Work Plan Implementation (Working Paper)       SCS/79/WP/84 SOUTH CHINA SEA FISHERIES DEVELOPMENT AND COORDINATING PROGRAMME REPORT ON SECOND REGIONAL CONSULTANCY LOW-COST WATER FILTRATION TABLE OF CONTENTS

SOUTH CHINA SEA FISHERIES DEVELOPMENT AND COORDINATING PROGRAMME
Manila, Philippines
November 1979

NOTICE OF COPYRIGHT

The copyright in this publication is vested in the Food and Agriculture Organization of the United Nations. This publication may not be reproduced, in whole or in part, by any method or process, without written permission from the copyright holder. Applications for such permission with a statement of the purpose and extent of the reproduction desired, should be made through and addressed to the Programme Leader, South China Sea Fisheries Development and Coordinating Programme, P. O. Box 1184, MCC, Makati, Metro Manila, Philippines.

REPORT ON
SECOND REGIONAL CONSULTANCY
LOW-COST WATER FILTRATION

by

George S. Cansdale, B.A., B.Sc., F.L.S., M.I.W.E.S.
Consultant

Project Document Identification

Work Plan Activity: 4 (e) (f)

4. Aquaculture

The objective will be to establish a programme of action for aquaculture development through the improvement of cultural practices in existing areas in particular countries, and the development of new areas. The Work Plan will be implemented through a permanent South China Sea Programme staff member and consultants. The work of consultants will usually be carried out in the individual countries; there will also be desk studies and consultations at the Programme's headquarters. The work will commence in 1974, and will continue over five years of the Programme. The work will involve:

5. Assistance in training of technical personnel - Training of technical personnel through fellowships and regional activities, e.g. working parties.

6. Aquatic pollution - It is intended to include on the staffing for Phase II specialization in aquatic pollution. Consultants should assist participating countries to minimize the impact of pollution, and elaborate and formulate project proposals for UNDP and/or bilateral agencies for possible funding. Programmes should include the protection of living aquatic resources from the influence of domestic and industrial wastes, related legal aspects af pollution control, industrial development and pollution, and advice on national monitoring programmes. Funds should be allocated under the fellowship component to allow for trained personnel in the region to travel to appropriate working parties.

Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or products presented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate further information available on related topics.

This electronic document has been scanned using optical character recognition (OCR) software. FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.

CONTENTS

INTRODUCTION

ABSTRACT

ACKNOWLEDGMENTS

1. ITINERARY AND ACTIVITIES

APPENDICES

Appendix 1 Extracts from a Report to: Mr. Bienvenido N. Garcia, Deputy Commissioner, National Pollution Control Commission, Manila

Appendix 2 Navotas Harbour - Sea Water Supply

Appendix 3 Investigation of Potential Sub-Sand Sources of Water at Miagao for New Campus for Fishery Faculty, U.P.

Appendix 4 Comment on Community and Industrial Water Supplies - Philippines

Appendix 4-A Copy of a Letter to Col. Rogelio L. Luis, Executive Director, Presidential Management Staff, Office of the President Following a Briefing at the Malacañang Office

Appendix 5 Sea Water Intake: appangi Point Fisheries Complex, Singapore

Appendix 6 Penang - Sea Water Intake for Researapp Institute and Aquarium

Appendix 7 Sea Water Abstractions in Capt. Hughes Bay and Ban Lamung

Appendix 8 Ban Lamung - Note on Iron Pollution

Appendix 9 appaappeongsao Fishery Station

Appendix 10 Community Water Supplies for Phang Nga Project

Appendix 11 Thailand: Conclusions

Appendix 12 Equipment

REPORT ON SECOND REGIONAL CONSULTANCY
LOW-COST WATER FILTRATION

by

George S. Cansdale, B.A., B.Sc., F.L.S., M.I.W.E.S.
Consultant¹

INTRODUCTION

Following the successful visit of the consultant George S. Cansdale to Southeast Asia in October-November 1978, and the publication of the Working Paper SCS/79/WP/80 in February 1979, FAO received several urgent requests from government departments in the region for a follow-up visit by the consultant. The requests came from the Philippines, Thailand, Malaysia and Singapore.

The South China Sea Fisheries Development and Coordinating Programme undertook the responsibility of arranging and directing the consultancy in close cooperation with the governments concerned and the relative FAO and UNDP offices. Funding was obtained from a variety of sources. The FAO country representative in the Philippines contributed towards the cost of the Philippine visit. Two FAO projects in Thailand contributed towards the cost of the Thailand visit. These were THA/75/008 Programme for the Expansion of Freshwater Prawn Farming in Thailand, and THA/75/012 Programme for the Formulation of Pond Management Techniques. The bulk of the overall cost was shared jointly by the Indian Ocean Programme and the South China Sea Programme.

Like the previous visit, this consultancy was a wide ranging one and several formidable problems were tackled and solutions developed in the very limited time available. Various techniques had to be adopted to suit particular conditions but all situations tackled were successfully dealt with. This is a tribute to the ingenuity and tenacity of the consultant and to the enthusiastic support and cooperation of the many government officers and FAO field staff involved.

¹ Address: Office - Sea Water Supplies, Ltd., North Parade, The Promenade,
Skegness Lincs PE25 1DB, England
Telephone: Skegness (0754) 4345

Home - Dove Cottage, Great Chesterford, Saffron Walden,
Essex CB 10 1PL, England
Telephone: 079983 (Saffron Walden) 274

The primary interest of the FAO Fisheries Department in the system is in relation to the benefits it can bring to fish farms, fish markets, and ice plants. But the greatest potential lies in village water supplies as the system could provide rural communities in the tropics, with an abundance of clean potable water at a very modest cost. This aspect has not been overlooked.

The successful demonstration at Marikina River, Manila on 30th August was brought to the attention of the Office of the President at which the consultant was asked to brief Presidential staff on 5th September. As a result, the government has decided to consider using the system, to considerable benefit and cost saving, in the Bicol River Basin Project.

Much follow-up work remains to be done in each of the countries visited so that local technical officers can acquire competence in the technology and so that fish farmers, fish plant and market managers and village authorities can be made aware of the benefits of the system. This further report on the subject is issued by the South China Sea Programme as a small step in that direction.

ABSTRACT

The report gives details of water filtration work undertaken by the consultant in the Philippines, Singapore, Malaysia and Thailand. Both marine and freshwater situations were tackled using SWS steel screen wells, box units and mini units. The appendices give fuller details of the problems encountered at each site, and of amendments to the system designed to overcome those problems. Not all sites were difficult, but many required a custom-designed modification to the system.

ACKNOWLEDGMENTS

This brief mission began with a request for follow-up work in the Philippines planned by the South China Sea Fisheries Development and Coordinating Programme, and a visit to Thailand under the auspices of the Programme for the Expansion of Freshwater Prawn Farming in Thailand, where the hatcheries had major water problems. An appeal for help in planning a sea intake for the Fisheries Research Institute at Penang was received and this was added to the itinerary. During briefing at Rome a further request was made -- for assistance with the intake at the Changi Point Fishery Complex at Singapore -- and it was possible also to include this. During the stay in Manila further projects called for attention, as listed in the itinerary and activities of the report.

To numerous officials, both senior and junior, I am grateful for encouragement and entertainment. Rather than offend by unwitting omissions or spelling errors I feel it is best to thank them all collectively, especially including those who worked alongside me in the water and proved to be apt pupils.

1. ITINERARY AND ACTIVITIES

Figure 1

ACTION OF SWS WATER FILTRATION SYSTEM

Suitable for gravel and sand bed rivers, streams and sea shores. In unsuitable sites, artificial bed is used.

ref. Cansdale, G. Low cost water filtration, FAO SCSP/79/WP/80 Manila 1979

APPENDIX 1
EXTRACTS FROM A REPORT TO: MR. BIENVENIDO N. GARCIA
DEPUTY COMMISSIONER, NATIONAL POLLUTION CONTROL COMMISSION
MANILA

by

George S. Cansdale
FAO Consultant (SWS Ltd.)

