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AN INTRODUCTION TO WATER REUSE SYSTEMS


Chapter 1

AN INTRODUCTION TO WATER REUSE SYSTEMS

Thomas M. Losordo

and

Michael B. Timmons

1.1 INTRODUCTION

The culture of freshwater and marine species has received considerable attention in the public and private sectors as a new agri-business to further diversify the agricultural and fisheries economies of developed and developing nations. Much of the commercial production of warmwatcr and coldwater species occurs in earthen ponds, tanks or floating net pens or cages.

With traditional systems designs, fish production requires large amounts of clean freshwater, precluding the production of fish in many areas. The amount of water required for pond production depends upon the pond seepage rate, rainfall, evaporation and culture intensity. In the catfish industry in the US, the water requirements vary from 2.5% to 600Cl, of the total pond volume on an annual basis. For "super-intensive" shrimp production as practiced in Hawaii, the water exchange rate could be high as 80% of the pond volume per day (Wyban and Sweeney, 1991). Comparatively, the production of fish in tanks and raceways utilizes even larger quantities of water to remove waste products from the production environment, typically 100 or more system volume exchanges per day. An example is given by Ray (1981) for the intensive production of catfish in raceways. The author estimated that the maximum carrying capacity of the system was 160,000 - 240,000 kg of fish for every available cubic meter per second (In3 S-1) of water flow. The yearly production capacity of the system was 3 to 4 times the carrying capacity. These figures can be used to estimate a water use of in excess of 32,000 L/ kg of annual production (960,000 kg / m3 s-1 }. Phillips et al, (1991) compiled the water requirements for various aquaculture production systems (Table 1.1). Table l.1 lists the water used per kg of production for various freshwater and marine species.

The authors (Phillips et al, 1991) concluded that "it seems inevitable that aquaculture will have to face increasingly tight restrictions over development in many areas of the world, as

 

 

T.M. Losordo and M.B. Timmons

TABLE 1.1.

Water Use Per kg of Production of Aguacultured Products (After Phillips et al. 1991)

                                                                                    Species and System         Country      Production Intensity Water Required

USA USA USA

UK

                       Qsgl ha I r 2 ow            

17,400

30 - 50

3,000

150,O()()

{~l kg.l 21,000 3,000 - 5,000 6,470

14,500 - 29,000 210,()(){)

252,000 11,000 - 21,340

~..                        . .......... .

Oreochromis niloticus (Nile Tilapia) ponds Oreochromis niloticus (Nile Tilapia) ponds [ctalurus punctatus (Channel Catfish) ponds I ctalurus punctatus (Channel Catfish) raceways Salmo gairdneri (Rainbow Trout) raceways Salmonids pond and tank

Pcnaeid Shrim[!, pond

Taiwan

Taiwan

4,200 - 11,000

concern over environmental impact and competition for resources grows". Indeed, concern over the impact of aquacultural wastes and effluents has already brought aquaculture under the scrutiny of many regulatory agencies in a number of developed countries. Aquaculture, as other traditional agricultural operations, creates wastes that when discharged to receiving waters, can have a detrimental impact to the local aquatic environment (NRC 1992). In general, aquacultural effluents from traditional production systems are characterized as high volume and relatively low

strength wastes (Phillips et aI. 1991). Most treatment technologies have been developed to

\

process more concentrated, domestic or industrial wastewaters. In essence, the treatment

processes for aquacultural wastewaters may parallel those of tertiary treatment processes for domestic or industrial wastes. In many cases, tertiary treatment of domestic waste waters is not applied due to the high cost of implementing the processes.

These concerns for water supply conservation and the environmental impacts of waste from aquacultural activities have focused attention on the development of technologies for water reuse. Tn their simplest form, serial water reuse systems increases the productive capacity of water (kg fish I L). Unless waste removal processes are implemented after the last water use, water reuse does nothing in addressing the environmental impact of aquaculture activities. Typically, reuse systems for the production of salmonids, utilize some form of settling basin at the end of each water use. In most cases, a significant fraction of the biochemical oxygen demand (BOD) and organic nitrogen waste produced can be removed with simple settling technology.

