Fine particle filtration in aquaculture


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Aquaculture is the fastest growing animal production industry in the world; almost every region is experiencing rapid growth in the farming of fish, molluscs, crustaceans and aquatic plants.

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Fine particle filtration in aquaculture

  1. 1. July | August 2013 Fine particle filtration in aquaculture The International magazine for the aquaculture feed industry International Aquafeed is published six times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2013 Perendale Publishers Ltd.All rights reserved.No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058 INCORPORATING f ish farming technolog y
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  3. 3. A quaculture is the fastest growing animal production industry in the world; almost every region is experiencing rapid growth in the farming of fish, molluscs, crustaceans and aquatic plants. Worth over AUD$200 billion globally, the aquaculture industry has been growing at a faster rate than the world’s population for the past five decades, resulting in a very competi- tive marketplace today. Such dramatic growth in the aquaculture industry has driven trends in filtration and oxygenation techniques forward to focus on high efficiency systems which offer fine particle filtration. This is due to the realisa- tion that systems chosen purely for their low cost may not necessarily deliver profit- able results. The health and growth of your fish depend greatly upon the filtration and oxygenation of the water in which they live. Therefore, it is vital you invest in a quality system so you can produce large, healthy fish as quickly as possible to increase your profit margin. “The filtration for aquaculture is very differ- ent to anything else, as you are filtering totally different material which is much larger in mass – such as pond weed, fish food and fish waste,” says Bryan Goh, director, Waterco Ltd, Australia, an international manufacturer, which produces a range of filtration solutions for commercial and domestic systems. Those using closed systems have taken particularly to recirculating filtration systems, which entail the same water being recircu- lated an infinite number of times after being properly filtered and slightly topped up to make up for the water which is lost through evaporation. Fine particles are defined as particulate matter that is 2.5 microns or less in diameter; therefore, they can be left behind by some filtration systems that are not designed to capture particles that small. Fine particle filtration is important for three reasons: 1. The amount of waste that fish produce can quickly destroy water clarity and reduce the amount of oxygen the fish can absorb, which in turn lowers their growth rate. The quicker this waste is removed; less oxygen will be used by the bacteria that are breaking it down 2. Substances that are toxic to fish in small quantities, such as ammonia and nitrite, need to be removed quickly before they use up a great deal of the oxygen in the water and impact on the health of your fish 3. Large amounts of feed can also intro- duce waste into the water and encour- age bacteria growth, which eat up the oxygen supply that your fish need; adequate filtration addresses this issue Types of filtration The movement towards fine particle filtra- tion has resulted in a few particular types of filtration and waste removal systems being favoured in the aquaculture industry. These include screens, gravitational settling, sand and bead filters, flotation/foam fractionation and centrifuges. Gravitational settling, also known as sedi- mentation, is a waste removal system that depends on the different densities of the water and waste particles drawing the waste particles down and out of the tank. However, waste particles in aquaculture are usually only slightly denser than the water and so can take time to settle. Faster separation is achieved when the density is vastly different; most aquaculture systems use 15-20 minute reten- tion times for waste. Filter screens Filter screens are a form of mechanical waste removal. Opening sizes can vary from Fine particle filtration in aquaculture by Katie Adema, journalist, Waterco Ltd, Australia 18 | InternAtIonAl AquAFeed | July-August 2013 FEATURE