The Consultant begins by referring to the original report on low-cost water filtration, SCS/79/WP/80, a copy of which was attached to this aide memoire:

“While much of it relates to water problems within the fishing industry, many of its solutions worked out are of general application and I feel that the method outlined in Appendix 5 on p. 42, which is also involved in Appendix 3 on p. 37, might well be of value as a low-cost emergency filter for flood water. As described, it is for use in a large aquarium tank but we are already using it in Britain and elsewhere for supplying water to households. Any plastic container can be used if it is strong: we normally use P.V.C. cisterns of 45 cm × 30 cm or C 40 cm diameter. The gravel should be 2–5 mm or close to that range, with surface of 5 cm clean sand.

Although a small electric pump is mentioned, the system works equally well with a small hand pump. This should not be able to deliver more than 1 m³/h, for that is maximum capacity of this small system. It shall be pumped to waste for at least 15 minutes to establish it and form a good filter surface. After that we would expect it to remove suspended particles down to about 3 micron, including larvae, etc., and also up to 50% of total bacteria. The main bacterial control is by biological filter which takes perhaps 8 days to build up at local temperatures. Because the organic debris has been removed, only low chlorine dosage would be needed to sterilize the filtrate.

As regards costs, this mini-unit retails in U.K. for ₤25 but your local labour costs are much lower and I would expect it to be distinctly less here. If you feel that this can be of value, we shall be glad to draft a small instruction card about it.

As regards pollution control generally, we are only now moving into this work. We have recently been approached by a large company specializing in this with a request for rights to use our system. We believe that its cost-effectiveness can make it very useful, especially to the small factory, one of its big advantage being that a test can be made quickly and cheaply”.

The consultant ends his report referring to his own background in ecology and expresses his personal interest in combating pollution.

Figure 2

APPENDIX 2
NAVOTAS HARBOUR - SEA WATER SUPPLY

During my time in Manila it was impossible to obtain suitable non-metallic pipes and fittings to complete the work. The armoured rubber hose could not be fixed securely to the only pipe obtainable when the trial was conducted (a 6 m length of 2" g.i. pipe) but enough pressure was generated to insert the jet probe, which showed that under c. 4 m water the shell/sand bed was covered by only a thin layer of silt/mud. This contrasts markedly with the smaller harbour where earlier tests had shown the silt layer to be up to c. 1 m deep. Before the pipe connection finally broke down the source had been test-pumped for long enough to show that the shell bed can become a good source of clean sea water.

The water consumption will not be even through the day but water will be drained at c. 8,000 g/h for 6 or 8 hours. An 8 hp pump has been ordered which will fill the storage quickly: twin wells will allow this. The following intake system is recommended.

1. Two (2) stainless steel screen wells. One of 2" × 12" length is already at the harbour. A further screen well of 3" × 12" is at FAO HQ Manila. (Since this larger well might be difficult to insert at a distance, it is probably better to supply a second screen of 2" × 12" and use the 3" screen where the water is shallower).

2. Two (2) rising pipes of 2" Durapipe or heavy PVC, c. 7 m long. It is essential to connect these to the screen wells by strong plastic, non-corrosive, fittings, and not by iron joints.

3. Sufficient flexible armoured hose from the end of each rising pipe and pump chamber, with strong permanent connections.

Method

The yellow test probe left with FAO at Bangkok is being returned to Manila shortly and will be available for jetting down to locate a suitable site: the steel screen well can then be pushed down alongside it. This needs careful placing and it may be best to tie together lightly the yellow probe and steel screen, each fixed to its PVC extension. Once the correct depth has been reached, as tested by sucking from one or other and with the top of the screen not less than 1 m deep, the yellow screen is withdrawn. It may prove simpler to use the jet end of the steel probe of SCS/79/WP/80 (Appendix 12) fixed firmly to a stout PVC pipe, in place of yellow probe.

When the screen well is in position develop very fully, with stop/starts and several short periods of pumping back, until the pump is at full volume and water is crystal clear. Repeat for second screen well at not less than 6 m distance.

Placing

The presence of fishing boats close to the wharf restricts the choice and necessitates a site rather close to the wall. If possible the screen should be inserted diagonally, taking it away from the wall but ensuring that it is clear of any ship's hull. At the same time this brings the top of the PVC pipe closer to harbour wall. The precise method of fastening the rising pipe to harbour wall, and the length of rigid PVC pipe to which the armoured flexible hose is firmly attached, must be decided on the spot, the main factors being protection against damage by ships and by vandals. Unless a suitably placed drainage pipe or gully exists, a channel must be prepared to take the pipelines across the roadway: this is used by heavy traffic and a strong cover is needed.

Plumbing

The 2 rising mains should meet at a Y-piece close to pump intake but with a straight run of c. 1 m from base of Y to present a non-turbulent flow to the impeller. This pump must be self-priming and it is not sufficient to rely on non-return valve. The two mains are jointed to Y-piece by hose couplings and a simple plumbing modification will allow one line to pump back the other if this is found necessary from time to time.

Distribution System

The design for this seems to have been settled, but the following suggestion for convenience and efficiency is made. There is great value in having a permanent head of water sufficient to serve the various outlets. This could be achieved by raising just one of the 3 spherical storage tanks to a height of c. 2 m: the pipe supplying the taps draws from the bottom. The line from the main pump goes into this tank, with overflow to No. 2, which is connected to No. 3 by a pipe at low level. A submersible pump, on float switch controlled by level in tank No. 1 will keep this full when demand requires. The diagram below suggests the connection.

Water Quality

It has been shown that physically clean water can be provided. It is expected that bacteria will be greatly reduced but the parameter must be monitored after about 10 days pumping on the pattern likely to be used.

figure 3 NAVOTAS FISH MARKET INSTALLATION

APPENDIX 3
INVESTIGATION OF POTENTIAL SUB-SAND SOURCES OF WATER AT MIAGAO FOR NEW CAMPUS FOR FISHERY FACULTY, U.P.

Three supplies will eventually be required:

1. 500 g/m for the campus community, including both potable and general purpose water.

2. At a rather later stage, 500 g/m for servicing fish farms.

3. 200 g/m sea water for the Marine Laboratory complex near the beach.

At the request of the World Bank Mission the general area of the above was inspected on 3rd September in company with Prof. Dureza of the Fishery Faculty, and Prof. B. Ravena, a member of the committee concerned with planning.

Site 1

If surface water is used, the most likely site will be in the section of the river described as Bagumbayan. The width varies but is an average of c. 40 m. Flow is not continuous across the whole bed and varies in depth from a few cm to c. 50 cm. Assurance was given by the staff that the dry season flow does not fall below the required 500 g/m, plus that already being taken for community use nearer the river mouth. There was no way of confirming this at this season. The bed consists of typical water-worn gravel with the following size ratio -1 mm 34%, 1–5 mm 49%, +5 mm 17%, which is ideal for sub-sand abstraction. However, there are large numbers of stones up to at least 20 cm in diameter throughout the bed but not firmly compacted. This is said to be of such a depth that no dam can be constructed because water could always find its way through the underlying gravel. At least 1 km of this reach seemed to be of this general character and therefore equally suitable for use: the point most accessible to the storage and distribution center can thus be chosen.

Although the large stones made deep penetration of the bed impossible, the test probe was inserted far enough to demonstrate sub-sand abstraction and to confirm that the bed made a most effective filter.

Site 2

Site 2 was on a smaller river at Lumangan, at a point just below the confluence of two main streams. The general character of the bed closely resembled that of Site 1 and the gravel is clearly derived from similar parent rocks, largely igneous, with much granite breakdown and quarzite.

No opinion was offered of the flow at different seasons but it was stated that in the dry season the stream runs beneath the bed surface at some points. Since the permeable gravel appears to be of considerable depth this might still yield a useful volume, but only dry season trials would quantify this. The surface water was too hot for fish pond use but subsand abstraction would tap the buried cooler zone and perhaps be of an acceptable temperature.

