analysis beperformed to determine what safety features need to be included in the systemdesign to assure the isolation of the fish from residual ozone. The analyticalresult of this task is that an ozone residual analyzer properly integratedinto the system controls can provide such assurance. A further conclusionis that no additional processes, such as activated carbon, need be added toscrub ozone residual from the system.

Table III describes the analysis results and demonstrates how theconclusion was drawn. The analysis essentially traces the makeup waterthrough the process and predicts the concentration of ozone at each treatmentstep. The analysis assumes a flow of 1000 gpm makeup water and 7200 gpm recyclewater (after wasting 10%) with these values derived from the SOW. A value

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for COD (4 25 mg/L) in the raw river water was derived from laboratory datacompleted by Dworshak operational personnel as reported by the Corps ofEngineers. This same data showed the raw river water COD usually is reducedby 1 mg/L by the sand filters in use. This reduction is reasonable andcan be attributed to removal of suspended solids by the sand filters.

Water from the existing biofilters averages about 11 mg/L COD and thisanalysis assumes one-half that value, or 5.5 mg/L COD, will be present inwater having been treated by biofilters in the nursery tank system. Eventhis reduced concentration of COD amounts to over 500 pounds per day ofchemically oxidizable matter for a liquid flowrate of approximately 8000 gpm. Itshould be noted that at least a portion of the COD in the recycle water will bein a readily oxidizable condition and will probably even include suspendedsolids. With this knowledge and knowing the highly turbulent nature of theaeration tank flow it seems safe to predict that any residual ozone injectedinto this water will be consumed.

Note that this analysis has assumed a worst case dosage situation of3 mg/L, that ozone half-life reduction has been assumed for only the holdingtank volume, that only 25% of the COD in the raw water is assumed to readilyreact with the dissolved ozone, and that even the flowrate ratio of makeupwater to recycle water (0.14 or 14%) is conservative. The result of thisanalysis is to conclude that there is ample safety margin to protect the fishand that with the present flow rate process there is no need to include treat-ment systems such as activated.carbon to scrub ozone from the disinfected make-up water.

TABLE III. OZONE CONCENTRATION IN PROCESS WATER

OZONE DEMAND (COD) INITIAL OZONE DOSAGEPROCESS LOCATION mg/1 pound/day 1 mg/1 3 mg/1

OZONE RESIDUALlb/day mg/1 lb/day mg/1

1. System makeup 4.25 51water inlet

2. Inlet to ozone 3.25 39 10.8 0.9 32.4 2.7contact tank

3. Inlet to ozone 2.44 29.25 1.05 0.09 22.65 1.89holding tank

4. Outlet from o- 2.44 29.25 0.53 0.045 11.33 0.94zone holding tank

5. Inlet to aera- 5.12 504.25 0.53 0.0005 11.33 0.12tion tower

6. Outlet from aer- 5.0 500 0 0, 0 0ation tower

Notes - Pertinent to respective system location:

1. Flow rates at system inlet assumed 1000 gpm for both dosages.

2. Assume 1 mg/1 reduction in COD due to sand filters; also 907. ofozone dosage is dissolved.

3. Assumes COD/ozone reaction is essentially instantaneous and thatonly 25% of COD is destroyed; also, 1:1 relationship in reaction.

4. No further COD reduction occurs in the makeup water; half life ofozone is fifteen minutes.

5. Assumes recycle flow of 8000 gpm is 10% wasted before injection toaeration towers; assumes COD of 5.5 mg/1 (one-half the value gen-erated by rearing ponds).

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Equipment Description

Selection and sizing

The task to size and select equipment is a function controlled byspecifics of geographic location, facility limitations, supply requirements,operational constraints, and economic considerations. In requesting quotationsfrom ozone generator manufacturers, four basic considerations were stressed:turn-down capability, power consumption, heat generation, and comparison ofdifferent capacity generators. These basic considerations were supplementedby specific requirements of ambient conditions, facility characteristics, etc.These requirements were expressed to leading manufacturers in the form ofa preliminary specification as shown in Table IV.

