THE SYMBIOTIC PURIFICATION.

INTRODUCTION.

The socio-economic development which the Mediterranean littoral has undergone in the past thirty years, together with the lack of rainfall in this area, has brought about a situation of structural shortage whose main characteristic is the lack of water resources and a progressive deterioration in its quality.

This set of problems has not stopped agricultural, industrial and tourist growth. This is because of the great amount of work carried out in search of alternative resources, the improvement of its efficiency, and the efficiency in growth systems, the decrease in wastage in distribution systems and the complete regulation of available water.

In spite of this, the established uses have not solved the grave future uncertainty  which threatens them, making it practically impossible to create new leisure, and sport and entertainment activities. Notwithstanding, the demand for these activities is increasing constantly among the population, but is now seen from the viewpoint of making it compatible with the environment and respecting natural resources such as water.

On the other hand, to find a solution to the impairment of surface watercourses, a considerable effort to improve the quality of urban  sewage is being carried out. This is being done by building new Purifying Stations of Urban Sewage (PSUS), which will adapt the spillage to legal requirements. Requirements which are now well below social expectations, which demand that terciary purification returns water to the environment with a quality similar to the one it had when it was collected for the first time.

 DEFINITION OF THE  PRODUCT. 

SYMBIOTIC PURIFICATION  has as its main characteristic the existence of two well-distinguished areas, the purification area and the growth area.

The purification area consists of a gravel layer, some 120 to 150 cm thick, which is isolated from the ground by means of an impermeable base. The sewage is applied by means of a net of subterranean drips, placed directly on the gravel, so that sewage percolates through it. Once the impermeable base is reached, the sewage, once purified, flows, attracted by the force of gravity, to the spillage, storage or pumping areas, so that it can be used again on other surfaces. At all times, the layer remains not saturated with water, i.e. air is present, so that sewage is purified under aerobic conditions.

The cultivation area is placed over the purification area just described and it is made of a substratum, usually sandy, some 30 to 50 cm thick (depending on the radicular capacity of the growth which is to be planted, and also depending on the permeability of the substratum itself), which can absorb, through capillarity, a small part of the humidity generated by the lower area. This substratum, which does not contribute to water purification in itself, favours its homogeneous distribution by acting as a drop disperser, thus improving the purification capacity of the bedding.

DESCRIPTION OF THE MANUFACTURE PROCESS.

GUIDE TO THE PROCESS.

Ø       Land movement.  

On land where symbiotic sewage farms are to be installed, a slight movement of the ground will be carried out to establish the flow, through the force of gravity, of the treated water to the pond or, directly, to the delivery points. This operation may be carried out either without having to take any soil to the rubbish dump, by using the Quart Model, or by excavating the volume which the bedding occupies (Green Model).

Ø       Waterproofing.

The waterproofing process is the same as the one used for small reservoirs. Thermo-sealed PVC and polyethylene layers are the ones which are most widely used.

Depending on the roughness of the land where the previous operation is to be carried out, it might be necessary to use of a geo-textile under the layer.

Ø       Infiltration bedding placement.

The placing of the percolation layer gravel over a impermeable layer, is a simple operation which can is achieved by unloading lorries directly on the filling area and, after that, redistributing it by using a shovel.l.

 Ø       Installation of the drip net.

Once the bedding surface has been levelled, the placing of drip lines is done manually. Thus there is no need to use any special machinery.

Optionally, some drainage guide tubes are installed for maintenance and drip lines replacement. Some planks of wood are also installed where the ends of the drip lines are inserted.

When the growth substratum is designed for golf course greens, the drip net is covered with  10 cm small diameter gravel, to reduce substantially the constant humidity of the substratum. In this case it is necessary to use water sprinklers in the growth area which use the treated water previously collected by the system itself.

Drips are placed at 30 cms distance from each other. And drip lines are placed at 30 cms distance from each other. This means having 11 drips per square metre, which means about 400 litres per square metre per day with drips of 1.6 litres per hour; and about 600 litres per square metre per day with drips of 2.3 litres per hour.

 Ø       Placing of the cultivation substratum.