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  5. 5. several millimeters to less than 0.001 micron. Fine filtration systems, such as microscreen drum filters which are already commonly used in aquaculture, typically require much larger filter screens and/or higher pressures to operate effectively than a screen with larger openings. Centrifuges and hydro clones Centrifuges and hydro clones are growing in popularity as they cross from domestic use into commercial use. Cylindrical in shape, the mechanism rotates the central chamber very rapidly, forcing waste particles that are denser than the water to the sides of the cylinder. A layer of water from the outer rim is then taken out, which removes most of the particles with it, leaving the clean water in the centre to be put back into the aquaculture system. Bruce Atkinson, aquaculture design and sales manager, Aquasonic, Australia, says cen- trifugal solutions such as Waterco’s new range of MultiCyclone filters can allow you to increase stocking rates. “The link between feed rates and MultiCyclones is fairly obvious for fish culture systems,” says Atkinson. “With the addition of the MultiCyclone, more efficient mechani- cal filtration takes place and hence greater volumes of feed can be introduced without system fouling caused by organic deposition and bacterial proliferation. “This means stocking rates can be increased, with subsequent improved pro- duction. MultiCyclones in fish culture systems are best deployed on the system return pump prior to, say, bag or cartridge polishing filters on the way back to the fish tank. ” Sand or bead filters Sand or bead filters can be either fixed bed and particle bed filters that con- sist of a box filled with sand or another particulate material. To achieve fine par- ticle filtration, the filter medium should be very fine grain and may also need to be pressurised. Water passes through the fixed bed either in a downward direction or and upward direction (down flow and up flow), and waste particles are removed by the sand/beads. The size of particles removed depends on the size of the filter medium, flow rate and waste characteris- tics. A sand/bead filter may need frequent backwashing if waste is very concentrated. Floatation or foam fractionation Floatation or foam fractionation is a form of chemical filtration; this type of filtration is able to retrieve very fine particles from an aquaculture sys- tem, and is consequently already Waterco’s commercial MultiCyclone July-August 2013 | InternAtIonAl AquAFeed | 19 FEATURE International Aquafeed has teamed up with to offer our readers a 15% discount The world’s finest brass-based fishing lures manufactured by hand in New Zealand Your order will be processed and dispatched from our production unit within 24 hours Even fi sh farmers like fi shing! A & AJ Gilbert Fishing Tackle, New Zealand REF: IAF303-PPL Place your order today at Die and roll re-working machines O&J Højtryk A/S Ørnevej 1, DK-6705 Esbjerg Ø CVR.: 73 66 86 11 Phone: +45 75 14 22 55 Fax: +45 82 28 91 41 mail: T3 (10 g Hydroyeast Aquaculture®/Kg diet), which were gave significantly (P ≤ 0.05) final body weight, AWG, RGR, ADG and SGR than the control (T1). But, no significant (P ≥ 0.05) differences between T2 and T3 for final weight, AWG and ADG, as well as in SR among all treatments. Female Data of growth performance parameters of adult females O. niloticus revealed that T7 (10 g Hydroyeast Aquaculture®/Kg diet) was the best treatment followed by T6 (5 g Hydroyeast Aquaculture®/Kg diet), which were gave significantly (P ≤ 0.05) increased final body weight, AWG, RGR, ADG and SGR than T8 (15 g Hydroyeast Aquaculture®/ Kg diet) and the control (T5). However, no significant (P ≥ 0.05) effects in SR among all treatments (Table 5). Feed and nutrients utilization Male Results of feed nutrients utilization param- eters of adult males O. niloticus were shown in Table 6, whereas T4 gave the highest significantly (P ≤ 0.05) increased FE, PER and the best FCR followed by T2 compared with the control (T1) and T3. In contrast, PPV or EU increased significantly (P ≤ 0.05) in T1 followed by T2 compared with T3 and T4. However, no significant (P ≥ 0.05) differ- ences in FI among all treatments. Female Adult females' O. niloticus fed 10 g Hydroyeast Aquaculture®/kg diet (T7) showed a significant (P ≤ 0.05) increase in FI, FE, PER and the best FCR followed by fish fed 5 g Hydroyeast Aquaculture®/kg diet (T6) compared with the control (T1). However, treatment 6 gave significantly (P ≤ 0.05) increase of PPV and EU among all treatments (Table 7). Generally, the differences between males and females within all treatments concerning, feed and nutrients utilization parameters may be due to the differences in sexes, metabolism, physiological responses and sexual behaviours of fish during this stage of life. Fish carcass composition Male Proximate chemical analysis of the whole