TABLE IV. OZONE GENERATION SYSTEM PRELIMINARY SPECIFICATION

Parameter Requirement

1. Ozone generator efficiency 1% by weight of air

2. Ozone generator pressure 15 gsig3. Feed gas dewpoint -60 FA. Inlet gas temperature to the

ozone generator 80 F5. Power 460 volt, 3 phase, 60 hz6. Production Capacity 36 lb/day with two options allowed:

a. 2 machines operating, 1 standbyb. 4 machines operating, 1 standby

7 Ambient Air Conditions Temperature of 90°F max andrelative humidity of 60 F

8. Elevation 1000-1500 ft. above si-a level9 Turndown 10:1Based on this specification, the manufacturers were asked to:

1. Provide budgetary estimates for each of the supply capacities.2. Provide power information on the system:

a. Total draw in Kw including auxiliariesb. Power consumed at 10% and 100% of designc. Power factor at design

3. List cooling water or cooling air requirements and a nominal valuefor BTU/lb ozone generated.

4. List all auxiliary equipment and include a breakdown of specificauxiliary equipment power requirements.

5. Include system installation in the budgetary estimates, spare partsfor one year, and startup assistance; in addition, Union Carbide andEmery were asked to quote on an ozone destruct device capable ofhandling 50 scfm of ozone containing air at saturated conditions.

Union Carbide, Emery, PCI, U.S. Ozonair, Crane, and OREC have allresponded to the specification. The quotations and literature received fromthese manufacturers were generally responsive to the criteria of the specifica-tions with the following exceptions:

1. PCI and Ozonair both offered machines rated at 2% ozone by weightof air for the preliminary design conditions and quoted powerconsumption based on that generator efficiency.

2. Union Carbide offers only an air-cooled ozone generator and instal-lation of this system would necessitate a modified mechanicalbuilding design and possible inclusion of gas (air) to liquid (makeupwater) heat exchangers to reclaim the heat produced by the generationof ozone.

3. Union Carbide does not offer an ozone generator or combination ofgenerators to exactly match the 36 pound/day ozone supply requirement.

Although these exceptions to the specification were significant, thereare other considerations in each manufacturers design that offset the impactof taking exception to the preliminary design conditions. The decision by PCI

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and Ozonair to offer 2% efficient generators would affect control selection andsizing, gas pipe setting, ozone analyzer range definition, diffuser flowrating, etc. However, the two manufacturer's quoted power consumption valuesat the higher efficiency are competitive with the other manufacturer'squotes at the specified lower efficiency. This is significant since 2% ozoneby weight in air as the feed gas to the contact tank dlffusers would resultin a higher driving force for dissolution of ozone. Thus, less ozone wouldbe lost into the ullage space off-gas and it is possible a smaller ozonedosage would be needed to attain a given level of disinfection. Likewise,even though the Union Carbide generator is oversized for the subject application,this generator is cost competitive with the smaller generators offered bythe other manufacturers. The extra capacity offered by the Union Carbidesystem could be very advantageous to the Phase II disinfection study on thisproject which involves the capability to disinfect an entire recycle flowsubsystem of SystemlV. Also, the Union Carbide Corporation offers a four-yearwarranty on the ozone generator dielectric cells - a warranty unmatched byany other manufacturer.

Power consumption

Power consumption in an ozone generation system is a critical operationcost item over the project life of a system. Ozone generators operating onoxygen feed typically require 4-5 KWH per each pound ozone produced. Ozonegenerators operating on air feed typically require 10-12 KWH per each poundof ozone produced. The increase in power consumption for air versus oxygenfeed is due to two causes:

1. Ozone generators are inherently less efficient on air compared tooxygen feed, i.e., a given flow rate of gas results in fewerpounds of ozone produced when air is the feed gas.

2. Air to be used as the feed gas must be filtered, compressed, anddried before being used as the supply gas to the ozone generator;the auxiliary equipment used to prepare the gas requires additionalpower.

Table V compares ozone generator quotations for power consumption atthe design conditions listed in the preliminary specification.

TABLE V. GENERATOR POWER CONSUMPTION

Manu-facturer

PCI

UnionCarbide

Ozonair

Crane

Emery

Orec

7. OzoneGenerated

22

11

22

11

11

11

ProductionCapacity

189

36.23

1912.

189

189

189

(2)(4)

4(1)(2)

(2)4(4)

(2)(4)

(2)(4)

(2)(4)

DrawKW

17.419.6

2727

N/A3

ti

•i

it

ii

n

2020

PowerKWH/lb(1007.)

11.513.0

14.22

13.9

9.99.9

12.012.0

12.312.3

13.513.5

ozone(107.)

