การออกแบบระบบน้ำหมุนเวียน

การออกแบบระบบน้ำหมุนเวียน
นิคม ละอองศิริวงศ์ สถาบันวิจัยการเพาะเลี้ยงสัตว์น้ำชายฝั่ง สำนักวิจัยและพัฒนาประมงชายฝั่ง กรมประมง The success of a commercial aquaculture enterprise depends on providing the optimum environment for rapid growth at the minimum cost of resources and capital. One of the major advantages of intensive recirculation systems is the ability to control the environment and its numerous water quality parameters to optimize fish health and growth rates. Although the aquatic environment is a complex eco-system consisting of several water quality variables, it is fortunate that only a few of these parameters play decisive roles.

Recirculating Aquaculture Systems
Recirculating aquaculture systems (RAS) are systems in which aquatic organisms are cultured in water which is serially reconditioned and reused.

source : Wik et al. (2009)

Why recirculate? Conserves water
Permits high density culture in locations where space and or water are limiting Minimizes volume of effluent, facilitating waste recovery Allows for increased control over the culture environment, especially indoors Improved biosecurity Environmentally sustainable

Recirculating System Applications
Broodstock maturation Larval rearing systems Nursery systems Nutrition and health research systems Short-term holding systems Ornamental and display tanks High density growout of food fish

Fish Food has an Impact (usually negative) on Water Quality
0.35 – 1.38 kg CO2 kg Oxygen kg Waste Solids 1 kg Feed kg Alkalinity kg NH3 & NH4

Characteristics of Culture Tank Effluent
High concentrations of suspended and dissolved solids High ammonia levels High concentration of CO2 Low levels of dissolved oxygen

Basic Components Recirc systems maintain fish at high densities: kg/m3 Water treated by several processes prior to recirc to culture units Question exists: which method is proven and economical? Main ones: screening, sedimentation, media filtration, biological filtration, aeration, disinfection

Production Capacity Depends Upon Treatment System Design & Scale
Oxygenation & Degassing Fish Culture Tank Waste Solids Removal Biological Filtration (Nitrification)

Your Technology Maintains Life Support and Must:
Remove Solid Wastes Settleable, Suspended, and Dissolved Convert Ammonia and Nitrite to Nitrate Remove Carbon Dioxide Add Oxygen Maintain Proper pH Control Pathogens Keep up with generation of waste

Bacteria Are Important in a Recirculating System
Bacteria Can Cause Trouble Consume Oxygen Create Toxic Ammonia Cause Disease Bacteria Also Make the System Run Biological Filtration

Bacteria Eat Wastes and Cause Changes in Water Quality
Bacteria Break Down Uneaten Feed and Waste to Create: Ammonia (toxic to fish) Consumes Oxygen (often referred to as BOD, BioChemical Oxygen Demand) These Bacteria are called Heterotrophic

Ammonia is also Consumed and Converted by Bacteria
Bacteria (Nitrosomonas) Convert Ammonia to Nitrite (NO2) Nitrite is also toxic to Fish Other Bacteria (Nitrobacter) Convert Nitrite to Nitrate (NO3) Nitrate is not generally very toxic to fish The Process is called Nitrification The Bacteria are called Nitrifying Bacteria Also referred to as Autotrophic Bacteria

Very Important Water Quality Parameters
Dissolved Oxygen (continuously monitor) Ammonia-Nitrogen (NH3 & NH4+) Nitrite-Nitrogen (NO2-) pH Alkalinity

Biological Nitrification is a Two Step Process
Nitrosomonas Bacteria NH3 & NH 4+ (un-ionize ammonia) (ionize ammonia) NO2 Nitrobacter Bacteria NO3 (nitrite) (nitrate)

Biological Nitrification Is All About:
Surface Area Living Space for the Nitrifying Bacteria Competition for that Space Food (ammonia or nitrite) > 0.07 mg / L Good Living Conditions DO going into the biofilter > 4 mg / L pH (7.2 – 8.8 for nitrosomonas; 7.2 – 9.0 for nitrobacter) Alkalinity > 200 mg / L as CaCO3

Required Unit Processes
Carbon Dioxide Removal Air Stone Diffuser Packed Column Fine & Dissolved Solids Removal Foam Fractionation Fish Culture Tank Round, Octagonal Rectangular or D-ended Disinfection Ultraviolet Light Ozone Contact Aeration or Oxygenation Air Stone Diffuser Packed Column Down-flow Contactor Low Head Oxygenator U-tube Waste Solids Removal Sedimentation Swirl Separators Screen Filters Bead Filters Double Drain Biological Filtration (Nitrification) Fluidized Bed Filters Mixed Bed Filters Trickling Filters Rotating Bio-Contactors