Like other aquaculture production systems, recirculating systems generate wastes and are not an end in themselves to reducing environmental impact. The wastes generated in recirculating systems are in two forms: particulate and dissolved. The majority of the BOD and inorganic and organic nutrients in the waste stream are carried in the particulate form, usually measured as total suspended solids (TSS) (Chen et aI. 1991). For this reason, the T'SS produced


4

r.lrr. Losordo and M.B. Timmons

Stocking Density: Mass of cultured product per volume of tank (ignores the effects of fish displacing part of the water volume).

Flow Through Rate: The volume of new water per unit time passing through a cuI ture tank.

Menn Ilydrnulic Residence Time: Refers to the time required at a given rate of flow for a complete volume of water in a tank to be exchanged, e.g. Q(flow rate) I V (volume of tank).

Specific Surface Area: Surface area per unit volume; usually referring to the surface area of a particular media used in filtration or settling components,

Carrying Capacity: The maxitnum mass of aquacultured product that can be maintained within a culture system; usually expressed as mass per unit volume of the culture system.

1.3 CURRENT S'l'A TUS

The demand for high quality aquacultured products and an increasing concern for resource conservation has led individuals and large corporations to invest time and money in commercial scale recirculating production systems. However, there are relatively few reports of profitable recirculating production systems in operation. There is little doubt that most fish reared in ponds, floating net pens, or raceways can be produced in commercial scale recirculating systems, In calculating the cost of producing fish in aquaculture, the investor must account for both fixed and variable costs. Fixed costs or expenses are generally incurred in approximately the same amount regardless of the volume of the production and sales of the operation, i.e. salaries, depreciation, payments on loans (Spiller and Gosman, 1984). A large portion of the fixed cost in a technologically intensive operation is in servicing the debt incurred in getting into the business and accounting for depreciation and maintenance costs. Servicing the debt, whether in the form (If borrowed capital or equity (your own funds) must be reflected in the cost of fish production. Recirculating systems have generally been expensive to build, which increases the cost of producing fish in these systems. Recent commercial scale recirculating production systems investment costs have generally exceeded US $4.00 - $8.00 invested per kg of annual production capacity, e.g. a system with the capacity to produce 100,000 kg of fish per year cost $400,000 - $800,000. In comparison, investment costs for commercial pond culture or raceway systems seldom exceed $2.20 - $3.30 per kg of annual production capacity.

The higher cost of producing fish in recirculating systems have caused these producers problems in the market place when in competition with producers using traditional pond

T.M. Losordo and M.B. Timmons

• Determine if active control of carbon dioxide levels in the culture water will be needed (Chapter 7);

• Provide for the control of pI-I and alkalinity control in the culture system (Chapter 8);

·    Provide for the removal of fine solids not normally removed through mechanical screening or settling by employing foam fractionation devices (Chapter 9);

·   Develop an overall management guide for the day to day operation of the system (Chapter 10);

• Define and select an appropriate alarm system (Chapter 11).

Considerable background information on the basic processes being presented are also given in each chapter to supplement the basic design information being provided. These chapters should provide the reader essentially all the required information in order to design and manage a water reuse system. Some of the chapters provide information that apply beyond water reuse systems, such as discharge control and effluent management from flow through systems and gas concentration control in any type of water system.

The book is written for engineers and biologists working in the area of intensive fish culture. The text should also prove useful as an academic textbook, a design manual for practicing aquaculturists and as a resource of current "state of the art" tnethodologies associated with water reuse systems.

1.4 I{EI?ERENCES

Chen, S., D. E. Coffin and R. F. Malone. 1991. Sludge management for recirculating aquacultural systems. Paper presented at the Workshop on Design of High Density Recirculating Aquacultural Systems, Louisiana State University, Baton Rouge, Louisiana, September 25-27, 1991.

Losordo, T.M., R.F. Malone and S. Chen. 1992. Water quality requirements and environmental impacts of recirculating aquaculture systems, Pages 1-19, In: Kissil, G.W. and L.Sa'ar. Proceedings of the USA-Israel Workshop on Mariculture and the Environment, June 8 - 10, 1992. Eliat, Israel.