7.15,5

18.418.0

N/AII

tl

II

11

II

5.05.0

PowerFactor

.95

.95

1.01.0

N/A

0.90.9

0.950.95

0.950.85

Notes: 1) lb 0,/Machine, (# machines operating, one standby).2) Basea on 70°F cooling air flow; power decreases to

12.9 KWH/lb 0, for 50°F cooling air.3) N/A - Not available.

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The values shown in Table V for KWH/pound ozone produced include thepower required for the ozone generator, the air compressor, and the air drier.A total system value for power consumption should include power for thecontact tank/holding tank ullage space air blower (0.1 hp) and the ozonedestruct unit (2KW). It should be apparent from the preceding section thatthere are significant differences in the design and performance capabilitiesof the competing machines. The significance of the difference is that aproperly drafted bid specification can emphasize criteria unique to the specificproject so that the most efficient system is contracted for, at a reasonablecost.

Electrical design

An ozone generation system is truly an integrated system with theperformance of the generator contingent upon continuous and regulated power,compressed and dried air, cooling water or air and output control (manualor from remote load stations). The criticalness of proper system performanceon the system as a whole does not seem to have been given equal considerationby all manufacturers in their electrical and control system designs.Consulting engineers, having recognized the importance of the design differences,are presently requiring inclusion of the following features in almost allfacilities where ozone application is an integral aspect of a process:

1. Power regulation to protect equipment from surge conditions.2. High and low power alarm contacts.3. Dewpoint sensors to monitor the drier output and shut down the

system if the output is out of tolerance.4. Low cooling water flow (or cooling air flow) alarm and shut-down.5. System shut-down for high ozone concentration in the ozone generator

vacinity.6. A single lamp test switch to test all control and alarm lamps pro-

vided with the generator.7. System interlock to preclude operation of the generator if an unsafe

condition exists.

Table VI summarizes a comparison of the electrical design featuresoffered by manufacturers responding to the specification.

TABLE V I . ELtCTRICM, DES:1: ) Or CZO'T GrvtEATIOV SYSTEM

Kanu-facttrer

rci

UnionCarbide

Ozon.tr

Emery

Crane

Orec

Ltcno:

I'alnCB

Y

H

H

Y

H

H

YHOPK/ACBfVrDev.in.TeripProt

MainPvrCnt

Y

Y

K

X

Y

N

Cnt

OzoneAlam

Y

N

H

OP

Y

Y

- Yes• 1.0

Ol rlonal, rot• Hot appllcabl

RemoteStart

Y

Y

a

Y

Y

11

Include:t

• Circuit breaker• Ptjier control

Dew,jolncInterlock

- Terr-eiatureFrotectloa

LouFlaiA l l

Y

Y

Y

Y

Y

R

In

•» Surgerm Prot.

Y

H

S

K

H

H

qjoted prlc*.

0»w.Alarm

Y

Y

N

OP

s

SysI / L

Y

Y

Y

Y

Y

Y

LouKaterFlov

Y

N/A

Y

Y

Y

Y

BlCatTei-o.

Y

Y

Y

H

H

Y

LampTest

Y

K

H

11

N

H

AialogIrput

Y

Y

N

H

N

X

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Cooling Water Requirements

The ozone generation system recommended for the application of Dworshakincludes subsystems that require cooling water or air to maintain the respectivesubsystem within an efficient operating temperature range. These subsystemsare for the ozone generator and the air compressor feeding the generator. Inaddition, the ozone destruct unit operates at approximately 300° F and thisunit can be designed to reclaim by heat exchanger much of the heat normallyvented to the atmosphere. Since the facility at Dworshak normally preheatsthe makeup water to match the temperature of the recycle water, it is a logicaldesign consideration to incorporate the cooling water requirements of theozone generation system into the heating system needed to preheat theSystem IV makeup water.

The ozone generator in realistic terms is an inefficient device - over90% of the input energy is lost as heat when air is used as the feed gas. Asan example, for a water cooled generator operating at 100% of output, approxi-mately 8 KWH generator power is required to produce one pound of ozone. Over7 KWH of the original 8 KWH input shows up as waste heat; this is approximately25,600 BTU per pound of ozone generated. Since ozone generators are moreefficient at cooler generator operating temperatures, this excess heat mustbe removed from the generator.

Likewise, the air compressor units supplied to provide compressed airto the ozone generators require water cooling due to frictional generation ofheat. A further source of heat is the 2 KW of power supplied to the ozonedestruct device to heat to catalyst to 300°F. A gas to liquid heat exchangercan be placed downstream of the destruct unit to reclaim much of this heat.