Unit Processes : Waste Solids Removal
GENERATION UNEATEN FEED & FECES Suspended Solids Solids that will not settle out in 1 hour under quiet conditions Sedimentation Swirl Separators Screen Filters Bead Filters Double Drain Settleable Solids

Removal Mechanisms Gravity separation Filtration Flotation
Settling tanks, tube settlers and hydrocyclones Filtration Screen, Granular meda, or porous media filter Flotation Foam Fractionation

Settling Basins Sedimentation: Advantages
Simplest technologies Little energy input Relatively inexpensive to install and operate No specialized operational skills Easily incorporated into new or existing facilities

Settling Basins Sedimentation: Disadvantages
Low hydraulic loading rates Poor removal of small suspended solids Large floor space requirements Resuspension of solids and leeching

HydroTech Drum Screen Filter
Backwash Spray Nozzles Waste Drain

Unit Processes: Biofiltration
Biofilter operation for aquaculture production systems has only been studied for about 25 years Earliest types were submerged filters, soon replaced by trickling filters, but same principles apply to all biofilters Various types: submerged, trickling, rotating biodisks, biodrums, fluidized beds, low-density media filters Submerged biofilters are the simplest and come directly from the sewage treatment industry Lately shown to be somewhat inefficient

Submerged Biofilters Characterized as downflow filters (top to bottom)
Relegated to novice culture systems Bacteria grow on a film at the surface of a sand substrate within a tank The medium is continuously submerged Most common medium is limestone rock (helps pH, until covered by bacteria) Others: oyster shell, clam shell, crushed coral, ceramic/plastic modules, glass/plastic beads Particle must be large than mm or will clog

Trickling Filters Similar in design as submerged filters with one major exception: medium is not submerged Bacteria adhering to medium are kept moist and in a semi-aerobic environment Seldom clog Can only function in downflow mode Media currently consist of plastic modules (light, large surface area) Sand cannot be used due to small void area

Submerged vs. Trickling Filters

Rotating Media Filters
Also referred to as rotating biocontactors (RBC’s) biodisks or biodrums Biodisks: series of flat or corrugated disks mounted on a horizontal shaft 40% of disk surface is submerged at a time, shaft and bearings above the water surface Disks separated from each other by at least 13 mm (0.5 in.) Most disks constructed from flat or corrugated fiberglass or plastic sheet material

Rotational speed: 2-6 rpm, but no faster than 1ft/sec (peripheral speed) This is the generator of the previously mentioned “biofloc”

Biodrums are variations of biodisks Cylindrical cages filled with media = more surface area Downside: more energy required to turn them

Fluidized Bed Reactors
Contained within a vertical plastic tube Sand media is supported by coarse gravel, supported by a perforated plate Media kept in various degrees of suspension by upward flow of water Usually pressurized and driven by a pump Only used for NH3 removal (not solids) Primary design criterion is upward flow rate and oxygen demand Capacity is 10x that of static filters Downside: requires high upward Q (60-65 gpm/m2)

Floating Bead Filters Low-density media filter
Use 3-5 mm poly beads in pressurized upflow mode Beads float above injection point Capable of solids capture and biofiltration Traps suspended particles while enhancing nitrification Can nitrify 270 mg TAN per m2 per day 1.0 m3 of beads can provide complete water treatment of wastes generated from kg feed per day ( kg fish/m3 media)

Trickling Filter Typical
Design Nitrification Rate 0.45 g TAN / m2 / day 90 g TAN / m3 / day (Losordo et al.) Approx. 3 kg feed per day per cubic meter of media ($212 - $353 / cubic meter) ExpoNet BioBlock 200 0.55m x 0.55m x 0.55 m each 200 m2 / m3 Net 200

Biological Nitrification Moving Bed Reactors
(RBC) Design Nitrification Rate g TAN / m2 / day g / m3 / day kg feed / day (Media Cost = US$ $1500 / m3 ) KMT Copy SSA = 850 / m2 / m3 ?? KMT SSA = 500 / m2 / m3 B-Cell SSA = 650 / m2 / m3

Biofilters Come in All Shapes and Sizes
Moving Bed Filters are low energy and compact Fluid Sand Beds are the most compact biofilter An RBC specifically designed for aquaculture Bead Filters combine nitrification with solids removal (RBC) Low Pressure Air Inflow Water Inflow from Culture Tank Water Return to Culture Biofilter MediaPlastic Blocks or Plastic Rings Rotating Water Distribution Arm Trickling Filters are the “work horse” of aquaculture 4/17/2017

