1. INTRODUCTION:

This report presents an applied research proposal for MBRC investigations of a small-scale combined solar salt and brine shrimp (Artemia) production unit The overall purpose of such research is to test possibilities for low-cost community units for the production of good quality solar salt (for fish preservation and sale) and Artemia cysts for the aquaculture sector.

The proposed integrated unit should provide opportunities to experiment with Artemia introductions in salt production operations involving selection of the most suitable Artemia strains, determination of critical parameters such as the maximum salinity- and temperatures in evaporation ponds and variations according to climatic conditions, identifying the temperature-salinity tolerances of selected strains, and evaluation of the growth and production performances of inoculated strains as well as their reproductive characteristics

As a result of this applied research it is expected that a well-designed and field tested technology package for the small-scale solar salt/ Artemia production could be developed and transferred to small-scale fisheries communities and other interested parties

2. PROJECT PROPOSAL

The proposal calls for general civil engineering works for the construction of small-scale solar salt/Artemia production unit at Tajura, within the MBRC premises Technical specifications are provided and should be read in conjunction with the relevant Libyan standard specifications

2.1 Existing Ground Levels:

The contractor, in close coordination with the MBRC specialist in brine shrimp artemia, should fully survey the existing ground levels on the beach side of MBRC, provide technical advice on soil characteristics, and establish a programme of work

2.2 Programme of Work:

The programme to be provided by the contractor should set out all the operations required to complete the works. A detailed time schedule should also be prepared, including specification of labour, materials and equipment to be used, as well as the time it will take to deliver and mobilise these requirements at the site.

3. MATERIALS

3.1 Aggregates for Concrete

Aggregates should be obtained from sources known to produce aggregates of good quality for concrete. They shall be chemically inert, strong, hard, durable, of limited porosity and free from adhering coatings, clay lumps, coal and coal residues, and organic matter and other impurities that may cause corrosion of the reinforcement or may have implications for the strength of the concrete.

3.2 Cement

Sulphate-resistant portland cement suitable for structures in direct contact with sea water and brine solutions shall be used for all the civil engineering works. The cement should comply with the Libyan standards of quality and should be of recent manufacture. If it has been stored for more than 120 days, the cement shall be tested for soundness before use on any of the works.

3.3 Pipes for Sea Water Supply and Drainage

High pressure type PVC pipes suitable for outdoor installations (ultra-violet proof additives included) shall be used. The PVC pipes may be supplied with PVC joints and plastic sluice or gate valves for drainage and supply connections. If plastic valves were not available monel valves could also be used. The sea water inlet piping should be branched to the main seawater pipe coming from the pump house. All inlet pipes will be of 1.5" (38mm) diameter; drainage pipes will be of same diameter.

3.4 Paint and Other Protective Coatings for Steel Bars

All paints are to be applied first with a quality priming and then an undercoating in order to prevent corrosion.

3.5 Steel Reinforcement

Mild steel round bars of 8mm diameter and 6mm diameter shall comply with the requirements of Libyan standards.

3.6 Timber

Timbers for the roofing structure shall be of the best quality, well seasoned and free from cracks, loose knots and other defects that may affect their strength. Quantity and dimensions shall be as noted below:

Table 1. Timber Requirements

3.7 Water

Water used for both mixing and curing concrete as well as for making mortar shall be fresh water (not brackish) and free from organic or inorganic matter in solution or suspension in such amounts that may impair the strength and durability of the concrete.

3.8 Concrete Mixes

Concrete mixes are suggested as per Table 2 below. It should be noted that these mix ratios assume that the sand and aggregate are damp. The concrete tank surfaces shall be smoothed using cement mortar, with a wooden float to give a very fine finish, with internal comers rounded as well as the junctions between walls and floors.

3.9 Placing of Reinforcement

Reinforcing steel bars shall be bent, tied and placed as shown in the drawings. Specifications are provided in Table 3. It is very important that the reinforcing bars be securely tied to themselves so that their correct position is maintained during placing of the concrete.

3.10 Plastic Cover

Adequate ultra-violet proof polyethylene transparent film (200u thick or thicker if available) should be used for the roof cover of the production unit (approx.: 60 m²). The placing of the plastic film should be done carefully to avoid punctures.

Table 2: Suggested Concrete Mixture

Table 3. Reinforcement specifications*

* Note: Reinforcement for the corners of ponds is with 8mmÆ bars.

4. SITE CLEARING AND PREPARATION

The contractor shall remove all superficial obstructions on the site of the unit, in such a way as to obtain a smooth and levelled surface area free of bushes, vegetation, rocks, and trees. This activity should be carried out in parallel to the demarcation of the site.

5. OPERATION OF PRODUCTION UNIT:

5.1 Production of Salt:

The entire system is protected by a green house type shelter with natural ventilation in order to get maximum evaporation at least 9 months a year. During Winter (December, January and February) evaporation is reduced.

For calculation purposes, the average value of evaporation could be considered as 1 cm/day during the nine prime months of operation. For proper management, the system has been divided into seven different pond units (Table 4). Sea water is stocked at the upper part of the unit (two evaporation ponds). Each time the initial volume has been reduced by half, brine is transferred to the next pond (Artemia production pond I), and then flows by gravity to the lower ponds (crystallisation ponds) in which salt precipitates. Each one of the seven ponds has a specific function. Evaporation occurs all along the system, although not at the same rate due to different concentration of brine in each of the ponds.

It is not possible, without experiment, to calculate the exact production of salt for the system. However a range of production can be indicated, using a minimum value calculated from the evaporation in the first two ponds only (21.6 m²), to a maximum value calculated from evaporation considered as constant over the whole system (47.50 m²).