Fresh Water - Recommendations

The river at Site 1 has apparently sufficient flow to supply all water needed. With minor bed modification, i.e. the removal of large stones by hand or by machine, this can be made into an excellent sub-sand abstraction zone. It is expected that only minimum further treatment will be needed, including low dosage chlorine for the potable supply. Water for general use and irrigation would not need this. This work can be undertaken by a local company and in a brief interim report made to the World Bank Mission on 4th September, the cost of such a system was suggested at around 130,000 at current costs. In the absence of some basic facts, such as the siting of storage, etc., and in the 12 hours available between return from Iloilo and meeting the Mission again, no detailed figuring was possible, but the above is considered to be of the right order of magnitude. It includes the abstraction system, primary pumps, and polishing treatment -- either chlorine or U/V -- for the potable water. It does not include piping, etc. beyond the pumps.

It is understood that the alternative method being considered is deep bore holes. From data available the capital cost of bore hole and pump would far exceed the total suggested above: equally important, maintenance of deep well pumps is much more sophisticated, while power costs for raising the water, even from 100m, are likely to be at least 3 times that of the surface water. It is suggested that very careful consideration be given to alternative methods before deciding on deep wells.

Note: Fears were expressed that the current flow in the larger river might be inadequate. Two comments are relevant:

1. Conservation measures, with hillside reclamation and reafforestation, are to be undertaken. This action should help spread the flow more evenly throughout the year and increase the minimum available.

2. The programme must clearly be phased to some degree. Experience in the first dry season, when the remaining flow can be monitored, will provide useful data, and point to any need for seasonal supplement.

Fish Farm Provision of 500 g/m

This is a later requirement and in the time available it could not be considered. One suggestion may be made. Presumably the various sections of the campus will have sewage treatment plants: if the effluent is of satisfactory quality, could it be fed into the stream running through Site 2 giving sufficient time for biodegredation of at least some of the excess nutrients, etc. to take place before it is abstracted again, sub-sand, for fisheries work?

Supply for Marine Research Laboratories

The beach at Sapa Miagao was examined and test-pumped. The particle size distribution seems suitable and the sand depth ample. Two complexes of two wells each will easily supply the 200 g/m required. The beach character suggests that very high quality water will be provided by subsand abstraction, i.e. water free from particles down to 2 micron, including all stages of plankton: almost complete removal of bacteria in the biological filter zone and avoidance of bringing in warm water at low tide. The use of sub-sand abstraction prevents any pipe fouling. No onshore treatment is needed and the water can be fed straight into all working systems.

Details of pump house siting have yet to be settled but a budget price of around 60,000 is suggested. This should include pump and pump house, assuming that this will be sited in the area immediately above high tide.

The need for water of correct salinity is noted. During installation this is carefully monitored before a well is finally established.

An interim report, including all relevant points in the above, was prepared for and submitted to the World Bank Mission at Manila on 4th September 1979.

Figure 4

APPENDIX 4
COMMENT ON COMMUNITY AND INDUSTRIAL WATER SUPPLIES -PHILIPPINES

Wider travel and the examination of further rivers and streams confirm the opinion expressed in WP/80 that many water courses in this country are ideal for sub-sand abstraction. It is most unfortunate that a strong tradition has been established that deep bore holes are the standard and only solution. The commitment to this method is suggested not only by the near impossibility of persuading most engineers to consider alternatives, but also by the fact that nearly 40 bore hole pumps are illustrated in the Manila telephone yellow pages. Parts of the islands have little or no surface water and here the deep bore hole may be the only technique for tapping permanent water, but in many areas this expensive method is wholly unnecessary. The cost of sinking a 100 m bore hole, which may be wholly wasted, approaches 100,000 and a suitable bore hole pump can cost up to twice this amount. The on-going costs are even more important, for a deep well pump may use at least 3 times the power required by a surface pump to move the same volume of water. In addition, deep bore hole water in a volcanic country is often highly mineralized, requiring special and expensive treatment, especially for such demanding uses as boiler feed. Where sub-sand abstraction can be used, it is likely to show a saving of over 50% and in many cases much higher, in capital costs alone. It is hard to avoid concluding that deeply entrenched vested interests help to ensure the continuance of the more expensive method.

Further scrutiny of river gravel specimens suggests that although the actual composition varies widely these generally form very suitable media. Analysis of two typical samples are as follows: Marikina River - 1 mm 46% (but very little 0.5 mm), 1–5 mm 43%, +5 mm 6%.

Numerous trials run in this river bed on the outskirts of Manila gave excellent results; careful examination of the particles shows that they are predominantly of granite and are all angular, with no sign of wear, which suggests that they have originated comparatively near the site. This is broadly true also for the -1 mm fraction, which includes many grains of quartz and some pumice.

In contrast, typical gravel being dug continuously from a river south of Manila for use as aggregate consists almost wholly of rounded water-worn particles: this sample was much more varied in origin, with several types of granite, schists and pumice, yet the size distribution is very similar, with -1 mm 40%, 1–5 mm 49% and +5 mm 11%. This too would form an ideal bed.

Figure 5

APPENDIX 4-A
COPY OF A LETTER TO COL. ROGELIO L. LUIS
EXECUTIVE DIRECTOR, PRESIDENTIAL MANAGEMENT STAFF
OFFICE OF THE PRESIDENT FOLLOWING A BRIEFING AT
THE MALACAÑANG OFFICE

“Thank you for the opportunity to talk to you and your colleagues about our work in low-cost filtration. We believe that the principle can be used to bring much improved water to many small communities far outside the reach of piped supplies and at a fraction of the cost of most other systems.

However, I must emphasize that we make no suggestion that it is the answer to all problems. A Working Paper SCS/79/WP/80 (attached) shows how it can be adapted to many situations. But it has no application where water can be obtained only from deep wells. In general the river beds in the Philippines have gravel layers ideal for working and we have been able to abstract clean potable water from relatively polluted streams at Marikina, Lucena, West Samar, Marinduque, and Iloilo.

The SWS system makes use of natural sand and gravel for its filter medium. The unit normally made in GRP for strength and durability is a simple device for cleaning the bed and making it more porous, and then for abstracting the water that has been cleaned by passing through the gravel bed. Filtration takes place in two parts: (i) the physical cleaning of the water occurs on the surface layer where a mat forms that can retain particles down to about 2 microns. This excludes larval forms of parasites. This process is complete within a short time, mostly in under an hour, by which time it is already removing about 80 per cent of bacteria; (ii) as oxygenated water is drawn through the bed, the whole zone becomes aerobic and a biological filter forms, taking 8-10 days at local temperatures. This is expected to reduce total bacteria by above 95 per cent and ammonia and BOD by 70–90 per cent.

Two sizes are currently made: the Village Unit has a capacity of 5,000 U.S. gallon/hour. The Mini Unit has a capacity of 200 U.S. gallon/ hour.

This system is now being used in about 20 countries and local manufacture is encouraged. Only one critical component is normally imported, this is the slotted plate, since it must be of precise shape and composition, and it is uneconomical to make locally except in very large numbers. A Philippine company is already preparing for production locally. Although the system is simple, correct installation is essential, and great stress is placed on training a local team.

The system has the following applications in S.E. Asia:

1. Village and town supplies.

2. Pollution control, bringing effluents to a condition allowing discharge into rivers.

3. Fish farming, providing clean water both salt and fresh, free from parasites, especially for rearing fry.

4. Abstracting the filtered water from harbours for use in washing fish, boxes, boats and fish markets.

5. Bulk supplies of clean sea water for Marine Laboratories, aquariums, and swimming pools.

As regards the Philippines, there seem to be three areas where the system could bring big benefits.

(1) Supplies for isolated communities. With few exceptions, these now use raw, untreated water. Our refiltered water is so obviously far superior that we have never encountered a case where it is refused. However, it could be that some individuals need convincing and this could be done by public example or use of test kits. The system would eliminate all amoebas and bilharzia parasites and would reduce bacteria by over 95 per cent. A simple test can verify the quality. Since petrol supplies are likely to become more difficult, we strongly advise that all village systems should have a hand pump supplied.