Biofilter Chemical Factors
pH: nitrification inhibition commences below pH 7; optimum slight > 7.0 Alkalinity: mg/L NH3 and NO2: NH3 inhibits Nitrosomonas sp. and Nitrobacter sp. at and mg/L, respectively O2: biofilter effluent > 2.0 mg/L Solids: µM best Salinity: normal culture ranges are OK, no sudden changes Temperature: C

Design Requirements The Following Unit Process are required in any design: Culture Tank Design Circulation Solids Removal Biofiltration / Nitrification Gas Transfer (Aeration / Oxygenation / CO2 Removal) For any design, some assumptions need to me made, hopefully based either on actual experience or reputable research.

Design Assumptions For any design, some assumptions need to be made, hopefully based either on actual experience or reputable research. For any design, some assumptions need to me made, hopefully based either on actual experience or reputable research.

Design Assumptions Assuming: 454,000 kg/yr production
Mean feeding rate: rfeed = 1.2% BW/day Feed conversion rate: FCR = 1.3 kg feed/kg fish produced Culture Density : 80 kg fish/m3 Oxygen Demand: kg O2/ kg feed For any design, some assumptions need to me made, hopefully based either on actual experience or reputable research. (these rates are an average over entire year)

System Biomass Estimation
Estimate of system’s average feeding biomass : Based on the design goals, the total biomass in the production system can be estimated from the Feed Conversion Rate (FCR) and the feed rate (rfeed).

Total Oxygen Requirements
Estimate the oxygen demand of system’s feeding fish: where: RDO = average DO consumption Rate = kg DO consumed by fish per day) aDO = average DO consumption proportionality constant = kg DO consumed per 1 kg feed Ranges from 0.4 to 1.0 kg O2/kg feed – cold water to warm water To estimate the oxygen demand of the system, the average dissolved oxygen consumed per kg of feed is used (aDO) and multiplied by the feed rate (rfeed) and the total biomass of the system (biomasssystem).

Total Flow Requirement – Oxygen Load
Estimate water flow (Q) required for fish’s O2 demand: Assuming oxygen: DOinlet = 18 mg/L DOeffluent= 4 mg/L steady state) If only aeration was employed, the change in DO across the culture tank would be only 4 mg/L, where the inlet would be at 90 to 95% saturation (8 mg/L) and the tank might be as low as 4 mg/L (Tilapia). A more aggressive, but usually achievable, inlet DO would be mg/L, which would produce an available DO across the culture tank of about 14 mg/L, with the tank DO raised to 6 mg/L. In practice, this is about the maximum DO loading that can be safely managed.

Total Tank Volume Requirements
Assume an average fish density across all culture tanks in the system: culture density = 80 kg fish/m3 A culture density of 80 kg/m3 is considered the average density found within the entire system. The maximum density in a culture tank might be 120 kg/m3 while other tanks in the same facility might be as low as 40 kg/m3. In reality, unless batch production is used in the entire facility, the average culture density found in facility will be considerably less than the maximum density that could be supported in a given culture tank. Also, because densities can vary between tanks, some tanks would receive more water than others to supply the extra oxygen needed to support these fish.

Check Culture Tank Exchange Rate
Rule of Thumb In general, a culture tank exchange every minutes provides good flushing of waste metabolites while maintaining hydraulics within circular culture tanks (when the tank inlet and outlet structures are designed properly. a culture tank exchange every minutes provides good flushing of waste metabolites while maintaining hydraulics within circular culture tanks

Number of Tanks Required
Assuming 9 m (30 ft) dia tanks water depth 2.3 m 7.5 ft culture volume per tank 150 m3 40,000 gal 10-11 culture tanks required Assuming 15 m (50 ft) dia tanks water depth 3.7 m 12 ft culture volume per tank 670 m3 177,000 gal 2-3 culture tanks required If future expansion of the farm is expected to achieve 2-4 times more production, then maybe choose 50 ft diameter tanks. Otherwise, choosing 30 ft tanks would be a okay choice to achieve 1 million lb maximum production. To use tanks as large as 50 ft diameter requires knowledge of tank inlet and outlet structure designs to ensure that good mixing is achieved and that safe rotational velocities can be maintained for fish health and for flushing settleable solids. If water must rotate about the axis of a culture tank once in seconds to achieve good solids flushing, then the fish swimming in larger (e.g., 50 ft tanks) must be capable of swimming at these speeds. Water velocities are greatest near the tank’s outside wall where the perimeter distance is D. Therefore, in a 50 ft tank fish swimming with the current near the tank’s outside wall would be swimming between ft/s. Maximum safe swimming velocities for salmonids are considered to be between 1-2 body length per second. However, in ‘Cornell-type’ dual-drain tanks the water velocity decreases as the fish swim closer to the center of the tank, which allows fish to select what velocity they want to swim against by moving to different locations in the culture tank.