Table 4. Management of brine during salt production cycle

5.1.1 Maximum production of salt

1. Quantity of water evaporated every day from the whole system is:

   47.50 × 0.01 = 0.475 m³ = 475 liters

2. Volume of water evaporated during nine months will be:

   4751 × 270 = 128,250 liters = 128 m³

3. Given that normal sea water salinity is 38 g/1 (38 kg/m³) the total annual production of raw salt should be around:

   128 m³ × 38 kg = 4864 kg/year

4. Since sodium chloride represents around 78% of total raw salt, the production of ‘edible salt’ can be estimated at:

   4864 kg × (78/100) = 3794 kg/year maximum

5.1.2 Minimum production of salt (Cycle method)

1. Considering that each cycle starts with the filling of ‘evaporation ponds 1 & II’, the total volume of brine initially received for evaporation at each cycle is:

   06.0 × 1.80 × 2 = 21.60 m²
   21.6 × 0.20 = 4.32 m³ = 4320 liters of sea water.

2. Considering the initial salinity of sea water (38 g/1), it is possible to obtain 28 g/1 of pure sodium chloride.

3. Therefore, the quantity of salt after each cycle can be about:

   4320 liters × 0.028 kg = 120 kg

4. This salt will be harvested from the crystallisation pond after complete evaporation.

5. The initial cycle should last for about 23 to 25 days. After this, there is enough brine in the system to harvest salt every 13/14 days.

6. Therefore, the following cycles can be expected:

   1. one initial 24-day cycle, and then,

   2. 13 successive cycles.

7. Thus, the expected annual production of the system could be estimated as follows:

   14 cycles/year × 120 kg NaCl/cycle= 1680 kg high purity salt/year.

   This is a minimum expected production, which could be improved by overlapping cycles. The evaporation ponds are never completely drained because it is necessary to keep phytoplankton for the next cycle.

5.2 Cycle of Production.

Most of the primary production (phytoplankton) is concentrated within the two evaporation ponds. For proper fertilisation, a quantity of 250 g of agricultural N/P/K fertiliser should be added to each cubic meter of sea water injected to the system.

Every day, 0.475m³ of sea water flows inside the circuit, so that:

0.475 × 250g = 11875g of fertiliser are needed.

At the beginning of the operation, haloresistant phytoplankton (Dunaliella sp./Asteromonas sp.) should be inoculated inside the two evaporation ponds. From there, concentrated sea water with phytoplankton flows to ‘Production pond I’ which has been inoculated with Artemia nauplii. Zooplankton multiplies in this pond as salinity is increasing.

Brine with phytoplankton and zooplankton then flows to ‘Production pond II’ where adult Artemia are still multiplying and females are starting to produce cysts. Adult Artemia are regularly collected with a scoop net (500μ mesh).

Brine next flows to ‘Production pond III’, carrying along cysts which arc collected with 200 μ mesh scoop net. Brine from Pond III no longer contains phytoplankton, zooplankton or fertiliser when it flows to the ‘Pre-crystallisation pond’ where calcium chloride precipitates. Finally, brine reaches the ‘Crystallisation pond’ in which sodium chloride is harvested. At this stage, brine level should be constant: a balance should occur between brine inlet, evaporation and harvest of salt.

5.3 Production of Artemia biomass (Ponds I & II)

According to data published in various countries, production of Artemia biomass in similar conditions, is between 700 g to 2100 g/m²/year. The total productive area of the pilot unit is:

(1.5 × 3.8 m) + (l × 3.8 m) = 9.5 m²

The expected range of production in the proposed system should thus be:

• from: 9.5 × 0.7 = 6.65 kg/year minimum.

• up to: 9.5 × 2.100 = 19.95 kg/year maximum.

5.4 Production of Artemia cysts (Ponds II & HI)

According to existing data, the production of cysts is between 2 and 23.5 g/m²/year.

The area of production in the pilot plant is:

(1 × 3.8)+ (0.7 × 3.8) = 6.46 m²

Thus, the expected range of production should be:

• from: 2 g × 6.46 = 12.92 g/year minimum,
• up to: 23.5 g × 6.46= 151.81 g/year maximum.

6. CONCLUSION:

The main operational inputs of the system should be:

• Sea water : 10.63 + 128 m³ = 138 m³/year
• NPK fertiliser: 43 kg/year
• Phytoplankton strains (Dunaliella sp & Asteromonas sp.)
• Artemia cysts: 50 g

The expected production of the proposed small-scale solar salt/Artemia unit can be summarised as follows:

• Salt (sodium chloride): from 1440 kg to 3794 kg/year
• Artemia biomass: from 6 to 20 kg/year
• Artemia cysts: from 13 to 152 g/year

7. REFERENCES:

Sorgeloos, P, D. A. Bentson, W. Decleir and E. Jaspers, 1987 Editors. ‘Artemia, Research and its applications.‘ Proceedings of the Second International Symposium on the brine shrimp Artemia, organised under the patronage of His Majesty the King of Belgium, University of Antwerpen / ARTEMIA REFERENCE CENTER, State University of Ghent, Universa Press, Wetteren, Belgium, 1987.

Oscar do Porto. 1988 ‘Fisheries Technology in the improvement of fish utilisation and marketing.’ FI: TCP/STL/6651, Field document No.2. February 1988.

F.Medina Pizzali. 1985 ‘Small-scale Solar Salt Production.’ FAO filmstrip I/R 4933/E/8.85, 1985