Mayo, R.D. 1991. Review of 'water reuse systems - water reuse in hatcheries. Pages 180­197. In: Brune, D.E. and l.R. Tomasso. Aquaculture and water quality. World Aquaculture Society, Advances in Aquaculture Volume 3. Baton Rouge, Louisiana, USA.

National Research Council. 1992. Marine Aquaculture: opportunities for growth. Report of the Committee on Assessment of Technology and Opportunity for Marine Aquaculture in the


نوشته شده توسط سجاد کاظمی در     بيان انتقادات و پيشنهادات


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Part three

Control and increase of production in

Fish cultivation

Introduction: The Concept of Production in fish cultivation

1 different concepts of production in fish cultivation the principal goal of fish cultivation in ponds is the production of fish of commercial value for eating or restocking generally in as large quantities as possible and in the shortest possible time.

However concepts differ sometimes very much so according to the objective. Principally there are

Three: quantity, quality and economic production.

Quantity production aims at producing as great a quantity of fish as possible for eating or restocking.

The principal aim in not to produce fish of high quality such as the production of graded fish.

Quantitative production means production which will give the most weight, this in followed notably in Africa with tilapias raised by the system of mixed age groups.

Quality production seeks to produce as high a quantity as possible of graded fish either for eating or restocking.

Production in terms of weight is never at maximum level although the fish of any given species produced are generally of uniform size and weight and of great commercial value.

This kind of farming corresponds in Africa to the rearing of tilapias by separate age groups.

According to bard (1962) this method can give a production equal to two-thirds in weight of quantitative production obtained by mixing age groups.

Economic production aims to produce as great a quantity of fish of high commercial value as possible.

The fish of high commercial value as possible.

The fish produced are either of high consumption value such as gourami in the far East, or fish for restocking, not to be eaten but with a high market value.

The production unit is not necessarily found in the weight but in individual fish.

This is the case when fingerling pike or pike-perch of 1 summer are produced in carp growing ponds.

Generally, in this case, the quantity produced in weight is not very high.

Methods of raising can be extensive, semi-intensive or intensive, depending on whether rearing is based on natural food only or whether it is more of less entirely artificial. Extensive farming

Produces a quantity of fish without artificial feeding, from rearing ponds which corresponds to natural productivity.

Intensive farming seeks to produce a maximum quantity of subjects or weight in a minimum of water by means of intensive or exclusive feeding.

Semi-intensive farming is intermediary.

2 means of increasing production

Whether production is quantitative, quantitative or economic, there are many systems of controlling and increasing output.

These are either biological or non-biological.

A non-biological methods for increasing production these are numerous and include:

I general technical and sanitary methods.

Quite apart from the methods given below and before applying them, general sanitary and technical are indispensable if the farm is to be run

The following points, therefore, must be observed; (1) different age groups must be represented normally and judiciously; (2) a sufficient oxygen content must be ensured; (3) action must be taken against disease and epizootics.

It is important to remember that all production factors ply their part and that each one must be given even more attention as in these ciroum-stances they are far from their optimum.

2 maintenance and improvement of ponds.

Quite apart from the upkeep of dikes, banks and other installations the maintenance and improvement of ponds include principally;
(a) action against excessive water plants. This is carried out principally by mechanical means (cutting), or by chemical means, as well as by biological means (grass eating fish) in certain cases.

These are discussed in chapter XII.

(b) The improvement and restoration of the bottoms of ponds.

The principal means used to this end are to empty the principal means used to this end are to empty the ponds and then when dry: to (1) leave the soil uncultivated or combine