A budget figure of 15,000 was suggested, covering unit, piping, petrol pump, hand pump, clips, labour, taxes, etc. Bulk production, tax concessions, prompt payment, self-help by the village, etc. could reduce this usefully. However, it is essential to compare it with more orthodox systems which have a much greater cost.

(2) Forming the actual intake for larger schemes, allowing the water to pass straight to main filters. Elsewhere, the saving at this stage can be 80 per cent, with much reduced use of chemicals. For large volumes a complex of units at 10 meters centers is used. For really large installations requiring over 100,000 gallons per hour, the system may be incorporated at considerable cost saving, but comprehensive engineering studies have to be completed first in view of the complexities involved.

(3) In areas liable to flooding. If a unit is carefully installed when water is low, it should be safe against wash-out in floods. The depth of water over it makes no difference to performance and it remains efficient, even if only a hand pump can be used. On page 42 of the Working Paper, a simple self-contained system is described that could be considered for use in emergencies. The small system could be stored already assembled. The efficiency could quickly be tested by running it in any dirty river. (If there is any interest in this, we will gladly prepare a card of working instructions).

Experience in a wide range of sites suggest that maintenance of SWS units is simple, with occasional disturbance of the surface, or a gentle pumping back if flow is reduced. At the very worst, the unit could be taken up and replaced nearby in a hour or so, but this is rarely ever necessary even after years of operation. Literature will shortly be ready covering all these points in detail.

A major advantage of this system is that a site can be quickly and simply assessed. For all larger schemes, a feasibility study is essential but our system entails minimum apparatus and expense.

We are aware that the simplicity of the system can be a barrier to understanding by men trained in sophisticated technology, but we believe that such an approach, with its reduced energy content, is increasingly necessary.”

APPENDIX 5
SEA WATER INTAKE: CHANGI POINT FISHERIES COMPLEX, SINGAPORE

Existing System

A supply of c. 24,000 g/h is currently brought in by two parallel systems, each capable of this volume and running alternately. The reduction of volume at low tide is thought to be of the order of 10% but the system seemed to be subject to other interruptions and the average through the day may be well below 24,000 g/h.

To avoid excessive suction head the duplicate intake system is in two sections, with a c. 100 m long pipe, its end in 4 ft. of water at lowest tide, bringing water by gravity to manholes from which twin 150 mm lines c. 24 m long run to the pumphouse. The water then passes through gravity sand filter.

Beach Sand

Extent

Beach probing was first hampered by pump problems, and only one length of suction hose was available. Later, when the pump was able to give near maximum flow, it was possible to probe deeply and in several places the sand bed was explored to a depth of over 4 m without reaching any base rock or clay.

Quality

Beach and shore to well below e.l.w. are forms of typical granite breakdown material from which the mica fraction has largely been lost. The translucent white quartz grains range in size from c. 0.5 mm to c. 4.0 mm, giving an ideal mixture for sub-sand working. The bed is permeated with grey clay particles, presumably from felspar breakdown, and in places where there are a few small lumps of soft clay. Pumping trials showed that this is easily leached out and, after 15 minutes of pumping, the filtrate was of high quality. Samples were taken and results are awaited.

Raw Water

This is typical of inshore water in such tropical regions, with a visible content of suspended solids: these seemed rather uniform and it is likely that they are mainly organic breakdown particles. This organic fraction, rather than mineral silt, may be causing the damage in the hatchery. At the ruling temperature of c. 30°C the already low D.O. is soon exhausted if the flow to the filter stops, making the bed anaerobic. Unless water is piped to waste on restarting the pumps, noxious breakdown products may enter the working systems.

Tides

The extreme tidal pattern became apparent only when the 1979 tables were studied in detail. The maximum difference between two consecutive high and low waters is 3.4 m and the minimum 1.0 m. High tide may vary from datum height of 3.4 to 2.3 m, but no two consecutive high waters vary by more than 0.5 m and usually by under 0.2 m. In contrast, low tides vary from datum -0.1 to +1.5 m and two consecutive low waters frequently differ by c. 1.0 m.

The varying heights of high water are rather unimportant, for the upper section of beach has a steep profile and horizontal distances are small. In contrast, the highest recordings for low water are near the foot of the steep section and below this the slope is very gentle, so that a drop of, say, 0.5 m can mean a horizontal recession of many meters. Analysis of the tables shows that while the distribution is very uneven, one low water in 22 tides falls below the datum of 0.3 m.

Discussion

The Changi Beach can yield unlimited volumes of high quality prefiltered water from stainless steel screen wells. The basic problem is to design a system with acceptable total suction head at all states of tide. The static head at lowest water is c. 5 m and this leaves room for little friction head. Three possible general solutions may be listed:

1. Use the existing twin 150 mm lines from pump house, connecting a sub-sand complex to each at the seaward end, i.e. near the manholes. This involves considerable labour and may not be economic. Friction head would be almost eliminated if it proved possible to modify plumbing in the pump house and allow either pump to draw from both 150 mm lines at the same time. Since sub-sand working obviates pipeline fouling there is no obvious reason why the two should not be used together.

2. Put in new intake mains

   1. to existing pump house or
   2. serviced by submersible pumps.

The detailed discussion of these three alternatives must await further data that has been requested, but a comment on pump house siting must be made. In all tidal systems the pump must be placed as low as possible, even if this requires a sunk chamber, for whereas an extra 1 m is of no importance on the delivery side it can be critical in the suction line. It is understood that an existing structure was used for the two Desmi pumps, which fill it uncomfortably. Serious consideration should be given to lowering the pump level and at the same time modifying and simplifying the plumbing if the existing lines can be used. The removal of elbows and valves on the suction side, especially near the pump intake, can extend the effective suction length by many meters.

The fact that the sand generally is of great depth reduces the adverse influence of the low tide pattern, for it should make it possible so to site the wells that the beach can serve as reservoir for the short period that the water recedes beyond them. This factor is basic on solving the problem and a series of tests has therefore been devised to decide the optimum siting. To save time these suggestions were sent direct to Mr. Chen Foo Yan shortly after I left Singapore. During my 2 days he and his staff worked with me and became familiar with techniques of survey, installation and development. They are well able to carry out these tests and, in due course, install the system.

Figure 6

APPENDIX 6
PENANG - SEA WATER INTAKE FOR RESEARCH INSTITUTE AND AQUARIUM

At present an open intake connected to a mono pump by a 75 mm PVC line supplies raw water to both Research Institute and Aquarium, pumping only when covered by the tide, which is not everyday. Three sumps, filled by gravity from the tide, hold about 160 m³ of raw water and serve as a reservoir.

The current combined needs of the Institute and Aquarium could be met by continuous supply of 2,000 g/h. The raw water is of bad quality, having flowed over about 200 m of mud-covered flats. It has a high content of mineral silt and much organic matter in suspension, but it was usually too cloudy to see individual particles. On-shore filtration is proving difficult and it is suspected that this is as much due to the organic debris as the silt. It is essential to devise a method of supplying pre-filtered water of high quality.

Site

This is probably the most difficult site on which a survey by the SWS team has yet been done. The four major adverse factors are:

1. Erosion of hillsides on Penang Island, resulting from bad farming, has resulted in deposits of mud on this and other beaches. Exploration was confined to the approx. 30 m on the landward side but this seems typical of the whole: the very soft black mud is up to 40 cm deep. Local opinion was that conditions have now stabized, in that tidal scour balances new deposits. This mud does not prevent sub-sand working but makes it much more difficult.

2. The beach profile has a rather steep upper sector of clean sand covered only by spring high water. Many tides barely reach it and the water runs to and fro over the gently sloping mud flats, receding at lowest point of spring tide to a distance of c. 150 m.