Tanks Design Summary Ten Production Tanks 9.14 m ( 30 ft )
Diameter 9.14 m ( 30 ft ) Water depth 2.3 m (7.5 ft) Culture volume per tank 150 m3 (40,000 gal) Oxygen Demand 117 kg O2/day (257 lbs/day) Flow Rate (30 min exchange) 5,000 Lpm (1,320gpm) Biomass Density 86 kg/m3 (0.72 lbs/gal) This is just one of many system designs that could be chosen based on the tank design, system yearly production and stocking density. Fewer larger tanks could be used, more smaller tanks. Any system design has to be based on decisions that best fit the management style, resources, site limitations and market demand for the product. Based on a system using 10 tanks at 150 m3 volume, the flow rate through each tank can be estimated from the exchange rate of 30 min and the volume as 5,000 Lpm or 1,320 gpm. Actual biomass density is slightly higher at 86 kg/m3, but still reasonable for an oxygen enriched system. The oxygen consumed in the tank increases slightly, but if the tank DO is reduced to 5 mg/L then the influent Oxygen concentration would have to be about 21 mg/L, easily reached with a LHO or Speece cone.

Removal solids design Settling Basin Dual-drain System Swirl Separator
Microscreen Filter Propeller Washed Bead Filter

Terms Used To Describe Biofilters:
Biofiltration/Nitrification Terms Used To Describe Biofilters: Void Space / porosity Cross-sectional Area Hydraulic Loading Rate Specific Surface Area It is helpful in any discussion of biofilter principals and advantages and disadvantages of the various choices to have a basic set of definitions and terminology. Generally, the following terms are used in the design and characterization of biofilters: Void space is the volume not occupied by biofilter media, and void ratio is that volume divided by the total volume of the biofilter. High void ratios reduce clogging by having large open spaces that allow solids to pass easily through the filter. Cross-sectional area refers to the area of the filter bed looking in the direction of the water flow. Filter top area is usually one of the last parameters selected in the filter design, to yield a desired hydraulic loading rate. Hydraulic loading rate is the volume of water pumped through the biofilter per unit of cross-sectional area of the filter per unit of time. Typically expressed as gpm/ft2 or m3/m2 day. There is usually both a minimum and a maximum hydraulic loading rate for biofilters. Specific surface area is the surface area of the media per unit volume. The higher the specific surface area of a media, the more bacteria can grow on a unit volume, and the greater the total ammonia removal per unit volume of filter. The media size, void ratio and specific surface area are all interrelated. The smaller the size, the larger the specific surface ratio and the smaller the void ratio.

Biofilter Design – Step 1
Step 1: Calculate the dissolved oxygen requirement (RDO). Assume a DO consumption of 1.0 kg/kg feed Both the MBB and Trickling Tower provide O2 for Nitrification or approximately 0.25 kg. Thus 0.75 kg O2 /kg feed. Based on the oxygen demand of the feed, the percent body weight feed per day, the stocking density and the volume of the tank, the daily oxygen demand can be determined. This should reflect the final production carrying capacity of the system, plus a little extra in case you can’t sell the fish when you expected too. In this case, a MBB and a Trickling Tower are to be used as biofilters for nitrification. Since both of these filters provide the oxygen required for nitrification, only the demand by the fish and any heterotrophic bacteria are used. This is an very difficult number to come by and is usually estimated from other similar systems and research.

Step 2: Calculate water flow requirement (Qtank) required for fish DO demand. Assume: DOinlet = 18 mg/L (pure oxygen aeration system) DOtank = 4 mg/L (warm water 24 Deg. C, Tilapia!!) The water flow is a simple mass balance assuming that all the oxygen is provided by the incoming water to the production tank.

Biofilter Design – Step 2 (cont)
Step 2: Check the Exchange rate (2-4 exchanges/hr) This is just a quick check to determine the tank exchange rate. For fingerling and sensitive species, the exchange rate should be from 2 to 4 times per hour. For finally growout and hardy species, 1 to 2 exchanges per hour may be adequate. A tank exchange rate of 2 exchanges per hour is OK!