The intent of this task definition in the SOW was to determine if thewaste heat produced in the ozone generation system could be used to substantial-ly pre-heat the makeup water entering the system. The result of this analysisis that the ozone generation system does not produce enough heat to markedlyincrease the temperature of the makeup water. This analysis is based on amakeup water inlet temperature of 50° F and flowrate of 1000 gpm,100% ozonegenerator supply (36 pounds of ozone/day) and 100% power applied to both theair compressor and the ozone destruct unit. Under these conditions thetemperature of the total makeup water flow would be increased less than 0.5°Fif all the excess heat from the three subsystems could be reclaimed.

Although this temperature increase is not significant, it is recommendedthat the makeup water still be used for cooling the ozone generation systemcomponents. This recommendation is based on two factors:

1. Such a use of the makeup water does increase the temperature of thiswater, and;

2. In any event, the ozone generation system must be cooled; use ofthe makeup water reclaims over one million BTU/ day that wouldotherwise be wasted.D

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Figure 3 describes the recommended cooling water arrangement and includescooling water flowrates to the respective subsystems.

dual fdrier

recai"er ,̂- ;

airintake

Make-upwatpr si'pply

air filtur ™ 7 i f'\. _ r^ii

Mr/Oicne

Cooling water

^ £_ 4_ Ccolir.j w«l-er return

FIG. 3

Safety Aspects of Ozone Equipment and Processes

General

Ozone is a potentially dangerous substance and safety of personnel is abasic consideration in the design of systems applying ozone for disinfection.At high concentrations, ozone has a pungent, disagreeable odor and is blue incolor. In applications for disinfecting water, ozone is in a much more diluteform in a mixture of air or oxygen. At these lower concentrations ozone iseffectively colorless but its odor is still very noticeable, being detectableby humans at concentrations below 0.1 parts per million (ppm).

The maximum allowable exposure level of ozone for an eight hour workshift is 0.1 ppm. Since toxicity is a result of ozone concentration and timeof exposure, higher concentrations can be tolerated for a short time. Anexposure of one part per million for ten minutes is considered non-toxic byhealth authorities.

Building and Facility Requirements

The definition of the permissable ozone exposure level as being 0.1 ppm

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average over an eight hour work shift requires a continuous sampling of theambient conditions of the ozone generator building to protect the operatingpersonnel. A sampler with intakes located around the ozone generator willcontinuously monitor the ambient condition for ozone and compare this level witha set point. If the ambient condition exceeds the set point value, a visualalarm will be activated and an audible alarm will sound a warning to personnel.Emergency ventilation of the building will also occur if ambient ozone concen-tration exceeds the allowable value.

The ozone contact tank will be a covered tank to allow the off-gas to becollected. A purge blower will be provided to allow for a rapid removal ot theullage gas above the water surface inside the contact tank. This blower will alsohave the capability to provide fresh air to any personnel working inside thedrained contact tank.

The vent lines from all ozone sampling units will be routed to the contacttank ullage space and then forced through the ozone destruct unit. The ozonegenerators will require routine checking and maintenance. Depending on the unit,its location in the building should allow for sufficient area to remove thedielectrics (corona discharge chambers) for routine cleaning or replacement.The area required will depend on the type ozone generator installed but willusually not require more than four feet clearance on two sides of any generator.

All of the ozone generators should be located in the same relative areaof the building. The area immediately surrounding the ozone generators isusually isolated with a safety screen to prevent accidental injury to .anypersonnel.

The ozone destruct device will also require a sufficient access area toperform routine checks as well as maintenance to the unit. This includesremoval of the catalyst as well as the heating elements.

Safety Manuals and Procedures

Certain basic safety procedures should be made mandatory for personnelwhen operating or maintaining the ozone generation system. All safety devicesshould be maintained on a regular basis with particular emphasis on theventilation system for the mechanical building. Repair work should be done on aregular, scheduled basis with full knowledge of supervisory personnel and shouldbe structured to conform to the respective manufacturer's procedures. Onlyrecommended pipe fitting compounds and gaskets should be used on lines carryingozone containing gas. In addition to these procedures, the specificationdeveloped during the design phase and detailed safety procedures formulated foroperating the system should be in compliance with the following manuals:

1. American Society for Testing and Materials (ASTM) Standard E.591-77-Standard Practice for Safety and Health Requirements Relating toOccupational Exposure to Ozone.