3. The tidal pattern is very complex, which probably makes continuous pumping impossible. Each of the four daily heights forms a wave pattern steadily increasing and then decreasing, the average daily move being c. 0.1 m. These four curves are not in phase, resulting in a maximum amplitude of 2.6 m and a minimum of 0.1 m. The maximum high water reading is 2.8 m above datum and the minimum 1.4 m. The maximum low water reading is 1.5 m (i.e. above the minimum high water) and the minimum is 0.1 m. Continuous pumping would be possible only from near ELW and this is not practical. However, see note below. To allow daily pumping a prepared site would need to be at about 1.4 m above datum. Neap tides, with negligible amplitude, stay around this point all day. For most other tides this is more or less mid-point, allowing at least six hours of pumping per tide.

4. Although the underlying bed of sand has high potential, it requires thorough cleaning and preparation, made more difficult by factors (1) (2) and (3). This is discussed in detail under Bed Characteristics below.

Note:

A new coastal road is planned to pass more or less through the pump house site and this may involve reclaiming the beach to perhaps 200 m. This basically alters the whole position and until this is confirmed there is little point in discussing a final solution in detail. However, two points must be made. First, if this scheme matures in something of this form, the new, artificial, shoreline will be near the present E.L.W. This will give much easier access to water, and the new sea wall may well change currents and reduce silt deposition. Second, when plans are first discussed with the Authorities it is essential to include provision for burying a large pipe under the roadway, etc. to take the delivery and effluent lines.

Bed Characteristics

Disregarding the recent surface deposits, the bed consists of an intimate mixture of almost translucent quartz grains and clay: the former is the basic constituent of granite with an ideal particle size distribution, from c. 0.5 mm to c. 5 mm. A random sample gave the following breakdown: c. -0.5 mm 21%, 0.5 – 1.0 mm 11%, 1–5 mm 59% and +5 mm 16%. The -0.5 mm fraction has 3 components: grey clay particles, fine quartz grains and organic debris. The latter was reduced by raising to red heat but unfortunately the container was upset and the weight loss could not be measured. It is unlikely to have been as much as 10% of the sample -- an estimate is 1% to 2% of the total. This would be true only of samples from near the surface. The lower bed consists only of clay and sand. The above 5 mm fraction is very variable and most of the 16% noted above was one long granite fragment. The clay is the breakdown product of the felspar crystals in the granite. Unfortunately, in much of the local granite, felspar forms a higher-than-usual fraction. Some of this clay is finely disseminated and mixed with the quartz. This is easily leached out, but much is present in a proportion high enough to bind quartz grains together and this makes working more difficult. The bed is said to be of great depth and is easily probed by water jet to 4 meters. After full cleaning and preparation this can form an excellent filter medium. Practical problems are discussed below.

Beach Trials

Probing near where the mud flats join the rather steeper sandy beach quickly confirmed the presence of unlimited quartz sand intermixed with clay, as discussed above. Exploring the mud-covered zone was more difficult and while the tide was making, preliminary soundings were made by drawing water from the sump and improvising a 30 m line. The bed under c. 30 cm mud was found to have the same general pattern as farther inshore, and after c. 20 minutes of jetting around a point to make the bed more permeable, an attempt was made to abstract water, first by the yellow test probe and then by a screen well with slots. However, at such distance it proved difficult to establish a fast enough flow through the suction line. As the tide rose over this zone, a boat was used as a pump platform and work proceeded much better. Unfortunately, the official working hours made it necessary to abandon this test and continue work inshore, where the tide now covered the first test site. After 20 minutes pumping, with the volume steadily increasing, the water was much better than the raw water, but work had to stop. It is worth comparing this with experience at Changi Point a few days before. The sand/gravel fraction there appeared identical but the clay fraction was almost entirely in the well dispersed form. Fast pumping was possible within minutes, allowing both clay and fine sand to be evacuated. In each of 2 trials at Changi Point the water was crystal clear and at full bore after 20 minutes, in contrast to the low volume filtrate at Penang in which there were numerous suspended particles.

Discussion

Two separate problems must be solved:

1. Bed preparation

The high potential of the bed to serve as both filter and reservoir can be realized only after full preparation and development. For each source a zone of at least 5 × 5 m must be jetted to a depth of 2–3 m. This will ‘boil out’ much of the clay which will be distributed by the tide. It will also break up compacted lumps and allow pumping at a rate fast enough to wash it throughly when development starts. During the site tests we were able to spend only an hour or so on each. If necessary several days should be spent in preparation but one whole day may be enough. The team was most cooperative and quickly understood the procedure. I am satisfied that the leaders can carry out the work themselves. The benefits of clean water are such that much effort will be fully justified.

2. Site location

This is complicated by the possible road works discussed above. If these are delayed by one year or more it will be well worthwhile to prepare a bed near the present intake, or as much farther out as suction head allows, even if this must be abandoned later. The site in the upper beach already worked and can be prepared and developed much more easily. There is a sound case for doing this, for perhaps this can be developed to a greater depth and have a usefully high storage capacity. As this work proceeds, salinity should be monitored in case a fresh water spring is tapped, but there was no sign of this during the two days on site.

Pump and Pipeline

The mono pump now in use has a theoretical suction lift of at least 6 m and probably 7 m. With a maximum tidal range of 2.8 m, careful planning can reduce the maximum total static head to little more than this figure, while correct dimensioning of pipework can cut friction head to a minimum. To calculate the maximum acceptable suction length, the following factors must be carefully considered.

1. Condition of pipeline

The fouling of the actual intake suggests that this might be extensive. On the other hand, heating up by the sun while empty might prevent colonization in the exposed part. Its condition should be checked.

2. Pipe design around pump

Each elbow may in effect add to the suction line an extra length in feet of 5 times the diameter in inches, i.e. c. 15 ft. On the suction side alone there are at least 3 such bends and one valve: together these could add as much friction as the actual length. The aim must be to have as direct a line as possible, with only smooth curves, from raw water intake to pump intake port. Friction head on the delivery side is much less important but should not be any higher than necessary.

3. Height of pump

It is standard practice in tidal situations to site the pump intake as low as possible, even in a sunk pump chamber. The mono pump could usefully be lowered, even if only to the existing floor. There seems no sound reason why it should not be placed distinctly lower than that. Assuming that the existing run from pump to intake is 30 m, the above rationalization could easily triple the acceptable length. (It is worth quoting one actual system recently installed. The tidal amplitude is up to 4.7 m and the recession c. 100 m. A sunk pump chamber has a mono pump capable of 4,000 g/h continuous through 110 m of 75 mm line, fed by twin wells).

Analysis of the tide tables suggests that datum plus 1.7 meters is probably the nearest point that can be drawn from daily, but 1.5 m would be better. Neap tides could be pumped for much of the day, since they are almost stationary around this point. Higher tides should supply water for at least half the 24 hours; the reservoir effect may markedly extend this time but only test pumping will quantify this.

The following measurements have now been made:

The implications of these distances on suction head are now being studied and suggestions for action will be made shortly.

Site Preparation

The following procedure is advised and Mr. Ong Kah Sin has already been given full notes on this. For each beach well, mark the central point and an approximate 3 m radius around it. Taking if need be several days, according to access, jet over this with a steel probe to a depth of c. 2.5 m. The object is to remove as much as possible of the fine material, break up the clay lumps and leave a permeable bed for the steel screen well. One screen of 3" diameter and 12" length has already been ordered. This is inserted by placing it alongside the steel jet. The PVC pipe should be cut off at c. 2 m and given an elbow which is pushed c. 20 cm below the surface so that the flexible hose attached to it can be buried. Develop very fully from as near as possible with numerous stop/starts and several reversals of flow until full volume is obtained, i.e. at least 5,000 g/h, and the water is crystal clear. If need be a whole day must be taken over this development, gradually increasing the flow. Then cut back to not more than 3,000 g/h and pump steadily for several hours before monitoring. If this is satisfactory, a further site can be prepared with at least 8 m between centers and the two linked to the suction line by flexible hose and Y-piece.