The technique used in the placing of the cultivation substratum is the same as that described for the percolator bedding.

The exact location of the drips and the thickness and nature of the substratum will depend on the type of cultivation that we want to implant.

 Ø       Building of integrated ponds.

Using the constructive model Quart, in which pieces of stone from 5 to 20 cms diametre are placed in the lowest topographic areas, a type of reservoir which is completely integrated in the water treatment system is obtained. This contributes notably to the aesthetic and purification performance.

The placing of the pieces of stone is carried out by mechanical means, which have to be given a finishing touch manually, so as to give the the pond a natural aspect. Aquatic plants will be used advantageously in this environment.

 Ø       Propulsion installations

The propulsion of the secondary flow to the drip net begins by the intake of the secondary flow of the PSUS.

The pumping group will be designed taking into account the surface of the bedding (entrance flow) and the work pressure of the drips (of 5 to 40 m.c.a.).

The automatic filtering system (100 micra) can either feed on the mentioned pumping group, or be united to a more precise system with less volume, which will be energy saving as a consequence.

This is a type of installation which is not very different from that typically used in watering by sprinklers, managed by its corresponding watering and automatic cleaning programme of nets and filters.

Ø       Delivery installations

It is advisable to carry out the final delivery of treated water in a natural way by, using the gravel used for the bedding and the pond, which, by means of the force of gravity, will take the water to the spillage place or storage deposit to be reused.

 Ø       Complementary irrigation installations

Some types of grass, such as the agrostis stolonifera used on golf greens, whose rooting is superficial need a complementary irrigation net with water sprinklers.

 Ø       Green belt areas planting

All plants are sowed in sand. Thus this is an extemely easy and economic task

Ø       Manufacture experience

The only manufacturing experience available has been provided by the two experimental symbiotic purifying plans which have been built so far.

Quart-Benager experience. Valencia                              Raal experience. Murcia

COMPETITIVE ADVANTAGES. INNOVATIVE APPROACH.

One thing to be taken into account is the fact that this is not only a new product, but also that it is an innovative one. It is more than an alternative; it is an economic tool in environment management, which can solve a great number of problems. Among these are the economic and environmental problems associated to the total purification of sewage and the lack of hydraulic resources needed in such important sectors as tourism and hydroponic agriculture.

Because this is a hybrid product it has to be compared on one hand with other purifying systems and on the other hand with the watering by sprinklers of green belt surfaces.

A greater increase in the hydraulic performance of the purifying system (without any evaporation losses): This is achieved by means of subterranean watering devices i.e. drips. The grass which grows on the surface only retains 2 % of the total amount of water. This amount is less than the amount which is lost using other purifying systems.

The quality of treated water increases due to the fact that the distribution of sewage using watering by sprinklers creates oxygenation conditions and flow in the percolation bedding which are suitable for the biotic mass in charge of the purifying process. The saturation of water treated with oxygen is the main characteristic and singularity of the symbiotic purifying plant.

As it looks good and is not muddy and has no unpleasant smell or aerosols, it is socially accepted. Thus, one of the greatest problems with current purifying systems is eliminated.

It is the only purifying plant that allows golf courses, greenhouses, parks, etc to be built on its surface. This brings about an economic and social appreciation of the purification process.

The connection of a golf course or any other green belt area to a purifying plant has the following competitive advantages:

The golf course is guaranteed its water supply. This guarantee is the same as the one the city centre where the water to be purified comes from has.

The golf course does not have any water expenses.

There is an environmental justification to create golf courses. This is because sewage can be purified thanks to a tertiary treatment.

The creation of superficial masses of water after its percolation through the purifying bedding adds beauty and environmental quality to the golf course. Lakes and rivers which spring from this bedding are highly valued in these sport and entertainment activities.

The re-use rejection disappears, because golf players will not notice any of the inconveniences of sewage being used to water the grass. This is so because the grass never comes into contact with non purified water.

In spite of this hybrid system being so innovative none of the spaces, installations and activities are in any way different to the conventional ones. The symbiotic purification only connects adequately techniques already known and of proven feasibility.