نوشته شده توسط سجاد کاظمی در     بيان انتقادات و پيشنهادات

Fish Cultivation in floating cages


Fish Cultivation in floating cages


The Cultivation of freshwater fish in bamboo or wooden cages has been practiced for many years in the far East (Figs. 224 and 225).
In recent years, the technology for the intensive rearing of fish in cages has been introduced and improved in several countries throughout the world, for coastal marine waters as well as for inland waters.
The aim is to produce large quantities of fish on limited surface areas, in facilities less expensive and more manageable than ponds or tanks.
The use of rearing cages makes the fish harvesting very easy.
Another great advantage is the possibility of using water bodies in which classical fish culture cannot be carried out: large, natural or artificial non-drainable water bodies, slowly-moving water bodies with enough depth, thermal effluents.
The feeding of fish is entirely artificial and cages should be well sited in order to avoid unfavorable sanitary conditions.
In theory, intensive rearing in cages is possible for all species which accept complete artificial feeding such as trcuts, carps, tilapias and American catfishes.
Many details about cage construction and cage culture in freshwaters have been given by Dahm (1975) and Coche (1978).
Fixed cages made from nets or screen can be used, similar to those sometimes used for fish storage (Figs. 479 and 480), but cages floating at the water’s surface are most commonly used.
The principle of these floating cages is identical to the one applied for floating holding nets (Fig. 481).
Polyamide nets are often used, sometimes metal nets are also used, or a rigid construction made of metal or plastic screen.
The mesh size must be large enough to allow good water renewal.
2
This may vary from 6 to 25 mm according to the species and size of the fish. For trout, the mesh size should not be smaller than one tenth of the length of the fish.
Floating is made possible by various means, such as barrels, usually in plastic, polystyrene floats, or closed PVC pipes. Floats can also be combined with working platforms which surround either a single cage or a series of them.
Cage management is easier with such working platforms.
Fish feeds are distributed either by hand or with automatic feeders.
Cages are often rectangular and dimensions may vary considerably.
Dahm (1975) considers as rather typical dimensions for cage culture in European inland waters.
Too large cages are difficult to handle, while too small cages may cause food losses because of the wild swimming of the feeding fish.
The cage walls should be at least 50 Cm (20 in) above the water’s surface.
In order to prevent bird predation, the cages are covered with either a net or a screen.
To protect the nets against rodents, a second net can be used, stronger and with larger mesh, or a light screen, or even a metal net.
A cheaper and generally sufficient solution to this problem consists of protecting the upper part of the net down to a 50 cm (20 in) depth, with plastified wire netting.
Floating cages are set up either in rather large standing waters or in slowly-running waters.
Often thermal effluents of power stations are used, if the water is clean enough.
The water depth below the cage bottom should be at least two or three metres, in order to avoid a lack of dissolved oxygen in case of an algal bloom. This will also reduce the risk of disease propagation, much higher in waters too rich in organic matter originating from fish faeces and waste feed.
In fact, floating cages should not be set up in standing waters less than five metres (5 yd) deep.
To be successful, enough dissolved oxygen should be present in the cages.
3
In standing waters, the water renewal is often due to wind-induced currents.
To take full advantage of such currents, it is advisable to set up the cages perpendicular to the main currents.
Net fouling organisms may also reduce water renewal.
Regular checks and maintenance are therefore necessary.
Anti-fouling preparations (copper salts,star) or special paints can be applied to slow down the development of fouling organisms.
If necessary, pumps or any other aerating systems can improve the water oxygen content (Chap.XII, Sect.III).
The size of the rearing facilities depends on many factors : fish species, water renewal, depth and surface of the water body, acceptable degree of eutrophication.
It can be considered that the wastes load produced by the intensive rearing of 100 kg (220 lb) of fish is equivalent to that of five inhabitants.
Mann (1974) reports that in an old 17-5 ba gravel-pit, 5-9 m (5-10 yd) deep, the distribution of about 100 tons of dry concentrated feeds for the anneal production.
Such production has been obtained in 40 cages with a total volume of nearly 2500 m3 which means an annual yield of 20 kg (42 lb) per m3 of cage.
Exceptionally high productions can be obtained in heated effluents of good quality and sufficient flow.
Coche (1978) reports average monthly productions of 35 kg (78 lb)/m3 for common carp, 20 kg (42 lb)/m3 for Ietalurus pumetatus, an American catfish, and 15 kg (33 lb)/m3 for rainbow trout.
For rainbow trout rearing in non-heated waters, an annual production of 25 kg (55 lb)/m3 is normal.
This production is attained with a stocking density of 10 kg (22lb)/m3 and a maximum final density of 35 kg (78 lb)/m3.
The conversion rate of dry pellets is about three.