2. Occupational Safety and Health Administration (OSHA) NationalInstitute of Occupational Safety and Health (NIOSH) Technical Standardand Supporting Documentation of Ozone; Draft Form.

3. General Requirements Safety Manual - EM385-1-1, Department of theArmy, Corps of Engineers, June 1, 1977; specific attention should begiven to subjects VI-Emergency Plans; X-Signals, Warning Signs andSignalmen; XV-Electrical Wiring and Apparatus; XXI-PressurizedEquipment Systems; XXVII-Work in Confined or Enclosed Space.

Materials

Suitable for ozone designs

Ozone is one of the strongest chemical oxidants used for water disinfec-tion. Materials compatibility with the gas and especially with the gas andwater or water vapor must be considered for any component in the systemexposed to the gas. Table VII lists suitable materials for ozone systems anduses to which the materials are normally applied.

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TABLE VII. OZONE SYSTEMS MATERIALS OF CONSTRUCTION

Material System usage In ozone application process

Type 304 or 316 stainless steel Gas piping from inlet filter, through airpreparation unit, through ozone generatorto contact tank diffusers; contact vessels;water gates and weirs, ozone sample lines.

Aluminum Gas piping from inlet filter through airpreparation unit to ozone generator.

Aluminum oxide Diffusers

Unplasticized PVC Ozone sample lines

Concrete Contact and holding vessels, channels, etc.

Teflon Ozone sample lines

Hypalon Gaskets

Viton Gaskets

The ozone generators are normally constructed from stainless steel,Hypalon, glass, or ceramic. Water cooled generators and auxiliaries normallyincorporate heat exchangers and after coolers with a copper shell and brasstube material, but stainless steel units can be provided at a minimal increasein cost.

Compatibility with fish

Steelhead trout, like other anadromous species, are sensitive to lowconcentrations of certain metals in water. Copper at concentrations below 20 mgper Liter has been shown to affect fingerling coho salmon and other juvenilesalmonids. A number of researchers have established a correlation thatindicates that cold water fish are more sensitive to low concentrations ofcopper in water with low total hardness. Since the water at Dworshak isrelatively low in total hardness, the use of copper or brass tubing should beavoided.

Zinc poisoning of fish in a trout hatchery has caused severe losses. Thezinc was dissolved from galvanized iron pipes in the system having acidicwater. Concentrations of 1 mg/L zinc have been shown to be lethal to trout.No galvanized materials should be used in the ozone generation system atDworshak.

Cadmium dissolved from cadmium plated metal has been found to be lethalto rainbow trout under certain conditions. Cadmium plated bolts and fastnersand screen devices are in common use and care sould be taken to insure againsttheir use in waters at any hatchery.

The examples listed above are representative of the results found in asearch of literature on toxicity of fish to metals. There does not appearto be any problem with the application of ozone to the hatchery water from amaterials standpoint. The generators, piping, and diffusers are all con-structed of materials not dangerous to the steelhead trout. The one possibleexception of the heat exchangers and aftercoolers can be rectified by specify-ing stainless steel units. Normal design and project managef'vigilance shouldbe used to preclude any use of galvanized or cadmium plated materials.

Budgetary Cost Estimate

Capital cost

A budgetary capital cost estimate has been developed for the ozone gen-eration system analyzed and described in preceedlng sections of this report.This cost estimate is for equipment developed from the design criteria defined

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previously. The estimate does not include costs for water piping, electricgrid, sand filters, ozone contact or holding tanks, heat exchangers, anystructural aspect of the mechanical building, or any valves associated withthe makeup water flow.

A budgetary estimate was developed for two alternatives each of whichwill supply 36 pounds/day of ozone on feed air; two machines operating withone standby, and four machines operating with one standby. Costs for eachalternative were developed for the following subsystems:

1. Ozone generation system - including air filters, air compressors,aftercoolers, water separators, receivers, oil filter systems,automatically regenerating driers and all interconnecting pipingbetween these components; air preparation components to be skid-mounted; ozone generators complete with necessary controls andelectrical components; estimate to include spare parts for oneyear, freight to Seattle, Washington, start up assistance andoperator training.

2. System controls and electrical components - including ambient airand residual ozone analyzers, controllers, control modules, inputand output buffers, timers, relays, control panel and ullagespace blower.