Step 3: Calculate TAN production by fish (PTAN) (Note: Feed is 35% protein) PTAN = F * PC * = F * 0.35 *0.092 = 0.032 where: PTAN = Production rate of total ammonia nitrogen, (kg/day) F = Feed rate (kg/day) PC = protein concentration in feed (decimal value) Determine the amount of ammonia produced by the fish based on total feed fed.

Ammonia Assimilation Rates
Media Type TAN Conversion Basis TAN Conversion Rate (15 to 20 Deg. C) (25 to 30 Deg. C) Trickling or RBC (100 – 300 m2/m3) Surface area of media 0.2 to 1.0 g/m2 day 1.0 to 2.0 g/m2 day Granular (bead/sand) (> 500 m2/m3) Volume of media 0.6 to 0.7 kg/m3 day 1.0 to 1.5 kg/m3 day Ammonia assimilation rates for biofilters based on Volumetric and Areal TAN conversion rates.

Biofilter Design – Step 4 (MBB)
Step 4: Calculate volume of media, Vmedia based on the Volumetric nitrification rate (VTR) Consider a Moving Bed BioReactor (MBB) Curler Advance X-1 has a 605 g TAN/m3 (17.14 g TAN/ft3). Calculate the volume of media required. This would be based on design information from manufacturer or research results. The above Curler Advanced media has a recommended design VTR rate of g TAN/ ft3 or 605 g TAN/m3. This is less than the table values and some research increases the value significantly dependent upon the incoming TAN levels (3-5 mg/L) and temperature.

Biofilter Design – Step 4 (MBB)
Step 4: Calculate volume of biofilter, Vbiofiler based on a fill ratio of 65%. This would require a tank (3200 gal) with dimensions of 7 ft diameter, 11 ft tall. Note that no safety factor was considered in this design!!!! It can be assumed that from 10 to 30% of the TAN will be removed by in-situ nitrification (on tank wall, pipe wall, suspended culture). This would require a tank (3200 gal): 7 ft in diameter and 11 ft tall.

Biofilter Design – Step 4 (Trickling Tower)
Step 4: Calculate the surface area (Amedia) required to remove PTAN from the Areal TAN removal rate (ATR) (0.45 g TAN/m2 day) Calculate the surface area (Amedia) required to remove PTAN from the Areal TAN removal rate (ATR). Based on experience with the submerged trickling tower, the estimated Areal TAN removal rate is 0.45 g TAN/m2 day. Note that for coldwater applications (12–15ºC) when TAN concentrations entering the trickling column are less than 1–2 mg/L, then the Areal TAN removal rate is only about 0.15–0.25 g TAN/m2 day. Note also that the Areal TAN removal rate drops to only 0.1–0.2 g TAN/m2 day for saltwater applications 24ºC) when TAN concentrations entering the trickling filter are 1–2 mg/L

Step 5: Calculate volume of media based on the specific surface area (SSA), example BioBlock = 200 m2/m3 (61 ft2/ft3) Calculate volume of media based on the specific surface area (SSA).

Step 6: Calculate the biofilter cross-sectional area from required flow for the fish oxygen demand (Qtank) and the hydraulic loading rate, HLR of 250 m3/m2 day (4.4 gpm/ft2). Calculate the biofilter cross-sectional area from required flow for the fish oxygen demand (Qtank) and the hydraulic loading rate, HLR. The hydraulic loading rate is dependent on the type of filter and media used and for this trickling tower a value of 250 m3/m2 was assumed.

From high school math class: area =  (Dia)2 / 4 diameter = [ 4 * area / ]1/2 The diameter of a two trickling towers, Dbiofilter, with this cross sectional area is: Finally use that math you learned in High School. Its often wiser to use three filters rather than one large one.

Step 8: Calculate the biofilter depth (Depthmedia) from the biofilter cross-sectional area (Amedia) and volume (Vmedia). Finally use that math you learned in High School. Its often wiser to use three filters rather than one large one. The final Trickling Tower is 15 ft in diameter and 12 ft tall plus distribution plate, etc.

การออกแบบระบบน้ำหมุนเวียน

Similar presentations

Presentation on theme: "การออกแบบระบบน้ำหมุนเวียน"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

การออกแบบระบบน้ำหมุนเวียน

Similar presentations

Presentation on theme: "การออกแบบระบบน้ำหมุนเวียน"— Presentation transcript:

Similar presentations

About project

Feedback