Emergency Supplies

The use of the zone alongside the pump house was also discussed. A similar procedure to the above should be followed but this site can be prepared much more easily than an offshore site, using water from the sump, and this would be a sound provision. It may also be worth converting the sump into an emergency sand filter, using one SWS unit as take off. A suggested procedure is as follows:

1. Clean out all sections thoroughly.

2. Prepare right hand (no. 1) section as a filter in these stages.

   1. Put down circle of stones (3–10 cm) more or less centrally for diameter of c. 1 m and depth of c. 15 cm. This stops the unit sealing on the bottom and gives lateral access to water.

   2. Using washed sand from the upper beach, put 10 cm depth over the stones and put unit in position with 2'' flexible hose fixed to it. If convenient, sift enough coarser material (3–5 m) to pre-pack unit before putting in position.

   3. Cover with washed coarse sand to 15 cm above top of unit.

3. Allow filling from the sea only to the left section, no. 3

4. Make up two 50 mm pipes to syphon water from 3 to 2 and from 2 to 1, but reaching only to 30 cm from the bottom. It is probably best to use PVC semi-rigid or similar with two elbows at the top. It may be necessary to cut down into the top of the partition to ensure that the pipe fills before water overflows to the next section. This general arrangement is suggested as a way of allowing some sedimentation before the water reaches the filter but this is only for consideration. It is hoped that the general idea of such a system is clear but more effective details may perhaps be worked out on the spot.

From time to time the filter surface may need to be raked gently and the dirty water pumped out.

Figure 7

APPENDIX 7
SEA WATER ABSTRACTIONS IN CAPT. HUGHES BAY AND BAN LAMUNG

All the beaches examined had sand of above 3 m in depth in the upper section, with ideal particle size distribution for forming beach wells. At Capt. Hughes Bay the colour of fine material evacuated during development suggested a minor degree of pollution. This is only tentative opinion and it is not important, for the site was pumping particle-free water at full volume in under 10 minutes. If the hatchery is established in this bay, an unlimited flow of high quality pre-filtered water is easily obtainable.

Ban Lamung is the site of a private hatchery and the upper beach is perhaps the most favourable on which the SWS system has ever been tested for it was pumping at full volume and high quality in about 5 minutes. The pump outlet was then attached to the existing rising main and, for the time available, clean water was delivered to the working systems nearly 400 m distance through a 50 mm pipeline. The flow was assessed at c. 10 m³/h, causing a friction head of at least 16 m, plus 2 or 3 m static head. Since the pump had a flow of c. 30 m³/h through a short delivery pipe the rising main is the limiting factor. If a larger pump was used to increase the flow to 13 m³/h, the head would then increase to over 30 m and the connection and lower part of the pipeline itself would be in danger of damage. A new 75 mm line would carry at least 25 m³/h without excessive head but the extra cost would not be justified. It is simpler and much cheaper to use the existing system and pipeline for a longer period daily. Establishment takes such a short time that it is probably best to insert the well daily and remove both pump and line when pumping is complete.

The first work was done when most of the beach was covered by the tide. A subsequent visit at low tide allowed more detailed exploration. While the more steeply shelving upper beach has a great depth of mixed sand, the lower and more level zone, most of which seems to be exposed only at very low tides, has a different texture, being of fine sand and silt with numerous broken shells. If it became necessary to pump continuously, this zone could be prepared as a source incorporating coarse sand from (the upper beach) perhaps 30 meters away. As demonstrated on site, the SWS unit is more suitable than a screen well in such terrain, since it is easy to gravel-pack, while the much greater perimeter makes it easier to pump at above the critical flow needed to evacuate fine particles and so develop the source. In addition, it is much more stable near the surface than a screen well. The area around such a permanent intake should be worked over very thoroughly as described in Appendix 6 (Penang).

Since the upper beach can be used for several hours over each high water, and, apart from spring tides, almost continuously it will be simpler to pump from a locally made PVC point installed and left in position as low down the beach as possible in order to give maximum hours of pumping while keeping the well in the coarser medium. This will tend to block easily but it can be taken up, cleaned and replaced in a very short time. Alternatively, it may be preferable to install daily at a suitable point the stainless steel screen well now at Ban Lamung.

APPENDIX 8
BAN LAMUNG - NOTE ON IRON POLLUTION

The site at Ban Lamung has fresh water which currently has a sufficiently high iron content to stain all tanks, so that advice was asked about possible treatment. The well has been pumped for only a few months on a routine of 3 or 4 hours daily. The iron precipitates slowly and most come out of solution in the working tanks. Iron in water can range from solid particles to chemical forms which are hard to precipitate, and while aeration usually converts the more soluble ferrous into the less soluble ferric compounds reaction may be delayed. The following suggestions are made for reducing this nuisance.

1. The opinion was expressed by local staff that the iron being sedimented is now rather less and this was again confirmed at the end of my visit. It may be that instead of being in the water itself iron is being leached from the bed. If this is so, the amount is finite and in time will cease to be noticeable. It is not uncommon for a bed to be cleaned just by pumping, and to expedite this the pump should be run as continuously as recharge rate allows for several weeks, any surplus being put into the ground at a distance from the well, while monitoring weekly for iron. A simple iron testing kit is easily available.

2. Construct a simple cascading column from an old oil drum or similar, putting in two perforated supports to hold coke, broken breeze blocks, etc. on the top layer and ditto with some finer gravel (1/2" to 2") on the lower. The first serves to give thorough aeration and a long contact time with the air. The lower layer takes out the coarse floc. This is simply made from scrap and quickly tested. If it works, several can be made and used alternately to allow cleaning out, etc. (A more elaborate and expensive version of this device can be seen at NIFI).

3. In some cases iron settles on the pipe wall to form a coating of ‘iron bacteria’ which are oxygen-demanding, and it may be helpful to run an intermittent pumping regime something as follows:

   1. Switch off pump, making sure that the non-return valve does not allow the pipe to empty.

   2. After an interval switch on again and pump to waste.

   3. Allow the water to go into system.

The time needed for (a) when the iron bacteria run out of oxygen and become detached from the wall, and (b) when the dirty water is run to waste can be found only by experiment, beginning with a twice-daily stop for about 15 minutes and working each way from this.

If none of the above is helpful, a series of settlement tanks plus added chlorine or air may be needed. Special iron filters can be bought but these are more expensive and need careful maintenance. We can only express the hope that the suggestion in no. 1 above is confirmed.

Figure 8

APPENDIX 9
CHACHEONGSAO FISHERY STATION

The fishery station uses brackishwater which can be drawn direct from the canal at only two periods of the year. During the rainy seasons the estuary supplying the canal has fresh water, so that salt water needed for mixing is drawn fron storage. In the dry seasons the Bangpagong estuary is salty and fresh water is drawn from the reservoir. Current total needs are for c. 200m³/d or 8 m³ (1,800 g/h). Storage capacity is adequate. The station has a number of large earth ponds but an almost unlimited depth of mud makes it impossible to construct an artificial bed in one of these. There are no natural sand beds but unlimited suitable sand/gravel is obtainable nearby.

An artificial bed with an approximate surface of 5 m × 5 m was prepared in one of the large concrete tanks with a cross section as in Appendix 1 of WP/80. The central core was of 30–50 mm stones. The unit was pre-packed with c. 2–5 mm gravel; the remainder was sand/gravel as supplied, of part river and part beach origin and was a mixture ranging from below 0.5 to 5.0 mm. The tank was filled with partly settled raw water. After fifteen minutes the clay fraction in the bed was largely evacuated and water was clean and physically acceptable for use, though still with a faint opalescence caused by a small clay particle. The water was then fed to the main system and the quality steadily improved over a further 2 hours pumping.

A mini unit was established in an existing sand bed within one of the smaller concrete tanks where the recirculation water was opaque with both mineral particles and organic debris. The mini unit was developed and run by gravity only, in the absence of a suitable hand or small electric pump, and it gave excellent quality. A reducing head of water made volume measurements difficult but at c. 60 cm head the flow through a 20 mm pipe was c. 0.5 m³/h. This flow will be much increased by full development using a suitable small pump.