adult male O. niloticus body at the start and at the end of the experiment is summarized in Table 8. These data indicated that there were significant (P ≤ 0.05) increases of DM and EC content in the control group (T1) compared with the dietary inclusion of Hydroyeast Aquaculture® (T2, T3 and T4), but CP content was increased significantly (P ≤ 0.05) in T1 or T2 than the T3 and T4. However, an unclear trend was observed in EE, where the increasing in EE content was not significant in T1 compared with T3 and T4 and significant as compared with T2. In contrast, of these results ash content increased significantly in T3 and T4 compared with T2 and the control T1. Generally, proximate chemical analysis of the whole fish body at the start, revealed higher DM, EE and EC than in the end of the experiment, but CP and ash were lower at the start than at the end of the experiment. Female Adult female O. niloticus fed the 5 g Hydroyeast Aquaculture®/kg diet (T6) table 9: effects of Hydroyeast aquaculture® probiotic on carcass composition of adult female O. niloticus % on dry matter basis treat. DM CP ee ash eC at the start of the experiment 24.3 59.2 23.6 17.1 557.5 at the start of the experiment t5 20.9b 53.9c 26.8a 19.1a 557.7b t6 22.4a 60.2a 24.1b 15.7b 566.9a t7 17.1d 55.7b 25.7a 18.5a 557.6b t8 18.4c 55.6bc 25.7a 18.6a 559.9b ± Se 0.09 0.50 0.44 0.29 2.54 P- value 0.0001 0.0001 0.015 0.0001 0.070 Means in the same column having different small letters are significantly differ (P ≤ 0.05). DM: Dry matter (%); CP: Crude protein (%); EE: Ether extract (%); EC: Energy content (Kcal/100 g), calculated according to NRC (1993); SE: Standard Error table 8: effects of Hydroyeast aquaculture® probiotic on carcass composition of adult male O. niloticus % on dry matter basis treat. DM CP ee ash eC at the start of the experiment 25.3 52.2 30.7 16.9 585.1 at the end of the experiment t1 24.8a 58.9a 25.2a 15.9c 570.4a t2 20.6b 58.1a 23.8b 18.1b 552.9b t3 18.2c 55.4b 24.3ab 20.3a 541.8c t4 17.9c 55.5b 24.8ab 19.7a 547.5bc ± Se 0.19 0.55 0.37 0.35 2.21 P- value 0.0001 0.003 0.123 0.0001 0.0001 Means in the same column having different small letters are significantly differ (P ≤ 0.05). DM: Dry matter (%); CP: Crude protein (%); EE: Ether extract (%); EC: Energy content (Kcal/100 g), calculated according to NRC (1993); SE: Standard Error FOCUS | PROBIOTICS gets fish into shape Reduces deformities in larvae and fry LARVIVA ProStart™ is the first early weaning diet with a unique probiotic approved by the European Food Safety Authorities for its documented effect in reducing the occurrence of vertebral deformities in fish larvae and fry.
  6. 6. used widely. It takes advantage of the surface tension and charges at the air/water interface, using bubbles to capture dissolved and very fine particle matter. In this system, an air stone in the bottom of a vertical pipe produces bubbles. As they rise through the pipe they collect dissolved minerals from the bulk liquid, and when the bubbles reach the surface and are removed, so are the waste particles. It’s a sim- ple, inexpensive form of filtration that can also remove dissolved pollutants from the water. This removal mechanism is particularly effective in saltwater applications, as formation of fine bubbles is much easier than in fresh water applications. It is quite common in aqua- culture to use a combination of different filtration and waste removal systems to achieve opti- mum water quality. Oxygen cones Oxygen concentration is worth mentioning in relation to fine particle filtration because the bacteria that break down fish waste and leftover feed use up a great deal of oxygen, which is paramount to fish health and growth. The longer this waste is left in the water, the smaller it becomes as it is broken down, causing it to be very difficult to remove. Therefore, this waste needs to be removed as quickly and as effectively as possible by your filtration system, which needs to be equipped to handle very small particles of waste. After filtration, an oxygen cone can be used to restore oxygen satura- tion to optimum levels. “Oxygen cones have the ability to increase O² levels in fish culture systems, with increased levels of O² being of great benefit to fish health in general,” says Atkinson. “In experiments carried out on halibut spe- cies, oxygen saturation levels were shown to have a positive effect on the growth and feed conversion ratio at 80 percent and 120 percent saturation. “The conclusion was that the oxygen saturation levels have a positive effect on growth and feed conversion ratios of fish, and in the case of Atlantic halibut, the growth rate is higher