3. Ozone dissolution system - gas piping, valves, diffusers.

4. Ozone destruct unit - to handle 50 scfm saturated air at 1%ozone concentration.

5. Ventilation blowers - mechanical building ventilation blower withcapacity of 2000 scfm.

The cost estimate for the two alternatives is as shown in Table VIII.

Annual cost

An annual cost estimate for the ozone generation system includes cost forOperation and Maintenance (O&M) for the system and depreciation of the systemover the useful life for the equipment. Depreciation, by the straight linemethod, is simply the initial capital investment divided by the project life,assuming no salvage value.

O&M costs, on the other hand, include power to operate the system,labor to operate and maintain the system, and any spare parts necessary tomaintain the system.

The power to operate the system is basically driven by the ozone genera-tor power requirements. At 100% of design supply capacity this value isapproximately 12 KWH per pound of ozone produced. The power to drive theozone generator should be added to the power to drive the ozone destructunit and ullage space blower for a complete system power requirement.

Labor to operate and maintain the system essentially consists of aboutone hour per day to inspect and verify unit operations and the followingbasic maintenance tasks:

1. Ozone generatora. Clean dielectrics once per yearb. Replace damaged dielectrics (4-5% dielectric failure per year).c. Manual rotation of operating units.

2. Air preparation packagea. Replace oil filters on operating air compressors every three

months.b. Replace drier media once per year.c. Normal lubrication once per monthd. Manual rotation of operating unit.

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TABLE VIII. CAPITAL COST ESTIMATE

Subsystem

1. Ozone generators

2. Controls and electrical

3. Ozone dissolution system

4. Ozone destruct unit

5. Ventilation blower

Subtotal - EquipmentCapital Cost

Installation Cost - 15%of equipment capital cost

Subtotal - Equipment Capitaland Installation Costs

Design engineering andinstallation supervisioncosts

Total - Capital, Engineeringand Installation Cost

Corps of Engineersodministrative cost (107.of total cost)

TOTAL - CAPITAL INVESTMENT

12

$

$

$

$

$

standbyoperating

85,000

13,010

700

3,000

2,500

104,210

15,630

119,840

45,000

164,840

16,484

181,324

14

$

$

$

$

standbyoperating

97,500

14,500

700

3,000

2,500

118,200

17,730

135,930

45,000

180,930

18.093

199,023

NOTES: 1. The budgetary item for design engineering does not includeservices such as soils Investigation or environmental impactstatements.

TABLE IX. ANNUAL COST ESTIMATE

$/year. 2 operating 4 operating

Annual Cost Item 1 standby 1 standby

1. Electricity at $0.025/KWH (includingozone generators and auxiliaries -12 KHH/# ozone produced; ozone de-struct unit - 2 KW; ullage spacepurge blower - 0.1 HP) $ 4,360 $ 4,360

2. 0 & M

a. operating and maintenance

b. spares

Depreciation

labor

$

31

_8

17

,460

,042

.242

,104 $

31

_9

17

,460

,118

,047

,985

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3. Instrumentationa. Calibrate instruments every two to three weeks.b. Clean probes, and samplers once per month.

4. Ozone destruct device - replace catalyst once per year.

The O&M requirements of the ozone generation system should average 450to 500 manhours per year. In addition, approximately 1% of the equipment capitalcost is normally estimated to provide spare parts, lubricants, etc.

Based on these assumptions, the annual cost of the system is as shown inTable IX.

Conclusions and Recommendations

1. The application of ozone as a sterilant for makeup water in the pro-posed nursery tank system appears to be feasible from design andeconomic standpoints.

2. The turndown requirements of the makeup water flow should be thoroughlyanalyzed prior to initiation of the project design phase. The presentwide range of makeup water flow rates imposes on the proposedequipment layout a requirement for multiple ozone generators and amore complex system than would be required for fewer machines.

3. It does not appear to be feasible to use the ozone generationsystem to provide significant heat input to the makeup water flow.

4. The requirement to isolate the fish population from any contact withresidual ozone can be met without adding additional processes toscrub the residual from the water.

5. The use of the respective components normally associated with ozonegeneration systems does not pose a threat to the fish populationfrom a materials compatibility consideration.

6. The proposed concept for ozone disinfection appears to offer theflexibility for design modification to disinfect any of the fourrespective subsystems in the nursery tank system. It is recommendedthat Phase II of the present study be authorized to properly definethe necessary modifications and resulting design and economic impacts.