The mini filter was demonstrated in the sand already part filling the center of a concrete tank and serving as a sand filter through which the water passed horizontally. This seems potentially dangerous since the water probably travels through only part of the cross section keeping this aerobic, while the remainder may become anaerobic. This may not cause any trouble but it is better to organize circuits so that the whole is fully used. A more positive method would be to use a series of mini units at about 1 m centers in a bed of sand/gravel 50 cm deep, the space above being filled with water. The levels overall do not allow gravity working, but this layout would probably make it possible to use air lifts for each individual mini unit. Formulae are available to calculate flow in an air lift system but it is generally best to work out details by trial and error.

The mini unit is proving effective when used in a container in aquarium circuits and in open small ornamental fish ponds and it is suggested that this is tried here with careful monitoring. (See Appendix 5 of SCS/79/WP/80). This pack can safely stand actually in the tank for the rate of downward flow to the filter surface will not draw down the larvae. Cleaning should be infrequent, especially if nylon, wool, etc. is placed on the filter surface to act as a strainer but it is easily achieved by lifting out one pack after putting in another few days earlier to build up efficiency or preferably, having sufficient mini units working to allow one to be taken out at any time for maintenance.

Quality

There was general agreement that even after the above short period of development the water from the larger filter was physically more than adequate for hatchery use but for recirculation systems the emphasis was placed on chemical parameters, in particular ammoniacal nitrogen. Conditions in Thailand are markedly different from those in temperate zones and monitoring of the relevant parameters is necessary but we are confident that if flow rates and bed size conform to those suggested, the biological filter zone will be more than sufficient to process the ammonia and other breakdown products in normal systems, even when more heavily stocked with larvae than at present. These rates should therefore be taken as a starting point and in many cases, after test running, it should be possible to increase the flow with safety. In English outdoor conditions it is found that bacterial removal and reduction of BOD and ammoniacal nitrogen run almost parallel and that the percentage removal remains more or less constant over a range of raw water values, the former remaining steady at about 97% and ammoniacal nitrogen at about 90%. In local systems the temperature is around 27°C at which the biological activity is much greater.

APPENDIX 10
COMMUNITY WATER SUPPLIES FOR PHANG NGA PROJECT

Although tentative plans had been made to visit this area, this was at once seen to be unnecessary when the problem was discussed with Mr. Akadij Artachinda. He was clearly so familiar with details of the problem -- and understood so quickly the potential of sub-sand working -- that a meeting was arranged at his office at the University to discuss possible solutions.

Water Available

A shallow well close to a brackishwater canal supplies c. 200 people. This is c. 1 m × 1 m in plan. The total depth is 3 m and stable water level at c. 1.5 m. It holds nearly 2 m³ when fully recharged, which is at the rate of c. 0.7 m³/h. The water is drawn by hand and put into storage jars of 200 liters, of which each boat holds 3. These are taken back to the compound by canal. After three boats have been loaded, they are then dependent on recharge which takes c. 1 hr per boatload. The total water available per day cannot therefore be greater than 2 m³ + about 11 × 0.7 m³, i.e. nearly 10 m³.

Quality

The water as drawn has an unacceptable amount of sediment, which is fairly coarse and settles out in about 24 hours if undisturbed. In the normal way it is not practical to allow this time.

Possible Methods of Improving Quality

1. Use of mini unit in well (a) in bed of introduced gravel, (b) in container of gravel, in both cases abstracting by hand pump. This would have the added advantage that the well could be covered over against abuse and pollution. Unless covered, in both (a) and (b) the water is still subject to contamination by pails used for dipping up water by those too impatient to wait for the pump.

2. Erecting overhead storage at the village and drawing filtered water by tap, as in Appendix 3 of SCS/79/WP/80. This would have the advantage that water can settle well and it is filtered as used, but it would be much more expensive and would require double handling of all water.

After some discussion it became clear that 1 (b) is the most acceptable and practical method. Since the water will be drawn through the surface by pumping, it will not be kept agitated by frequent dipping. Further, the container stands on the bottom with its intake surface well above it, thus keeping clear of the worst silt. Appendix 5 of SCS/79/WP/80 describes this procedure in detail. In addition, it is essential to ensure that the plastic container is strong enough to be lifted in and out by ropes on either side. Nylon, wool or old clean cloth over the surface would hold macroscopic particles and thus extend each filter run, but this is likely to be in many weeks rather than days. A few holes in the bottom will allow water to drain out and so reduce weight when lifted. Since the water enters the sides and bottom of the well, there is no need to fit the hard plastic shield shown in the diagram of Appendix 3. Various models of pump are available. The decision about permanent mounting or removal daily must be made according to local conditions and the danger of either theft or vandalism.

Increased Supply

Although the theoretical yield of 10 m³/d should be enough for a community of 200 people, seeing that it is all carried, the pattern of collection and slow recharge may prevent the whole from being used. Any suggestions for increasing supply are only tentative. Proximity of brackishwater makes it risky to deepen the well which might have the effect of only increasing storage. It is also impossible to predict the results of increasing its cross section to, say, 2 m². Since there are other wells in the vicinity, it may be best to try digging a second well at not less than 10 m center, but time would be well spent studying the draw-down and recharge pattern in nearby wells and seeking to trace the direction of any underground flow.

Figure 9

APPENDIX 11
THAILAND: CONCLUSIONS

The primary reason for visiting Bangkok was to help in solving problems of unsatisfactory water in Macrobrachium hatchery systems. Methods of abstracting pre-filtered sea water from the natural bed were taught and had already been applied before the visit ended. The technique of using both village units for primary filtration and mini units for recirculation, in wholly artificial beds was shown in Chacheongsao. In this case also a permanent source was created and this had been supplying clean water for some four days before the mission ended.

Abstraction from in situ beds is clearly impossible on the vast Central Plain, where the canal's base usually consists of almost bottomless mud. For the numerous isolated communities who still take much of their household water from these canals it seems that the mini unit methods in Appendix 3 and 5 of SCS/79/WP/80 could bring much improved water at minimal cost. Throughout this region there are numerous fish ponds. While it can hardly be economic to filter the whole supply it seems that the general method described in Appendix 1 SCS/79/WP/80 and as in Appendix 9 could well be used for that part of the supply needed for the actual hatchery and the early fry stages, as well as for any sensitive species that might be kept.

It was clear that many beaches to the east of Bangkok are ideal for providing by sub-sand abstraction the marine part of the water supplies for Macrobrachium culture, removing any need for settlement or filtration. It is understood that the same is true of beaches on the Isthmus of Kra. It is likely that this method will be adopted fairly widely, in places with the use of homemade hardware, resulting in much saving of labour and improved results. The application to fresh water is equally valuable since in many hatcheries this can be taken only from the canals and is high in silt. The provision of sediment-free water is directly helpful to the stock and also allows fuller use of water.

Thanks to the initiative of Michael New, many contacts were made with a wide range of persons interested in water, whether for human use or in fish farming, and discussions were held with all those listed in the itinerary and activities. It was unfortunate that the nearest practical sites for demonstrating these techniques were at Chacheongsao and Ban Lamung, but a total of some 25 people were present at the former or at both sites on the 21st September.

APPENDIX 12
EQUIPMENT

All pumps supplied were well able to handle the volume required and were fully self-priming, but unsuitable armoured hose caused much waste of time and frustration, especially during development. This was no fault of the organizers for, except in Thailand, little was available other than standard lengths of wire-lined rubber hose. This type is heavy and cumbersome and it is supplied in set lengths only, with special ends for attaching to the male pump ports. This pattern can be wasteful and inefficient in several ways. A short length cannot be cut off, while even a 15 m run involves joins, and even more important long term, its durability is suspect. For instance, the length used at Iloilo had been bought less than twelve months before, but in the sea trials it collapsed in two places and the wire reinforcement was found to have rusted through.

The armoured plastic hose supplied at Bangkok was much better, but this also had special rubber ends. One such joint broke down under pressure on the delivery side -- pumping to a head of c. 60 ft. -- and another joint came right off when twisted, so that the hose had to be fastened directly to the pump.