نوشته شده توسط سجاد کاظمی در     بيان انتقادات و پيشنهادات

nutritional disease

 

The earliest recognized nutritional disease syndrome of cultured penaeids was originally named "black death" to describe the typical, large black (melanized) lesions that occur in dying shrimp (Lightner et al. 1977; Magarelli et al. 1979). The disease occurs in penaeids reared in closed systems, aquaria, or flow­through systems in which most or all diet is artificial and without adequate ascorbic acid supplementation. The disease has not been observed in shrimp cultured in ponds, tanks, or raceways where there was primary productivity (growth of algae) (Lightner et al, 1979). Shrimp with black death typically display blackened (melanized hemocytic) lesions in tissues with a high collagen content. Such lesions are present in the stomach wall, hindgut wall, gills, and subcuticular tissues at various locations in shrimp, especially at the junction of body and appendage cuticular segments. There is often a terminal bacterial septicemia in shrimp with clinical signs of black death disease; Vibrio spp. and other opportunistic bacteria are typically isolated from the hemolymph of affected shrimp.

Black death disease has not been observed in subadult and adult shrimp and is apparently confined to the juvenile stages of the species. Penaeid shrimp apparently have a limited ability to synthesize the vitamin that meets the nutritional requirements of the older life stages, but not of the more rapidly growing juveniles stages (Magarelli et al. 1979)

نوشته شده توسط سجاد کاظمی در     بيان انتقادات و پيشنهادات

زبان تخصصی قسمت ششم

The female brood fish are taken out and wipend gently with a towel to remove all adhering water , after which the eggs are stripped and collected in a dry bowl ( fing .2.2 ) . depending on the size of the fish and consequently the quantity of eggs two or four females may be stripped at a time . afterwards the male are stripped and the milt is poured over the eggs evenly so as cover as many eggs as possible , the they are mixed well with a feather or spoon and allowed to stand for a minute or tow . the water is poured in slowly to fill the bowl and allowed to stand for about 10 min . at first one of the eggs stick to the pan , but they swell with water , the volume is increased and finally the stick to the pan only by a tiny point and can be detached easily . because of the excessive amount of milt the water is clouds and therefore is replaced several times until the eggs are seen to be very clean and the water clear . the eggs are then poured slowly on to incubation trays where they are uniformly spread out in one or several layers .

Lesson III

Artificial breeding of sturgeons

Different  phases of sturgeon cultivation are similar to those of other restocking cultivations based on the capture of brood fish from open water , followed by artificial fertilization and hatching . according to each group ,sturgeons reproduce either in the spring at the end of that season or in the autumn , but in general between april and august and sometimes up to October ( fig . 2 .3 ).

In order to hasten maturity and spawning , sturgeon pituitary gland extract is injected at the rate of 2 – 2 .5 mg dry weight per kg body weight in females and half of that in males . carp pituitary injection at the rate of 4-5 mg per kg body weight is also reported to be effective .  injected fish are held in tanks until they are ripe . between 24 and 36 hours after injection the brood fish should be mature .

Artificial fertilization in sturgeons differs slightly from the method generally used for other fish . as the fish are too large and difficult to handle and the structure of the oviduct allows only partial stripping , they have to be killed for eggs collection . a ripe female is stunned and suspended from a hook . the abdomen is slit open to remove the eggs , taking care prevent loss of loose eggs through the genital opening when pressure is exerted . the eggs are collected in a pan placed under the fish . they are given a first washing which lasts a maximum of 5 minutes . the removes the blood and the mucus . a little water is then poured in the eggs which are sprinkled immediately by the milt from two or three males . mixing is done with the hands and the eggs then allowed to rest for 3 4 minutes until fertilization is terminated . this coincides with the hardening of the shell which will be both resistant and elastic .

The a second washing is done to remove excessive sperm and the sticky coating covering the eggs . in this way the eggs will neither stick together nor to the bottom of the hatching apparatus . the water used for hatching should contain 10 per cent finely powdered clay or chalk . running water should be used or renewed  several times . gradually the viscosity will disappear and after 20 to 30 minutes the second washing should be terminated salmon incubators can be used for hatching on the temperature and the species . but is seldom more than six days at 15°c . the yolk sac is absorbed in 5 – 10 days.

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