when the oxygen level is between 80 percent and 120 percent.” The correct combination of oxy- gen, fresh water and food is essential for fish production, and maintaining water oxygen levels is a careful balancing act. Waterco’s specially created Oxygen Cone allows the oxygen levels in water to be managed more effectively for higher quantities of fish per volume of water. The industry standard for most species of fish is up to 50 kg of stock to 1,000 litres of water; with an oxygen cone, you can increase your productivity and stocking rates. Oxygen cones inject oxygen into the water delivery line and into the fish culture tanks. The Oxygen Cone is shaped to optimise the satu- ration of gases in water - up to 100 percent. Water and oxygen enter at the top of the cone at relatively high speed and then the stream of water pushes the oxygen bubbles down until they completely dissolve. “Several studies have investigated the rela- tionship between oxygen saturation and fish food intake,” says Atkinson “In 1976, Randolph and Clemens found that feeding patterns of channel catfish varied with temperature and oxygen availability. When the oxygen content drops below 59 percent, a fish starts to lose its appetite. Rainbow trout (Oncorhynchus mykiss) appetite is reduced when oxygen saturation falls below approximately 60 percent.” “From these studies, using varied species it can be concluded that by increasing oxygen saturation with the use of a saturation ves- sel such as a Waterco Oxygen Cone, the farmer can increase his production significantly and save on food costs as well because of improved feed conversion ratios.” More InforMatIon: Waterco Ltd Tel: +44 1795 521733 Email: Website: Aquasonic P/L Aquaculture Supplies Tel: +61 2 6586 4933 Email: Website: In focus: koi ponds Although koi ponds are most commonly used as an aesthetic addition to a backyard, they rely on a delicate balance of filtration and oxygenation to keep the fish healthy, just like a tank used for commercial aquaculture. The large amount of waste these fast growing fish produce also makes them a good example of the impor- tance of fine particle filtration and oxygen saturation. A koi pond usually requires both a mechanical filter and a biological filter to maintain water clarity and fish health. A turnover rate of at least 1.5 times per hour will ensure good circulation, aeration and filtration. “In many cases, large pre-filter systems are required, such as vortex chambers and/or sieves as well as a main filtration system that in many cases is used both as a mechanical as well as a biological filter. This literally traps the solid wastes and removes them from the water flow and provides a large surface area to support the growth of beneficial bacteria that breaks down pollutants in the water,” explains Bryan Goh, director, Waterco, Australia. “Such filters can be single or multimedia chambers as well as bead filters. The filtration system is not only designed based on the volume of water but also the quantity and size of fish, anticipated feeding cycles and the amount of fish waste.” Filtration needs to be backed up with adequate oxy- gen saturation levels, delivered by oxygen cones, water plants and/or aeration. One thousand litres of water saturated with oxygen at 8 parts per million contains only 8 grams of dissolved oxygen. The health of koi fish is compromised when oxygen levels fall below 6 ppm, something that 10 kg of fish which consume about three grams of oxygen per hour can bring about in about 40 minutes without the help of adequate filtration and oxygenation. 20 | InternAtIonAl AquAFeed | July-August 2013 FEATURE
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  8. 8. LINKS • See the full issue • Visit the International Aquafeed website • Contact the International Aquafeed Team • Subscribe to International Aquafeed Maintaining ingredient quality in extruded feeds Fine particle filtration in aquaculture Effect of probiotic, Hydroyeast Aquaculture – as growth promoter for adult Nile tilapia Volume 16 Issue 4 2013 - JulY | August INCORPORATING fIsh fARmING TeChNOlOGy EXPERT TOPIC – channel catfish This digital re-print is part of the July | August 2013 edition of International Aquafeed magazine. Content from the magazine is available to view free-of-charge, both as a full online magazine on our website, and as an archive of individual features on the docstoc website. Please click here to view our other publications on To purchase a paper copy of the magazine, or to subscribe to the paper edition please contact our Circulation and Subscriptions Manager on the link above. INFORMATION FOR ADVERTISERS - CLICK HERE