(13 November 1978)
This is a typical fish pond complex with water persistently coloured by clay particles and algae. In spite of pump problems and transport delays, an artificial bed was successfully established using local sand and the SWS method of providing clean water demonstrated. The procedure was similar to that described for Sukabumi in Java and other centres. The detailed method of applying this in fish farms is given in Appendix 1.
(14 November 1978)
A stream 3 to 5 m wide flows through the training area site. Its bed is of deep gravel/sand, well assorted and varying from under 1 mm to c. 3 cm. The bed was excavated and the Unit installed by local staff. Development was straightforward and fast, and top quality water was obtained in about 20 minutes. The pump, although marked as self-priming, was by no means satisfactory and pumped only after both suction and delivery line had been filled with water. It was also difficult to control at low speed, but the site quality made this unimportant. The Unit was taken up, and installed and developed again by the local staff. The method of blowing the Unit out of the bed when it was necessary to move it was then demonstrated.
A well used by the families of workers, totalling about 30 persons, was inspected. Water was of top quality, having travelled through a wide belt of gravel/sand, and when inspected, the water was c. 1.5 m below ground level. The Project Manager wishes to cover the well over and use a small hand-operated pump. An SWS mini-Unit, buried in the existing sand and connected by a 1" pipe to a small pump, would give improved water and allow a concrete slab to be placed over it and thus stop pollution from surface drainage. At times of flood, this well seems to be in danger of being flooded and the use of the mini-Unit would exclude any silt, etc. that might seep in.
(15 November 1978)
The sea edge alongside the existing fish market area was inspected in the hope of finding conditions which would allow the use of stainless steel screen wells. Hand probing by a 1" pipe suggested that sand underlay a deposit of deep mud. The water was about 1 m deep but it was possible to take a shovelful of mud to a depth of about 30 cm. This included fragments of gravel and shell. A nearby beach consisted of a shell/sand mixture, with some mud content, and this appeared to extend under the sea. It was, therefore, considered worthwhile to explore further with the trial jet probe. The work was continued on the afternoon of 17th when the existence of a permeable zone was confirmed, mostly shell fragments under some 50 cm of mud/silt. After 15 minutes pumping, the filtrate was free of suspended matter.
The sea bed immediately off the steps leading to the fish market is, therefore, a potential source of unlimited clean sea water. Detailed suggestions for exploiting this is given in Appendix 6.
If need be, a supply could be pumped from here by pipeline to the main market but the area immediately off-shore there is well worth prospecting, for if the underlying stratum runs through, as seems likely, pumping would be simpler. A similar method of test-probing should be used, with extension pipes to take the probe down. See Appendix 6.
(16 November 1978)
Unfortunately, a message received at the UP Marine Biology Department was incomplete, and valuable time was wasted locating suitable suction hose and spare pump.
The site where it was hoped to run trials was 90 minutes' journey from the town and as the plane arrived 2 hours late, this journey was impossible. It was, therefore, decided to develop a site at Anawan, on the outskirts of Iloilo, where a small gravel bottomed stream provided adverse conditions. The gravel was heavily charged with black silt and the slowly flowing water was rich in algae and organic matter. Disturbance during installation was such that the surface water remained completely turbid throughout the trial. Four stop/starts were given and the system pumped for a total of 30 minutes, when the filtrate was crystal clear. The purpose of the trial had then been served and the Unit was taken up.
In the hope of demonstrating the SWS test probe on the beach, it was connected to the delivery line and pumped from an open intake, but the maximum flow was far below the needed velocity for jetting down and nothing could be done. The nearby beach was then inspected; the sand found had a wide grain size distribution and was probably ideal for abstraction.
The UP representative stated that the potential sites for fresh-water abstraction were much more favourable than that used and he was confident that the system could be applied there. The general solution to these supply problems was then discussed and it was promised that a full list of the requirements would be sent to FAO Manila. From this, detailed suggestions will be made for systems to supply the three different flows, two of fresh water and one of salt water.
(17 November 1978)
A river near the town of Marikina, about one hour from the centre of Manila, had been explored earlier in the week and the successful use of the SWS Unit was demonstrated. The river at this point has large areas of gravel/sand either exposed or up to 50 cm below the surface. Although there is a considerable fine content, this is easily evacuated, giving a free-flowing clean bed.
After 15 minutes, the filtrate was cleaner than the raw river water and it continued to improve until the trial ended after thirty minutes' pumping. Fine sand had almost stopped and development seemed nearly complete. This site is ideal for demonstrating, for it can be approached closely by road and is convenient for spectators. It is not easily located and it is unfortunate that several intending visitors failed to find the spot. A demonstration is being arranged at which representatives from the various departments concerned with water and health can be present. It is suggested that a Unit be established the previous day and pumped for 6 or 8 hours before being seen by interested visitors. Having viewed the finished product, they can then see the Unit taken up and installed anew. This is a convenient way of demonstrating the whole process in minimum time, which should be well under 1 hour.
(18 November '78)
A visit was made to the Estate of the Manila Pineapple Corporation in company with several officials to comment on the possible use of SWS systems for improving the water supply to estate villages and also for general purposes. The valley bottoms varied widely, with some reaches fastflowing and rocky, and others with fine sand and mud, but there are large areas with sand/gravel where sub-sand abstraction of large volumes is possible. In some cases, in particular the main supply of c. 4,000 g/h, the terrain should allow gravity abstraction through SWS Units placed in the intake in the hills above.
Water for the textile factory is pumped a considerable distance in two stages to a big reservoir and then to overhead tanks for ready use. Storage in shallow ponds invariably allows algae growth. It would be simple to install a Unit in an artificial bed and abstract much improved water, but unless silt or intake blocking is a major problem, it is probably not worth abstracting sub-sand at source.
Two large settling ponds are filled with effluent from the factory. Although the blue-green colour is presumably due to dissolved dye, the water also contains much material in suspension which would be removed by sub-sand abstraction. Only an actual trial will show how much of the colour and the suspended solids will be removed, but this can be simply tested in an artificial bed. The object here is to make the water suitable for re-use, not to bring it to potable standard.
The combination of topography and geology provide conditions which are often ideal for sub-sand abstraction from the river itself. This method could be used widely to provide good quality water at low cost for community, industrial and agricultural uses as well as for fishery work. Most of the sand/gravel is of more mixed origin than the largely granitederived quartz sand of Java and Sumatra and it can be quickly processed into a very permeable medium. This gravel is extracted by hand in great volumes for use as aggregate, etc. and for road repair, so it is easily and cheaply available for making artificial beds at fish farms.
Experience at Navotas Fishing Harbour, where conditions appeared hopeless, suggest that it is well worth making deep probe tests at all fishing harbours where clean sea water can be used for fish-washing, etc. and thus, save fresh water. The inspection of several beaches also showed that the surface sand can be misleading, since a thin layer of fine sand often underlies coarser and more suitable material. Here too, deep probing is always worthwhile.