7. The use of ozone is inherently more efficient if oxygen can be sup-plied as the feed gas, especially if process off-gas (primarilyoxygen) can be used in other parts of the system. It is recommendedthat a study effort be authorized to investigate the use of trucked-inliquid oxygen or on-site generated gaseous oxygen as a feed gas tothe proposed ozone system. The recommended study scope shouldencompass the use of off-gas oxygen to enhance dissolved oxygenconcentrations in the recycle water to lessen stress on the fish andimprove performance of the biofliters.

Key Words

Trout hatchery, ozone disinfection

References

1. ASTM E. 591-77, Standard Practice for Safety and Health RequirementsRelating to Occupational Exposure to Ozone, 1977.

2. COLBERG.P.J. et al., (1977). Ozonation of makeup water for salmonid fishrearing facilities, Idaho Water Resources Research Institute, ProjectA-053-IDA.

3. P.J. COLBERG, and A.J. LINGG. Effect of ozone on microbial fish pathogens,ammonia, nitrate, nitrite, BOD in simulated reuse hatchery water.

4. DAILEY, LEO and MORROW. (1973). On-stream analysis of ozone residual,First International Symposium on Ozone for Water and Wastewater Treatment.

5. P.H. DAVIES et al. (1973). Effects of chemical variations in aquaticenvironments, Vol. Ill - Lead toxicity in rainbow trout, EPA-R3-73-001c.

6. R. EISLER. (1973) Annotated bibliography on biological effects ofmetals in aquatic environments (No.1-567), EPA-R3-73-007.

7. H.W. EVERHART and R.A. FREEMAN. 1973. Effects of chemical variations inaquatic environments, Vol. II - Toxic effects of aqueous aluminum to

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rainbow t rou t , EPA-R3-73-011b.8. B.V. JONES and H.K. UYEDA, 1974. Materials for oxygenated wastewater

plants , Symposium of new trends in water and sewage treatment using pureoxygen and ozone.

9. H.W. LORZ and B.P. MCPHERSON. 1977. Effects of copper and zinc onsmoltification of Coho salmon, EPA-600/3-77-032.

10. K.W. MURPHY. 1975. The use of ozone in recycled oceanarium water,Aquatic Applications of Ozone - 101 Workshop Series .

11. V.A. NEWILL. 1973. Health aspects of exposure to ozone, Firs t InternationalSymposium on Ozone for Water and Wastewater Treatment.

12. K.L. RAKNESS. 1977. Personal communication on ozone dissolution pract iceat Estes Park, Colorado Sewage Treatment Plant .

13. B.D. ROSELUND. 1975. Disinfection of hatchery influent by ozonation andthe effects of ozonated water on rainbow t rou t , Aquatic Applications ofOzone - 101 Workshop Series .

14. W.S. SEASE. 1975. Ozone mass transfer and contact systems. Second In t .Symposium on Ozone Technology.

15. D.G. STEVENS. 1977. Survival and immune response of coho salmon exposedto copper. EPA-600/3-77-031.

16. Technical Standard and Supporting Documentation for Ozone - Draft Form,1977, NIOSH/OSHA Standards Completion Program.

17. R.A. TUBB (Ed.). 1977. Recent Advances in Fish Toxicology, EPA-600/3-77-085.

18. Water re-use meeting report . 1977. U.S. Fish and Wildlife Service,Dworshak National Fish Hatchery.

19. C.S. WYNN et a l . , 1973. Pi lot plant for t e r t i a r y treatment of wastewaterwith ozone, EPA-R2-73-146.

Die Moglichkeit Ozon zur Wasserreinigung in Fischbruttankenzu verwenden wurde ira Dworshak National Fish Hatchery festgestellt .Ansazt von 3 mg/L Ozon in das vom Clearwater Fluss eingeleiteteWasser verhindert den Eintri t t von krankheitstragenden Organismenund von Algen in das Wassersystem der Fischbrutanstalt.

L1 ozone est un de'sinf ectant convenable pour 1'eau ^supplemen-taire dans le reservoir d'un systeme recirculant proje'te' a DworshakNational Fish Hatchery.^L'addition de 3 mg/L de l'ozone a l'eausupplementaire peut empecher 1'introduction des organismes patho-genes et l'algue dans le reservoir par l'eau amenee de North Forkde Clearwater River.

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the feasibility of ozone for purification of hatchery waters

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