For permanent installations especially in the sea it is essential to fit the most durable armoured hose that can be obtained, for the extra cost is negligible as a percentage of the whole and in the long run it is a big economy. The type mostly used in U.K. and widely overseas has the brand name of ‘Heliflex’, made in several grades and in sizes from 37 mm to 150 mm. The marine grade has shown itself able to withstand heavy duty in rough sea conditions on rocky shores for above seven years. In normal sub-sand working it is largely buried and protected from abrasion since it is not subject to any movement so it is expected to have a serviceable life of at least 10 years. Other major advantages are that it is made in 30 m lengths, quickly cut and easily joined, and therefore less wasteful and ideal for rapid laying in a tidal situation. Secondly, the PVC material is partly thermoplastic and when heated by hot water or blow-lamp can be shrunk or expanded before fastening with stainless steel clips to make a very firm connection. Thirdly, the friction loss is less than in other armoured hoses. Priority should be given to identifying such material among what is obtainable or arranging to import it as a vital component of the system.

In some countries the duty on plastic materials is punitively heavy but there are also territories, especially in Africa where equipment to be used in water treatment attracts only nominal or no duty. In all cases enquiry should be made to see whether this applies. Current U.K. prices vary from about ₤2.50 per meter for 37 mm to ₤4.70 per meter for marine 50 mm and ₤6.50 per meter for marine 75 mm. The fact that precise lengths are used with no waste will often compensate for the possible higher cost per meter. Systems vary widely but few are likely to require more than about 1 m per 2 m³/h (500 g/h), i.e. about 10 m for a single unit system providing 20–22 m³/h. This is a near enough figure for budget purposes and it allows calculation of any extra prime cost of armoured hose. When durability is taken into account, it is likely to be very much cheaper.

Locally made polybutylene and high density polyethylene pipes may be available in some sizes. These are made in long lengths and are flexible to some degree, but the specimens examined were not really suitable for attaching to the unit and it was not easy to connect them.

PUBLICATIONS OF THE SOUTH CHINA SEA FISHERIES DEVELOPMENT AND COORDINATING PROGRAMME

WORKING PAPERS

NOTE: Copies of these papers can be obtained by writing to the Programme in Manila, Philippines.

COORDINATING COMMITTEE REPORTS

WORKSHOP REPORTS

SCS MANUALS

PERIODIC PROGRESS REPORTS

FISHERIES TECHNICAL PAPERS

FAO species identification sheets for fishery purposes. Eastern Indian Ocean (Fishing area 57) and Western Central Pacific (Fishing area 71) Rome, FAO, 1974. 4 vols.

TECHNICAL REPORTS CONTRIBUTED TO SYMPOSIA/MEETINGS, ETC.

Rabanal, H.R. 1975 FAO activities in inland fisheries and aquaculture with particular reference to Asia and the Far East. Manila, South China Sea Fisheries Programme. 17p. (Contributed to the First Fisheries Research Congress, Philippine Council for Agriculture and Resources Research, 7–10 March 1975, Legaspi City, Philippines)

Rabanal. 1975 Preliminary report on the Macrobrachium fishery in the Indo-Pacific region. Manila, South China Sea Fisheries Programme. 20p. (Contributed to the International Conference on Prawn Farming, Vung Rau, Vietnam, 31 March – 4 April 1975)

Rabanal. 1975 Distribution and occurrence of milkfish Chanos chanos (Forskal). Manila, South China Sea Fisheries Programme, 1975. 18p. (Contributed to the National Bangus Symposium. Manila, 25–26 July 1975)

Rabanal. 1976 Mangrove and their utilization for aquaculture. Manila, South China Sea Fisheries Programme. 20p. (Contributed to the National Workshop on Mangrove Ecology held in Phuket, Thailand, 10–16 January 1976)

Rabanal. 1976 Report of project identification misson to Bangladesh on inland fisheries and aquaculture. Manila, Asian Development Bank. 56p.

Rabanal. 1976 Aquaculture 1976: Focus Southeast Asia. Manila, South China Sea Fisheries Programme. 12p. (Talk delivered at the National Convention of the Federation of Fish Producers of the Philippines, Iloilo City, 26 August 1976)

Simpson, A.C. 1976 Some proposals for research related to the understanding of mangrove ecology and the utilization of mangrove areas. Manila, South China Sea Fisheries Programme. 10p. (Contributed to the National Workshop on Mangrove Ecology held in Phuket, Thailand, 10–16 January 1976)

Cook, H.L. 1976 Some aspects of shrimp culture research with particular reference to Philippine species. Manila, South China Sea Fisheries Programme. 7p. (Contributed to the Philippine Council for Agriculture and Resources Research (PCARR) Fisheries Workshop, Subic, Zambales, Philippines, 15–17 January 1976)

Rabanal, H. R. 1976 The resources in inland waters: their utilization and management. Manila, South China Sea Fisheries Programme. 21p. (Talk delivered before the Phi Sigma Biological Society as a contribution to the Deogracias V. Villadolid Memorial lecture series. Manila, Philippines, 26 November 1976)

Rabanal, H. R. 1977 Aquaculture in the Philippines. Manila, South China Sea Fisheries Programme. 15p. (Talk delivered before the United States Peace Corps Volunteers, Los Baños, Laguna, Philippines - 11 January 1977)

Rabanal. 1977 Aquaculture in Southeast Asia. Manila, South China Sea Fisheries Programme. 10p. (Paper contributed to the Fifth FAO/SIDA Workshop on Aquatic Pollution in relation to Protection of Living Resources. Manila, Philippines, 17–27 February 1977)

Simpson, A.C. 1977 Fisheries research and development in the Philippines: Some recommendations with special reference to resource management. Manila, South China Sea Fisheries Programme. 16p.

Rabanal, H. R. 1977 Aquaculture management. Manila, South China Sea Fisheries Programme. 12p. (Contribution to the BFAR/FAO-UNDP Training of Regional Trainors in Aquaculture. Lucena, Quezon, Philippines, 19 September to 27 October 1977)

Rabanal. 1977 Recent trends in aquaculture. Manila, South China Sea Fisheries Programme. 13p. (Paper contributed to the Seminar/Workshop for Fishery Schools' Administrators, conducted by the Bureau of Fisheries and Aquatic Resources. Manila, Philippines, 24–28 October 1977)

Rabanal. 1977 Forest conservation and aquaculture develoment of mangroves. Manila, South China Sea Fisheries Programme. 15p. (Paper contributed to the International Workshop on Mangrove and Estuarine Area Development for the Indo-Pacific region. 14–19 November 1977, Manila Philippines)

Rabanal, H.R. and R. O. Juliano. 1979 Aquaculture extension: How it could be a potent force in fisheries development in the ASEAN region. Manila, South China Sea Fisheries Programme, 1979. (Paper contributed to the First ASEAN Seminar/Workshop on Fisheries Extension, Manila 18–25 February 1979)

Thomson, D. B. 1979 Marine fisheries extension. Manila, South China Sea Fisheries Programme, 1979. 41p. (Paper contributed to the First ASEAN Seminar/ Workshop on Fisheries Extension, Manila, 18–25 February, 1979)

Thomson. 1979 Training requirements of the fisheries of Southeast Asia. Manila, South China Sea Fisheries Programme, 1979. 11p. (Paper presented at the SEAFDEC Consultative Meeting on Fisheries Training, Bangkok, 14–18 May 1979)

Rabanal, H.R. 1979 Production and recent innovation in design and management in aquaculture industry in Southeast Asia. Manila, South China Sea Fisheries Programme, 1979. 7p. (Paper contributed to the Asian Seminar and Tour sponsored by the Bank of America, Manila, 6–9 November 1979)

Thomson, D.B. 1979 The challenge of 1980's for fisheries education, training and extension. Manila, South China Sea Fisheries Programme, 1979. 11p. (Paper presented at the First International Symposium on Fishery Education, Fish Processing and Marketing Systems. Mexico, December 1979)